The Bell YOH-4 (originally YHO-4) was a single-engine, single-rotor light

helicopter A helicopter is a type of rotorcraft in which Lift (force), lift and thrust are supplied by horizontally spinning Helicopter rotor, rotors. This allows the helicopter to VTOL, take off and land vertically, to hover (helicopter), hover, and ...

, developed for the

United States Army The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...

Light Observation Helicopter The Light Observation Helicopter (LOH) program was a United States Army program to evaluate, develop and field a light scout helicopter to replace the Army's aging Bell OH-13 Sioux. It gained impetus with the advent of the Vietnam War, and was a ...

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 The Bell OH-58 Kiowa is a family of single-engine single-rotor military helicopters used for observation, utility, and direct fire support. It was produced by the American manufacturer Bell Helicopter and is closely related to the Model 206A ...

was selected.

Development

On 14 October 1960, the

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

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 Hiller Aircraft Corporation is an American private aerospace company, based in Firebaugh, California. It was founded in 1942 as Hiller Industries by Stanley Hiller to develop helicopters. History Stanley Hiller, then seventeen, established t ...

and Hughes Tool Co., Aircraft Division. In January 1961, Bell submitted Design 250 (D-250), which would eventually be designated as the ''YHO-4''.Beechy, Robert
"U.S Army Aircraft Acquisition Programs".
''Uncommon Aircraft 2006''. 18 November 2005. Accessed on 19 September 2006. On 19 May 1961, Bell and Hiller were announced as winners of the design competition.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. Oh4a001

Bell produced five prototypes of the D-250, as Model 206, in 1962, the first prototype making its maiden flight on 8 December 1962. 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''. The YOH-4A also became known as the ''Ugly Duckling'' in comparison to the other contending aircraft.Aastad, Andy
"The Introduction to the JetRanger".
''Rotor Magazine''. Helicopter Association International. Winter 2006-2007. Accessed on 5 April 2009. Following a flyoff of the Bell, Hughes and Fairchild-Hiller prototypes, the

Hughes OH-6 The Hughes OH-6 Cayuse is a single-engine light helicopter designed and produced by the American aerospace company Hughes Helicopters. Its formal name is derived from the Cayuse people, while its "Loach" nickname is derived from Light Observation ...

was selected in May 1965. 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.

Variants

;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

; *

Surviving aircraft

The remaining OH-4A ''62-4202'' is in storage at the

United States Army Aviation Museum The United States Army Aviation Museum is an aviation museum located on Fort Novosel near Daleville, Alabama. It has the largest collection of helicopters held by a museum in the world.Phillips 1992, p. 37.Purner 2004, p. 204. The museum feature ...

Fort Novosel Fort Rucker is a United States Army post located primarily in Dale County, Alabama, United States. It was formerly named in honor of Chief Warrant Officer Michael J. Novosel, an Army aviator and Medal of Honor recipient. It was previously name ...

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

.8 December 1962
/ref>

Specifications (OH-4A)

References

Notes

Citations

;Bibliography * Spenser, Jay P. "Bell Helicopter". ''Whirlybirds, A History of the U.S. Helicopter Pioneers''. University of Washington Press, 1998. .

External links

{{DEFAULTSORT:Bell Yoh-4 United States military helicopters 1960s United States military reconnaissance aircraft 1960s United States helicopters H-004, O Single-turbine helicopters Aircraft first flown in 1962