fbpx
Wikipedia

Boeing 307 Stratoliner

July 05, 2023

The Boeing Model 307 Stratoliner (or Strato-Clipper in Pan American service, or C-75 in USAAF service) is an American stressed-skin four-engine low-wing tailwheel monoplane airliner derived from the B-17 Flying Fortress bomber, which entered commercial service in July 1940. It was the first airliner in revenue service with a pressurized cabin, which with supercharged engines, allowed it to cruise above the weather. As such it represented a major advance over contemporaries, with a cruising speed of 220 mph (350 km/h) at 20,000 ft (6,100 m) compared to the Douglas DC-3s 160 mph (260 km/h), at 8,000 ft (2,400 m) then in service.[4] When it entered commercial service it had a crew of five to six, including two pilots, a flight engineer, two flight attendants and an optional navigator, and had a capacity for 33 passengers, which later modifications increased, first to 38, and eventually to 60.

Boeing 307/C-75 Stratoliner
Role Airliner
National origin United States
Manufacturer Boeing
First flight December 31, 1938[1][2]
Introduction July 4, 1940 with Pan American Airways[1][3]
Status Last operational example wrecked on March 13, 1975,
One survivor in museum
Primary users Transcontinental & Western Air
Aigle Azur
United States Army Air Forces
Pan American Airways
Number built 10
Developed from Boeing B-17 Flying Fortress

Development

 
Boeing S-307 Stratoliner production line - note the early B-17s to the rear
 
Prototype Model 307 NX19901 with the small tail as initially designed, and which caused its loss

In 1935, Pan American Airways, United Airlines, American Airlines, Eastern Air Lines and Transcontinental & Western Air (T&WA) had each signed a contract with Douglas to develop the 40 passenger DC-4 (later known as the DC-4E).[5] Each company contributed $100,000[notes 1] to development costs and agreed to not operate other aircraft with a maximum weight of 43,000 to 75,000 lb (20,000 to 34,000 kg) for revenue service.[5] Due to development problems and poor performance, all of the airlines dropped out of the DC-4 program and cancelled their orders, but a requirement for a large 4 engine airliner remained.[6][7]

D.W. Tommy Tomlinson at T&WA carried out five years of high altitude flight research, with a Northrop Gamma and a Douglas DC-1, which helped determine that T&WA would need a four-engine airliner with a pressurized cabin.[8] During this period, He also test flew the XB-17 and determined that it would provide an ideal basis for an airliner, and so Boeing was approached with the idea.[7] A ceiling of at least 16,000 ft (4,900 m) was required to avoid summertime "chop" over the Rocky Mountains, and to allow the aircraft to fly around the thunderstorms that can sometimes block mountain passes, which meant a pressurized cabin would be the most comfortable for passengers on long flights.[9] In 1935, Boeing then designed a four-engine airliner using components from the Boeing Model 299 B-17 Flying Fortress heavy bomber as the Model 307. It combined the wings, tail, rudder, undercarriage, and engines from the B-17 with a new, much larger pressurized circular cross-section fuselage with a maximum diameter of 138 in (3.5 m).[10]

The pressurization system required extensive testing, which was carried out over many months, progressively increasing the air pressure after each successful test, and each time, the highly polished fuselage was coated with soapy water while the fuselage pressurized, for workers to look for the bubbles that would indicate a leak, much like testing a bicycle inner tube.[11]

Before the first aircraft had rolled out, T&WA's chief engineer discovered that the extruded metal tubing used for the wing spars was defective, with stress corrosion cracks produced by cold rolling the tubing to increase tensile strength.[9] Affected aircraft included the prototype, the first Pan Am machine, and some early production B-17s, and resulted in T&WA having to have their engineers manually inspect every tube that was to be incorporated into their aircraft.[9]

 
Wreck of the prototype, NX19901

The first aircraft completed, registration NX19901, crashed on March 18, 1939.[12] while being demonstrated after having been recently fitted with instruments to measure flight control forces.[13] The Boeing 307 took off at 1257hrs (local time) from Boeing Field in Seattle with ten occupants,[13] and they climbed to an altitude of 11,000 ft (3,400 m) where stability tests were made and while carrying out side-slips near Alder, the aircraft stalled and entered a spin.[13] It made two to three turns before the pilot was able to stop the spin using the engines,[12] however the ensuing high speed dive and the forces that resulted from attempting to pull up before hitting the ground, resulted in the left outer wing tearing off with one engine still attached, followed by the right wing, just outside the outer engine, both of which also tore off parts of the tail as a result of the aileron cables pulling them against the fuselage, which then caused the aircraft to pancake into a forested area at 1317hrs.[2][14] All ten aboard were killed,[14] which included T&WA's representative, KLM's technical director, a Dutch Air Ministry representative, Boeing's test pilot, as well as their Chief Aerodynamicist and their Chief Engineer.[12] Parachutes were available but the force of the spin prevented their use.[2]

The crash delayed the program by over a year, beginning with a three-month investigation by the US Civil Aeronautics Authority, the precursor to the current Federal Aviation Administration, and Boeing to determine the causes.[2] Flight and wind tunnel testing showed that both an extended dorsal fin and an enlarged vertical tail were needed to prevent the rudder stalling in a yaw, and solutions were flight tested on NC19903, including an intermediate solution consisting of just an extended dorsal fin.[15] The resulting redesign was also incorporated into the redesign of the rear fuselage of the B-17E bomber.[16] The wings were reinforced and Handley Page slots were added to the outer wing leading edges to improve low speed aileron control while the inboard flaps were also extended.[2][14] The first several aircraft, including NC19902, NC19903, and NC19904 were all rolled out with the small tail and then modified later.

Test flights resumed on May 19, 1939, after the changes had been incorporated,[14] and on June 20, 1939, the first flight was made with the "supercharged cabin" pressurization system on.[6]

On March 13, 1940, Approved Type Certificate (ATC) number 719 was assigned to the Pan Am Boeing 307s, allowing commercial deliveries to commence.[6] A second ATC was issued for the TWA aircraft, number 726, due to the numerous differences between the Pan Am and T&WA aircraft.[17]

 
TWA Boeing SA-307B NC19905 on May 17, 1940, after the engines iced up and it made a forced landing

T&WA was concerned about excessive undercarriage stiffness from their experience with the test flights with the XB-17, which were to be modified for the airliner.[7] T&WA flight tested the modified undercarriage, and in hard landings, easily exceeded the contract's minimum required 500 ft/s (150 m/s) descent rate with a successful 800 ft/s (240 m/s) landing descent.[18]

T&WA was also concerned about the engine carburetor intake heaters being deliberately restricted by Boeing to prevent cooking the engines, which could potentially leave crews unable to clear ice.[19] Their point was made when icing problems during a test flight on May 17, 1940, with NC19905, while carrying dignitaries in overcast conditions in the mountains resulted in three of the four engines failing, while the fourth was losing power, despite every measure being taken to clear the ice. This resulted in the aircraft making a belly landing in a field with a partially lowered undercarriage,[19] just south of Lamar, Colorado.[20] T&WA then modified the carburetor heating themselves and the aircraft was repaired and returned to service.[19]

Boeing made claims both in their period advertising and in their current web site that it was the first high-altitude commercial transport, and the first with a flight engineer.[21] However its first flight on December 31, 1938, was later than that of the Renard R-35 which also had a pressurized cabin for passengers and which flew on April 1, 1938.[22] As for employing a flight engineer, it was preceded in the US on a commercial aircraft by Maddux Air Lines Ford Trimotors, whose "Mate" had the same responsibilities as a flight engineer.[23] Additionally, all German World War One Riesenflugzeug multi-engine bombers had flight engineers as they were integral to the specification.[24]

Design

 
TWA Boeing SA-307B NC19907 'Zuni' 402 landing with slotted flaps lowered, prewar
 
Pan Am Boeing S-307 Stratoliner NC19902 Clipper Rainbow with blanking plates installed on engines to prevent engine over-cooling

As built, the Stratoliner used the all-metal stressed-skin cantilever wings from the B-17C mounted low on the fuselage to a constant chord center section faired to the fuselage,[25][26] with four 1,100 hp (820 kW) Wright GR-1820 Cyclone air-cooled radial engines. TWA examples used GR-1820-G105A engines fitted with two stage superchargers for high altitude performance, while the Pan Am examples used the GR-1820-G102 with a single stage supercharger.[25][27][28] Engine exhaust collector rings designed to reduce noise, and exhaust mufflers were installed.[29] TWA aircraft were fitted with cowl flaps, to adjust engine cooling air, while Pan Am aircraft had fixed cowling rings without cowling gills.[27] When operating in cooler conditions, the Pan Am aircraft could be fitted with a blanking disk that covered part of the front of the engine. Both versions had sufficient power to maintain altitude on only two engines,[28] one of the KLM requirements.[30] Both used three bladed Hamilton Standard Hydromatic constant speed propellers,[26] and new high octane fuels were developed to help the engines operate under the increased supercharger pressure.[31] Both versions had trailing edge flaps controlled with electric motors,[8] although SA-307B for T&WA and the SB-307B for Hughes featured slotted flaps with prominent external hinges, while the Pan Am examples had simpler split flaps with flush hinges, similar to those used on the B-17s.[27][23] All of the fuel was carried in the wings, with a 212.5 US gal (804 L; 176.9 imp gal) tank mounted between the inboard nacelle and the fuselage, and a 425 US gal (1,610 L; 354 imp gal) main fuel tank as well as a 212.5 US gal (804 L; 176.9 imp gal) fuel tank located between the inner and outer nacelles, on both sides of the aircraft, providing a total of 1,700 US gal (6,400 L; 1,400 imp gal) of fuel in six tanks.[27] With the fuselage being 3.5 ft (1.1 m) wider than on the B-17, the span had increased from 103 ft 9 in (31.62 m) to 107 ft 3 in (32.69 m) compared to early B-17s.[11] After being modified, the SA-307B-1s used the wings and elevators from the B-17G with split flaps, and 1,200 hp (890 kW) Cyclones.[26] On most, but not all examples, the leading edges of the wings, horizontal stabilizer and fin were fitted with rubber expanding type de-icing boots, which would inflate and deflate repeatedly to break ice from the flying surfaces.[26] All movable surfaces, including the rudder, ailerons and elevators had fabric over a metal structure, and were aerodynamically balanced and fitted with adjustable trim tabs to lighten flight loads.[26][29] The rudder and elevators also had hydraulic boost, to lighten control forces.[27] The partially retractable main undercarriage had hydraulic brakes and used Goodyear 55x19x23 tires, and was raised and lowered with electric motors.[26] Manual backups were provided for electrically driven systems, but the power had to be turned off before being used.[32] A parking brake was provided, along with an emergency air brake system run off a bottle of compressed air, while the tailwheel was fully retractable.[26][33]

 
Passengers on Pan Am Strato-Clipper in the Raymond Loewy-designed interior. Seats on the left could be folded into sleeper bunks

The fuselage was described as being dirigible shaped, and was an elongated teardrop, with a constant 11.5 ft (3.5 m) diameter tube lengthening it at its widest point.[28][34] The circular section fuselage was of all metal construction, skinned with 24ST Alclad[26][27] and capable of maintaining a cabin pressure equivalent to 8,000 ft (2,400 m) when flying at a 16,000 ft (4,900 m) altitude, and a 12,000 ft (3,700 m) cabin pressure when at 20,000 ft (6,100 m),[9] with a maximum pressure difference of 2.5 lb/sq ft (12 kg/m2).[31] The structure was designed with strength reserves so as to handle as much as 6 lb/sq ft (29 kg/m2), but a pressure relief valve prevented the pressure difference from exceeding 2.65 lb/sq ft (12.9 kg/m2).[34][35] The structure consisted of continuous longitudinal stiffeners spaced every 9 degrees around the fuselage with radial hoop stiffeners mounted every 16 in (410 mm) along the fuselage, reinforcing the similarity to a dirigible.[36] The skin seams were sealed with tape impregnated with sealing compound trapped between lapped joints which were secured with two rows of rivets spaced 5⁄8 in (16 mm) apart, while doors and hatches were sealed with soft rubber gaskets and control cables entered the pressurized cabin through specially developed glands designed to allow free movement of the cables, with a negligible amount of air leakage.[34] The main cockpit windows were made from 5⁄8 in (16 mm) thick safety glass, while the rest of the windows were made of Plexiglass or Lucite sealed into rubber channels[34] A large ram-air scoop on the cabin roof was provided to supply cooling air while at lower altitudes, and was shut off when the cabin was pressurized at higher altitudes.[27] The cockpit was fitted with an autopilot, radios[26] and a radio direction finder (RDF) for navigation.[37]

The noted industrial designer Raymond Loewy designed the passenger cabin, with furnishings provided by Marshall Field's.[28] It was divided into four compartments, each with six deep comfortable reclining chairs which could be converted into 16 sleeping berths.[26][38] Each compartment was provided with adjustable air conditioning vents, reading lights, and a call button.[38] Nine additional seats were provided along the port side of the aircraft, while washrooms which doubled as dressing rooms were provided at both ends of the cabin.[26] The rear washroom was for women and was named the "ladies charm room". Its walls were covered in heavy plate glass mirrors, and it contained in its 34 sq ft (3.2 m2) area two dressing tables, each with a sink, plush upholstered stools, soft indirect lighting provided by fluorescent lamps, ashtrays, hot and cold running water, shelves with towels, and a separate cubicle for the toilet.[8][38] The men's washroom was in front as the "Men's Lounge", and also had a separate cubicle for the toilet, two sinks, and outlets to run an electric razor.[8] A galley of just 28 sq ft (2.6 m2) provided hot food was situated at the rear of the cabin,[26][38] behind which was positioned the rear hemispherical pressure bulkhead.[34] Up to 412 cu ft (11.7 m3) or 6,590 lb (2,990 kg) of baggage could be stowed under the floor of the cabin, both between the wing spars, and behind the rear spar, which was accessible in flight through a hatch in the cabin floor, or on the ground through three hatches on the underside of the fuselage.[34][38] Extensive use was made of the latest in sound proofing, and the Dynafocal engine shock mounts were designed to reduce vibrations from being felt by the passengers.[8][33] The air conditioning system used both electrical and mechanical systems,[29] which drew air in through vents in leading edge of each wing near the roots to bring outside air to two engine driven superchargers that compressed the air, which was then passed through radiator condensers to cool the air, and it was then run through channels to the vents in the cabin.[29] External hookups allowed ground air conditioner units to cool the cabin air when the engines were off.[29]

Crew

 
Newly graduated Hostesses lined up in front of Zuni, TWA's Stratoliner NC19907, in early to mid-1940.

The Stratoliners were normally flown with a pilot and co-pilot, and both Pan Am and T&WA aircraft carried a flight engineer to reduce the workload on the two pilots, by monitoring the engines for any problems and fine tuning them, while they also controlled fuel consumption from each of the tanks to maintain the aircraft's fore-aft and lateral balance. Too much fuel used in one tank could result in the aircraft becoming uncontrollable. They also monitored other aircraft systems, including hydraulics and the cabin pressurization system.[39] The Flight engineer was also an Aircraft Maintenance Engineer (AME) and aside from operating the radio, which required training in Morse code, he was also responsible for all technical issues, and would carry out repairs and maintenance on the 307s.[23] Pan Am aircraft had one additional crew member compared to T&WA aircraft. Because they made long overwater flights, they carried a navigator, who was not yet considered necessary by the CAA for overland flights, which were served by a network of beacons across the continent,[39] when the aircraft were not being flown by visual flight rules (VFR).

Both T&WA and Pan Am normally carried two flight attendants. T&WA began using Hostesses (as they called them) as cabin crew in late 1935, while Pan Am continued to use male stewards until late in WW2.[40]

C-75 conversion

 
42-88623 Cherokee loading up following conversion to C-75 standard

Following the entry of the United States into World War II in December 1941, long-range transports were needed to ferry government and military officials around the globe and many aircraft, including T&WA's Boeing 307s, were pressed into service. Beginning in February 1942, these were flown to Albuquerque, New Mexico for conversion, which included the removal of the plush, but heavy civilian fittings, including the massive mirrors in the women's "charm room" and the pressurization system to save weight.[41] The sound insulation was also stripped out leaving the cabin much noisier than it had been.[42] The forward men's washroom, and two of the four forward compartments were replaced with five gravity fed 212.5 US gal (804 L; 176.9 imp gal) fuel tanks and a 45 US gal (170 L; 37 imp gal) oil tank fed with a wobble pump, along with a rest area for the crew.[41][43] A desk was added behind the pilot for a radio operator, who had a 50 watt Bendix TA-12 high frequency Morse transmitter, and a BC-348 tunable receiver. A 400 ft (120 m) trailing wire antenna was used with a 5 lb (2.3 kg) lead weight on the end - which the radio operator needed to remember to reel in, by hand, when landing. Inexperience sometimes led to either the antenna being torn off, or lashing against the fuselage. An astrodome was fitted and the perspex top windows which produced excessive parallax were replaced with optically flat glass, to allow the navigator to take star shots (the angle between stars and the horizon could be used to determine how far north or south they were), necessary to determine their position when crossing large bodies of water.[41] The SA-307B-1s retained the astrodomes when converted back from C-75 in 1944. To further aid navigation, a B-3 driftmeter was installed, along with an aperiodic compass that did not lag or lead in turns as a conventional compass does.[41] Mae West life vests and life rafts were also provided.[41]

The landing gear was strengthened, and the maximum takeoff weight was increased from 45,000 to 56,000 lb (20,000 to 25,000 kg), leaving the Stratoliner underpowered, and the climb suffered accordingly.[10][44][45] The overloading burnt out engines and destroyed piston rings, but closely monitoring engine oil consumption often caught failures before they occurred.[42]

Passenger facilities were reduced to 4 bunks which when folded away allowed seating for 12, along with 4 seats along the opposite side of the aircraft.[41] Removable tables were provided in the cabin to lay out maps and do paperwork.[42] The exterior was then camouflaged in standard USAAF colours, with olive drab upper surfaces and neutral grey undersides,[10][45] and each aircraft had its name painted on the nose and over the cabin door, which would also be used by many later operators.[45] The names had previously been used in TWA publicity, but not painted on the aircraft.[8]

After three years the USAAF had amassed sufficient long range transports that it no longer needed the C-75s, and they sold the fleet back to TWA, who paid to have them converted back to civil standard under Boeing's SA-307B-1 designation. CAA concerns over cracks in the wing spar tubing led to the TWA Stratoliners getting new B-17G wings and horizontal tail, with the leading edge of the longer span, narrower chord horizontal stabilizer[46] moved about 3 ft (0.91 m) to the rear,[47] while more powerful versions of the same Wright Cyclone engines increased power from 1,100 to 1,200 hp (820 to 890 kW),[47] but without the B-17G's turbosuperchargers. New propellers and landing gear were also installed.[48] The change to the tailplane required that the structural bulkhead supporting the forward spar be moved aft, while the rear bulkhead was reworked and additional fuselage stiffeners were added.[33] The tailwheel switched to using B-17G wheels and 26" smooth tread tires, which required that the wheel well be enlarged, and structure supporting the tailwheel reinforced.[33] The main undercarriage wheels, tires, tubes & brakes remained unchanged, although the legs themselves were strengthened.[33] The fuselages were stripped to bare metal and rewired with a 24VDC 1800 amp system from the B-29 Superfortress, replacing the original 24VDC 800 amp system.[47] Maximum weight was increased to 54,000 lb (24,000 kg) and the maximum landing weight rose to 47,000 lb (21,000 kg).[49] Slots were re-incorporated into the wingtip leading edges,[46] as they had been with the pre-war airliners. The cabin was redesigned and passenger capacity was increased from 33 to 38,[46][50] with the cabin now divided into a 10-seat front section and a 28-seat rear section, with no sleepers.[49] The cabin pressurization system was never re-installed[46][47] The B-17G wings came with turbo-supercharger ducting for the engines that was not needed for the simpler supercharger installation used on the Stratoliner, while one duct opening was retained on each wing between the engine nacelles, to provide additional cabin air.[48] Further mods made by TWA included improved sound proofing and temperature control[49] and on March 15, 1945, the B-1 recertification tests were completed to the CAA's satisfaction.[49] The estimated cost to repurchase and refurbish the five aircraft was $2 million.[notes 2][49]

Variants

 
Prototype of the S-307, with the small tail used initially on the first three examples built.
300
Original unpressurized 35,200 lb (16,000 kg) proposal with seating for 16-24 passengers which began as a four-engined Boeing 247.[5][51]
 
Ex-Pan Am Inter-American Inc. Boeing S-307 Strato-Clipper N19903 after returning to the US from Haiti, before being bought by the Smithsonian.
 
