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Bell 206 / HO-4 / OH-4A

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In 1960 the US Army launched a design competition for a new aircraft which it certified as a Light Observation Helicopter (LOH). The specification called for four seats, a 181-kg (400-lb) payload and cruising speed of around 193 km/h (120mph). Design proposals were put forward by 12 US helicopter manufacturers from whom Bell, HilIer and Hughes were each contracted to build five prototypes for competitive evaluation. From the tests which followed, the Hughes HO-6 (later OH-6A) was selected for production as the US Army’s LOH.


The Bell aircraft featured two-bladed main and tail rotors, skid landing gear, and a conventional pod-and-boom layout with a protruding 'bubble' nose.  Manu-facturer's flight test programme with the Bell OH-4A light observation helicopter (first flown on 8 December 1962) was completed in August 1963, and during this programme a number of modifications were introduced. These include the addition of a vertical fin above the tailboom to improve static and dynamic directional stability; the lengthening of the cabin nose by ten inches to reduce drag and improve balance; the moving forward of the horizontal stabiliser by thirty inches to improve longitudinal stability, and the addition of external stiffeners at the junction of the under-side of the fuselage and the tailboom. Machine gun and grenade launcher armament have been tested on the ground and in the air.


The JetRanger was fundamentally the same as the OH-4A (formerly HO-4) prototypes, except for fuselage modifications to provide seating for five.
After losing the competition the company built a new prototype which it designated as the Model 206A JetRanger.

YOH-4A
Engine: Allison T63-A-5  turboshaft, 250hp /185kW
Main rotor diameter: 10.14m
Fuselage length: 11.79m
Height: 2.69m
Take-off weight: 1145kg
Max speed: 217km/h
Cruising speed: 179km/h
Service ceiling: 6100m
Range: 455km
Seats: 4

 

 


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