During 1946, Bell Helicopter began development of a new utility helicopter, the Model 42, much larger than the Model 47, which utilized a scaled-up version of the Model 47's rotor system. Three prototypes were built, but serious rotor problems and complexity of mechanical systems precluded production. The initial Model 42 variant was civilian, but the United States Air Force ordered the development of its military variant, the Model 48. Two prototypes were ordered as the XR-12, powered by a single 540 hp (403 kW) Pratt & Whitney R-1340-AN-1radial engine and featuring seating for five. Of very similar construction to the Model 42, the Model 48 had a shorter rotor mast. A production batch of 34 helicopters was ordered, under the designation R-12A, but cancelled in 1947.[1]
Another enlarged prototype (the XR-12B, Model 48A) with seats for eight plus two pilots and a more powerful 600 hp (447 kW) Pratt & Whitney R-1340-55 engine was also ordered, followed by ten pre-series YR-12B helicopters, with a glazed nose, instead of the car-like nose of the Model 42 and XR-12. While under flight test the helicopter was redesignated the H-12, but the results were not satisfactory, as there were major problems with the main rotor due to blade weaving and poor rotor governor performance.[1]
Operational historyedit
No production H-12 aircraft were built but the prototypes and preproduction aircraft were used for various test and development programs.[1]
Variantsedit
Model 42
Bell's initial foray into the civilian luxury helicopter market, seating five. Three prototypes were built but serious problems precluded production.
Model 48
Company designation for the military version of the Model 42, given the designation R-12. Two built as XR-12s and a production contract for 34 was cancelled in 1947.
Model 48A
The more powerful derivative of the Model 48 with a 600 hp engine and ten seats. One XR-12B/XH-12B prototype was produced and a preproduction batch of ten were also built as YR-12B/YH-12Bs
XR-12
Prototype, redesignated XH-12, two built.
R-12A
Production version, 34 on order canceled.
XR-12B
Prototype with more powerful engine and increased seating, redesignated XH-12B, one built.
YR-12B
As XR-12B but with R-1340-55 engines, redesignated YH-12B, ten built.
^. aer.ita.br. Archived from the original on 24 December 2012. Retrieved 18 October 2014.
Bibliography
Andrade, John M. U.S.Military Aircraft Designation and Serials since 1909. Leicester, UK: Midland Counties Publications, 1979. ISBN0-904597-22-9.
The Illustrated Encyclopedia of Aircraft (Part Work 1982–1985). London, Orbis Publishing, 1985.
Pelletier, A.J. Bell Aircraft since 1935. London: Putnam & Company Ltd., 1992. ISBN1-55750-056-8.
External linksedit
Wikimedia Commons has media related to Bell 48.
Copter Ferry Hops To The Front – Popular Science (December 1950)
The Unknown Helicopter – Vertical
February 13, 2024
bell, bell, later, redesignated, company, model, american, 1940s, military, utility, helicopter, built, bell, helicopter, company, 12yh, 12brole, military, utility, helicoptermanufacturer, bell, aircraftfirst, flight, 1946status, productionprimary, user, unite. The Bell R 12 later redesignated H 12 company Model 48 was an American 1940s military utility helicopter built by the Bell Helicopter company 2 R 12 H 12YH 12BRole Military utility helicopterManufacturer Bell AircraftFirst flight 1946Status Pre productionPrimary user United States Air ForceNumber built 13 1 Contents 1 Design and development 2 Operational history 3 Variants 4 Operators 5 Specifications XR 12B 6 See also 7 References 8 External linksDesign and development editDuring 1946 Bell Helicopter began development of a new utility helicopter the Model 42 much larger than the Model 47 which utilized a scaled up version of the Model 47 s rotor system Three prototypes were built but serious rotor problems and complexity of mechanical systems precluded production The initial Model 42 variant was civilian but the United States Air Force ordered the development of its military variant the Model 48 Two prototypes were ordered as the XR 12 powered by a single 540 hp 403 kW Pratt amp Whitney R 1340 AN 1 radial engine and featuring seating for five Of very similar construction to the Model 42 the Model 48 had a shorter rotor mast A production batch of 34 helicopters was ordered under the designation R 12A but cancelled in 1947 1 Another enlarged prototype the XR 12B Model 48A with seats for eight plus two pilots and a more powerful 600 hp 447 kW Pratt amp Whitney R 1340 55 engine was also ordered followed by ten pre series YR 12B helicopters with a glazed nose instead of the car like nose of the Model 42 and XR 12 While under flight test the helicopter was redesignated the H 12 but the results were not satisfactory as there were major problems with the main rotor due to blade weaving and poor rotor governor performance 1 Operational history editNo production H 12 aircraft were built but the prototypes and preproduction aircraft were used for various test and development programs 1 Variants editModel 42 Bell s initial foray into the civilian luxury helicopter market seating five Three prototypes were built but serious problems precluded production Model 48 Company designation for the military version of the Model 42 given the designation R 12 Two built as XR 12s and a production contract for 34 was cancelled in 1947 Model 48A The more powerful derivative of the Model 48 with a 600 hp engine and ten seats One XR 12B XH 12B prototype was produced and a preproduction batch of ten were also built as YR 12B YH 12Bs XR 12 Prototype redesignated XH 12 two built R 12A Production version 34 on order canceled XR 12B Prototype with more powerful engine and increased seating redesignated XH 12B one built YR 12B As XR 12B but with R 1340 55 engines redesignated YH 12B ten built XH 12 XR 12 redesignated in 1947 XH 12B XR 12B redesignated in 1947 YH 12B YR 12B redesignated in 1947 1 Operators edit nbsp United StatesUnited States Air Force 3 Specifications XR 12B editData from Bell Aircraft since 1935 1 General characteristicsCrew one Capacity nine Length 56 ft 9 in 17 30 m Height 11 ft 3 25 in 3 4354 m Gross weight 6 286 lb 2 851 kg Powerplant 1 Pratt amp Whitney R 1340 55 Wasp 9 cyl air cooled radial piston engine 600 hp 450 kW Main rotor diameter 47 ft 6 in 14 48 m Main rotor area 1 772 sq ft 164 6 m2 Performance Maximum speed 105 mph 169 km h 91 kn Cruise speed 90 mph 140 km h 78 kn Range 300 mi 480 km 260 nmi Service ceiling 12 800 ft 3 900 m Service ceilingAbsolute ceiling 15 000 ft 4 572 m Hover ceiling 4 350 ft 1 326 m See also editRelated development Bell Model 47 Agusta Bell AB 102Aircraft of comparable role configuration and era Sikorsky H 19 ChickasawReferences editNotes a b c d e f Pelletier 1992 p 92 Pelletier 1992 p 91 Bell Model 48 aer ita br Archived from the original on 24 December 2012 Retrieved 18 October 2014 BibliographyAndrade John M U S Military Aircraft Designation and Serials since 1909 Leicester UK Midland Counties Publications 1979 ISBN 0 904597 22 9 The Illustrated Encyclopedia of Aircraft Part Work 1982 1985 London Orbis Publishing 1985 Pelletier A J Bell Aircraft since 1935 London Putnam amp Company Ltd 1992 ISBN 1 55750 056 8 External links edit nbsp Wikimedia Commons has media related to Bell 48 Copter Ferry Hops To The Front Popular Science December 1950 The Unknown Helicopter Vertical Retrieved from https en wikipedia org w index php title Bell H 12 amp oldid 1182769108, wikipedia, wiki, book, books, library,