T&WA Boeing SA-307B Cherokee as built.
PAA-307 or S-307 Strato-Clipper
Designation for three aircraft built for Pan Am under ATC 719.[17] Visible external differences included engine cowlings without cowl flaps.[52] Four 1,100 hp (820 kW) Wright GR-1820-G102A Cyclone engines were fitted, with single-speed superchargers.[27][53] Crew of six.[1] Strato-Clipper was Pan Am's name for the type.[1]
SA-307B
Designation for five aircraft built for T&WA under ATC 726.[17] These differed externally from the Pan Am aircraft in having large external flap actuators.[52] Four 1,100 hp (820 kW) Wright GR-1820-G105A Cyclone engines were fitted, with two-speed superchargers.[28] Crew of five.[28]
SB-307B
Designation for one uncertified aircraft built for Howard Hughes.[17]
C-75
Five Trans World SA-307Bs were impressed into the USAAF. The cabin pressurization was removed to save weight, and the external flap actuators replaced.
SA-307B-1
The C-75s were overhauled and updated with modified B-17G wings (with 307 wing slots) and larger tailplanes mounted further aft.[54] 1,200 hp (890 kW) Wright GR-1820-G205A Cyclone engines were fitted,[26] along with B-29 electrical systems.
307C
50 passenger development with more powerful versions of the same Cyclone engines, boosted to 1,350 hp (1,010 kW). Boeing wanted $267,230 + 13,000 per engine (or $319,230[notes 3]) but development was cancelled in favour of the 377 Stratocruiser, based on the B-29.[47]
316
Airliner project developed from the XB-15 with pressurized cabin similar to that used on the Stratoliners, offered to KLM as a larger Stratoliner but not followed through with.[55]
322
Development of 307 with similar fuselage but with a mid-mounted wing and a nosewheel, as a bomber. Eventually evolved into the B-29.

Operational history

Ten 307s were built. NC19906 was temporarily marked as NX1940 and NC1940 for publicity purposes.[56]

C/N Registration Delivery Customer Model Names (fleet number) Other identities FInal Disposition
1994 NX19901 none S-307 none none Crashed and destroyed during test flight, March 18, 1939
1995 NC19902 Pan American Airways[31] S-307 Clipper Rainbow F-BHHR, XW-TAC Wrecked during emergency landing in bad weather, May 22, 1961
1996 NC19905 Transcontinental & Western Air[56] SA-307B/after 1944 SA-307B-1 Comanche (400) 42-88624/288624, F-BELV, XW-TAA Possibly shot down, crashed and destroyed, October 18, 1965
1997 NX19904 Howard Hughes[6] SB-307B The "Flying Penthouse", Shamrock NC19904 Damaged on ground during storm, converted to houseboat, now in Florida Air Museum
1998 NC19906 Transcontinental & Western Air[56] SA-307B/after 1944 SA-307B-1 Cherokee (401) 42-88623/288623, NX1940, NC1940, F-BELU, XW-TFP Forced to ditch in Mekong River, aircraft was never recovered, March 13, 1975
1999 NC19907 Transcontinental & Western Air[56] SA-307B/after 1944 SA-307B-1 Zuni (402) 42-88625/288625, F-BELX, XW-TAB, XW-TFR Crashed and destroyed during a forced landing after multiple engine failure during take-off, June 27, 1974
2000 NC19908 Transcontinental & Western Air[56] SA-307B/after 1944 SA-307B-1 Apache (403) 42-88626/288626, F-BELY, XW-PGR Damaged during collision with another aircraft on ground, written off, February 27, 1971
2001 NC19909 Transcontinental & Western Air[56] SA-307B/after 1944 SA-307B-1 Navajo (404) 288627, F-BELZ Crashed and destroyed after collision with a mountainside, December 29, 1962
2002 NC19910 Pan American Airways[31] S-307 Clipper Comet, Quito HC 004, N75385 Destroyed by fire after forced landing, May 10, 1958
2003 NC19903 Pan American Airways[31] S-307 Clipper Flying Cloud 2003, N9307R, N19903[57] Restored to flying condition, now in Smithsonian Museum

Prototype

 
Boeing 307 prototype from above, showing off the wing and tail planform

The first Boeing 307 Stratoliner, serial 1994, registration NX19901, made its first flight from Boeing Field, near Seattle on December 31, 1938, prior to its intended delivery to Pan Am following testing and certification.[58] As related above, it crashed on a test-flight on March 18, 1939, killing all 10 occupants, and forced several design changes, of which the fin and rudder are the most immediately obvious.

Koninklijke Luchtvaart Maatschappij N.V. (KLM)

KLM was considering four-engine airliners for the European routes, and a longer ranged four-engine aircraft for their routes to the Netherlands East Indies (now Indonesia). Aircraft considered included the Douglas DC-4(E), the Boeing 307, the Junkers Ju 90, the Focke-Wulf Fw 200 Condor, and the Bloch 160, of which only the DC-4 and 307 came close to meeting their requirements[55]

Boeing made a proposal to KLM on September 20, 1936, for exclusive option on 10 certified 307s for $2.4 million[notes 4] with options for 18 aircraft and with first delivery in 14 months.[59] By January 14, 1937, the price had increased for 18 aircraft to $265,000 each, not including pressurization equipment.[59] KLM let Boeing know that they were interested in 4 aircraft, for use as an interim measure pending a larger more suitable design, and they that they would use it for familiarization training with four engine aircraft.[30] They required that it fly on just two engines, use Pratt & Whitney automatic mixture controls, have a 2,500 mi (4,000 km) range, be able to carry freight or mail, and have moderate tire ground pressure.[30] KLM then requested a quote for three 307s, either with Wright Cyclones and with Pratt & Whitney 1830 engines, fitted with constant speed propellers and automatic carburettor mixture control and with additional fuel to provide a range of 3,400 mi (5,500 km).[55] Boeing responded that the price for three aircraft would be $289,000 each if fitted with Cyclone engines or $314,000 if fitted with R-1830s, plus $3,100 - $4,000 per aircraft to increasing fuel capacity to either 1,700 US gal (6,400 L; 1,400 imp gal) or 2,125 US gal (8,040 L; 1,769 imp gal), provided that the US Government gave export permission on the engines.[55] After not hearing back, Boeing sent a new quote to KLM for $300,000 per aircraft, or $320,000 for the pressurized version[55] December 20, 1938, the KLM board made the decision to order two four-engine aircraft, with consideration of the Boeing 307 and Focke Wulf Fw 200 Condor, however the Condor was not suitable for the East Indies route.[13]

Following T&WA defaulting on payments, the first three T&WA aircraft were offered to KLM in late 1939 but a quick decision was needed by Saturday, March 18, 1939, but KLM was unable to make that decision before the offer expired, and requested an extension.[13] On March 21, 1939, KLM confirmed that they still planned to buy 307s and insisted that they were content with Boeing's progress.[6] Ultimately though, KLM did not buy the 307s because their representatives' test flight insurance coverage was rejected, and KLM found Boeing's response to providing for the next of kin unsatisfactory, a disagreement that was not cleared up until after World War 2.[6] The insurance coverage on the aircraft was sufficiently large that it had the insurance industry worried about fallout, and as was the norm at the time, neither passengers nor crew could get coverage from any insurance company, but the aircraft itself was covered for a replacement cost of $500,000, with hull coverage and passenger liability, carried by Aero Insurance Underwriters and Associated Aviation Underwriters, despite the fact that Boeing was offering to sell the aircraft to KLM for much less than that.[60]

Australian National Airways (ANA)

Another company that Boeing was in discussions with was Australian National Airways, who they quoted $310,000 per Stratoliner, or $340,000 for a pressurized version, on July 27, 1938,[55] but nothing came of these discussions and ANA never operated the type.

Howard Hughes and Cosmic Muffin

 
Howard Hughes's SB-307B after conversion into The "Flying Penthouse"

The first customer delivery was to millionaire Howard Hughes on July 13, 1939.[6] He bought aircraft serial number 1997[61] registered as NX19904 for $315,000[notes 5][62] for a round-the-world flight, hoping to break his own record of 91 hours 14 minutes set between July 10 and 14 in 1938 in a Lockheed Model 14 Super Electra. Hughes' Stratoliner was fitted with extra fuel tanks and was ready for the first leg of the round-the-world attempt when Nazi Germany invaded Poland on September 1, 1939, causing the attempt to be cancelled.[8] Hughes' aircraft was stored in Glendale, California for the duration of the war, prior to being converted into a flying condo.[63] Hughes had the extra fuel tanks removed, and for around $250,000,[notes 6] he had it fitted with much more powerful Wright R-2600 engines for its transformation into "The Flying Penthouse", which included a Master Bedroom, two bathrooms, a galley and a bar as well as a living room.[63] In 1949, Hughes spent an additional $100,000[notes 7] renovating it so he could sell it, which, like the T&WA and Pan Am aircraft now included an interior designed by Raymond Loewy.[62] Oil tycoon Glenn McCarthy bought it to coincide with the opening of his new Shamrock Hotel and he renamed it Shamrock and had it repainted, however McCarthy defaulted on payments and it was returned to Hughes.[62] It languished unflown until August 1965, when it was damaged beyond repair by Hurricane Cleo, with only about 500 hours on the airframe.[64] It was then bought for $69 by Kenneth W. London, who cut the damaged wings and tail off, built a hull under it, and installed a pair of V-8 engines to convert it into a houseboat which he named Londonaire.[65] After various repossessions, deaths and failed sales later, it became the Cosmic Muffin, in which form it still survives.

Transcontinental & Western Air (T&WA or TWA)

 
TWA Boeing SA-307B NC19905 Comanche undersides, showing off just how wide the 11.5 ft (3.5 m) fuselage was. The external arms for the slotted flaps are visible here, as are the hatches on the underside through which baggage was loaded.

As one of the companies sponsoring the development of the Douglas DC-4, Transcontinental & Western Air lost interest due to delays and poor performance, but the agreement they signed with Douglas limited the maximum weight of any replacement design to 43,000 lbs.[30] After discussing their needs with Boeing, T&WA signed a contract with Boeing to buy six 307s with an option for 13 more for $1,590,000 on January 29, 1937, with deliveries to be made in mid-1938.[9] T&WA defaulted on their payments though and the T&WA markings which had already been applied to their airframes were removed.[11] T&WA filed a lawsuit against Boeing for default of contract, and Boeing sued T&WA for breach of contract over the non-payment.[2] Hughes had begun secretly buying up T&WA shares[66] and by March 1939, Hughes has a controlling interest in Trans-World Airlines (or TWA - as it was rebranded once he had taken over), with roughly 46% of the shares.[2] By August 1939, TWA and Boeing had resumed negotiations so TWA would get five 307s, and Hughes would get one.[2] The cost to TWA had risen, and was now $1,750,000[notes 8] or $350,000[notes 9] per aircraft - three times the cost for Douglas DC-3s.[8] In early 1940, Hughes bought up all remaining outstanding TWA shares not otherwise reserved for employees.[2]

TWA received its first Stratoliner on May 6, 1940, and the last of their five was delivered on June 4, 1940.[56][67] It was not their first four engine airliner, as one of their parent companies, Western Air Express had operated the Fokker F-32. All five were named in TWA promotional material for North American Indigenous tribes - names that would be used throughout their careers, continuing long after they left TWA. War intervened in December 1941, and civil aircraft production was halted, preventing any further deliveries.[68][69] TWA first service flight was chosen to be on July 8, 1940, to coincide with anniversary of TAT's 48 hour coast-coast service, which had used trains for night legs.[3] TWA's Stratoliners flew between Los Angeles and New York, making three stops.

TWA's Burbank - La Guardia flight via Chicago was 2 hours quicker than for a DC-3 (13:40 east and 15:38 west) with 3 stops in each direction.[3] The main route was La Guardia, NY to Chicago, Illinois to Kansas City, Missouri to Albuquerque, New Mexico to Burbank California and the reverse.[3]

1940 was the best year for TWA, with 50% increase in passenger traffic over 1939, but they were still running exclusively in the red.[32] On September 9, 1940, a TWA Stratoliner from Chicago to New York set a commercial speed record flying the 778 mi (1,252 km) in two hours and 52 minutes at an average speed of 271.4 mph (436.8 km/h).[70] and a few weeks later, on September 26, a TWA New York bound Stratoliner at 17,000 ft (5,200 m) with a jetstream providing a strong tailwind reached a ground speed of 387 mph (623 km/h).[71]

 
Map of 1940 TWA Boeing 307 routes
1940 TWA Boeing 307 routes and fares[72]
Flight
No.		 Route Route name Price
(1 way)		 Price
(return)		 Sleeper
surcharge
7 New York to Burbank (via CHI, MKC and ABQ) Super Sky Chief $149.95[notes 10] $269.90[notes 11] $119.95[notes 12]
8 Burbank to New York (via ABQ, MKC and CHI) Super Sky Chief $149.95[notes 10] $269.90[notes 11] $119.95[notes 12]
40 Kansas City to New York (via Chicago) Times Square[notes 13] $66.45[notes 14] $119.60[notes 15] $8.80[notes 16]
41 New York to Chicago (non-stop) Times Square[notes 13] $44.95[notes 17] $80.90[notes 18] $5.60[notes 19]
42 Chicago to New York (non-stop) Sky Century $44.95[notes 17] $80.90[notes 18] $5.60[notes 19]
45 New York to Kansas City (via Chicago) Star Duster $66.45[notes 14] $119.60[notes 15] $8.80[notes 16]

Flight 45 added additional stops at Philadelphia and Pittsburgh on December 1, 1940.[73]

TWA ICD Wartime operations

C/N Old TWA
Registration		 Name USAAF Serial Also marked as
1996 NC19905 Comanche 42-88624 288624
1998 NC19906 Cherokee 42-88623 288623
1999 NC19907 Zuni 42-88625 288625
2000 NC19908 Apache 42-88626 288626
2001 NC19909 Navajo 42-88627 288627

On December 14, 1941, representatives from various airlines as well as the Air Transport Association of America (ATA) met with Colonel Robert Olds of the Air Corps Ferrying Command (later renamed Air Transport Command) over the use of their airliners in wartime.[74] Pan Am had already signed a contract on the 13th, in which it would keep its 307s, but sell the 314s to the government.[74] T&WA sold all five of its 307s to the USAAF, but would then operate them on behalf of the USAAF on a cost plus basis though a new subsidiary.[74] At the time the Stratoliner was the only available landplane transport capable of transatlantic flights with any payload. Seaplanes were too slow and not numerous enough, while the Douglas C-54 Skymaster would not enter service until March 1942 and took months to be available in any numbers, aside from a few ad-hoc conversions from Consolidated B-24 Liberator bombers, the Consolidated C-87 Liberator Express would not be ready until September 1942, and the Lockheed C-69 Constellation would not fly until January 1943, while aircraft with two engines were considered unsafe for ocean crossings with VIPs on board.[74]

On the entry of the United States into World War II, Pan Am continued operating its Stratoliners on routes to Central and South America, but under direction of the Army Air Forces' Air Transport Command,[74] All five TWA Stratoliners were withdrawn from operations on December 24, 1941, while TWA created a subsidiary, the Intercontinental Division (ICD), whose civilian crews would operate them on behalf of the United States Army Air Forces.[43] Otis Bryan was made head of the ICD[41] The Stratoliners were sold to the USAAF, who assigned the type the C-75 designation, and each of them was given a USAAF serial number.[43] The first of these was accepted by the USAAF on March 1, 1941, and the last one on December 17, 1942.[43] ICD crews included pilots, 1st & 2nd officers, navigators, flight engineers, flight radio operators and pursers.[75] ICD Supervisor pilots and captains were paid $1100/month,[notes 20] first officers $800/month,[notes 21] Navigators $600/month,[notes 22] Flight Engineers (FEs) $500/month[notes 23] and Flight Radio Operators (FROs) $400/month.[notes 24][45] Personnel were issued with USAAF uniforms which they wore with rank stripes (two solid stripes for a captain) but with civilian insignia.[45]

 
USAAF C-75 42-88624 Comanche in wartime camouflage

The first ICD service flight began on February 26, when a 307 flew south to Brazil from Washington, before crossing the South Atlantic to Africa, and north to Cairo, before continuing on to Prestwick, Scotland where they arrived on April 20, 1942,[43] having primarily carried 25,000 rounds of armour piercing shells to British troops in Cairo, who were facing Rommel and his Afrika Corps.[76] ICD was initially set up at the crowded Washington Bolling Field but was soon transferred all of their operations to nearby Washington National Airport.[77] Passengers continued to be loaded at Bolling Field, after flying the short hop from Washington National Airport.[78]

The first north Atlantic crossing was in March 1942, when a flight from Washington to Prestwick carried senior military and government officials to Europe, which included the Army Chief of Staff General George C. Marshall, General Dwight D. Eisenhower (to command Operation Torch for the invasion of North Africa), Deputy Chief of Staff of Army Ground Forces General Mark W. Clark, Operation Torch Air Force liaison officer Colonel Hoyt Vandenberg, Chief of the Navy's Bureau of Aeronautics Rear Admiral John Henry Towers, who oversaw Navy aircraft procurement and training, and presidential advisors W. Averell Harriman and Harry Hopkins who were crossing to negotiate the lend-lease program.[76] From April 22, regular crossings were being made.[43] and ICD was growing rapidly, growing from 71 personnel in January, to 343 by April, and they were now making 16 ocean crossings a month.[77] Following his April 1942 raid on Tokyo, but before it had been made public, Jimmy Doolittle took a C-75 from Karachi in India through Khartoum, Kano, Accra, Robertsfield Airport, crossed the Atlantic to Natal in Brazil, and headed north to Belem, and from there with an additional fuel stop to Washington, DC, arriving in time for the news of the raid to be made public.[44] Many of the surviving members of the raid followed soon after in another Stratoliner.[44]

The North Atlantic ferry route was set up with help from former Arctic explorer Colonel Bernt Balchen, who assisted with Bluie East Two and Bluie East Eight in Greenland to reduce the Gander, Newfoundland - Scotland leg distance.[77] The first aircraft to land at these fields, which were north of the Arctic Circle, was an ICD C-75, on April 20, 1942.[77]

Marshall, Eisenhower, "Hap" Arnold and Admirals King and Towers flew to London from Washington via Montreal, Gander and Prestwick on May 23, 1942, and returned to Washington via Prestwick, Reykjavik and Gander.[42] On June 20, 1942, Air Corps Ferrying Command became Air Transport Command[42]

The exiled (but not yet deposed) King Peter II of Yugoslavia was flown in July 1942 from London[42] to Washington to meet with North American leaders, with the engines leaned out so much that the last leg of the trip was able to skip numerous stops, so that they ended up being in the air for 21 hours 16 minutes when they arrived in Washington.[79]

