The Boeing YB-40 Flying Fortress was a modification for operational testing purposes of the B-17 Flying Fortressbomber aircraft, converted to act as a heavily armed gunship to support other bombers during World War II. At the time of its development, long-range fighter aircraft such as the North American P-51 Mustang were just entering quantity production, and thus were not yet available to accompany bombers all the way from England to Germany and back.
YB-40 Flying Fortress
The prototype XB-40 was a Boeing B-17F modified by Lockheed Vega (Project V-139) by converting the second production B-17F-1-BO (s/n 41-24341).
Close-up of the array of .50-caliber guns on the Boeing YB-40 Flying Fortress.
Work on the prototype, Project V-139, began in September 1942 by converting the second production B-17F-1-BO (serial number 41-24341) built. Conversion work was done by Lockheed's Vega company.
The aircraft differed from the standard B-17 in that a second manned dorsal turret was installed in the former radio compartment, just behind the bomb bay and forward of the ventral ball turret's location. The single .50-caliber light-barrel (12.7 mm) Browning machine gun at each waist station was replaced by two of them mounted side by side as a twin-mount emplacement, with a mount for each pair of these being very much like the tail gun setup in general appearance. The bombardier's equipment was also replaced by two .50-caliber light-barrel Browning AN/M2 machine guns in a remotely operated Bendix designed "chin"-location turret, directly beneath the bombardier's location in the extreme nose.[1]
The existing "cheek" machine guns (on the sides of the forward fuselage at the bombardier station), initially removed from the configuration, were restored in England to provide a total of 16 guns, and the bomb bay was converted to an ammunition magazine. Additional armor plating was installed to protect crew positions.[1]
The aircraft's gross weight was some 4,000 lb (1,800 kg) greater than a fully armed B-17. An indication of the burden this placed on the YB-40 is that while the B-17F on which it was based was rated to climb to 20,000 ft (6,100 m) in 25 minutes, the YB-40 was rated at 48 minutes. Part of the decreased performance was due to the weight increase, and part was due to the greater aerodynamic drag of the gun stations.[2]
The first flight of the XB-40 was on 10 November 1942. The first order of 13 YB-40s was made in October 1942. A follow-up order for 12 more was made in January 1943. The modifications were performed by Douglas Aircraft at their Tulsa, Oklahoma center, and the first aircraft were completed by the end of March 1943. Twenty service test aircraft were ordered, Vega Project V-140, as YB-40 along with four crew trainers designated TB-40.[2]
Because Vega had higher priority production projects, the YB-40/TB-40 assembly job was transferred to Douglas. A variety of different armament configurations was tried. Some YB-40s were fitted with four-gun nose and tail turrets. Some carried cannon of up to 40 mm in caliber, and a few carried up to as many as 30 guns of various calibers in multiple hand-held positions in the waist as well as in additional power turrets above and below the fuselage.[1]
Externally, the XB-40 had the symmetrical waist windows of the standard B-17F and the second dorsal turret integrated into a dorsal fairing. In contrast, most of the YB-40s had the positions of the waist windows staggered for better freedom of movement for the waist gunners, and the aft dorsal turret was moved slightly backwards so that it stood clear of the dorsal fairing.[2]
Operational history
World War II emblem of the 327th Bombardment Squadron, featuring characters (Alley Oop and Dinny) from the Alley Oop comic strip
The YB-40's mission was to provide a heavily armed escort capable of accompanying bombers all the way to the target and back. Of the initial order of 13, one (serial 43-5732) was lost on the delivery flight from Iceland to the UK in May 1943; it force-landed in a peat bog on a Scottish island after running out of fuel. Although removed to Stornoway and repaired, it never flew in combat. The remaining 12 were allocated to the 92d Bombardment Group (Heavy), being assigned to the 327th Bombardment Squadron, stationed at RAF Alconbury (AAF-102) on 8 May 1943.
YB-40s flew in the following operational missions:
29 May 1943 – attacked submarine pens and locks at Saint-Nazaire. Smaller strikes were made at Rennes naval depot and U-boat yards at La Pallice. In the attack, seven YB-40s were dispatched to Saint-Nazaire; they were unable to keep up with B-17s on their return from the target and modification of the waist and tail gun feeds and ammunition supplies was found to be needed. The YB-40s were sent to Technical Service Command at the Abbots Ripton 2nd Strategic Air Depot for modifications.
