Bell YOH-4

Infobox Aircraft
name= YHO-4 / YOH-4


caption= YOH-4A LOH in flight
type= Observation/scout helicopter
national origin = United States
manufacturer= Bell Helicopter
first flight= 8 December 1962cite web|url=http://www.webcitation.org/5J1mlLyeb|title=Bell 206 JetRanger|author=Johan Visschedijk
date=16 October 2003]
introduced=
retired=
status=
primary user= United States Army
more users=
produced=
number built= 5
developed from=
variants with their own articles= Bell 206

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 reopended the LOH competition, and the 206A-based OH-58 Kiowa was selected.

Development

In October 1960, the Army submitted a request for proposals (RFP) for the Light Observation Helicopter (LOH). Bell, along with 12 other manufacturers (including Fairchild-Hiller and Hughes Tool Co. Aircraft Division), entered the competition. [cite web|url=http://www.webcitation.org/5JRs1SFaO|title=The Cessna CH-1 Helicopter|author=Steve Remington|publisher=CollectAir (commercemarketplace.com)|work=|date=] In January 1961, Bell proposed their Model 206 design,cite web|url=http://www.vtol.org/History.htm#_Toc486998807|title=US and Russian Helicopter Development In the 20th Century|author=Michael J. Hirschberg and David K. Daley|date=7 July 2000|publisher= [http://www.vtol.org American Helicopter Society] |accessdate=2007-04-20] which was selected out of the design phase of the Navy-run competition by the Armycite paper|title=George A. Spangenberg Oral History|author=George A. Spangenberg, edited by Judith Spangenberg-Currier|url=http://www.georgespangenberg.com/gasoralhistory.pdf|format=pdf pp.187-190|publisher=www.spangenberg.org ] and designated as the YHO-4A.cite web|url=http://www.webcitation.org/5J1lvgxQH|title=U.S Army Aircraft Acquisition Programs|work=Uncommon Aircraft 2006|author=Robert Beechy|date=18 November 2005] [cite web|url=http://www.globalsecurity.org/military/systems/aircraft/rotary-desig.htm|title=Rotary Aircraft Designation Crosswalk|publisher=GlobalSecurity.org]

Bell produced 5 prototypes in 1962 to submit to the Army for the Test and Evaluation phase, 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 as YOH-4A. During the flight testing phase, the power problems of the YOH-4A eliminated it from consideration for selection.Verify source|date=April 2008

After the failed military contract bid, Bell attempted to market the Model 206, but it didn't fare well at all commercially. Bell's market research showed that customers found the body design mostly unpalatable. Bell redesigned the body of the airframe to a more sleek and aesthetic design and reintroduced it as the Bell 206A JetRanger, and Bell found they had a commercial success on their hands. [cite web|url=http://www.webcitation.org/5J1n1TMLZ|title=American Helicopter Museum: Bell 206 JetRanger]

In 1967, the Army reopened the LOH competition for bids because Hughes Helicopters couldn't meet the contractual production demands.Fact|date=February 2007 Bell resubmitted for the program using the Model 206A.LOH Lot 2] Fairchild-Hiller did not resubmit their bid with the YOH-5A, which they had somewhat-successfully marketed as the FH-1100. In the end, Bell underbid Hughes to win the contract and the Bell 206A was designated as the OH-58A.

Variants

;YHO-4:Bell 206 powered by a 250shp T63-A-5 for Army evaluation, five built later re-designated YOH-4A;YOH-4A:YHO-4s re-designated.

Operators

;USA
* United States Army

pecifications (OH-4A)

aircraft specifications
plane or copter?=copter
jet or prop?=prop

ref= U.S. Army Aircraft Since 1947 [cite book |last=Harding |first=Stephen |title=U.S. Army Aircraft Since 1947 |year=1997 |publisher=Schiffer Publishing Ltd. |location=Atglen, PA, USA |isbn=96-69996 |pages=42 ]

crew= 1 pilot, up to 3 passengers or 2 stretchers
span main= 33 ft 3 in
span alt= m
length main= 38 ft 8 in
length alt= m
height main= 8 ft 10 in
height alt= m
empty weight main= 1,536 lb
empty weight alt= kg
loaded weight main=
loaded weight alt=
max takeoff weight main= 2,537 lb
max takeoff weight alt= kg
more general=

engine (prop)= Allison T63-A-5
type of prop= turboshaft
number of props= 1
power main= 250 shp
power alt= 6 kW

max speed main= knots
max speed alt= 135 mph, km/h
cruise speed main= knots
cruise speed alt= 111 mph, km/h
range main= 283 mi
range alt=
ceiling main= 20,000 ft
ceiling alt=
climb rate main=
climb rate alt=
loading main=
loading alt=
power/mass main=
power/mass alt=

armament=

ee also

aircontent
related=
* Bell 206
* OH-58 Kiowa

similar aircraft=
* Fairchild Hiller YOH-5
* OH-6 Cayuse

lists=
* List of active United States military aircraft

see also=
* U.S. Helicopter Armament Subsystems

References

External links

* [http://www.globalsecurity.org/military/systems/aircraft/oh-4.htm HO-4/OH-4 page on GlobalSecurity.org]