 
Boeing C-75 ICD primary wartime transatlantic routes after July 1942, when the airfield at Ascension Island shortened the South Atlantic crossing. Bluie Two and Eight were added in 1942 as diversionary airfields in case excessive headwinds were encountered in the North Atlantic. When conditions allowed it, usually on summer eastbound crossings, direct flights were sometimes made between Gander and Prestwick.[80]

On July 10, 1942, Ascension Island's airfield opened in South Atlantic,[79] shortening the hazardous transatlantic leg enough that smaller aircraft could now make the crossing, and the ICD C-75s would routinely lead flights of USAAF twin-engined aircraft, such as Douglas A-20s across.[79]

In November 1943, a C-75 carried Soong Mei-Ling, wife of the Chinese Nationalist warlord Chiang Kai-Shek, from Chungking to Washington to receive medical care and to negotiate military aid for China.[81]

Two main routes were flown, between Washington, D.C. and Cairo across the South Atlantic, and between New York and Prestwick, Scotland, across the North Atlantic.[82] They often flew non-stop the 2,122 mi (3,415 km) between Gander, Newfoundland and Prestwick, Scotland in the north, and the 2,500 mi (4,100 km) between Natal, Brazil and Accra, Ghana in the south. After July 1942 a refueling stop at Ascension Island was added in the South Atlantic.[83] In the north, stops at Iceland or Greenland were often necessary, when flying west against unusually strong prevailing winds. As Douglas C-54 Skymasters took over the Gander to Prestwick route, the C-75s operated between Marrakech and Prestwick over the Atlantic.[82]

ICD C-75s crossing the Atlantic had to be careful to avoid Allied convoys and German U-boats, to avoid being shot at.[84] Cherokee was returning American troops from Reykjavik to Gander at 1,000 ft (300 m), and was shot at by a US Navy ship that left over 200 holes in the aircraft's tail, and which nearly severed the elevator controls.[84] Many transatlantic trips were made at night, so the navigator could get good star sightings.[76]

By 1944 the USAAF had enough long range transports that it no longer needed the small number of C-75s it had, and sold the fleet back to TWA, with the aircraft being transferred between January 6, 1944 and December 19, 1944.[10][56] On August 11, 1942, ICD had received the first of 12 C-54s.[79] and Pan Am would also supplement their Stratoliners with 12 C-54s.[79] TWA received two C-54s in August and had 5 by September, and a full allotment of 12 by November, along with the first three C-87s, to supplement the C-75s.[85] At the same time Curtiss C-46 Commandos, Douglas C-47s and C-53s provided feeder links to the C-75s, C-54s and C-87s, as their range was inadequate for the Atlantic.[85]

By the time they were withdrawn, over 3000 trans-oceanic crossings had been made,[25] and they had flown 21,284 while in USAAF service with the ICD.[47] The sole accident occurred during night landing at Natal in Brazil when an undercarriage leg was torn off by a mound of dirt.[47]

It cost TWA about $2 million[notes 25] to have the five aircraft rebuilt by Boeing and the first of them resumed passenger service on April 1, 1945. The CAA recertified these as SA-307B-1 civilian airliners with their original registration numbers.

TWA post-war service and disposal

 
TWA Boeing SA-307B-1 N19909 'Navajo' fleet number 404, as it appeared when offering coach class seating only, and showing the rearward location of the higher aspect ratio B-17G tailplane, whose hinges were now lined up with the rudder hinge.

On April 1, 1945, the first post-war civil commercial flight was made by Zuni, now as a SA-307B-1, from La Guardia to San Francisco via Pittsburgh, Saint Louis, Kansas City, Albuquerque, and Burbank,[49] but the second transcontinental flight did not happen until a month later, when on May 1, 1945, a flight was made from Washington, DC to Spokane, Washington, via Dayton Municipal Airport, St Louis, Kansas City, Albuquerque and Burbank, reflected a loosening of the tightly controlled government access to routes.[86] TWA's fare structure remained the same as pre-war.[86] New TWA flight routes were added with routes 370 & 371 between La Guardia and Spokane with intermediate stops in Chicago, Albuquerque, for fuel, and Burbank and routes 48 & 49 between La Guardia and Kansas City with a stop in St Louis.[86] At this time, the TWA Stratoliners were briefly the sole four-engine commercial airliner in domestic service in the US.[86]

On July 10, 1939, TWA had signed a contract with Lockheed to develop the Constellation, which was to be capable of 5 miles/min (350 mph (560 km/h)) compared to the Stratoliner's 4 miles/min (246 mph (396 km/h)),[8] but with production diverted to military for the duration of the war, the first TWA Constellations did not enter service until February 1946 and were soon grounded dealing with the usual teething problems encountered with a new type, from July 11 to September 20, 1946, while the Douglas DC-4s began arriving in 1946 in small numbers and the Douglas DC-6 similarly, from 1947.[86] At the same time, due to strong competition from war-surplus non-sked flights operating cheaply purchased war-surplus Douglas C-54s, in May 1949 the Stratoliner's were downgraded to a coach-only service with the fares slashed by a third.[87] The first coach service, from New York La Guardia to Chicago via Pittsburgh was made on June 1, 1949, with a full load of 38 passengers.[88]

In November 1950, TWA introduced the similarly sized but cheaper to operate twin-engine Martin 2-0-2A on domestic routes,[89] and transferred some DC-4s from international routes to domestic service,[87] supplementing the Stratoliners which were mainly being used for service between La Guardia and cities in the mid-west,[46] until TWA finally phased them out between April and July 1951.[90] At that time the aircraft had an average of 25,205 hours flying time, each, with Cherokee having the most with 26,324 hours,[87] and they had covered 7,500,000 mi (12,100,000 km) while in ICD service.[48]

Pan American Airways (Pan Am)

 
Lineup of all three Pan Am Strato-Clippers
C/N Registration Name Namesake
1995 NC19902 Clipper Rainbow[31] Clipper ship "Rainbow"
2002 NC19910 Clipper Comet[31] Clipper ship "Comet"
2003 NC19903 Clipper Flying Cloud[31] Clipper ship "Flying Cloud"

In 1937 Pan American Airways placed their first order for two Stratoliners, which they soon increased to six. Deliveries to Pan Am started in March 1940,[67] and they had received their first three before war intervened and civil aircraft production halted.[68][69] The other three would not be built.[2] All three were named for historically notable Clipper ships. Pan Am carried out their first revenue flight on July 4, 1940,[3] with service between Miami, Brownsville, Texas and Los Angeles.[67] Unlike TWA, Pan Am did not exclusively assign their aircraft to specific routes, and instead they were used for their Latin American routes and ranged from Miami and Los Angeles to Brazil.

 
Aerovias Ecuatorianas C.A. (AREA) Boeing S-307 Strato-Clipper HC 004

At the same time TWA's Stratoliners were getting new wings and tails, Pan Am's 307s were being modified in Miami to repair the cracked spar tubing with doublers, and did not get new wings or engines, and the maximum gross weight remained the same.[63] Pan-Am flights then resumed between Miami, the Caribbean and Belem,[51] until all three were sold to the "Airline Training Company" of Miami in late 1948 and early 1949,[64] before being sold on to other operators.

The former Clipper Comet NC19910, was sold to Aerovias Ecuatorianas (AREA) in Ecuador, in 1951, who used it as Quito with the registration HC 004 to provide service between Ecuador and Miami. From 1955, it was with Quaker City Airways for two years as N75385, making non-scheduled charter flights.[91] On May 10, 1958, while still carrying the same registration and after having been stored for some time, it was being readied to be ferried to Boeing for modification for use as a crop duster, but flight tests were carried out despite finding fuel leaks whose source could not be determined, and with untested auxiliary fuel tanks installed in the cabin. During the flight test, it caught fire, and while the crew landed it safely on a boulder-strewn mesa and the crew escaped unharmed, the airframe was destroyed by the fire.[64][92]

The former Clipper Rainbow NC19902, was to have been sold to the short lived Mercury Airways of South Africa, and was even given a South African registration, ZS-BWU, however the sale was never completed, and likewise, it was supposed to have been sold to Aerovias Ecuatorianas, with registration HC-SJC-003, but that sale also appears to have fallen through, and in 1951 it was sold to Aigle Azur as F-BHHR.[93]

The former Clipper Flying Cloud NC19903, was purchased by the Corps d'Aviation d'Garde d'Haiti (Haitian Air Force) in 1954 and assigned the number 2003, but plans to use it for a passenger service by the Compagnie Haïtienne de Transports Aériens (CoHaTA) were cancelled and it was fitted out as a Presidential transport. When François "Papa Doc" Duvalier came into power in 1957 he chose not to use it, and instead had the aircraft sold the same year, with the money from the sale going toward five North American T-6G Texan training aircraft.[94] This aircraft returned to the U.S. and after briefly being registered as N9307R and N19903, is now restored and at the Smithsonian Museum as NC19903.[57][95]

Aigle Azur and Union Aéromaritime de Transport

 
Aigle Azur Extrême-Orient Boeing S-307 Strato-Clipper F-BHHR in New York just before delivery
 
Aigle Azur Boeing SA-307B-1 F-BELV on the ramp

TWA sold all five TWA SA-307B-1s to the French operator Aigle Azur (French for Blue Eagle) in April 1951, for $525,000,[notes 26] along with their remaining supply of spares.[63] Aigle Azur received them between May 14, 1951, and December 19, 1951.[56] and modified these for 48 passengers in Bordeau, and used them on scheduled flights between Paris and North and Central Africa (Casablanca, Dakar, Tunis) Madagascar, French West Africa and French Equatorial Africa and later in 1952, to French Indo-China.[46][63][96]

The Stratoliners were no longer competitive against the larger and faster Douglas DC-6 and Lockheed Constellation then entering service,[46] which on May 1, 1955, led to Aigle Azur along with its subsidiary in Asia, Aigle Azur Indochine, being bought by Union Aéromaritime de Transport (UAT). On the same date, Aigle Azur Indochine was renamed Aigle Azur Extreme-Orient. On September 16, 1955, F-BELV, F-BELX, F-BELY, and F-BELZ were transferred from Europe to Aigle Azur Extreme-Orient, mainly for charter work.[97] During 1955 and 1956, F-BELU and F-BELY and F-BELZ returned to Europe to be leased to Airnautic.[98] The former Pan Am aircraft, F-BHHR had joined Aigle Azur in 1951 and was transferred to Aigle Azur Extreme-Orient in March 1957.[93] Aigle Azur Extrême-Orient branding was retained for several years before the aircraft were repainted in UAT Aéromaritime colors.

After four years in service in Asia, during which it was briefly leased to Air Laos Transport Aériens (later renamed Royal Air Lao) and assigned the Laotian XW registration XW-TAC, F-BHHR was destroyed in an accident on May 22, 1961, while being operated by Aigle Azur Extreme-Orient on a non-scheduled Saigon-Vientiane passenger flight, with 28 on board. It had departed from Tan Son Nhat International Airport in Saigon and was heading for Vientiane when the number four engine had to be shut down, and when it returned to land, it overshot the runway in deteriorating weather, and a violent squall or microburst blew it sideways, causing it to hit the ground. All 28 people on board survived but the aircraft was wrecked.[99]

Union Aéromaritime de Transport merged with Transports Aériens Intercontinentaux, to become Union de Transports Aériens UTA on October 1, 1963, but by then had already sold all of its Stratoliners to CITCA.

Airnautic

 
Airnautic Boeing SA-307B-1 F-BELY

Airnautic (or Air Nautic) received three ex-Aigle Azur SA-307B-1s in 1955 and 1956 including, F-BELU,[100] F-BELY,[101] and F-BELZ,[102] which were operated in southern Europe around the Mediterranean providing charter flights, especially around Corsica.

On December 29, 1962, F-BELZ collided with a mountain while on a charter flight with 22 basketball players and fans while flying from Bastia to Ajaccio, on the island of Corsica.[96][102][103] It was flying at an altitude of about 7,500 ft (2,300 m), despite having been cleared for 12,000 ft (3,700 m) and at 12:12pm slammed into a sheer rock face just 165 ft (50 m) from the peak, before falling about 330 ft (100 m) down the side of the mountain.[103]

In 1965, F-BELY and F-BELU were returned to CITCA, who then leased them to other operators.[100][101]

Air France became the principal shareholder of Airnautic in 1962, at which time it purchased DC-6s,[104] and in 1966 Airnautic ceased to exist, having been absorbed into Air France.

Compagnie Internationale de Transports Civil Aériens (CITCA)

 
Boeing SA-307B-1 Stratoliner F-BELX, likely while with Cambodia Air Commercial
 
SA-307B-1 F-BELU with the CIC/ICC
 
Royal Air Lao SA-307B-1 XW-TFP two days before ditching in the Mekong river

Compagnie Internationale de Transports Civil Aériens (CITCA) bought five Stratoliners, F-BELU F-BELV F-BELX F-BELY F-BELZ, which were leased out to other operators.[97][98][100][101][102]

In 1965, Cambodia Air Commercial leased F-BELY as XW-PGR, and F-BELU as XW-TFP, before both went to Royal Air Lao the same year,[100][101] which then leased all five of the CITCA Stratoliners, which were also assigned Laotian XW registrations, and F-BELV, became XW-TAA, and F-BELX, became XW-TFR.[97][98] The Air Laos Transport Aériens and Royal Air Lao Stratoliners were flown between Vientiane and Hong Kong with a large detour around North Vietnam.[96] Royal Air Laos was operating XW-TFP and XW-PGR when they were destroyed in accidents,[100][101] while F-BELV would be leased to Royal Air Cambodge.[97]

On February 27, 1971, XW-PGR collided with a Lao Air Force Douglas C-47 while landing at Luang Prabang, Laos, and damage to the left wing was unrepairable due to a lack of spares.[64][105]

The Commission Internationale de Contrôle (International Control Commission in English) (CIC/ICC) and its successor International Commission of Control and Supervision leased three aircraft in 1964, under their old French registrations of F-BELV, F-BELU, and F-BELX, which now had seating for as many as 60, and were used to provide what were often hazardous diplomatic flights around south-east Asia until 1974, when it suspended operations with the impending defeat of US forces in Vietnam.[46][97][98] They were flown under diplomatic immunity along specially delineated 20 mi (32 km) wide corridors between Saigon in South Vietnam, Vientiane in Laos, Phnom Penh in Cambodia, and Hanoi in North Vietnam.[96] Passengers usually included diplomats, members of the Red Cross, press, businessmen and Control Commission officials.[96]

When F-BELV disappeared on October 18, 1965, it was flying from Vientiane-Wattay Airport, in Laos to the Hanoi-Gia Lam Airport, in Vietnam.[64][106] and was supposed to have been cleared to fly at 11,800 ft (3,600 m) and 165 kn (190 mph; 306 km/h).[107] On this flight, there were five CIC delegates from India, three from Canada and one from Poland, as well as four French crew members,[107] all of whom died.[106] Due to radio interference, a message indicating that their clearance period had been delayed was never received.[107] Poor communications meant it took until the next day, and around 19 hours before anyone realized the aircraft had gone missing as the destination airport had assumed it had returned to its point of origin, and that airport was unaware it had not arrived at its destination.[107] The search for the downed aircraft was delayed further due to the need to negotiate access to the likely crash area, with several warring parties wary from previous experience of the search mission being a cover for either intelligence gathering, or other military activities.[107] A Canadian investigation long after the war determined that it had likely been shot down by North Vietnamese anti-aircraft fire, but they were unable to determine if it was intentional or not.[106]

XW-TFR (previously F-BELX and briefly XW-TAB) had been returned to Cambodia Air Commercial when it was destroyed in an accident on June 27, 1974, following three of the four engines failing while climbing out from Battambang Airport. During the forced landing it collided with trees causing extensive damage, including tearing one wing off before the aircraft caught fire. 17 passengers and two crew members out of the 39 on board died in the crash that the crash investigation blamed on poor maintenance.[46][96][108]

The pilot of XW-TFP was forced to ditch in the Mekong river on March 13, 1975, near the Laos-Thailand border while on a flight from Hong Kong to Vientiane. Both the pilot and co-pilot escaped the wreck but were captured by the communist Pathet Lao and held until May. The wreckage was still there in 1986.[109]

Operators

 
Pan Am Boeing S-307 Strato-Clipper NC19910 Clipper Comet

Civilian operators

 
TWA Stratoliner pre-war, at Chicago airport
 
Quaker City Airways Boeing S-307 Stratoliner N75385
  United States
  Ecuador
  • Aerovias Ecuatorianas CA/AREA Ecuador, operated an ex-Pan Am aircraft as HC 004.[112]
  France
 
UAT Aeromaritime Boeing SA-307B-1 F-BELV
  Laos
  Cambodia

Military operators

  Haiti
  • Haitian Air Corps
    • Compagnie Haïtienne de Transports Aériens (CoHaTA) (a Military transport organization) operated one ex-Pan Am 307.[94]
  United States
  • United States Army Air Forces operated five ex-TWA SA-307Bs as C-75s. Three Pan Am 307s operated under USAAF direction, but ownership remained with Pan Am.