15 June 1943 – four YB-40s were dispatched from Alconbury in a raid on Le Mans after completion of additional modifications.
22 June 1943 – attack on the I.G. Farben synthetic rubber plant at Hüls. The plant, representing a large percentage of the Germany's synthetic rubber producing capacity, was severely damaged. In the raid, 11 YB-40s were dispatched; aircraft 42-5735 was lost, being first damaged by flak and later shot down by a Focke-Wulf Fw 190A-2 of JG 1 over Pont, Germany. The 10 crew members survived and were taken prisoner.
25 June 1943 – attack on Blohm & Voss U-boat machine shops at Oldenburg. This was the secondary target, as the primary at Hamburg was obscured by clouds. In this raid, seven YB-40s were dispatched, of which two aborted. Two German aircraft were claimed as destroyed.
26 June 1943 – scheduled but aborted participation in attack on the Luftwaffe air depot at Villacoublay, France (primary target) and also the Luftwaffe airfield at Poissy, France. The five YB-40s assigned to the attack were unable to form up with the bombing squadron, and returned to base.
28 June 1943 – attack on the U-boat pens at Saint-Nazaire. In the raid, the only serviceable lock entrance to the pens was destroyed. In this attack, six YB-40s were dispatched, and one German aircraft was claimed as destroyed.
29 June 1943 – scheduled participation in attack on the Luftwaffe air depot at Villacoublay, but aircraft returned to Alconbury due to clouds obscuring the target. In the raid, two YB-40s dispatched, one aborted.
4 July 1943 – attacks on aircraft factories at Nantes and Le Mans, France. In these raids, two YB-40s were dispatched to Nantes and one to Le Mans.
10 July 1943 – attack on Caen/Carpiquet airfield. In this raid, five YB-40s were dispatched.
14 July 1943 – attacked Luftwaffe air depot at Villacoublay. In this raid, five YB-40s were dispatched.
17 July 1943 – YB-40s recalled from a raid on Hannover due to bad weather. In this raid, two YB-40s were dispatched.
24 July 1943 – YB-40s recalled from an attack on Bergen, Norway due to cloud cover. In this raid, one YB-40 was dispatched.
28 July 1943 – attack on the Fieseler aircraft factory at Kassel. In this raid, two YB-40s were dispatched.
29 July 1943 – attack on U-boat yards at Kiel. In this raid, two YB-40s were dispatched.
Summary
Boeing YB-40 Flying Fortress, 42-5736 ("Tampa Tornado") on display at RAF Kimbolton, England, 2 October 1943 when it was shown to those attending a party for local children.
Altogether of the 59 aircraft dispatched, 48 sorties were credited. Five confirmed and two probable German fighter kills were claimed, and one YB-40 was lost, shot down on 22 June mission to Hüls, Germany. Tactics were revised on the final five missions by placing a pair of YB-40s in the lead element of the strike to protect the mission commander.
The original design concept of the YB-40 never played out as intended in practice. Luftwaffe fighter chief Adolf Galland considered the gunship's handful of combat victories to be "insignificant" and not worth the cost of the aircraft.[3] The increased weight from the additional machine guns and ammunition nearly cut the YB-40's climb rate in half from that of a B-17F, and in level flight it had difficulty keeping up with standard Flying Fortresses, especially after they had dropped their bombs. Despite the overall failure of the project as an operational aircraft, it led directly to the Bendix chin turret's fitment on the last 65 (86 according to some sources)[4] Douglas-built aircraft starting with the B-17F-70-DL production block,[5][note 1] and were part of the standardized modifications conspicuous on the final production variant of the B-17, the B-17G:
Chin turret (first introduced on the last 86 Douglas-built "final production" blocks of the B-17F-DL aircraft)
Offset waist gun positions
Improved tail gunner station with much larger windows, usually nicknamed the "Cheyenne", after the Cheyenne Modification Center.
