View source for Bell YOH-4

{{Short description|Light helicopter}}
<!-- This article is a part of [[Wikipedia:WikiProject Aircraft]]. Please see [[Wikipedia:WikiProject Aircraft/page content]] for recommended layout. -->
{{Infobox aircraft
 |name= YHO-4 / YOH-4
 |image= File:Oh4a002.jpg
 |image_border= yes
 |caption= YOH-4A LOH in flight
 |type= Observation/scout helicopter
 |national_origin = United States
 |manufacturer= [[Bell Helicopter]]
 |first_flight= 8 December 1962<ref name="1000photos-1">{{cite web 
 |url=http://1000aircraftphotos.com/HistoryBriefs/Bell206.htm 
 |title=Bell 206 JetRanger 
 |author=Johan Visschedijk 
 |date=16 October 2003 
 |url-status=dead
 |archiveurl=https://web.archive.org/web/20060914180524/http://www.1000aircraftphotos.com/HistoryBriefs/Bell206.htm
 |archivedate=September 14, 2006
 }}</ref>
 |introduction= 
 |retired=
 |status= 
 |primary_user= [[United States Army]]
 |more_users= 
 |produced= 
 |number_built= 5<ref name=Harding/>
 |developed_from=
 |variants=
 |developed_into= [[Bell 206 JetRanger]]
}}

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 206|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.

==Development==
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 Helicopters|Hughes Tool Co., Aircraft Division]].<ref>Remington, Steve. {{usurped|1=[https://web.archive.org/web/20061006192405/http://www.commercemarketplace.com/home/CollectAir/cessna.html "The Cessna CH-1 Helicopter".]}} CollectAir.com</ref> In January 1961, Bell submitted Design 250 (D-250), which would eventually be designated as the ''YHO-4''.<ref name="LOH-1">Beechy, Robert. [http://fire.prohosting.com/hud607/uncommon/reference/usa/army.html "U.S Army Aircraft Acquisition Programs".] {{webarchive|url=https://web.archive.org/web/20061118064815/http://fire.prohosting.com/hud607/uncommon/reference/usa/army.html |date=2006-11-18 }} ''Uncommon Aircraft 2006''. 18 November 2005. Accessed on 19 September 2006.</ref> On 19 May 1961, Bell and Hiller were announced as winners of the design competition.<ref group=note>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.</ref><ref>Spangenberg, George A. ''{{usurped|1=[https://web.archive.org/web/20080910202517/http://www.georgespangenberg.com/gasoralhistory.pdf George A. Spangenberg Oral History]}}''.  www.spangenberg.org. Judith Spangenberg-Currier, ed. pp.187-190. Accessed on 29 April 2008.</ref>

[[File:Oh4a001.jpg|thumb|right|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.<ref name="1000photos-1" /> That same year, all aircraft began to be designated according to the new [[1962 United States Tri-Service aircraft designation system|Joint Services designation system]], so the prototype aircraft were redesignated ''YOH-4A''.<ref name="1000photos-1" /> The YOH-4A also became known as the ''Ugly Duckling'' in comparison to the other contending aircraft.<ref name="aastad">Aastad, Andy. [http://rotormagazine.org/Portals/24/pdf/winter2006_7/32.pdf "The Introduction to the JetRanger".] {{webarchive |url=https://web.archive.org/web/20080910202517/http://rotormagazine.org/Portals/24/pdf/winter2006_7/32.pdf |date=September 10, 2008 }} ''Rotor Magazine''. Helicopter Association International. Winter 2006-2007. Accessed on 5 April 2009.</ref>  Following a flyoff of the Bell, Hughes and Fairchild-Hiller prototypes, the [[Hughes OH-6 Cayuse|Hughes OH-6]] was selected in May 1965.<ref>Spenser 1998, p. 263.</ref>