Accidents and incidents

The Boeing 307 was involved in eight hull-loss incidents with 67 fatalities. Four of the ten incidents involved fatalities, with one likely being shot down while in a war zone.[113]

Date Operator Model C/N Reg'n Location Occupants Fatalities Synopsis Sources
March 18,
1939		 Boeing S-307 1994 NX19901 Alder,
Washington		 10 10 Airframe severely overstressed after difficult spin recovery while carrying several customer representatives. [114]
May 17,
1940		 TWA SA-307B 1999 NC19905 Pritchett,
Colorado		 19 0 Carb ice caused loss of power while flying in mountains which resulted in a wheels up landing in field. Aircraft was repaired and returned to service. [115]
May 10,
1958		 unknown S-307 2002 N75385 Madras,
Oregon		 2 0 Known fuel leak in cabin caused fire during test flight that consumed airframe once it had landed on a rock strewn mesa. [92]
May 22,
1961		 Aigle Azur
Extrême Orient		 S-307 1995 F-BHHR Ho Chi Minh,
North Vietnam		 28 0 Engine failure forced it to return after takeoff and aircraft destroyed after being blown off the runway by a wind gust while landing. [99]
December 29,
1962		 Airnautic SA-307B-1 2001 F-BELZ Monte Renoso,
Corsica		 25 25 Collided with the tip of a mountain on Bastia-Nice-Ajaccio-Nice-Ajaccio-Bastia charter flight, for the worst 307 accident. [103]
October 18,
1965		 ICC/CIC SA-307B-1 1996 F-BELV Between Vientiane,
and
Hanoi, Vietnam		 13 13 Likely shot down by North Vietnamese AA fire while on a scheduled non-commercial diplomatic flight carrying CIC/ICC observers. [106]
February 27,
1971		 Royal Air Lao SA-307B-1 2000 XW-PGR Luang Prabang,
Laos		 2+ 0 Damaged wing in collision with Royal Lao Air Force Douglas C-47 while landing, and a lack of spares prevented repairs. [105]
June 27,
1974		 Cambodia Air Commercial (CACO) SA-307B-1 1999 XW-TFR Battambang Airport,
Cambodia		 39 19 Three engines failed during takeoff due to poor maintenance, and the forced landing destroyed the aircraft after a tree tore the right wing off. [116]
March 13,
1975		 Royal Air Lao SA-307B-1 1998 XW-TFP Mekong River,
Laos		 2 0 Forced landing on Hong Kong-Vientiane cargo flight. Both pilots imprisoned by Pathet Lao. The wreck was located in 1986. [109]
March 28,
2002		 National Air and Space Museum S-307 2003 N19903 Elliott Bay,
Washington		 4 0 Ran out of fuel and ditched on its final delivery flight to the Smithsonian, following restoration. Raised and re-restored. [117]

Surviving aircraft

 
Restored ex-Pan Am Stratoliner NC19903 displayed in the Steven F. Udvar-Hazy Center

The sole intact Boeing 307 Stratoliner, NC19903 is preserved in flying condition at the Smithsonian's Steven F. Udvar-Hazy Center. After having been restored to flying condition, it was being delivered to the Smithsonian on what was to be its last flight when it ran out of fuel and ditched in Elliott Bay near Seattle, Washington in March 2002.[118] Despite the incident, it was raised and again restored, and it completed its flight to the Smithsonian, where it was placed on display.[119]

The forward fuselage of Howard Hughes' 307 (NX19904) also survives, although it was stripped of flying surfaces and the rear fuselage, and converted into a houseboat. The aircraft was awaiting restoration at Fort Lauderdale International Airport in August 1964 when it was severely damaged when Hurricane Cleo tore it loose from its tiedowns, and it was blown into a stand of trees. The aircraft was later salvaged and converted into a house boat and the interior remains notable for the additions made when owned by Howard Hughes.[120][121] It is now part of the Florida Air Museum's collection.[122]

Specifications (Boeing SA-307B, ATC#726)

 
Boeing SA-307B Stratoliner 3-view drawing

Data from Juptner, Joseph P. (1980). US Civil Aircraft: Vol. 8 (ATC 701 - 800). Aero Publishers. pp. 102–104. ISBN 978-0816891788.[123]

General characteristics

  • Crew: Five, including pilot, co-pilot, flight engineer and 2 flight attendants
  • Capacity: Daytime seating for 33, nighttime capacity 25, in 16 berths and 9 reclining chairs
  • Length: 74 ft 4 in (22.66 m)
  • Wingspan: 107 ft 3 in (32.69 m) [notes 28]
  • Wing chord: 19 ft 0 in (5.79 m) at root and 9 ft 4.5 in (2.858 m) at tip rib[124]
  • Height: 20 ft 9 in (6.32 m) at rudder
  • Undercarriage track: 295 in (7.5 m)
  • Wing area: 1,486 sq ft (138.1 m2)
  • Airfoil: NACA 0018 at root, NACA 0010 at tip
  • Wing dihedral: 4.5° from chord line[124]
  • Wing incidence: 3.5° constant root to tip[124]
  • Empty weight: 30,000 lb (13,608 kg) to 31,200 lb (14,200 kg) in overload condition.
  • Gross weight: 45,000 lb (20,412 kg)
  • Maximum load: 15,000 lb (6,800 kg), with 30 passengers, 650 lbs of baggage and 1,275 US gal (4,830 L; 1,062 imp gal)/5,750 lb (2,610 kg) of fuel,
  • Fuel capacity: 1,275 US gal (4,830 L; 1,062 imp gal) normal, carried within the wings. Overload up to 1,800 US gal (6,800 L; 1,500 imp gal)
  • Fuel consumption: 200 US gal (760 L; 170 imp gal)/hr
  • Oil capacity: 100–180 US gal (380–680 L; 83–150 imp gal)
  • Powerplant: 4 × Wright GR-1820-G105A Cyclone air-cooled radial engines with two-stage superchargers, 1,100 hp (820 kW) each at 2400 rpm for sea level takeoff, reduced to 900 hp (670 kW) at 2300 rpm at 17,300 ft (5,300 m)
  • Propellers: 3-bladed Hamilton Standard all-metal Hydromatic constant-speed propellers, 11 ft 6 in (3.51 m) diameter [124]

Performance

  • Maximum speed: 250 mph (400 km/h, 220 kn) at 16,200 ft (4,900 m)
  • Cruise speed: 222 mph (357 km/h, 193 kn) at 19,000 ft (5,800 m) and 75% power
  • Minimum control speed: 70 mph (110 km/h, 61 kn) with flaps
  • Takeofff run: 1,800 ft (550 m)
  • Landing run: 2,050 ft (620 m)
  • Range: 1,300 mi (2,100 km, 1,100 nmi) at 19,000 ft (5,800 m) & 75% power
  • Service ceiling: 23,800 ft (7,300 m) , reduced to 18,000 ft (5,500 m) when on three engines
  • Cruising altitude: 15,000–20,000 ft (4,600–6,100 m)[124]
  • Absolute ceiling: 25,200 ft (7,700 m)[124]
  • Rate of climb: 1,200 ft/min (6.1 m/s) initial, from sea level
  • Wing loading: 30 lb/sq ft (150 kg/m2) [124]
  • Power loading: 12.5 lb/hp (7.6 kg/kW) takeoff, 10.25 lb/hp (6.23 kg/kW) cruise[124]

See also

Related development

Aircraft of comparable role, configuration, and era

Related lists

Notes

  1. ^ equivalent to $2,134,466.02 in 2022
  2. ^ equivalent to $32,510,166.36 in 2022
  3. ^ equivalent to $5,306,821.59 in 2022
  4. ^ equivalent to $50,612,949.64 in 2022
  5. ^ equivalent to $6,627,057.42 in 2022
  6. ^ equivalent to $3,751,706.48 in 2022
  7. ^ equivalent to $1,229,930.07 in 2022
  8. ^ equivalent to $37,353,155.34 in 2022
  9. ^ equivalent to $37,353,155.34 in 2022
  10. ^ a b One-way airfair equivalent to $3,132.21 in 2022
  11. ^ a b Return airfair equivalent to $5,637.77 in 2022
  12. ^ a b Sleeper surcharge equivalent to $2,505.56 in 2022
  13. ^ a b Daytime flights only
  14. ^ a b One-way airfair equivalent to $1,388.03 in 2022
  15. ^ a b Return airfair equivalent to $2,498.25 in 2022
  16. ^ a b Sleeper surcharge equivalent to $183.82 in 2022
  17. ^ a b One-way airfair equivalent to $938.93 in 2022
  18. ^ a b Return airfair equivalent to $1,689.87 in 2022
  19. ^ a b Sleeper surcharge equivalent to $116.97 in 2022
  20. ^ equivalent to $21,885.52 in 2022
  21. ^ equivalent to $15,916.74 in 2022
  22. ^ equivalent to $11,937.56 in 2022
  23. ^ equivalent to $9,947.96 in 2022
  24. ^ equivalent to $7,958.37 in 2022
  25. ^ equivalent to $33,247,637.05 in 2022
  26. ^ equivalent to $5,919,038.46 in 2022
  27. ^ a b c Original operator, received aircraft from Boeing.
  28. ^ Span was greater than for the B-17 because of the wider fuselage

References

  1. ^ a b c d Juptner, 2000, p.75
  2. ^ a b c d e f g h i j Betts, 1990, p.61
  3. ^ a b c d e Betts, 1990, p.71
  4. ^ Davies, 2000, p.52
  5. ^ a b c Dijkstra, 2016, p.75
  6. ^ a b c d e f g Dijkstra, 2016, p.81
  7. ^ a b c Betts, 1990, p.55
  8. ^ a b c d e f g h i Betts, 1990, p.65
  9. ^ a b c d e Betts, 1990, p.57
  10. ^ a b c d Betts, 1993
  11. ^ a b c Betts, 1990, p.59
  12. ^ a b c Air Safety Board Report involving NX19901, of the Boeing Aircraft Company, near Alder, Washington, March 18, 1939
  13. ^ a b c d e Dijkstra, 2016, p.79
  14. ^ a b c d Dijkstra, 2016, p.80
  15. ^ "Boeing 307 N19903". Goleta Air and Space Museum. Retrieved May 21, 2020.
  16. ^ Abzug & Larrabee, 2005, p. unk.
  17. ^ a b c d Bowers, 1989, p.231
  18. ^ Betts, 1990, p.67
  19. ^ a b c Betts, 1990, p.69
  20. ^ Betts, 1994, p.51
  21. ^ Boeing, Historical Snapshot, 1995-2022
  22. ^ De Wulf, 1978, pp.147-149
  23. ^ a b c Betts, 1990, p.63
  24. ^ Haddow, 1962, p.2
  25. ^ a b c Juptner, 1980, p.102
  26. ^ a b c d e f g h i j k l m Juptner, 1980, p.104
  27. ^ a b c d e f g h Minshall, 1940, p.116
  28. ^ a b c d e f Juptner, 1980, p.103
  29. ^ a b c d e McLarren, 1938, p.40
  30. ^ a b c d Dijkstra, 2016, p.77
  31. ^ a b c d e f g h Davies, 1987, p.49
  32. ^ a b Betts, 1990, p.73
  33. ^ a b c d e Beall, 1945, p.149
  34. ^ a b c d e f Minshall, 1940, p.49
  35. ^ Minshall, 1940, p.47
  36. ^ Minshall, 1940, p.48
  37. ^ Betts, 1992, p.82
  38. ^ a b c d e McLarren, 1938, p.31
  39. ^ a b Davies, 2000, p.49
  40. ^ Davies, 2000, p.48
  41. ^ a b c d e f g Betts, 1992, p.61
  42. ^ a b c d e f Betts, 1992, p.69
  43. ^ a b c d e f Davies, 2000, p.46
  44. ^ a b c Betts, 1992, p.68
  45. ^ a b c d e Betts, 1992, p.62
  46. ^ a b c d e f g h i Hardy, 1982, p.31
  47. ^ a b c d e f g Betts, 1994, p.52
  48. ^ a b c Beall, 1945, p.148
  49. ^ a b c d e f Betts, 1994, p.53
  50. ^ Bowers 1989, pp. 234–235.
  51. ^ a b Hardy, 1982, p.30
  52. ^ a b Bowers, 1989, p.232
  53. ^ Juptner, 2000, p.76
  54. ^ Bowers, 1989, p.235
  55. ^ a b c d e f Dijkstra, 2016, p.78
  56. ^ a b c d e f g h i Davies, 2000, p.44-45
  57. ^ a b "REGISTRATION DETAILS FOR NC19903 (NATIONAL AIR & SPACE MUSEUM) BOEING 307 STRATOLINER". planelogger.com. Retrieved July 17, 2022.
  58. ^ Ford 2004, p. 55.
  59. ^ a b Dijkstra, 2016, p.76
  60. ^ Cartwright, 1939, p.3
  61. ^ Betts, 1994, p.62
  62. ^ a b c Marrett, 2004, p.95
  63. ^ a b c d e Betts, 1994, p.57
  64. ^ a b c d e Betts, 1994, p.59
  65. ^ Marrett, 2004, p.231
  66. ^ Betts, 1990, p.
  67. ^ a b c Betts, 1989, p.75
  68. ^ a b Bowers 1989, p. 231.
  69. ^ a b Noah, 1972, p.148
  70. ^ Gardner, 1940, p.9
  71. ^ Gardner, 1940, p.10
  72. ^ Larsson, Björn; Zekria, David (March 10, 2022). "Airliner Timetable images". Retrieved March 10, 2022.
  73. ^ Betts, 1990, p.72
  74. ^ a b c d e Betts, 1992, p.59
  75. ^ Betts, 1992, p.60
  76. ^ a b c Betts, 1992, p.65
  77. ^ a b c d Betts, 1992, p.67
  78. ^ Betts, 1992, p.84
  79. ^ a b c d e Betts, 1992, p.70
  80. ^ Betts, 1992, p.76
  81. ^ Betts, 1992, p.75
  82. ^ a b Berry, Peter. "Transatlantic Flight 1938–1945 (Part I 1938–1943)". AAHS Journal, Volume 40, Issue 2, 1995.
  83. ^ Berry, Peter. "Transatlantic Flight 1938–1945 (Part II 1943–1945)". AAHS Journal, Volume 40, Issue 3, 1995.
  84. ^ a b Betts, 1992, p.74
  85. ^ a b Betts, 1992, p.72
  86. ^ a b c d e Betts, 1994, p.54
  87. ^ a b c Betts, 1994, p.56
  88. ^ Wood, Robert H., ed. (June 13, 1949). "Shortlines". Aviation Week. Albany, NY: McGraw-Hill. p. 49.
  89. ^ Davies, 2000, p.50
  90. ^ Hardy, Air International February 1994, p. 70.
  91. ^ "REGISTRATION DETAILS FOR N75385 (QUAKER CITY AIRWAYS) BOEING 307 STRATOLINER". planelogger.com. Retrieved July 17, 2022.
  92. ^ a b Accident description for N75385 at the Aviation Safety Network. Retrieved on May 5, 2013.
  93. ^ a b "REGISTRATION DETAILS FOR F-BHHR (AIGLE AZUR EXTREME-ORIENT) BOEING 307 STRATOLINER". planelogger.com. Retrieved July 17, 2022.
  94. ^ a b Hagedorn, 1993, p.133
  95. ^ Hardy, Air International February 1994, p. 71.
  96. ^ a b c d e f Betts, 1994, p.58
  97. ^ a b c d e "REGISTRATION DETAILS FOR XW-TAA (INTERNATIONAL CONTROL COMMISSIION) BOEING 307 STRATOLINER". planelogger.com. Retrieved July 17, 2022.
  98. ^ a b c d "REGISTRATION DETAILS FOR XW-TFR (CAMBODGIA AIR COMMERCIAL) BOEING 307 STRATOLINER". planelogger.com. Retrieved July 17, 2022.
  99. ^ a b Accident description for F-BHHR at the Aviation Safety Network. Retrieved on May 5, 2013.
  100. ^ a b c d e "REGISTRATION DETAILS FOR XW-TFP (CAMBODIA AC-ROYAL AIR LAO) BOEING 307 STRATOLINER". planelogger.com. Retrieved July 17, 2022.
  101. ^ a b c d e "REGISTRATION DETAILS FOR XW-PGR (CAMBODIA AC-ROYAL AIR LAO) BOEING 307 STRATOLINER". planelogger.com. Retrieved July 17, 2022.
  102. ^ a b c "REGISTRATION DETAILS FOR F-BELZ (AIRNAUTIC) BOEING 307 STRATOLINER STRATOLINER". planelogger.com. Retrieved July 17, 2022.
  103. ^ a b c Accident description for F-BELZ at the Aviation Safety Network. Retrieved on July 16, 2022.
  104. ^ Flight International, April 12, 1962, p.389
  105. ^ a b Accident description for XW-PGR at the Aviation Safety Network. Retrieved on July 16, 2022.
  106. ^ a b c d Accident description for F-BELV at the Aviation Safety Network. Retrieved on June 30, 2015.
  107. ^ a b c d e Wynn, 2020, (no page numbers in digital edition)
  108. ^ Accident description for XW-TFR at the Aviation Safety Network. Retrieved on September 15, 2017.
  109. ^ a b Accident description for XW-TFP at the Aviation Safety Network. Retrieved on July 16, 2022.
  110. ^ Civil Aeronautics Board Reports. Vol. 28. US. 1958. Retrieved May 23, 2020.
  111. ^ "Crash of a Boeing 307 Stratoliner near Madras". Bureau of Aircraft Accidents Archives. US. May 10, 1958. Retrieved May 23, 2020.
  112. ^ "Profile for: AREA Ecuador". from the original on March 4, 2016. Retrieved January 27, 2014.
  113. ^ "Accident statistics for Boeing 307". Aviation Safety Network. Archived from the original on November 24, 2013. Retrieved November 22, 2013.
  114. ^ Accident description for NX19901 at the Aviation Safety Network. Retrieved on July 17, 2022.
  115. ^ Accident description for NC19905 at the Aviation Safety Network. Retrieved on July 17, 2022.
  116. ^ Accident description for XW-TFR at the Aviation Safety Network. Retrieved on May 5, 2013.
  117. ^ Accident description for N19903 at the Aviation Safety Network. Retrieved on July 18, 2022.
  118. ^ "4 escape injury as historic Stratoliner ditches in Elliott Bay". October 23, 2012, at the Wayback Machine Seattle Post-Intelligencer (original post). Retrieved June 4, 2012.
  119. ^ Whitford, Ellen. "Once More with Feeling". June 29, 2011, at the Wayback Machine Boeing Frontiers Online, September 2003. Retrieved January 28, 2012.
  120. ^ Mitcham, Mary Lynn (April 2005). "It's a Boat! It's a Plane! It's..." Boating. Vol. 74, no. 4. Bonnier Corporation. p. 36. Retrieved June 8, 2017.
  121. ^ Ginns Britten, Elizabeth (September 2004). "Flying the Friendly Seas". Power & Motoryacht. from the original on July 12, 2012. Retrieved June 8, 2017.
  122. ^ . Sun ‘n Fun. US. October 19, 2016. Archived from the original on January 31, 2020. Retrieved February 1, 2020.
  123. ^ Juptner, 1980, pp.102-104
  124. ^ a b c d e f g h Abel, 1991, p.37
  125. ^ Hauet, André. "Renard R.35 - Un avion stratosphérique belge en 1938. (technique)". Aérostories (in French). Retrieved June 17, 2022.

Bibliography

  • none given (2022). "Historical Snapshot: Model 307 Stratoliner - Boeing". Boeing.
  • Abzug, Malcolm J.; Larrabee, E. Eugene (2005). Airplane Stability and Control: A History of the Technologies that Made Aviation Possible. Cambridge, UK: Cambridge University Press. ISBN 978-0521021289.
  • Abel, Drina Welch, ed. (1991). Paul Matt Scale Airplane Drawings. Vol. 1. Destin, Florida: Aviation Heritage/Aviation Book Co. p. 37. ISBN 978-0943691046.
  • Beall, Wellwood E. (March 1945). "Rebuilding the Boeing Stratoliners". Aviation. Vol. 44, no. 3. Albany, NY: McGraw-Hill. pp. 148–151.
  • Betts, Ed (November 1989). "The La Guardia Airport 50 years". TARPA Topics. Belhaven, NC: the Active Retired Pilot's Association of TWA. pp. 66–75.
  • Betts, Ed (August 1990). "The Boeing "Stratoliner" (1935 thru 1940)". TARPA Topics. Belhaven, NC: the Active Retired Pilot's Association of TWA. pp. 55–74.
  • Betts, Ed (February 1992). "The Intercontinental Division". TARPA Topics. Belhaven, NC: the Active Retired Pilot's Association of TWA. pp. 59–85.
  • Betts, Ed (1993). "The Boeing Stratoliners and TWA". American Aviation Historical Society Journal. 38 (3).
  • Betts, Ed (August 1994). "The Boeing 307 Stratoliners 1945-1951". TARPA Topics. Belhaven, NC: the Active Retired Pilot's Association of TWA. pp. 51–62.
  • Bowers, Peter M (1989). Boeing Aircraft since 1916 (Third ed.). London: Putnam. ISBN 978-0851778044.
  • Cartwright, C.M., ed. (March 23, 1939). ""Stratoliner" Crash sets insured loss record in Aviation - $500,000 Plane Covered for Full Replacement Cost: Partly Reinsured Abroad". The National Underwriter. Vol. 43, no. 12. Chicago, IL: National Underwriter Co.
  • Davies, R.E.G. (1987). Pan Am - an Airline and its Aircraft - An illustrated history of the world's greatest airline and the airplanes that revolutionized air transport from 1927 to the present. New York City: Orion Books. p. 49. ISBN 978-0517566398.
  • Davies, R.E.G. (2000). TWA - an Airline and its Aircraft - 75 years of pioneering progress. McLean, Virginia: Paladwr Press. ISBN 978-1888962161.
  • De Wulf, Herman (September 1978). "A Belgian Rare Avis". Air International. Vol. 15, no. 3. Bromley, UK: Fine Scroll. pp. 147–149.
  • Dietrich, Noah; Thomas, Bob (1972). Howard, The Amazing Mr. Hughes. Greenwich: Fawcett Publications. p. 148. ISBN 978-0449136522.
  • Dijkstra, Ronald (2016). "Boeing 100 jaar - 80 jaar samenwerking met de KLM". Luchtvaart Historisch Tijdschrift LUCHTVAARTKENNIS (en:Aviation Historical Magazine AVIATION KNOWLEDGE) (in Dutch). Vol. 3, no. 65. Holland: Vereeniging ter Bevordering van de Luchtscheepvaart (en:Association for the Promotion of Aviation). pp. 75–82. ISSN 1381-9100.
  • Ford, Daniel (March–April 2004). "First and Last Strat: Boeing's Model 307 and its Survivors". Air Enthusiast. Vol. 110. pp. 54–60. ISSN 0143-5450.
  • Gardner, Lester D., ed. (November 1940). "News Review". Journal of the Aeronautical Sciences Aeronautical Review Section. Easton, Pennsylvania: Institute of the Aeronautical Sciences. 8 (1): 9–10. doi:10.2514/8.10434.
  • Haddow, G.W.; Grosz, Peter M. (1962). The German Giants, The Story of the R-planes 1914–1919. London: Putman.
  • Hagedorn, Daniel P. (1993). Central American and Caribbean Air Forces. Kent, UK: Air-Britain (Historians). p. 133. ISBN 978-0851302102.
  • McLarren, Robert (July 1938). "The Plane on the cover". Model Airplane News. Vol. 9, no. 1. Mount Morris, IL: Jay Publishing. pp. 31 & 40.
  • Hardy, Michael John (1982). Boeing. World Aircraft. NY: Beaufort Books. p. 30. ISBN 978-0850595079.
  • Hardy, Mike (January 2004). "The Stratoliner Story (Part 1)". Air International. Vol. 46, no. 1. pp. 21–24. ISSN 0306-5634.
  • Hardy, Mike (February 2004). "The Stratoliner Story (Part 2)". Air International. Vol. 46, no. 2. pp. 69–72. ISSN 0306-5634.
  • Juptner, Joseph P. (1980). US Civil Aircraft: Vol. 8 (ATC 701 - 800). Aero Publishers. pp. 75–77 & 102–104. ISBN 978-0816891788.
  • Marrett, George J. (2004). Howard Hughes : aviator. Annapolis: Naval Institute Press. ISBN 978-1591145103.
  • Minshall, R. J. (May 1940). "Into the Sub-Stratosphere". Aviation. pp. 47–49.