Once the test program ended, most of the surviving aircraft returned to the U.S. in November 1943 and were used as trainers. 42-5736 ("Tampa Tornado") was flown to RAF Kimbolton on 2 October 1943 where it was put on display and later used as a group transport. It was returned to the United States on 28 March 1944. All of the aircraft were sent to reclamation, mostly at RFC Ontario in May 1945, being broken up and smelted. A couple of the YB-40s can be seen in the 1946 movie The Best Years of Our Lives, in the famous scene shot at the Ontario "graveyard". No airframes were sold on the civil market.
YB-40: Conversions of B-17F-35-VEs 42-5920, 5921, 5923, 5924, 5925, and 5927 (Not deployed to ETO)
TB-40: Conversions of B-17F-25-VEs 42-5833 and 5834; B-17F-30-VE 42-5872, and B-17F-35-VE 42-5926 (5833 deployed to ETO, but not used in combat; remainder stayed in the United States).
^Lyman, Troy (12 May 2003). "B17 — Queen of the Sky — The B-17F". b17queenofthesky.com. Troy Lyman's B-17 Flying Fortress Site. Retrieved 24 June 2014. "...factories were trying to fine a more effective solution to the B-17's lack of forward firepower...This solution was the Bendex Chin Turret. This turret had originally been used on the YB-40 gunship project. While this experiment proved unsuccessful, the chin turret was found to be a major improvement to the B-17's forward firepower. This turret was fitted to the last eighty-six B-17Fs to come off the Douglas assembly line starting with block B-17F-75-DL.
^"B-17F-70-DL: 42-3483 to 42-3503 | Production-block | B-17 Bomber Flying Fortress – The Queen Of The Skies" (in German). Retrieved 6 November 2020.
^"42-3492 / Paper Doll | B-17 Bomber Flying Fortress – The Queen Of The Skies" (in German). Retrieved 13 November 2020.
^Drury, Bob; Clavin, Tom (September 2016). "Suicide Run: The Final Flight of Old 666". HistoryNet.com. World History Group. Retrieved 29 October 2019.
Bibliography
Bishop, Cliff T. Fortresses of the Big Triangle First. Elsenham, UK: East Anglia Books, 1986. ISBN1-869987-00-4.
Freeman, Roger A. The Mighty Eighth War Diary. St. Paul, Minnesota: Motorbooks International, 1990. ISBN0-87938-495-6.
Freeman, Roger A. The Mighty Eighth War Manual. St. Paul, Minnesota: Motorbooks International, 1991. ISBN0-87938-513-8.
Galland, Adolf. The First and the Last: Germany's Fighter Force in WWII (Fortunes of War). South Miami, Florida: Cerberus Press, 2005. ISBN1-84145-020-0.
Levine, Alan J. The Strategic Bombing of Germany, 1940–1945. Westport, Connecticut: Praeger, 1992. ISBN0-275-94319-4.
External links
Wikimedia Commons has media related to Boeing YB-40.