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 206|Bell 206A JetRanger]].<ref>{{cite web |url=http://www.helicoptermuseum.org/AircraftDetails.asp?HelicopterID=12 |title=American Helicopter Museum: Bell 206 JetRanger |access-date=2009-06-28 |archive-url=https://web.archive.org/web/20061002214153/http://www.helicoptermuseum.org/AircraftDetails.asp?HelicopterID=12 |archive-date=2006-10-02 |url-status=dead }}</ref>

==Variants==
[[File:Oh58-004.jpg|thumb|right|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==
;{{USA}}
* [[United States Army]]

==Surviving aircraft==
The remaining OH-4A ''62-4202'' is in storage at the [[United States Army Aviation Museum]], [[Fort Novosel]], [[Alabama]].<ref>[http://www.thisdayinaviation.com/tag/62-4201/ 8 December 1962]</ref>

==Specifications (OH-4A)==
{{Aircraft specs
|ref= U.S. Army Aircraft Since 1947<ref name=Harding>{{cite book |last=Harding |first=Stephen |title=U.S. Army Aircraft Since 1947 |year=1997 |publisher=Schiffer Publishing Ltd. |location=Atglen, PA, USA |isbn=978-0-933424-53-1 |page=[https://archive.org/details/usarmyaircraftsi0000hard/page/42 42] |url-access=registration |url=https://archive.org/details/usarmyaircraftsi0000hard/page/42 }}</ref>
|prime units?=kts
<!--
        General characteristics
-->
|crew= 1 pilot
|capacity=up to 3 passengers or 2 stretchers
|length ft=38
|length in=8
|length note=
|width ft=<!-- if applicable -->
|width in=<!-- if applicable -->
|width note=
|height ft=8
|height in=10
|height note=
|empty weight lb=1536
|empty weight note=
|gross weight lb=
|gross weight note=
|max takeoff weight lb=2537
|max takeoff weight note=
|fuel capacity=
|more general=
<!--
        Powerplant
-->
|eng1 number=1
|eng1 name=[[Allison T63-A-5]]
|eng1 type=[[turboshaft]] engine
|eng1 shp=250
|eng1 note=

|rot number=1
|rot dia ft=33
|rot dia in=3
|rot area sqft=842.3
|rot area note=<BR>
*'''Blade section:''' - [[NACA airfoil|NACA 0012 mod (11.3%)]]<ref name="Selig">{{cite web |last1=Lednicer |first1=David |title=The Incomplete Guide to Airfoil Usage |url=https://m-selig.ae.illinois.edu/ads/aircraft.html |website=m-selig.ae.illinois.edu |accessdate=16 April 2019}}</ref>
<!--
        Performance
-->
|max speed kts=117
|max speed note=
|cruise speed kts=96
|cruise speed note=
|never exceed speed kts=
|never exceed speed note=
|range nmi=246
|range note=
|ferry range nmi=
|ferry range note=
|endurance=<!-- if range unknown -->
|ceiling ft=20000
|ceiling note=
|climb rate ftmin=
|climb rate note=
|time to altitude=
|disk loading lb/sqft=
|disk loading note=
|fuel consumption lb/mi=
|power/mass=
|more performance=
|avionics=
}}

==See also==
{{aircontent
|see also=
* [[U.S. Helicopter Armament Subsystems#OH-6 Cayuse .28and MD Helicopters MD 500.29|U.S. Helicopter Armament Subsystems]]
|related=
* [[Bell 206]]
* [[Bell OH-58 Kiowa]]
|similar aircraft=
* [[Fairchild Hiller FH-1100|Fairchild Hiller YOH-5]]
* [[Hughes OH-6 Cayuse]]
|lists=
* [[List of active United States military aircraft]]
}}

==References==
===Notes===
{{Reflist |group="note"}}

===Citations===
{{reflist|1}}
;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==
{{Commons}}
* [http://www.globalsecurity.org/military/systems/aircraft/oh-4.htm HO-4/OH-4 page on GlobalSecurity.org]

{{Bell Aircraft}}
{{JetRanger family}}
{{US Army helicopters}}
{{US helicopters}}

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