External links

 
Wikimedia Commons has media related to Boeing 307.
  • T&WA promotional video with footage of Stratoliner

July 05, 2023
boeing, stratoliner, boeing, model, stratoliner, strato, clipper, american, service, usaaf, service, american, stressed, skin, four, engine, wing, tailwheel, monoplane, airliner, derived, from, flying, fortress, bomber, which, entered, commercial, service, jul. The Boeing Model 307 Stratoliner or Strato Clipper in Pan American service or C 75 in USAAF service is an American stressed skin four engine low wing tailwheel monoplane airliner derived from the B 17 Flying Fortress bomber which entered commercial service in July 1940 It was the first airliner in revenue service with a pressurized cabin which with supercharged engines allowed it to cruise above the weather As such it represented a major advance over contemporaries with a cruising speed of 220 mph 350 km h at 20 000 ft 6 100 m compared to the Douglas DC 3s 160 mph 260 km h at 8 000 ft 2 400 m then in service 4 When it entered commercial service it had a crew of five to six including two pilots a flight engineer two flight attendants and an optional navigator and had a capacity for 33 passengers which later modifications increased first to 38 and eventually to 60 Boeing 307 C 75 StratolinerRole AirlinerNational origin United StatesManufacturer BoeingFirst flight December 31 1938 1 2 Introduction July 4 1940 with Pan American Airways 1 3 Status Last operational example wrecked on March 13 1975 One survivor in museumPrimary users Transcontinental amp Western AirAigle AzurUnited States Army Air ForcesPan American AirwaysNumber built 10Developed from Boeing B 17 Flying Fortress Contents 1 Development 2 Design 2 1 Crew 2 2 C 75 conversion 3 Variants 4 Operational history 4 1 Prototype 4 2 Koninklijke Luchtvaart Maatschappij N V KLM 4 3 Australian National Airways ANA 4 4 Howard Hughes and Cosmic Muffin 4 5 Transcontinental amp Western Air T amp WA or TWA 4 5 1 TWA ICD Wartime operations 4 5 2 TWA post war service and disposal 4 6 Pan American Airways Pan Am 4 7 Aigle Azur and Union Aeromaritime de Transport 4 8 Airnautic 4 9 Compagnie Internationale de Transports Civil Aeriens CITCA 5 Operators 5 1 Civilian operators 5 2 Military operators 6 Accidents and incidents 7 Surviving aircraft 8 Specifications Boeing SA 307B ATC 726 9 See also 10 Notes 11 References 12 Bibliography 13 External linksDevelopment Edit Boeing S 307 Stratoliner production line note the early B 17s to the rear Prototype Model 307 NX19901 with the small tail as initially designed and which caused its loss In 1935 Pan American Airways United Airlines American Airlines Eastern Air Lines and Transcontinental amp Western Air T amp WA had each signed a contract with Douglas to develop the 40 passenger DC 4 later known as the DC 4E 5 Each company contributed 100 000 notes 1 to development costs and agreed to not operate other aircraft with a maximum weight of 43 000 to 75 000 lb 20 000 to 34 000 kg for revenue service 5 Due to development problems and poor performance all of the airlines dropped out of the DC 4 program and cancelled their orders but a requirement for a large 4 engine airliner remained 6 7 D W Tommy Tomlinson at T amp WA carried out five years of high altitude flight research with a Northrop Gamma and a Douglas DC 1 which helped determine that T amp WA would need a four engine airliner with a pressurized cabin 8 During this period He also test flew the XB 17 and determined that it would provide an ideal basis for an airliner and so Boeing was approached with the idea 7 A ceiling of at least 16 000 ft 4 900 m was required to avoid summertime chop over the Rocky Mountains and to allow the aircraft to fly around the thunderstorms that can sometimes block mountain passes which meant a pressurized cabin would be the most comfortable for passengers on long flights 9 In 1935 Boeing then designed a four engine airliner using components from the Boeing Model 299 B 17 Flying Fortress heavy bomber as the Model 307 It combined the wings tail rudder undercarriage and engines from the B 17 with a new much larger pressurized circular cross section fuselage with a maximum diameter of 138 in 3 5 m 10 The pressurization system required extensive testing which was carried out over many months progressively increasing the air pressure after each successful test and each time the highly polished fuselage was coated with soapy water while the fuselage pressurized for workers to look for the bubbles that would indicate a leak much like testing a bicycle inner tube 11 Before the first aircraft had rolled out T amp WA s chief engineer discovered that the extruded metal tubing used for the wing spars was defective with stress corrosion cracks produced by cold rolling the tubing to increase tensile strength 9 Affected aircraft included the prototype the first Pan Am machine and some early production B 17s and resulted in T amp WA having to have their engineers manually inspect every tube that was to be incorporated into their aircraft 9 Wreck of the prototype NX19901 The first aircraft completed registration NX19901 crashed on March 18 1939 12 while being demonstrated after having been recently fitted with instruments to measure flight control forces 13 The Boeing 307 took off at 1257hrs local time from Boeing Field in Seattle with ten occupants 13 and they climbed to an altitude of 11 000 ft 3 400 m where stability tests were made and while carrying out side slips near Alder the aircraft stalled and entered a spin 13 It made two to three turns before the pilot was able to stop the spin using the engines 12 however the ensuing high speed dive and the forces that resulted from attempting to pull up before hitting the ground resulted in the left outer wing tearing off with one engine still attached followed by the right wing just outside the outer engine both of which also tore off parts of the tail as a result of the aileron cables pulling them against the fuselage which then caused the aircraft to pancake into a forested area at 1317hrs 2 14 All ten aboard were killed 14 which included T amp WA s representative KLM s technical director a Dutch Air Ministry representative Boeing s test pilot as well as their Chief Aerodynamicist and their Chief Engineer 12 Parachutes were available but the force of the spin prevented their use 2 The crash delayed the program by over a year beginning with a three month investigation by the US Civil Aeronautics Authority the precursor to the current Federal Aviation Administration and Boeing to determine the causes 2 Flight and wind tunnel testing showed that both an extended dorsal fin and an enlarged vertical tail were needed to prevent the rudder stalling in a yaw and solutions were flight tested on NC19903 including an intermediate solution consisting of just an extended dorsal fin 15 The resulting redesign was also incorporated into the redesign of the rear fuselage of the B 17E bomber 16 The wings were reinforced and Handley Page slots were added to the outer wing leading edges to improve low speed aileron control while the inboard flaps were also extended 2 14 The first several aircraft including NC19902 NC19903 and NC19904 were all rolled out with the small tail and then modified later Test flights resumed on May 19 1939 after the changes had been incorporated 14 and on June 20 1939 the first flight was made with the supercharged cabin pressurization system on 6 On March 13 1940 Approved Type Certificate ATC number 719 was assigned to the Pan Am Boeing 307s allowing commercial deliveries to commence 6 A second ATC was issued for the TWA aircraft number 726 due to the numerous differences between the Pan Am and T amp WA aircraft 17 TWA Boeing SA 307B NC19905 on May 17 1940 after the engines iced up and it made a forced landing T amp WA was concerned about excessive undercarriage stiffness from their experience with the test flights with the XB 17 which were to be modified for the airliner 7 T amp WA flight tested the modified undercarriage and in hard landings easily exceeded the contract s minimum required 500 ft s 150 m s descent rate with a successful 800 ft s 240 m s landing descent 18 T amp WA was also concerned about the engine carburetor intake heaters being deliberately restricted by Boeing to prevent cooking the engines which could potentially leave crews unable to clear ice 19 Their point was made when icing problems during a test flight on May 17 1940 with NC19905 while carrying dignitaries in overcast conditions in the mountains resulted in three of the four engines failing while the fourth was losing power despite every measure being taken to clear the ice This resulted in the aircraft making a belly landing in a field with a partially lowered undercarriage 19 just south of Lamar Colorado 20 T amp WA then modified the carburetor heating themselves and the aircraft was repaired and returned to service 19 Boeing made claims both in their period advertising and in their current web site that it was the first high altitude commercial transport and the first with a flight engineer 21 However its first flight on December 31 1938 was later than that of the Renard R 35 which also had a pressurized cabin for passengers and which flew on April 1 1938 22 As for employing a flight engineer it was preceded in the US on a commercial aircraft by Maddux Air Lines Ford Trimotors whose Mate had the same responsibilities as a flight engineer 23 Additionally all German World War One Riesenflugzeug multi engine bombers had flight engineers as they were integral to the specification 24 Design Edit TWA Boeing SA 307B NC19907 Zuni 402 landing with slotted flaps lowered prewar Pan Am Boeing S 307 Stratoliner NC19902 Clipper Rainbow with blanking plates installed on engines to prevent engine over cooling As built the Stratoliner used the all metal stressed skin cantilever wings from the B 17C mounted low on the fuselage to a constant chord center section faired to the fuselage 25 26 with four 1 100 hp 820 kW Wright GR 1820 Cyclone air cooled radial engines TWA examples used GR 1820 G105A engines fitted with two stage superchargers for high altitude performance while the Pan Am examples used the GR 1820 G102 with a single stage supercharger 25 27 28 Engine exhaust collector rings designed to reduce noise and exhaust mufflers were installed 29 TWA aircraft were fitted with cowl flaps to adjust engine cooling air while Pan Am aircraft had fixed cowling rings without cowling gills 27 When operating in cooler conditions the Pan Am aircraft could be fitted with a blanking disk that covered part of the front of the engine Both versions had sufficient power to maintain altitude on only two engines 28 one of the KLM requirements 30 Both used three bladed Hamilton Standard Hydromatic constant speed propellers 26 and new high octane fuels were developed to help the engines operate under the increased supercharger pressure 31 Both versions had trailing edge flaps controlled with electric motors 8 although SA 307B for T amp WA and the SB 307B for Hughes featured slotted flaps with prominent external hinges while the Pan Am examples had simpler split flaps with flush hinges similar to those used on the B 17s 27 23 All of the fuel was carried in the wings with a 212 5 US gal 804 L 176 9 imp gal tank mounted between the inboard nacelle and the fuselage and a 425 US gal 1 610 L 354 imp gal main fuel tank as well as a 212 5 US gal 804 L 176 9 imp gal fuel tank located between the inner and outer nacelles on both sides of the aircraft providing a total of 1 700 US gal 6 400 L 1 400 imp gal of fuel in six tanks 27 With the fuselage being 3 5 ft 1 1 m wider than on the B 17 the span had increased from 103 ft 9 in 31 62 m to 107 ft 3 in 32 69 m compared to early B 17s 11 After being modified the SA 307B 1s used the wings and elevators from the B 17G with split flaps and 1 200 hp 890 kW Cyclones 26 On most but not all examples the leading edges of the wings horizontal stabilizer and fin were fitted with rubber expanding type de icing boots which would inflate and deflate repeatedly to break ice from the flying surfaces 26 All movable surfaces including the rudder ailerons and elevators had fabric over a metal structure and were aerodynamically balanced and fitted with adjustable trim tabs to lighten flight loads 26 29 The rudder and elevators also had hydraulic boost to lighten control forces 27 The partially retractable main undercarriage had hydraulic brakes and used Goodyear 55x19x23 tires and was raised and lowered with electric motors 26 Manual backups were provided for electrically driven systems but the power had to be turned off before being used 32 A parking brake was provided along with an emergency air brake system run off a bottle of compressed air while the tailwheel was fully retractable 26 33 Passengers on Pan Am Strato Clipper in the Raymond Loewy designed interior Seats on the left could be folded into sleeper bunks The fuselage was described as being dirigible shaped and was an elongated teardrop with a constant 11 5 ft 3 5 m diameter tube lengthening it at its widest point 28 34 The circular section fuselage was of all metal construction skinned with 24ST Alclad 26 27 and capable of maintaining a cabin pressure equivalent to 8 000 ft 2 400 m when flying at a 16 000 ft 4 900 m altitude and a 12 000 ft 3 700 m cabin pressure when at 20 000 ft 6 100 m 9 with a maximum pressure difference of 2 5 lb sq ft 12 kg m2 31 The structure was designed with strength reserves so as to handle as much as 6 lb sq ft 29 kg m2 but a pressure relief valve prevented the pressure difference from exceeding 2 65 lb sq ft 12 9 kg m2 34 35 The structure consisted of continuous longitudinal stiffeners spaced every 9 degrees around the fuselage with radial hoop stiffeners mounted every 16 in 410 mm along the fuselage reinforcing the similarity to a dirigible 36 The skin seams were sealed with tape impregnated with sealing compound trapped between lapped joints which were secured with two rows of rivets spaced 5 8 in 16 mm apart while doors and hatches were sealed with soft rubber gaskets and control cables entered the pressurized cabin through specially developed glands designed to allow free movement of the cables with a negligible amount of air leakage 34 The main cockpit windows were made from 5 8 in 16 mm thick safety glass while the rest of the windows were made of Plexiglass or Lucite sealed into rubber channels 34 A large ram air scoop on the cabin roof was provided to supply cooling air while at lower altitudes and was shut off when the cabin was pressurized at higher altitudes 27 The cockpit was fitted with an autopilot radios 26 and a radio direction finder RDF for navigation 37 The noted industrial designer Raymond Loewy designed the passenger cabin with furnishings provided by Marshall Field s 28 It was divided into four compartments each with six deep comfortable reclining chairs which could be converted into 16 sleeping berths 26 38 Each compartment was provided with adjustable air conditioning vents reading lights and a call button 38 Nine additional seats were provided along the port side of the aircraft while washrooms which doubled as dressing rooms were provided at both ends of the cabin 26 The rear washroom was for women and was named the ladies charm room Its walls were covered in heavy plate glass mirrors and it contained in its 34 sq ft 3 2 m2 area two dressing tables each with a sink plush upholstered stools soft indirect lighting provided by fluorescent lamps ashtrays hot and cold running water shelves with towels and a separate cubicle for the toilet 8 38 The men s washroom was in front as the Men s Lounge and also had a separate cubicle for the toilet two sinks and outlets to run an electric razor 8 A galley of just 28 sq ft 2 6 m2 provided hot food was situated at the rear of the cabin 26 38 behind which was positioned the rear hemispherical pressure bulkhead 34 Up to 412 cu ft 11 7 m3 or 6 590 lb 2 990 kg of baggage could be stowed under the floor of the cabin both between the wing spars and behind the rear spar which was accessible in flight through a hatch in the cabin floor or on the ground through three hatches on the underside of the fuselage 34 38 Extensive use was made of the latest in sound proofing and the Dynafocal engine shock mounts were designed to reduce vibrations from being felt by the passengers 8 33 The air conditioning system used both electrical and mechanical systems 29 which drew air in through vents in leading edge of each wing near the roots to bring outside air to two engine driven superchargers that compressed the air which was then passed through radiator condensers to cool the air and it was then run through channels to the vents in the cabin 29 External hookups allowed ground air conditioner units to cool the cabin air when the engines were off 29 Crew Edit Newly graduated Hostesses lined up in front of Zuni TWA s Stratoliner NC19907 in early to mid 1940 The Stratoliners were normally flown with a pilot and co pilot and both Pan Am and T amp WA aircraft carried a flight engineer to reduce the workload on the two pilots by monitoring the engines for any problems and fine tuning them while they also controlled fuel consumption from each of the tanks to maintain the aircraft s fore aft and lateral balance Too much fuel used in one tank could result in the aircraft becoming uncontrollable They also monitored other aircraft systems including hydraulics and the cabin pressurization system 39 The Flight engineer was also an Aircraft Maintenance Engineer AME and aside from operating the radio which required training in Morse code he was also responsible for all technical issues and would carry out repairs and maintenance on the 307s 23 Pan Am aircraft had one additional crew member compared to T amp WA aircraft Because they made long overwater flights they carried a navigator who was not yet considered necessary by the CAA for overland flights which were served by a network of beacons across the continent 39 when the aircraft were not being flown by visual flight rules VFR Both T amp WA and Pan Am normally carried two flight attendants T amp WA began using Hostesses as they called them as cabin crew in late 1935 while Pan Am continued to use male stewards until late in WW2 40 C 75 conversion Edit 42 88623 Cherokee loading up following conversion to C 75 standard Following the entry of the United States into World War II in December 1941 long range transports were needed to ferry government and military officials around the globe and many aircraft including T amp WA s Boeing 307s were pressed into service Beginning in February 1942 these were flown to Albuquerque New Mexico for conversion which included the removal of the plush but heavy civilian fittings including the massive mirrors in the women s charm room and the pressurization system to save weight 41 The sound insulation was also stripped out leaving the cabin much noisier than it had been 42 The forward men s washroom and two of the four forward compartments were replaced with five gravity fed 212 5 US gal 804 L 176 9 imp gal fuel tanks and a 45 US gal 170 L 37 imp gal oil tank fed with a wobble pump along with a rest area for the crew 41 43 A desk was added behind the pilot for a radio operator who had a 50 watt Bendix TA 12 high frequency Morse transmitter and a BC 348 tunable receiver A 400 ft 120 m trailing wire antenna was used with a 5 lb 2 3 kg lead weight on the end which the radio operator needed to remember to reel in by hand when landing Inexperience sometimes led to either the antenna being torn off or lashing against the fuselage An astrodome was fitted and the perspex top windows which produced excessive parallax were replaced with