The YB-40 gunship was both more and less than planners expected
August 21, 2023
boeing, flying, fortress, modification, operational, testing, purposes, flying, fortress, bomber, aircraft, converted, heavily, armed, gunship, support, other, bombers, during, world, time, development, long, range, fighter, aircraft, such, north, american, mu. The Boeing YB 40 Flying Fortress was a modification for operational testing purposes of the B 17 Flying Fortress bomber aircraft converted to act as a heavily armed gunship to support other bombers during World War II At the time of its development long range fighter aircraft such as the North American P 51 Mustang were just entering quantity production and thus were not yet available to accompany bombers all the way from England to Germany and back YB 40 Flying FortressThe prototype XB 40 was a Boeing B 17F modified by Lockheed Vega Project V 139 by converting the second production B 17F 1 BO s n 41 24341 Role Bomber escortBuilt by Lockheed VegaFirst flight 10 November 1942Introduction 29 May 1943Retired October 1943Primary user United States Army Air ForcesNumber built 25Developed from Boeing B 17 Flying Fortress Contents 1 Design and development 2 Operational history 2 1 Summary 3 Operators 4 Specifications YB 40 5 See also 6 References 6 1 Notes 6 2 Citations 6 3 Bibliography 7 External linksDesign and development Close up of the array of 50 caliber guns on the Boeing YB 40 Flying Fortress Work on the prototype Project V 139 began in September 1942 by converting the second production B 17F 1 BO serial number 41 24341 built Conversion work was done by Lockheed s Vega company The aircraft differed from the standard B 17 in that a second manned dorsal turret was installed in the former radio compartment just behind the bomb bay and forward of the ventral ball turret s location The single 50 caliber light barrel 12 7 mm Browning machine gun at each waist station was replaced by two of them mounted side by side as a twin mount emplacement with a mount for each pair of these being very much like the tail gun setup in general appearance The bombardier s equipment was also replaced by two 50 caliber light barrel Browning AN M2 machine guns in a remotely operated Bendix designed chin location turret directly beneath the bombardier s location in the extreme nose 1 The existing cheek machine guns on the sides of the forward fuselage at the bombardier station initially removed from the configuration were restored in England to provide a total of 16 guns and the bomb bay was converted to an ammunition magazine Additional armor plating was installed to protect crew positions 1 The aircraft s gross weight was some 4 000 lb 1 800 kg greater than a fully armed B 17 An indication of the burden this placed on the YB 40 is that while the B 17F on which it was based was rated to climb to 20 000 ft 6 100 m in 25 minutes the YB 40 was rated at 48 minutes Part of the decreased performance was due to the weight increase and part was due to the greater aerodynamic drag of the gun stations 2 The first flight of the XB 40 was on 10 November 1942 The first order of 13 YB 40s was made in October 1942 A follow up order for 12 more was made in January 1943 The modifications were performed by Douglas Aircraft at their Tulsa Oklahoma center and the first aircraft were completed by the end of March 1943 Twenty service test aircraft were ordered Vega Project V 140 as YB 40 along with four crew trainers designated TB 40 2 Because Vega had higher priority production projects the YB 40 TB 40 assembly job was transferred to Douglas A variety of different armament configurations was tried Some YB 40s were fitted with four gun nose and tail turrets Some carried cannon of up to 40 mm in caliber and a few carried up to as many as 30 guns of various calibers in multiple hand held positions in the waist as well as in additional power turrets above and below the fuselage 1 Externally the XB 40 had the symmetrical waist windows of the standard B 17F and the second dorsal turret integrated into a dorsal fairing In contrast most of the YB 40s had the positions of the waist windows staggered for better freedom of movement for the waist gunners and the aft dorsal turret was moved slightly backwards so that it stood clear of the dorsal fairing 2 Operational history World War II emblem of the 327th Bombardment Squadron featuring characters Alley Oop and Dinny from the Alley Oop comic stripThe YB 40 s mission was to provide a heavily armed escort capable of accompanying bombers all the way to the target and back Of the initial order of 13 one serial 43 5732 was lost on the