The Bell YOH-4 (originally YHO-4) was a single-engine, single-rotor light helicopter, developed for the United States Army's Light Observation Helicopter program. While the YOH-4A was unsuccessful in the original LOH competition, Bell redesigned it as the sleek Bell 206A JetRanger for the commercial market, and enjoyed instant and lasting success. In 1967, the Army reopened the LOH competition, and the 206A-based OH-58 Kiowa was selected.
On 14 October 1960, the United States Navy solicited responses from 25 aircraft manufacturers to a request for proposals (RFP) on behalf of the Army for the Light Observation Helicopter (LOH). Bell entered the competition along with 12 other manufacturers, including Hiller Aircraft and Hughes Tool Co., Aircraft Division.[3] In January 1961, Bell submitted Design 250 (D-250), which would eventually be designated as the YHO-4.[4] On 19 May 1961, Bell and Hiller were announced as winners of the design competition.[note 1][5]
YOH-4A LOH
Bell produced five prototypes of the D-250, as Model 206, in 1962, the first prototype making its maiden flight on 8 December 1962.[1] That same year, all aircraft began to be designated according to the new Joint Services designation system, so the prototype aircraft were redesignated YOH-4A.[1] The YOH-4A also became known as the Ugly Duckling in comparison to the other contending aircraft.[6] Following a flyoff of the Bell, Hughes and Fairchild-Hiller prototypes, the Hughes OH-6 was selected in May 1965.[7]
After the failed military contract bid, Bell attempted to market the Model 206, but it did not fare well commercially. Bell's market research showed that customers found the body design mostly unpalatable. Bell would eventually redesign the body of the airframe to a more sleek and aesthetic design and reintroduced it as the Bell 206A JetRanger.[8]
Variantsedit
OH-58 Kiowa
YHO-4
Bell 206 powered by a 250shp T63-A-5 for Army evaluation, five built later redesignated YOH-4A
^The Navy, which was assisting the Army in the selection phase, recommended the Hiller Model 1100, while the Army team preferred the Bell D-250, and then the 1100. The Selection Board accepted both aircraft for an evaluation test. Afterwards, the acting Army Chief of Staff directed the Selection Board to include the Hughes 369 in the fly-off competition.
Citationsedit
^ abcJohan Visschedijk (16 October 2003). . Archived from the original on September 14, 2006.
^ abHarding, Stephen (1997). U.S. Army Aircraft Since 1947. Atglen, PA, USA: Schiffer Publishing Ltd. p. 42. ISBN978-0-933424-53-1.
^Beechy, Robert. "U.S Army Aircraft Acquisition Programs". 2006-11-18 at the Wayback MachineUncommon Aircraft 2006. 18 November 2005. Accessed on 19 September 2006.
^Spangenberg, George A. George A. Spangenberg Oral History 2008-09-10 at the Wayback Machine. www.spangenberg.org. Judith Spangenberg-Currier, ed. pp.187-190. Accessed on 29 April 2008.
^Aastad, Andy. "The Introduction to the JetRanger". September 10, 2008, at the Wayback MachineRotor Magazine. Helicopter Association International. Winter 2006-2007. Accessed on 5 April 2009.
^Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.
Bibliography
Spenser, Jay P. "Bell Helicopter". Whirlybirds, A History of the U.S. Helicopter Pioneers. University of Washington Press, 1998. ISBN0-295-98058-3.
External linksedit
Wikimedia Commons has media related to Bell YOH-4.