optically flat glass to allow the navigator to take star shots the angle between stars and the horizon could be used to determine how far north or south they were necessary to determine their position when crossing large bodies of water 41 The SA 307B 1s retained the astrodomes when converted back from C 75 in 1944 To further aid navigation a B 3 driftmeter was installed along with an aperiodic compass that did not lag or lead in turns as a conventional compass does 41 Mae West life vests and life rafts were also provided 41 The landing gear was strengthened and the maximum takeoff weight was increased from 45 000 to 56 000 lb 20 000 to 25 000 kg leaving the Stratoliner underpowered and the climb suffered accordingly 10 44 45 The overloading burnt out engines and destroyed piston rings but closely monitoring engine oil consumption often caught failures before they occurred 42 Passenger facilities were reduced to 4 bunks which when folded away allowed seating for 12 along with 4 seats along the opposite side of the aircraft 41 Removable tables were provided in the cabin to lay out maps and do paperwork 42 The exterior was then camouflaged in standard USAAF colours with olive drab upper surfaces and neutral grey undersides 10 45 and each aircraft had its name painted on the nose and over the cabin door which would also be used by many later operators 45 The names had previously been used in TWA publicity but not painted on the aircraft 8 After three years the USAAF had amassed sufficient long range transports that it no longer needed the C 75s and they sold the fleet back to TWA who paid to have them converted back to civil standard under Boeing s SA 307B 1 designation CAA concerns over cracks in the wing spar tubing led to the TWA Stratoliners getting new B 17G wings and horizontal tail with the leading edge of the longer span narrower chord horizontal stabilizer 46 moved about 3 ft 0 91 m to the rear 47 while more powerful versions of the same Wright Cyclone engines increased power from 1 100 to 1 200 hp 820 to 890 kW 47 but without the B 17G s turbosuperchargers New propellers and landing gear were also installed 48 The change to the tailplane required that the structural bulkhead supporting the forward spar be moved aft while the rear bulkhead was reworked and additional fuselage stiffeners were added 33 The tailwheel switched to using B 17G wheels and 26 smooth tread tires which required that the wheel well be enlarged and structure supporting the tailwheel reinforced 33 The main undercarriage wheels tires tubes amp brakes remained unchanged although the legs themselves were strengthened 33 The fuselages were stripped to bare metal and rewired with a 24VDC 1800 amp system from the B 29 Superfortress replacing the original 24VDC 800 amp system 47 Maximum weight was increased to 54 000 lb 24 000 kg and the maximum landing weight rose to 47 000 lb 21 000 kg 49 Slots were re incorporated into the wingtip leading edges 46 as they had been with the pre war airliners The cabin was redesigned and passenger capacity was increased from 33 to 38 46 50 with the cabin now divided into a 10 seat front section and a 28 seat rear section with no sleepers 49 The cabin pressurization system was never re installed 46 47 The B 17G wings came with turbo supercharger ducting for the engines that was not needed for the simpler supercharger installation used on the Stratoliner while one duct opening was retained on each wing between the engine nacelles to provide additional cabin air 48 Further mods made by TWA included improved sound proofing and temperature control 49 and on March 15 1945 the B 1 recertification tests were completed to the CAA s satisfaction 49 The estimated cost to repurchase and refurbish the five aircraft was 2 million notes 2 49 Variants Edit Prototype of the S 307 with the small tail used initially on the first three examples built 300 Original unpressurized 35 200 lb 16 000 kg proposal with seating for 16 24 passengers which began as a four engined Boeing 247 5 51 Ex Pan Am Inter American Inc Boeing S 307 Strato Clipper N19903 after returning to the US from Haiti before being bought by the Smithsonian T amp WA Boeing SA 307B Cherokee as built PAA 307 or S 307 Strato Clipper Designation for three aircraft built for Pan Am under ATC 719 17 Visible external differences included engine cowlings without cowl flaps 52 Four 1 100 hp 820 kW Wright GR 1820 G102A Cyclone engines were fitted with single speed superchargers 27 53 Crew of six 1 Strato Clipper was Pan Am s name for the type 1 SA 307B Designation for five aircraft built for T amp WA under ATC 726 17 These differed externally from the Pan Am aircraft in having large external flap actuators 52 Four 1 100 hp 820 kW Wright GR 1820 G105A Cyclone engines were fitted with two speed superchargers 28 Crew of five 28 SB 307B Designation for one uncertified aircraft built for Howard Hughes 17 C 75 Five Trans World SA 307Bs were impressed into the USAAF The cabin pressurization was removed to save weight and the external flap actuators replaced SA 307B 1 The C 75s were overhauled and updated with modified B 17G wings with 307 wing slots and larger tailplanes mounted further aft 54 1 200 hp 890 kW Wright GR 1820 G205A Cyclone engines were fitted 26 along with B 29 electrical systems 307C 50 passenger development with more powerful versions of the same Cyclone engines boosted to 1 350 hp 1 010 kW Boeing wanted 267 230 13 000 per engine or 319 230 notes 3 but development was cancelled in favour of the 377 Stratocruiser based on the B 29 47 316 Airliner project developed from the XB 15 with pressurized cabin similar to that used on the Stratoliners offered to KLM as a larger Stratoliner but not followed through with 55 322 Development of 307 with similar fuselage but with a mid mounted wing and a nosewheel as a bomber Eventually evolved into the B 29 Operational history EditTen 307s were built NC19906 was temporarily marked as NX1940 and NC1940 for publicity purposes 56 C N Registration Delivery Customer Model Names fleet number Other identities FInal Disposition1994 NX19901 none S 307 none none Crashed and destroyed during test flight March 18 19391995 NC19902 Pan American Airways 31 S 307 Clipper Rainbow F BHHR XW TAC Wrecked during emergency landing in bad weather May 22 19611996 NC19905 Transcontinental amp Western Air 56 SA 307B after 1944 SA 307B 1 Comanche 400 42 88624 288624 F BELV XW TAA Possibly shot down crashed and destroyed October 18 19651997 NX19904 Howard Hughes 6 SB 307B The Flying Penthouse Shamrock NC19904 Damaged on ground during storm converted to houseboat now in Florida Air Museum1998 NC19906 Transcontinental amp Western Air 56 SA 307B after 1944 SA 307B 1 Cherokee 401 42 88623 288623 NX1940 NC1940 F BELU XW TFP Forced to ditch in Mekong River aircraft was never recovered March 13 19751999 NC19907 Transcontinental amp Western Air 56 SA 307B after 1944 SA 307B 1 Zuni 402 42 88625 288625 F BELX XW TAB XW TFR Crashed and destroyed during a forced landing after multiple engine failure during take off June 27 19742000 NC19908 Transcontinental amp Western Air 56 SA 307B after 1944 SA 307B 1 Apache 403 42 88626 288626 F BELY XW PGR Damaged during collision with another aircraft on ground written off February 27 19712001 NC19909 Transcontinental amp Western Air 56 SA 307B after 1944 SA 307B 1 Navajo 404 288627 F BELZ Crashed and destroyed after collision with a mountainside December 29 19622002 NC19910 Pan American Airways 31 S 307 Clipper Comet Quito HC 004 N75385 Destroyed by fire after forced landing May 10 19582003 NC19903 Pan American Airways 31 S 307 Clipper Flying Cloud 2003 N9307R N19903 57 Restored to flying condition now in Smithsonian MuseumPrototype Edit Boeing 307 prototype from above showing off the wing and tail planform The first Boeing 307 Stratoliner serial 1994 registration NX19901 made its first flight from Boeing Field near Seattle on December 31 1938 prior to its intended delivery to Pan Am following testing and certification 58 As related above it crashed on a test flight on March 18 1939 killing all 10 occupants and forced several design changes of which the fin and rudder are the most immediately obvious Koninklijke Luchtvaart Maatschappij N V KLM Edit KLM was considering four engine airliners for the European routes and a longer ranged four engine aircraft for their routes to the Netherlands East Indies now Indonesia Aircraft considered included the Douglas DC 4 E the Boeing 307 the Junkers Ju 90 the Focke Wulf Fw 200 Condor and the Bloch 160 of which only the DC 4 and 307 came close to meeting their requirements 55 Boeing made a proposal to KLM on September 20 1936 for exclusive option on 10 certified 307s for 2 4 million notes 4 with options for 18 aircraft and with first delivery in 14 months 59 By January 14 1937 the price had increased for 18 aircraft to 265 000 each not including pressurization equipment 59 KLM let Boeing know that they were interested in 4 aircraft for use as an interim measure pending a larger more suitable design and they that they would use it for familiarization training with four engine aircraft 30 They required that it fly on just two engines use Pratt amp Whitney automatic mixture controls have a 2 500 mi 4 000 km range be able to carry freight or mail and have moderate tire ground pressure 30 KLM then requested a quote for three 307s either with Wright Cyclones and with Pratt amp Whitney 1830 engines fitted with constant speed propellers and automatic carburettor mixture control and with additional fuel to provide a range of 3 400 mi 5 500 km 55 Boeing responded that the price for three aircraft would be 289 000 each if fitted with Cyclone engines or 314 000 if fitted with R 1830s plus 3 100 4 000 per aircraft to increasing fuel capacity to either 1 700 US gal 6 400 L 1 400 imp gal or 2 125 US gal 8 040 L 1 769 imp gal provided that the US Government gave export permission on the engines 55 After not hearing back Boeing sent a new quote to KLM for 300 000 per aircraft or 320 000 for the pressurized version 55 December 20 1938 the KLM board made the decision to order two four engine aircraft with consideration of the Boeing 307 and Focke Wulf Fw 200 Condor however the Condor was not suitable for the East Indies route 13 Following T amp WA defaulting on payments the first three T amp WA aircraft were offered to KLM in late 1939 but a quick decision was needed by Saturday March 18 1939 but KLM was unable to make that decision before the offer expired and requested an extension 13 On March 21 1939 KLM confirmed that they still planned to buy 307s and insisted that they were content with Boeing s progress 6 Ultimately though KLM did not buy the 307s because their representatives test flight insurance coverage was rejected and KLM found Boeing s response to providing for the next of kin unsatisfactory a disagreement that was not cleared up until after World War 2 6 The insurance coverage on the aircraft was sufficiently large that it had the insurance industry worried about fallout and as was the norm at the time neither passengers nor crew could get coverage from any insurance company but the aircraft itself was covered for a replacement cost of 500 000 with hull coverage and passenger liability carried by Aero Insurance Underwriters and Associated Aviation Underwriters despite the fact that Boeing was offering to sell the aircraft to KLM for much less than that 60 Australian National Airways ANA Edit Another company that Boeing was in discussions with was Australian National Airways who they quoted 310 000 per Stratoliner or 340 000 for a pressurized version on July 27 1938 55 but nothing came of these discussions and ANA never operated the type Howard Hughes and Cosmic Muffin Edit Howard Hughes s SB 307B after conversion into The Flying Penthouse The first customer delivery was to millionaire Howard Hughes on July 13 1939 6 He bought aircraft serial number 1997 61 registered as NX19904 for 315 000 notes 5 62 for a round the world flight hoping to break his own record of 91 hours 14 minutes set between July 10 and 14 in 1938 in a Lockheed Model 14 Super Electra Hughes Stratoliner was fitted with extra fuel tanks and was ready for the first leg of the round the world attempt when Nazi Germany invaded Poland on September 1 1939 causing the attempt to be cancelled 8 Hughes aircraft was stored in Glendale California for the duration of the war prior to being converted into a flying condo 63 Hughes had the extra fuel tanks removed and for around 250 000 notes 6 he had it fitted with much more powerful Wright R 2600 engines for its transformation into The Flying Penthouse which included a Master Bedroom two bathrooms a galley and a bar as well as a living room 63 In 1949 Hughes spent an additional 100 000 notes 7 renovating it so he could sell it which like the T amp WA and Pan Am aircraft now included an interior designed by Raymond Loewy 62 Oil tycoon Glenn McCarthy bought it to coincide with the opening of his new Shamrock Hotel and he renamed it Shamrock and had it repainted however McCarthy defaulted on payments and it was returned to Hughes 62 It languished unflown until August 1965 when it was damaged beyond repair by Hurricane Cleo with only about 500 hours on the airframe 64 It was then bought for 69 by Kenneth W London who cut the damaged wings and tail off built a hull under it and installed a pair of V 8 engines to convert it into a houseboat which he named Londonaire 65 After various repossessions deaths and failed sales later it became the Cosmic Muffin in which form it still survives Transcontinental amp Western Air T amp WA or TWA Edit TWA Boeing SA 307B NC19905 Comanche undersides showing off just how wide the 11 5 ft 3 5 m fuselage was The external arms for the slotted flaps are visible here as are the hatches on the underside through which baggage was loaded As one of the companies sponsoring the development of the Douglas DC 4 Transcontinental amp Western Air lost interest due to delays and poor performance but the agreement they signed with Douglas limited the maximum weight of any replacement design to 43 000 lbs 30 After discussing their needs with Boeing T amp WA signed a contract with Boeing to buy six 307s with an option for 13 more for 1 590 000 on January 29 1937 with deliveries to be made in mid 1938 9 T amp WA defaulted on their payments though and the T amp WA markings which had already been applied to their airframes were removed 11 T amp WA filed a lawsuit against Boeing for default of contract and Boeing sued T amp WA for breach of contract over the non payment 2 Hughes had begun secretly buying up T amp WA shares 66 and by March 1939 Hughes has a controlling interest in Trans World Airlines or TWA as it was rebranded once he had taken over with roughly 46 of the shares 2 By August 1939 TWA and Boeing had resumed negotiations so TWA would get five 307s and Hughes would get one 2 The cost to TWA had risen and was now 1 750 000 notes 8 or 350 000 notes 9 per aircraft three times the cost for Douglas DC 3s 8 In early 1940 Hughes bought up all remaining outstanding TWA shares not otherwise reserved for employees 2 TWA received its first Stratoliner on May 6 1940 and the last of their five was delivered on June 4 1940 56 67 It was not their first four engine airliner as one of their parent companies Western Air Express had operated the Fokker F 32 All five were named in TWA promotional material for North American Indigenous tribes names that would be used throughout their careers continuing long after they left TWA War intervened in December 1941 and civil aircraft production was halted preventing any further deliveries 68 69 TWA first service flight was chosen to be on July 8 1940 to coincide with anniversary of TAT s 48 hour coast coast service which had used trains for night legs 3 TWA s Stratoliners flew between Los Angeles and New York making three stops TWA s Burbank La Guardia flight via Chicago was 2 hours quicker than for a DC 3 13 40 east and 15 38 west with 3 stops in each direction 3 The main route was La Guardia NY to Chicago Illinois to Kansas City Missouri to Albuquerque New Mexico to Burbank California and the reverse 3 1940 was the best year for TWA with 50 increase in passenger traffic over 1939 but they were still running exclusively in the red 32 On September 9 1940 a TWA Stratoliner from Chicago to New York set a commercial speed record flying the 778 mi 1 252 km in two hours and 52 minutes at an average speed of 271 4 mph 436 8 km h 70 and a few weeks later on September 26 a TWA New York bound Stratoliner at 17 000 ft 5 200 m with a jetstream providing a strong tailwind reached a ground speed of 387 mph 623 km h 71 Map of 1940 TWA Boeing 307 routes 1940 TWA Boeing 307 routes and fares 72 FlightNo Route Route name Price 1 way Price return Sleepersurcharge7 New York to Burbank via CHI MKC and ABQ Super Sky Chief 149 95 notes 10 269 90 notes 11 119 95 notes 12 8 Burbank to New York via ABQ MKC and CHI Super Sky Chief 149 95 notes 10 269 90 notes 11 119 95 notes 12 40 Kansas City to New York via Chicago Times Square notes 13 66 45 notes 14 119 60 notes 15 8 80 notes 16 41 New York to Chicago non stop Times Square notes 13 44 95 notes 17 80 90 notes 18 5 60 notes 19 42 Chicago to New York non stop Sky Century 44 95 notes 17 80 90 notes 18 5 60 notes 19 45 New York to Kansas City via Chicago Star Duster 66 45 notes 14 119 60 notes 15 8 80 notes 16 Flight 45 added additional stops at Philadelphia and Pittsburgh on December 1 1940 73 TWA ICD Wartime operations Edit C N Old TWARegistration Name USAAF Serial Also marked as1996 NC19905 Comanche 42 88624 2886241998 NC19906 Cherokee 42 88623 2886231999 NC19907 Zuni 42 88625 2886252000 NC19908 Apache 42 88626 2886262001 NC19909 Navajo 42 88627 288627On December 14 1941 representatives from various airlines as well as the Air Transport Association of America ATA met with Colonel Robert Olds of the Air Corps Ferrying Command later renamed Air Transport Command over the use of their airliners in wartime 74 Pan Am had already signed a contract on the 13th in which it would keep its 307s but sell the 314s to the government 74 T amp WA sold all five of its 307s to the USAAF but would then operate them on behalf of the USAAF on a cost plus basis though a new subsidiary 74 At the time the Stratoliner was the only available landplane transport capable of transatlantic flights with any payload Seaplanes were too slow and not numerous enough while the Douglas C 54 Skymaster would not enter service until March 1942 and took months to be available in any numbers aside from a few ad hoc conversions from Consolidated B 24 Liberator bombers the Consolidated C 87 Liberator Express would not be ready until September 1942 and the Lockheed C 69 Constellation would not fly until January 1943 while aircraft with two engines were considered unsafe for ocean crossings with VIPs on board 74 On the entry of the United States into World War II Pan Am continued operating its Stratoliners on routes to Central and South America but under direction of the Army Air Forces Air Transport Command 74 All five TWA Stratoliners were withdrawn from operations on December 24 1941 while TWA created a subsidiary the Intercontinental Division ICD whose civilian crews would operate them on behalf of the United States Army Air Forces 43 Otis Bryan was made head of the ICD 41 The Stratoliners were sold to the USAAF who assigned the type the C 75 designation and each of them was given a USAAF serial number 43 The first of these was accepted by the USAAF on March 1 1941 and the last one on December 17 1942 43 ICD crews included pilots 1st amp 2nd officers navigators flight engineers flight radio operators and pursers 75 ICD Supervisor pilots