delivery flight from Iceland to the UK in May 1943 it force landed in a peat bog on a Scottish island after running out of fuel Although removed to Stornoway and repaired it never flew in combat The remaining 12 were allocated to the 92d Bombardment Group Heavy being assigned to the 327th Bombardment Squadron stationed at RAF Alconbury AAF 102 on 8 May 1943 YB 40s flew in the following operational missions 29 May 1943 attacked submarine pens and locks at Saint Nazaire Smaller strikes were made at Rennes naval depot and U boat yards at La Pallice In the attack seven YB 40s were dispatched to Saint Nazaire they were unable to keep up with B 17s on their return from the target and modification of the waist and tail gun feeds and ammunition supplies was found to be needed The YB 40s were sent to Technical Service Command at the Abbots Ripton 2nd Strategic Air Depot for modifications 15 June 1943 four YB 40s were dispatched from Alconbury in a raid on Le Mans after completion of additional modifications 22 June 1943 attack on the I G Farben synthetic rubber plant at Huls The plant representing a large percentage of the Germany s synthetic rubber producing capacity was severely damaged In the raid 11 YB 40s were dispatched aircraft 42 5735 was lost being first damaged by flak and later shot down by a Focke Wulf Fw 190A 2 of JG 1 over Pont Germany The 10 crew members survived and were taken prisoner 25 June 1943 attack on Blohm amp Voss U boat machine shops at Oldenburg This was the secondary target as the primary at Hamburg was obscured by clouds In this raid seven YB 40s were dispatched of which two aborted Two German aircraft were claimed as destroyed 26 June 1943 scheduled but aborted participation in attack on the Luftwaffe air depot at Villacoublay France primary target and also the Luftwaffe airfield at Poissy France The five YB 40s assigned to the attack were unable to form up with the bombing squadron and returned to base 28 June 1943 attack on the U boat pens at Saint Nazaire In the raid the only serviceable lock entrance to the pens was destroyed In this attack six YB 40s were dispatched and one German aircraft was claimed as destroyed 29 June 1943 scheduled participation in attack on the Luftwaffe air depot at Villacoublay but aircraft returned to Alconbury due to clouds obscuring the target In the raid two YB 40s dispatched one aborted 4 July 1943 attacks on aircraft factories at Nantes and Le Mans France In these raids two YB 40s were dispatched to Nantes and one to Le Mans 10 July 1943 attack on Caen Carpiquet airfield In this raid five YB 40s were dispatched 14 July 1943 attacked Luftwaffe air depot at Villacoublay In this raid five YB 40s were dispatched 17 July 1943 YB 40s recalled from a raid on Hannover due to bad weather In this raid two YB 40s were dispatched 24 July 1943 YB 40s recalled from an attack on Bergen Norway due to cloud cover In this raid one YB 40 was dispatched 28 July 1943 attack on the Fieseler aircraft factory at Kassel In this raid two YB 40s were dispatched 29 July 1943 attack on U boat yards at Kiel In this raid two YB 40s were dispatched Summary Boeing YB 40 Flying Fortress 42 5736 Tampa Tornado on display at RAF Kimbolton England 2 October 1943 when it was shown to those attending a party for local children Altogether of the 59 aircraft dispatched 48 sorties were credited Five confirmed and two probable German fighter kills were claimed and one YB 40 was lost shot down on 22 June mission to Huls Germany Tactics were revised on the final five missions by placing a pair of YB 40s in the lead element of the strike to protect the mission commander The original design concept of the YB 40 never played out as intended in practice Luftwaffe fighter chief Adolf Galland considered the gunship s handful of combat victories to be insignificant and not worth the cost of the aircraft 3 The increased weight from the additional machine guns and ammunition nearly cut the YB 40 s climb rate in half from that of a B 17F and in level flight it had difficulty keeping up with standard Flying Fortresses especially after they had dropped their bombs Despite the overall failure of the project as an operational aircraft it led directly to the Bendix chin turret s fitment on the last 65 86 according to some sources 4 Douglas built aircraft starting with the B 17F 70 DL production block 5 note 1 and were part of the standardized modifications conspicuous on the final production variant of the B 17 the B 17G Chin turret first introduced on the last 86 Douglas built final production blocks of the B 17F DL aircraft Offset waist gun positions Improved tail gunner