HO-4/OH-4 page on GlobalSecurity.org
January 01, 1970
bell, originally, single, engine, single, rotor, light, helicopter, developed, united, states, army, light, observation, helicopter, program, while, unsuccessful, original, competition, bell, redesigned, sleek, bell, 206a, jetranger, commercial, market, enjoye. The Bell YOH 4 originally YHO 4 was a single engine single rotor light helicopter developed for the United States Army s Light Observation Helicopter program While the YOH 4A was unsuccessful in the original LOH competition Bell redesigned it as the sleek Bell 206A JetRanger for the commercial market and enjoyed instant and lasting success In 1967 the Army reopened the LOH competition and the 206A based OH 58 Kiowa was selected YHO 4 YOH 4 YOH 4A LOH in flight Role Observation scout helicopter National origin United States Manufacturer Bell Helicopter First flight 8 December 1962 1 Primary user United States Army Number built 5 2 Developed into Bell 206 JetRanger Contents 1 Development 2 Variants 3 Operators 4 Surviving aircraft 5 Specifications OH 4A 6 See also 7 References 7 1 Notes 7 2 Citations 8 External linksDevelopment editOn 14 October 1960 the United States Navy solicited responses from 25 aircraft manufacturers to a request for proposals RFP on behalf of the Army for the Light Observation Helicopter LOH Bell entered the competition along with 12 other manufacturers including Hiller Aircraft and Hughes Tool Co Aircraft Division 3 In January 1961 Bell submitted Design 250 D 250 which would eventually be designated as the YHO 4 4 On 19 May 1961 Bell and Hiller were announced as winners of the design competition note 1 5 nbsp YOH 4A LOH Bell produced five prototypes of the D 250 as Model 206 in 1962 the first prototype making its maiden flight on 8 December 1962 1 That same year all aircraft began to be designated according to the new Joint Services designation system so the prototype aircraft were redesignated YOH 4A 1 The YOH 4A also became known as the Ugly Duckling in comparison to the other contending aircraft 6 Following a flyoff of the Bell Hughes and Fairchild Hiller prototypes the Hughes OH 6 was selected in May 1965 7 After the failed military contract bid Bell attempted to market the Model 206 but it did not fare well commercially Bell s market research showed that customers found the body design mostly unpalatable Bell would eventually redesign the body of the airframe to a more sleek and aesthetic design and reintroduced it as the Bell 206A JetRanger 8 Variants edit nbsp OH 58 Kiowa YHO 4 Bell 206 powered by a 250shp T63 A 5 for Army evaluation five built later redesignated YOH 4A YOH 4A YHO 4s redesignated Operators edit nbsp United States United States ArmySurviving aircraft editThe remaining OH 4A 62 4202 is in storage at the United States Army Aviation Museum Fort Novosel Alabama 9 Specifications OH 4A editData from U S Army Aircraft Since 1947 2 General characteristicsCrew 1 pilot Capacity up to 3 passengers or 2 stretchers Length 38 ft 8 in 11 79 m Height 8 ft 10 in 2 69 m Empty weight 1 536 lb 697 kg Max takeoff weight 2 537 lb 1 151 kg Powerplant 1 Allison T63 A 5 turboshaft engine 250 shp 190 kW Main rotor diameter 33 ft 3 in 10 13 m Main rotor area 842 3 sq ft 78 25 m2 Blade section NACA 0012 mod 11 3 10 Performance Maximum speed 117 kn 135 mph 217 km h Cruise speed 96 kn 110 mph 178 km h Range 246 nmi 283 mi 456 km Service ceiling 20 000 ft 6 100 m See also editU S Helicopter Armament Subsystems Related development Bell 206 Bell OH 58 Kiowa Aircraft of comparable role configuration and era Fairchild Hiller YOH 5 Hughes OH 6 Cayuse Related lists List of active United States military aircraftReferences editNotes edit The Navy which was assisting the Army in the selection phase recommended the Hiller Model 1100 while the Army team preferred the Bell D 250 and then the 1100 The Selection Board accepted both aircraft for an evaluation test Afterwards the acting Army Chief of Staff directed the Selection Board to include the Hughes 369 in the fly off competition Citations edit a b c Johan Visschedijk 16 October 2003 Bell 206 JetRanger Archived from the original on September 14 2006 a b Harding Stephen 1997 U S Army Aircraft Since 1947 Atglen PA USA Schiffer Publishing Ltd p 42 ISBN 978 0 933424 53 1 Remington Steve The Cessna CH 1 Helicopter CollectAir com Beechy Robert U S Army Aircraft Acquisition Programs Archived 2006 11 18 at the Wayback Machine Uncommon Aircraft 2006 18 November 2005 Accessed on 19 September 2006 Spangenberg George A George A Spangenberg Oral History Archived 2008 09 10 at the Wayback Machine www spangenberg org Judith Spangenberg Currier ed pp 187 190 Accessed on 29 April 2008 Aastad Andy The Introduction to the JetRanger Archived September 10 2008 at the Wayback Machine Rotor Magazine Helicopter Association International Winter 2006 2007 Accessed on 5 April 2009 Spenser 1998 p 263 American Helicopter Museum Bell 206 JetRanger Archived from the original on 2006 10 02 Retrieved 2009 06 28 8 December 1962 Lednicer David The Incomplete Guide to Airfoil Usage m selig ae illinois edu Retrieved 16 April 2019 Bibliography Spenser Jay P Bell Helicopter Whirlybirds A History of the U S Helicopter Pioneers University of Washington Press 1998 ISBN 0 295 98058 3 External links edit nbsp Wikimedia Commons has media related to Bell YOH 4 HO 4 OH 4 page on GlobalSecurity org Retrieved from https en wikipedia org w index php title Bell YOH 4 amp oldid 1211915531, wikipedia, wiki, book, books, library,