and captains were paid 1100 month notes 20 first officers 800 month notes 21 Navigators 600 month notes 22 Flight Engineers FEs 500 month notes 23 and Flight Radio Operators FROs 400 month notes 24 45 Personnel were issued with USAAF uniforms which they wore with rank stripes two solid stripes for a captain but with civilian insignia 45 USAAF C 75 42 88624 Comanche in wartime camouflage The first ICD service flight began on February 26 when a 307 flew south to Brazil from Washington before crossing the South Atlantic to Africa and north to Cairo before continuing on to Prestwick Scotland where they arrived on April 20 1942 43 having primarily carried 25 000 rounds of armour piercing shells to British troops in Cairo who were facing Rommel and his Afrika Corps 76 ICD was initially set up at the crowded Washington Bolling Field but was soon transferred all of their operations to nearby Washington National Airport 77 Passengers continued to be loaded at Bolling Field after flying the short hop from Washington National Airport 78 The first north Atlantic crossing was in March 1942 when a flight from Washington to Prestwick carried senior military and government officials to Europe which included the Army Chief of Staff General George C Marshall General Dwight D Eisenhower to command Operation Torch for the invasion of North Africa Deputy Chief of Staff of Army Ground Forces General Mark W Clark Operation Torch Air Force liaison officer Colonel Hoyt Vandenberg Chief of the Navy s Bureau of Aeronautics Rear Admiral John Henry Towers who oversaw Navy aircraft procurement and training and presidential advisors W Averell Harriman and Harry Hopkins who were crossing to negotiate the lend lease program 76 From April 22 regular crossings were being made 43 and ICD was growing rapidly growing from 71 personnel in January to 343 by April and they were now making 16 ocean crossings a month 77 Following his April 1942 raid on Tokyo but before it had been made public Jimmy Doolittle took a C 75 from Karachi in India through Khartoum Kano Accra Robertsfield Airport crossed the Atlantic to Natal in Brazil and headed north to Belem and from there with an additional fuel stop to Washington DC arriving in time for the news of the raid to be made public 44 Many of the surviving members of the raid followed soon after in another Stratoliner 44 The North Atlantic ferry route was set up with help from former Arctic explorer Colonel Bernt Balchen who assisted with Bluie East Two and Bluie East Eight in Greenland to reduce the Gander Newfoundland Scotland leg distance 77 The first aircraft to land at these fields which were north of the Arctic Circle was an ICD C 75 on April 20 1942 77 Marshall Eisenhower Hap Arnold and Admirals King and Towers flew to London from Washington via Montreal Gander and Prestwick on May 23 1942 and returned to Washington via Prestwick Reykjavik and Gander 42 On June 20 1942 Air Corps Ferrying Command became Air Transport Command 42 The exiled but not yet deposed King Peter II of Yugoslavia was flown in July 1942 from London 42 to Washington to meet with North American leaders with the engines leaned out so much that the last leg of the trip was able to skip numerous stops so that they ended up being in the air for 21 hours 16 minutes when they arrived in Washington 79 Boeing C 75 ICD primary wartime transatlantic routes after July 1942 when the airfield at Ascension Island shortened the South Atlantic crossing Bluie Two and Eight were added in 1942 as diversionary airfields in case excessive headwinds were encountered in the North Atlantic When conditions allowed it usually on summer eastbound crossings direct flights were sometimes made between Gander and Prestwick 80 On July 10 1942 Ascension Island s airfield opened in South Atlantic 79 shortening the hazardous transatlantic leg enough that smaller aircraft could now make the crossing and the ICD C 75s would routinely lead flights of USAAF twin engined aircraft such as Douglas A 20s across 79 In November 1943 a C 75 carried Soong Mei Ling wife of the Chinese Nationalist warlord Chiang Kai Shek from Chungking to Washington to receive medical care and to negotiate military aid for China 81 Two main routes were flown between Washington D C and Cairo across the South Atlantic and between New York and Prestwick Scotland across the North Atlantic 82 They often flew non stop the 2 122 mi 3 415 km between Gander Newfoundland and Prestwick Scotland in the north and the 2 500 mi 4 100 km between Natal Brazil and Accra Ghana in the south After July 1942 a refueling stop at Ascension Island was added in the South Atlantic 83 In the north stops at Iceland or Greenland were often necessary when flying west against unusually strong prevailing winds As Douglas C 54 Skymasters took over the Gander to Prestwick route the C 75s operated between Marrakech and Prestwick over the Atlantic 82 ICD C 75s crossing the Atlantic had to be careful to avoid Allied convoys and German U boats to avoid being shot at 84 Cherokee was returning American troops from Reykjavik to Gander at 1 000 ft 300 m and was shot at by a US Navy ship that left over 200 holes in the aircraft s tail and which nearly severed the elevator controls 84 Many transatlantic trips were made at night so the navigator could get good star sightings 76 By 1944 the USAAF had enough long range transports that it no longer needed the small number of C 75s it had and sold the fleet back to TWA with the aircraft being transferred between January 6 1944 and December 19 1944 10 56 On August 11 1942 ICD had received the first of 12 C 54s 79 and Pan Am would also supplement their Stratoliners with 12 C 54s 79 TWA received two C 54s in August and had 5 by September and a full allotment of 12 by November along with the first three C 87s to supplement the C 75s 85 At the same time Curtiss C 46 Commandos Douglas C 47s and C 53s provided feeder links to the C 75s C 54s and C 87s as their range was inadequate for the Atlantic 85 By the time they were withdrawn over 3000 trans oceanic crossings had been made 25 and they had flown 21 284 while in USAAF service with the ICD 47 The sole accident occurred during night landing at Natal in Brazil when an undercarriage leg was torn off by a mound of dirt 47 It cost TWA about 2 million notes 25 to have the five aircraft rebuilt by Boeing and the first of them resumed passenger service on April 1 1945 The CAA recertified these as SA 307B 1 civilian airliners with their original registration numbers TWA post war service and disposal Edit TWA Boeing SA 307B 1 N19909 Navajo fleet number 404 as it appeared when offering coach class seating only and showing the rearward location of the higher aspect ratio B 17G tailplane whose hinges were now lined up with the rudder hinge On April 1 1945 the first post war civil commercial flight was made by Zuni now as a SA 307B 1 from La Guardia to San Francisco via Pittsburgh Saint Louis Kansas City Albuquerque and Burbank 49 but the second transcontinental flight did not happen until a month later when on May 1 1945 a flight was made from Washington DC to Spokane Washington via Dayton Municipal Airport St Louis Kansas City Albuquerque and Burbank reflected a loosening of the tightly controlled government access to routes 86 TWA s fare structure remained the same as pre war 86 New TWA flight routes were added with routes 370 amp 371 between La Guardia and Spokane with intermediate stops in Chicago Albuquerque for fuel and Burbank and routes 48 amp 49 between La Guardia and Kansas City with a stop in St Louis 86 At this time the TWA Stratoliners were briefly the sole four engine commercial airliner in domestic service in the US 86 On July 10 1939 TWA had signed a contract with Lockheed to develop the Constellation which was to be capable of 5 miles min 350 mph 560 km h compared to the Stratoliner s 4 miles min 246 mph 396 km h 8 but with production diverted to military for the duration of the war the first TWA Constellations did not enter service until February 1946 and were soon grounded dealing with the usual teething problems encountered with a new type from July 11 to September 20 1946 while the Douglas DC 4s began arriving in 1946 in small numbers and the Douglas DC 6 similarly from 1947 86 At the same time due to strong competition from war surplus non sked flights operating cheaply purchased war surplus Douglas C 54s in May 1949 the Stratoliner s were downgraded to a coach only service with the fares slashed by a third 87 The first coach service from New York La Guardia to Chicago via Pittsburgh was made on June 1 1949 with a full load of 38 passengers 88 In November 1950 TWA introduced the similarly sized but cheaper to operate twin engine Martin 2 0 2A on domestic routes 89 and transferred some DC 4s from international routes to domestic service 87 supplementing the Stratoliners which were mainly being used for service between La Guardia and cities in the mid west 46 until TWA finally phased them out between April and July 1951 90 At that time the aircraft had an average of 25 205 hours flying time each with Cherokee having the most with 26 324 hours 87 and they had covered 7 500 000 mi 12 100 000 km while in ICD service 48 Pan American Airways Pan Am Edit Lineup of all three Pan Am Strato Clippers C N Registration Name Namesake1995 NC19902 Clipper Rainbow 31 Clipper ship Rainbow 2002 NC19910 Clipper Comet 31 Clipper ship Comet 2003 NC19903 Clipper Flying Cloud 31 Clipper ship Flying Cloud In 1937 Pan American Airways placed their first order for two Stratoliners which they soon increased to six Deliveries to Pan Am started in March 1940 67 and they had received their first three before war intervened and civil aircraft production halted 68 69 The other three would not be built 2 All three were named for historically notable Clipper ships Pan Am carried out their first revenue flight on July 4 1940 3 with service between Miami Brownsville Texas and Los Angeles 67 Unlike TWA Pan Am did not exclusively assign their aircraft to specific routes and instead they were used for their Latin American routes and ranged from Miami and Los Angeles to Brazil Aerovias Ecuatorianas C A AREA Boeing S 307 Strato Clipper HC 004 At the same time TWA s Stratoliners were getting new wings and tails Pan Am s 307s were being modified in Miami to repair the cracked spar tubing with doublers and did not get new wings or engines and the maximum gross weight remained the same 63 Pan Am flights then resumed between Miami the Caribbean and Belem 51 until all three were sold to the Airline Training Company of Miami in late 1948 and early 1949 64 before being sold on to other operators The former Clipper Comet NC19910 was sold to Aerovias Ecuatorianas AREA in Ecuador in 1951 who used it as Quito with the registration HC 004 to provide service between Ecuador and Miami From 1955 it was with Quaker City Airways for two years as N75385 making non scheduled charter flights 91 On May 10 1958 while still carrying the same registration and after having been stored for some time it was being readied to be ferried to Boeing for modification for use as a crop duster but flight tests were carried out despite finding fuel leaks whose source could not be determined and with untested auxiliary fuel tanks installed in the cabin During the flight test it caught fire and while the crew landed it safely on a boulder strewn mesa and the crew escaped unharmed the airframe was destroyed by the fire 64 92 The former Clipper Rainbow NC19902 was to have been sold to the short lived Mercury Airways of South Africa and was even given a South African registration ZS BWU however the sale was never completed and likewise it was supposed to have been sold to Aerovias Ecuatorianas with registration HC SJC 003 but that sale also appears to have fallen through and in 1951 it was sold to Aigle Azur as F BHHR 93 The former Clipper Flying Cloud NC19903 was purchased by the Corps d Aviation d Garde d Haiti Haitian Air Force in 1954 and assigned the number 2003 but plans to use it for a passenger service by the Compagnie Haitienne de Transports Aeriens CoHaTA were cancelled and it was fitted out as a Presidential transport When Francois Papa Doc Duvalier came into power in 1957 he chose not to use it and instead had the aircraft sold the same year with the money from the sale going toward five North American T 6G Texan training aircraft 94 This aircraft returned to the U S and after briefly being registered as N9307R and N19903 is now restored and at the Smithsonian Museum as NC19903 57 95 Aigle Azur and Union Aeromaritime de Transport Edit Aigle Azur Extreme Orient Boeing S 307 Strato Clipper F BHHR in New York just before delivery Aigle Azur Boeing SA 307B 1 F BELV on the ramp TWA sold all five TWA SA 307B 1s to the French operator Aigle Azur French for Blue Eagle in April 1951 for 525 000 notes 26 along with their remaining supply of spares 63 Aigle Azur received them between May 14 1951 and December 19 1951 56 and modified these for 48 passengers in Bordeau and used them on scheduled flights between Paris and North and Central Africa Casablanca Dakar Tunis Madagascar French West Africa and French Equatorial Africa and later in 1952 to French Indo China 46 63 96 The Stratoliners were no longer competitive against the larger and faster Douglas DC 6 and Lockheed Constellation then entering service 46 which on May 1 1955 led to Aigle Azur along with its subsidiary in Asia Aigle Azur Indochine being bought by Union Aeromaritime de Transport UAT On the same date Aigle Azur Indochine was renamed Aigle Azur Extreme Orient On September 16 1955 F BELV F BELX F BELY and F BELZ were transferred from Europe to Aigle Azur Extreme Orient mainly for charter work 97 During 1955 and 1956 F BELU and F BELY and F BELZ returned to Europe to be leased to Airnautic 98 The former Pan Am aircraft F BHHR had joined Aigle Azur in 1951 and was transferred to Aigle Azur Extreme Orient in March 1957 93 Aigle Azur Extreme Orient branding was retained for several years before the aircraft were repainted in UAT Aeromaritime colors After four years in service in Asia during which it was briefly leased to Air Laos Transport Aeriens later renamed Royal Air Lao and assigned the Laotian XW registration XW TAC F BHHR was destroyed in an accident on May 22 1961 while being operated by Aigle Azur Extreme Orient on a non scheduled Saigon Vientiane passenger flight with 28 on board It had departed from Tan Son Nhat International Airport in Saigon and was heading for Vientiane when the number four engine had to be shut down and when it returned to land it overshot the runway in deteriorating weather and a violent squall or microburst blew it sideways causing it to hit the ground All 28 people on board survived but the aircraft was wrecked 99 Union Aeromaritime de Transport merged with Transports Aeriens Intercontinentaux to become Union de Transports Aeriens UTA on October 1 1963 but by then had already sold all of its Stratoliners to CITCA Airnautic Edit Airnautic Boeing SA 307B 1 F BELY Airnautic or Air Nautic received three ex Aigle Azur SA 307B 1s in 1955 and 1956 including F BELU 100 F BELY 101 and F BELZ 102 which were operated in southern Europe around the Mediterranean providing charter flights especially around Corsica On December 29 1962 F BELZ collided with a mountain while on a charter flight with 22 basketball players and fans while flying from Bastia to Ajaccio on the island of Corsica 96 102 103 It was flying at an altitude of about 7 500 ft 2 300 m despite having been cleared for 12 000 ft 3 700 m and at 12 12pm slammed into a sheer rock face just 165 ft 50 m from the peak before falling about 330 ft 100 m down the side of the mountain 103 In 1965 F BELY and F BELU were returned to CITCA who then leased them to other operators 100 101 Air France became the principal shareholder of Airnautic in 1962 at which time it purchased DC 6s 104 and in 1966 Airnautic ceased to exist having been absorbed into Air France Compagnie Internationale de Transports Civil Aeriens CITCA Edit Boeing SA 307B 1 Stratoliner F BELX likely while with Cambodia Air Commercial SA 307B 1 F BELU with the CIC ICC Royal Air Lao SA 307B 1 XW TFP two days before ditching in the Mekong river Compagnie Internationale de Transports Civil Aeriens CITCA bought five Stratoliners F BELU F BELV F BELX F BELY F BELZ which were leased out to other operators 97 98 100 101 102 In 1965 Cambodia Air Commercial leased F BELY as XW PGR and F BELU as XW TFP before both went to Royal Air Lao the same year 100 101 which then leased all five of the CITCA Stratoliners which were also assigned Laotian XW registrations and F BELV became XW TAA and F BELX became XW TFR 97 98 The Air Laos Transport Aeriens and Royal Air Lao Stratoliners were flown between Vientiane and Hong Kong with a large detour around North Vietnam 96 Royal Air Laos was operating XW TFP and XW PGR when they were destroyed in accidents 100 101 while F BELV would be leased to Royal Air Cambodge 97 On February 27 1971 XW PGR collided with a Lao Air Force Douglas C 47 while landing at Luang Prabang Laos and damage to the left wing was unrepairable due to a lack of spares 64 105 The Commission Internationale de Controle International Control Commission in English CIC ICC and its successor International Commission of Control and Supervision leased three aircraft in 1964 under their old French registrations of F BELV F BELU and F BELX which now had seating for as many as 60 and were used to provide what were often hazardous diplomatic flights around south east Asia until 1974 when it suspended operations with the impending defeat of US forces in Vietnam 46 97 98 They were flown under diplomatic immunity along specially delineated 20 mi 32 km wide corridors between Saigon in South Vietnam Vientiane in Laos Phnom Penh in Cambodia and Hanoi in North Vietnam 96 Passengers usually included diplomats members of the Red Cross press businessmen and Control Commission officials 96 When F BELV disappeared on October 18 1965 it was flying from Vientiane Wattay Airport in Laos to the Hanoi Gia Lam Airport in Vietnam 64 106 and was supposed to have been cleared to fly at 11 800 ft 3 600 m and 165 kn 190 mph 306 km h 107 On this flight there were five CIC delegates from India three from Canada and one from Poland as well as four French crew members 107 all of whom died 106 Due to radio interference a message indicating that their clearance period had been delayed was never received 107 Poor communications meant it took until the next day and around 19 hours before anyone realized the aircraft had gone missing as the destination airport had assumed it had returned to its point of origin and that airport was unaware it had not arrived at its destination 107 The search for the downed aircraft was delayed further due to the need to negotiate access to the likely crash area with several warring parties wary from previous experience of the search mission being a cover for either intelligence gathering or other military activities 107 A Canadian investigation long after the war determined that it had likely been shot down by North Vietnamese anti aircraft fire but they were unable to determine if it was intentional or not 106 XW TFR previously F BELX and briefly XW TAB had been returned to Cambodia Air Commercial when it was destroyed in an accident on June 27 1974 following three of the four engines failing while climbing out from Battambang Airport During the forced landing it collided with trees causing extensive damage including tearing one wing off before the aircraft caught fire 17 passengers and two crew members out of the 39 on board died in the crash that the crash investigation blamed on poor maintenance 46 96 108 The pilot of