station with much larger windows usually nicknamed the Cheyenne after the Cheyenne Modification Center Once the test program ended most of the surviving aircraft returned to the U S in November 1943 and were used as trainers 42 5736 Tampa Tornado was flown to RAF Kimbolton on 2 October 1943 where it was put on display and later used as a group transport It was returned to the United States on 28 March 1944 All of the aircraft were sent to reclamation mostly at RFC Ontario in May 1945 being broken up and smelted A couple of the YB 40s can be seen in the 1946 movie The Best Years of Our Lives in the famous scene shot at the Ontario graveyard No airframes were sold on the civil market Operators United StatesUnited States Army Air ForcesXB 40 Conversion of B 17F 1 BO 41 24342 Not deployed to ETO YB 40 Conversions of B 17F 10 VE 42 5732 5733 Peoria Prowler 5734 Seymour Angel 5735 Wango Wango 5736 Tampa Tornado 5737 Dakota Demon 5738 Boston Tea Party 5739 Lufkin Ruffian 5740 Monticello 5741 Chicago 5742 Plain Dealing Express 5743 Woolaroc 5744 Dollie Madison All deployed to ETO YB 40 Conversions of B 17F 35 VEs 42 5920 5921 5923 5924 5925 and 5927 Not deployed to ETO TB 40 Conversions of B 17F 25 VEs 42 5833 and 5834 B 17F 30 VE 42 5872 and B 17F 35 VE 42 5926 5833 deployed to ETO but not used in combat remainder stayed in the United States Specifications YB 40 Data from citation needed General characteristicsCrew 10 Length 74 ft 9 in 22 6 m Wingspan 103 ft 9 in 31 4 m Height 19 ft 1 in 5 8 m Wing area 1 527 sq ft 141 9 m2 Empty weight 54 900 lb 24 900 kg Gross weight 63 500 lb 28 800 kg Max takeoff weight 74 000 lb 33 565 kg Powerplant 4 Wright R 1820 65 Cyclone turbosupercharged radial engines 1 200 hp 895 kW eachPerformance Maximum speed 292 mph 470 km h 254 kn Cruise speed 196 mph 315 km h 170 kn Range 2 260 mi 3 640 km 1 960 nmi Service ceiling 29 200 ft 8 900 m Rate of climb 416 ft min 2 11 m s Wing loading 47 2 lb sq ft 231 kg m2 Power mass 0 066 hp lb 0 11 kW kg Armament Guns 18 or more 50 in 12 7 mm M2 Browning machine guns Typically used 14 16 with room for up to 30 citation needed Ammunition carried citation needed Location RoundsNose 2 200Front top turret 2 500Aft top turret 3 300Ball turret 300Waist guns 1 200Tail guns 1 200Total 10 700See alsoRelated development Consolidated XB 41 Liberator Old 666 a modified B 17E Flying Fortress based in New Guinea that had a total of nineteen 50 caliber machine guns installed 7 ReferencesNotes Most sources say that the turret was introduced on the B 17F 75 DL but photographic evidence indicates that the F 70 DL also had the turret 6 Citations a b c Bishop 1986 pp 69 73 246 247 a b c Freeman 1991 pp 154 155 Levine 1992 p 90 Lyman Troy 12 May 2003 B17 Queen of the Sky The B 17F b17queenofthesky com Troy Lyman s B 17 Flying Fortress Site Retrieved 24 June 2014 factories were trying to fine a more effective solution to the B 17 s lack of forward firepower This solution was the Bendex Chin Turret This turret had originally been used on the YB 40 gunship project While this experiment proved unsuccessful the chin turret was found to be a major improvement to the B 17 s forward firepower This turret was fitted to the last eighty six B 17Fs to come off the Douglas assembly line starting with block B 17F 75 DL B 17F 70 DL 42 3483 to 42 3503 Production block B 17 Bomber Flying Fortress The Queen Of The Skies in German Retrieved 6 November 2020 42 3492 Paper Doll B 17 Bomber Flying Fortress The Queen Of The Skies in German Retrieved 13 November 2020 Drury Bob Clavin Tom September 2016 Suicide Run The Final Flight of Old 666 HistoryNet com World History Group Retrieved 29 October 2019 Bibliography Bishop Cliff T Fortresses of the Big Triangle First Elsenham UK East Anglia Books 1986 ISBN 1 869987 00 4 Freeman Roger A The Mighty Eighth War Diary St Paul Minnesota Motorbooks International 1990 ISBN 0 87938 495 6 Freeman Roger A The Mighty Eighth War Manual St Paul Minnesota Motorbooks International 1991 ISBN 0 87938 513 8 Galland Adolf The First and the Last Germany s Fighter Force in WWII Fortunes of War South Miami Florida Cerberus Press 2005 ISBN 1 84145 020 0 Levine Alan J The Strategic Bombing of Germany 1940 1945 Westport Connecticut Praeger 1992 ISBN 0 275 94319 4 External links Wikimedia Commons has media related to Boeing YB 40 YB 40 Gun Ship Completes a Successful Mission USAF Factsheet Boeing YB 40 Flying Fortress The YB 40 gunship was both more and less than planners expected Retrieved from https en wikipedia org w index php title Boeing YB 40 Flying Fortress amp oldid 1114534231, wikipedia, wiki, book, books, library,