XW TFP was forced to ditch in the Mekong river on March 13 1975 near the Laos Thailand border while on a flight from Hong Kong to Vientiane Both the pilot and co pilot escaped the wreck but were captured by the communist Pathet Lao and held until May The wreckage was still there in 1986 109 Operators Edit Pan Am Boeing S 307 Strato Clipper NC19910 Clipper Comet Civilian operators Edit TWA Stratoliner pre war at Chicago airport Quaker City Airways Boeing S 307 Stratoliner N75385 United StatesHoward Hughes bought one aircraft notes 27 Inter American Inc IA bought ex Pan Am Clipper Flying Cloud from the Haitian Government Pan American Airways PAA Pan Am received three aircraft notes 27 Trans World Airlines TWA received five aircraft notes 27 Quaker City Airways 110 operated ex Pan Am Clipper Comet 111 EcuadorAerovias Ecuatorianas CA AREA Ecuador operated an ex Pan Am aircraft as HC 004 112 France UAT Aeromaritime Boeing SA 307B 1 F BELV Aigle Azur en Blue Eagle operated five ex TWA aircraft and one Pan Am aircraft all bought in 1951 Air Nautic or Airnautic operated three aircraft Commission Internationale de Controle International Control Commission in English CIC ICC and its successor International Commission of Control and Supervision operated at least three aircraft leased from UAT and CITCA Compagnie Internationale de Transports Civil Aeriens CITCA leased out ex UAT aircraft to other operators Union Aeromaritime de Transport UAT operated the Aigle Azur aircraft after buying them out Laosອາກາດລາວ Fr Air Laos Air Laos Transport Aeriens leased one ex Pan Am ex Aigle Azur aircraft before being renamed Royal Air Lao ລາຊະວ ງ ສາຍການບ ນ ພາສາລາວ En Royal Air Lao operated four ex Aigle Azur aircraft Cambodiaអ ក សចរណ ភ ម ន ទ កម ព ជ Fr Royal Air Cambodge operated one aircraft with French registration Cambodia Air Commerciale operated several aircraft under Laos registrations Military operators Edit HaitiHaitian Air Corps Compagnie Haitienne de Transports Aeriens CoHaTA a Military transport organization operated one ex Pan Am 307 94 United StatesUnited States Army Air Forces operated five ex TWA SA 307Bs as C 75s Three Pan Am 307s operated under USAAF direction but ownership remained with Pan Am Accidents and incidents EditThe Boeing 307 was involved in eight hull loss incidents with 67 fatalities Four of the ten incidents involved fatalities with one likely being shot down while in a war zone 113 Date Operator Model C N Reg n Location Occupants Fatalities Synopsis SourcesMarch 18 1939 Boeing S 307 1994 NX19901 Alder Washington 10 10 Airframe severely overstressed after difficult spin recovery while carrying several customer representatives 114 May 17 1940 TWA SA 307B 1999 NC19905 Pritchett Colorado 19 0 Carb ice caused loss of power while flying in mountains which resulted in a wheels up landing in field Aircraft was repaired and returned to service 115 May 10 1958 unknown S 307 2002 N75385 Madras Oregon 2 0 Known fuel leak in cabin caused fire during test flight that consumed airframe once it had landed on a rock strewn mesa 92 May 22 1961 Aigle AzurExtreme Orient S 307 1995 F BHHR Ho Chi Minh North Vietnam 28 0 Engine failure forced it to return after takeoff and aircraft destroyed after being blown off the runway by a wind gust while landing 99 December 29 1962 Airnautic SA 307B 1 2001 F BELZ Monte Renoso Corsica 25 25 Collided with the tip of a mountain on Bastia Nice Ajaccio Nice Ajaccio Bastia charter flight for the worst 307 accident 103 October 18 1965 ICC CIC SA 307B 1 1996 F BELV Between Vientiane andHanoi Vietnam 13 13 Likely shot down by North Vietnamese AA fire while on a scheduled non commercial diplomatic flight carrying CIC ICC observers 106 February 27 1971 Royal Air Lao SA 307B 1 2000 XW PGR Luang Prabang Laos 2 0 Damaged wing in collision with Royal Lao Air Force Douglas C 47 while landing and a lack of spares prevented repairs 105 June 27 1974 Cambodia Air Commercial CACO SA 307B 1 1999 XW TFR Battambang Airport Cambodia 39 19 Three engines failed during takeoff due to poor maintenance and the forced landing destroyed the aircraft after a tree tore the right wing off 116 March 13 1975 Royal Air Lao SA 307B 1 1998 XW TFP Mekong River Laos 2 0 Forced landing on Hong Kong Vientiane cargo flight Both pilots imprisoned by Pathet Lao The wreck was located in 1986 109 March 28 2002 National Air and Space Museum S 307 2003 N19903 Elliott Bay Washington 4 0 Ran out of fuel and ditched on its final delivery flight to the Smithsonian following restoration Raised and re restored 117 Surviving aircraft Edit Restored ex Pan Am Stratoliner NC19903 displayed in the Steven F Udvar Hazy Center The sole intact Boeing 307 Stratoliner NC19903 is preserved in flying condition at the Smithsonian s Steven F Udvar Hazy Center After having been restored to flying condition it was being delivered to the Smithsonian on what was to be its last flight when it ran out of fuel and ditched in Elliott Bay near Seattle Washington in March 2002 118 Despite the incident it was raised and again restored and it completed its flight to the Smithsonian where it was placed on display 119 The forward fuselage of Howard Hughes 307 NX19904 also survives although it was stripped of flying surfaces and the rear fuselage and converted into a houseboat The aircraft was awaiting restoration at Fort Lauderdale International Airport in August 1964 when it was severely damaged when Hurricane Cleo tore it loose from its tiedowns and it was blown into a stand of trees The aircraft was later salvaged and converted into a house boat and the interior remains notable for the additions made when owned by Howard Hughes 120 121 It is now part of the Florida Air Museum s collection 122 Specifications Boeing SA 307B ATC 726 Edit Boeing SA 307B Stratoliner 3 view drawing Data from Juptner Joseph P 1980 US Civil Aircraft Vol 8 ATC 701 800 Aero Publishers pp 102 104 ISBN 978 0816891788 123 General characteristicsCrew Five including pilot co pilot flight engineer and 2 flight attendants Capacity Daytime seating for 33 nighttime capacity 25 in 16 berths and 9 reclining chairs Length 74 ft 4 in 22 66 m Wingspan 107 ft 3 in 32 69 m notes 28 Wing chord 19 ft 0 in 5 79 m at root and 9 ft 4 5 in 2 858 m at tip rib 124 Height 20 ft 9 in 6 32 m at rudder Undercarriage track 295 in 7 5 m Wing area 1 486 sq ft 138 1 m2 Airfoil NACA 0018 at root NACA 0010 at tip Wing dihedral 4 5 from chord line 124 Wing incidence 3 5 constant root to tip 124 Empty weight 30 000 lb 13 608 kg to 31 200 lb 14 200 kg in overload condition Gross weight 45 000 lb 20 412 kg Maximum load 15 000 lb 6 800 kg with 30 passengers 650 lbs of baggage and 1 275 US gal 4 830 L 1 062 imp gal 5 750 lb 2 610 kg of fuel Fuel capacity 1 275 US gal 4 830 L 1 062 imp gal normal carried within the wings Overload up to 1 800 US gal 6 800 L 1 500 imp gal Fuel consumption 200 US gal 760 L 170 imp gal hr Oil capacity 100 180 US gal 380 680 L 83 150 imp gal Powerplant 4 Wright GR 1820 G105A Cyclone air cooled radial engines with two stage superchargers 1 100 hp 820 kW each at 2400 rpm for sea level takeoff reduced to 900 hp 670 kW at 2300 rpm at 17 300 ft 5 300 m Propellers 3 bladed Hamilton Standard all metal Hydromatic constant speed propellers 11 ft 6 in 3 51 m diameter 124 Performance Maximum speed 250 mph 400 km h 220 kn at 16 200 ft 4 900 m Cruise speed 222 mph 357 km h 193 kn at 19 000 ft 5 800 m and 75 power Minimum control speed 70 mph 110 km h 61 kn with flaps Takeofff run 1 800 ft 550 m Landing run 2 050 ft 620 m Range 1 300 mi 2 100 km 1 100 nmi at 19 000 ft 5 800 m amp 75 power Service ceiling 23 800 ft 7 300 m reduced to 18 000 ft 5 500 m when on three engines Cruising altitude 15 000 20 000 ft 4 600 6 100 m 124 Absolute ceiling 25 200 ft 7 700 m 124 Rate of climb 1 200 ft min 6 1 m s initial from sea level Wing loading 30 lb sq ft 150 kg m2 124 Power loading 12 5 lb hp 7 6 kg kW takeoff 10 25 lb hp 6 23 kg kW cruise 124 See also EditBoeing 377 Stratocruiser Renard R 35 first airliner with a pressurized cabin 125 Related development Boeing B 17 Flying FortressAircraft of comparable role configuration and era de Havilland Albatross Bloch MB 160 Douglas DC 4E Fairey FC1 project only Focke Wulf Fw 200 Condor Junkers Ju 90 Lockheed Model 44 Excalibur project only Piaggio P 108C Potez 662 Short S 32 project only Related lists List of aircraft of World War II List of civil aircraft List of military aircraft of the United StatesNotes Edit equivalent to 2 134 466 02 in 2022 equivalent to 32 510 166 36 in 2022 equivalent to 5 306 821 59 in 2022 equivalent to 50 612 949 64 in 2022 equivalent to 6 627 057 42 in 2022 equivalent to 3 751 706 48 in 2022 equivalent to 1 229 930 07 in 2022 equivalent to 37 353 155 34 in 2022 equivalent to 37 353 155 34 in 2022 a b One way airfair equivalent to 3 132 21 in 2022 a b Return airfair equivalent to 5 637 77 in 2022 a b Sleeper surcharge equivalent to 2 505 56 in 2022 a b Daytime flights only a b One way airfair equivalent to 1 388 03 in 2022 a b Return airfair equivalent to 2 498 25 in 2022 a b Sleeper surcharge equivalent to 183 82 in 2022 a b One way airfair equivalent to 938 93 in 2022 a b Return airfair equivalent to 1 689 87 in 2022 a b Sleeper surcharge equivalent to 116 97 in 2022 equivalent to 21 885 52 in 2022 equivalent to 15 916 74 in 2022 equivalent to 11 937 56 in 2022 equivalent to 9 947 96 in 2022 equivalent to 7 958 37 in 2022 equivalent to 33 247 637 05 in 2022 equivalent to 5 919 038 46 in 2022 a b c Original operator received aircraft from Boeing Span was greater than for the B 17 because of the wider fuselageReferences Edit a b c d Juptner 2000 p 75 a b c d e f g h i j Betts 1990 p 61 a b c d e Betts 1990 p 71 Davies 2000 p 52 a b c Dijkstra 2016 p 75 a b c d e f g Dijkstra 2016 p 81 a b c Betts 1990 p 55 a b c d e f g h i Betts 1990 p 65 a b c d e Betts 1990 p 57 a b c d Betts 1993 a b c Betts 1990 p 59 a b c Air Safety Board Report involving NX19901 of the Boeing Aircraft Company near Alder Washington March 18 1939 a b c d e Dijkstra 2016 p 79 a b c d Dijkstra 2016 p 80 Boeing 307 N19903 Goleta Air and Space Museum Retrieved May 21 2020 Abzug amp Larrabee 2005 p unk a b c d Bowers 1989 p 231 Betts 1990 p 67 a b c Betts 1990 p 69 Betts 1994 p 51 Boeing Historical Snapshot 1995 2022 De Wulf 1978 pp 147 149 a b c Betts 1990 p 63 Haddow 1962 p 2 a b c Juptner 1980 p 102 a b c d e f g h i j k l m Juptner 1980 p 104 a b c d e f g h Minshall 1940 p 116 a b c d e f Juptner 1980 p 103 a b c d e McLarren 1938 p 40 a b c d Dijkstra 2016 p 77 a b c d e f g h Davies 1987 p 49 a b Betts 1990 p 73 a b c d e Beall 1945 p 149 a b c d e f Minshall 1940 p 49 Minshall 1940 p 47 Minshall 1940 p 48 Betts 1992 p 82 a b c d e McLarren 1938 p 31 a b Davies 2000 p 49 Davies 2000 p 48 a b c d e f g Betts 1992 p 61 a b c d e f Betts 1992 p 69 a b c d e f Davies 2000 p 46 a b c Betts 1992 p 68 a b c d e Betts 1992 p 62 a b c d e f g h i Hardy 1982 p 31 a b c d e f g Betts 1994 p 52 a b c Beall 1945 p 148 a b c d e f Betts 1994 p 53 Bowers 1989 pp 234 235 a b Hardy 1982 p 30 a b Bowers 1989 p 232 Juptner 2000 p 76 Bowers 1989 p 235 a b c d e f Dijkstra 2016 p 78 a b c d e f g h i Davies 2000 p 44 45 a b REGISTRATION DETAILS FOR NC19903 NATIONAL AIR amp SPACE MUSEUM BOEING 307 STRATOLINER planelogger com Retrieved July 17 2022 Ford 2004 p 55 a b Dijkstra 2016 p 76 Cartwright 1939 p 3 Betts 1994 p 62 a b c Marrett 2004 p 95 a b c d e Betts 1994 p 57 a b c d e Betts 1994 p 59 Marrett 2004 p 231 Betts 1990 p a b c Betts 1989 p 75 a b Bowers 1989 p 231 a b Noah 1972 p 148 Gardner 1940 p 9 Gardner 1940 p 10 Larsson Bjorn Zekria David March 10 2022 Airliner Timetable images Retrieved March 10 2022 Betts 1990 p 72 a b c d e Betts 1992 p 59 Betts 1992 p 60 a b c Betts 1992 p 65 a b c d Betts 1992 p 67 Betts 1992 p 84 a b c d e Betts 1992 p 70 Betts 1992 p 76 Betts 1992 p 75 a b Berry Peter Transatlantic Flight 1938 1945 Part I 1938 1943 AAHS Journal Volume 40 Issue 2 1995 Berry Peter Transatlantic Flight 1938 1945 Part II 1943 1945 AAHS Journal Volume 40 Issue 3 1995 a b Betts 1992 p 74 a b Betts 1992 p 72 a b c d e Betts 1994 p 54 a b c Betts 1994 p 56 Wood Robert H ed June 13 1949 Shortlines Aviation Week Albany NY McGraw Hill p 49 Davies 2000 p 50 Hardy Air International February 1994 p 70 REGISTRATION DETAILS FOR N75385 QUAKER CITY AIRWAYS BOEING 307 STRATOLINER planelogger com Retrieved July 17 2022 a b Accident description for N75385 at the Aviation Safety Network Retrieved on May 5 2013 a b REGISTRATION DETAILS FOR F BHHR AIGLE AZUR EXTREME ORIENT BOEING 307 STRATOLINER planelogger com Retrieved July 17 2022 a b Hagedorn 1993 p 133 Hardy Air International February 1994 p 71 a b c d e f Betts 1994 p 58 a b c d e REGISTRATION DETAILS FOR XW TAA INTERNATIONAL CONTROL COMMISSIION BOEING 307 STRATOLINER planelogger com Retrieved July 17 2022 a b c d REGISTRATION DETAILS FOR XW TFR CAMBODGIA AIR COMMERCIAL BOEING 307 STRATOLINER planelogger com Retrieved July 17 2022 a b Accident description for F BHHR at the Aviation Safety Network Retrieved on May 5 2013 a b c d e REGISTRATION DETAILS FOR XW TFP CAMBODIA AC ROYAL AIR LAO BOEING 307 STRATOLINER planelogger com Retrieved July 17 2022 a b c d e REGISTRATION DETAILS FOR XW PGR CAMBODIA AC ROYAL AIR LAO BOEING 307 STRATOLINER planelogger com Retrieved July 17 2022 a b c REGISTRATION DETAILS FOR F BELZ AIRNAUTIC BOEING 307 STRATOLINER STRATOLINER planelogger com Retrieved July 17 2022 a b c Accident description for F BELZ at the Aviation Safety Network Retrieved on July 16 2022 Flight International April 12 1962 p 389 a b Accident description for XW PGR at the Aviation Safety Network Retrieved on July 16 2022 a b c d Accident description for F BELV at the Aviation Safety Network Retrieved on June 30 2015 a b c d e Wynn 2020 no page numbers in digital edition Accident description for XW TFR at the Aviation Safety Network Retrieved on September 15 2017 a b Accident description for XW TFP at the Aviation Safety Network Retrieved on July 16 2022 Civil Aeronautics Board Reports Vol 28 US 1958 Retrieved May 23 2020 Crash of a Boeing 307 Stratoliner near Madras Bureau of Aircraft Accidents Archives US May 10 1958 Retrieved May 23 2020 Profile for AREA Ecuador Archived from the original on March 4 2016 Retrieved January 27 2014 Accident statistics for Boeing 307 Aviation Safety Network Archived from the original on November 24 2013 Retrieved November 22 2013 Accident description for NX19901 at the Aviation Safety Network Retrieved on July 17 2022 Accident description for NC19905 at the Aviation Safety Network Retrieved on July 17 2022 Accident description for XW TFR at the Aviation Safety Network Retrieved on May 5 2013 Accident description for N19903 at the Aviation Safety Network Retrieved on July 18 2022 4 escape injury as historic Stratoliner ditches in Elliott Bay Archived October 23 2012 at the Wayback Machine Seattle Post Intelligencer original post Retrieved June 4 2012 Whitford Ellen Once More with Feeling Archived June 29 2011 at the Wayback Machine Boeing Frontiers Online September 2003 Retrieved January 28 2012 Mitcham Mary Lynn April 2005 It s a Boat It s a Plane It s Boating Vol 74 no 4 Bonnier Corporation p 36 Retrieved June 8 2017 Ginns Britten Elizabeth September 2004 Flying the Friendly Seas Power amp Motoryacht Archived from the original on July 12 2012 Retrieved June 8 2017 The Cosmic Muffin Comes to Aerospace Discovery at the Florida Air Museum Sun n Fun US October 19 2016 Archived from the original on January 31 2020 Retrieved February 1 2020 Juptner 1980 pp 102 104 a b c d e f g h Abel 1991 p 37 Hauet Andre Renard R 35 Un avion stratospherique belge en 1938 technique Aerostories in French Retrieved June 17 2022 Bibliography Editnone given 2022 Historical Snapshot Model 307 Stratoliner Boeing Boeing Abzug Malcolm J Larrabee E Eugene 2005 Airplane Stability and Control A History of the Technologies that Made Aviation Possible Cambridge UK Cambridge University Press ISBN 978 0521021289 Abel Drina Welch ed 1991 Paul Matt Scale Airplane Drawings Vol 1 Destin Florida Aviation Heritage Aviation Book Co p 37 ISBN 978 0943691046 Beall Wellwood E March 1945 Rebuilding the Boeing Stratoliners Aviation Vol 44 no 3 Albany NY McGraw Hill pp 148 151 Betts Ed November 1989 The La Guardia Airport 50 years TARPA Topics Belhaven NC the Active Retired Pilot s Association of TWA pp 66 75 Betts Ed August 1990 The Boeing Stratoliner 1935 thru 1940 TARPA Topics Belhaven NC the Active Retired Pilot s Association of TWA pp 55 74 Betts Ed February 1992 The Intercontinental Division TARPA Topics Belhaven NC the Active Retired Pilot s Association of TWA pp 59 85 Betts Ed 1993 The Boeing Stratoliners and TWA American Aviation Historical Society Journal 38 3 Betts Ed August 1994 The Boeing 307 Stratoliners 1945 1951 TARPA Topics Belhaven NC the Active Retired Pilot s Association of TWA pp 51 62 Bowers Peter M 1989 Boeing Aircraft since 1916 Third ed London Putnam ISBN 978 0851778044 Cartwright C M ed March 23 1939 Stratoliner Crash sets insured loss record in Aviation 500 000 Plane Covered for Full Replacement Cost Partly Reinsured Abroad The National Underwriter Vol 43 no 12 Chicago IL National Underwriter Co Davies R E G 1987 Pan Am an Airline and its Aircraft An illustrated history of the world s greatest airline and the airplanes that revolutionized air transport from 1927 to the present New York City Orion Books p 49 ISBN 978 0517566398 Davies R E G 2000 TWA an Airline and its Aircraft 75 years of pioneering progress McLean Virginia Paladwr Press ISBN 978 1888962161 De Wulf Herman September 1978 A Belgian Rare Avis Air International Vol 15 no 3 Bromley UK Fine Scroll pp 147 149 Dietrich Noah Thomas Bob 1972 Howard The Amazing Mr Hughes Greenwich Fawcett Publications p 148 ISBN 978 0449136522 Dijkstra Ronald 2016 Boeing 100 jaar 80 jaar samenwerking met de KLM Luchtvaart Historisch Tijdschrift LUCHTVAARTKENNIS en Aviation Historical Magazine AVIATION KNOWLEDGE in Dutch Vol 3 no 65 Holland Vereeniging ter Bevordering van de Luchtscheepvaart en Association for the Promotion of Aviation pp 75 82 ISSN 1381 9100 Ford Daniel March April 2004 First and Last Strat Boeing s Model 307 and its Survivors Air Enthusiast Vol 110 pp 54 60 ISSN 0143 5450 Gardner Lester D ed November 1940 News Review Journal of the Aeronautical Sciences Aeronautical Review Section Easton Pennsylvania Institute of the Aeronautical Sciences 8 1 9 10 doi 10 2514 8 10434 Haddow G W Grosz Peter M 1962 The German Giants The Story of the R planes 1914 1919 London Putman Hagedorn Daniel P 1993 Central American and Caribbean Air Forces Kent UK Air Britain Historians p 133 ISBN 978 0851302102 McLarren Robert July 1938 The Plane on the cover Model Airplane News Vol 9 no 1 Mount Morris IL Jay Publishing pp 31 amp 40 Hardy Michael John 1982 Boeing World Aircraft NY Beaufort Books p 30 ISBN 978 0850595079 Hardy Mike January 2004 The Stratoliner Story Part 1 Air International Vol 46 no 1 pp 21 24 ISSN 0306 5634 Hardy Mike February 2004 The Stratoliner Story Part 2 Air International Vol 46 no 2 pp 69 72 ISSN 0306 5634 Juptner Joseph P 1980 US Civil Aircraft Vol 8 ATC 701 800 Aero Publishers pp 75 77 amp 102 104 ISBN 978 0816891788 Marrett George J 2004 Howard Hughes aviator Annapolis Naval Institute Press ISBN 978 1591145103 Minshall R J May 1940 Into the Sub Stratosphere Aviation pp 47 49 External links Edit Wikimedia Commons has media related to Boeing 307 T amp WA promotional video with footage of Stratoliner Retrieved from https en wikipedia org w index php title Boeing 307 Stratoliner amp oldid 1163380423, wikipedia, wiki, book, books, library,

article

, read, download, free, free download, mp3, video, mp4, 3gp, jpg, jpeg, gif, png, picture, music, song, movie, book, game, games.