|Bell 206A "Jet Ranger" / OH-58 "Kiowa"|
The Bell 206 series - comprising the JetRanger and its longer, more powerful brother, the 206L LongRanger - virtually created the modern light helicopter market in North America, and have become familiar sights around the world. Bell 206s are seen everywhere, doing everything from ferrying VIPs to swanky race meetings to mounting fire-watching patrols over remote forests.
The 206 originated in Bell's unsuccessful 1964 bid for a US Army light observation helicopter contract. Although the majority of the 7,000 helicopters delivered by Bell have been for military use, well over 2,300 have been sold to civil operators, along with many of the 1,000 aircraft built by Agusta.
Commercial owners like the JetRanger's flexibility and low operating costs. Pilots speak well of its roominess, ease of handling and excellent visibility.
One image which represents what the Bell 206 is all about is that of a US Park Service LongRanger crew rescuing victims from Washington's icy Potomac River in the aftermath of the crash of Air Florida Flight 90 in January 1982.
R.Jackson "Helicopters. Military, Civilian, and Rescue Rotorcraft", 2005
In 1960 the US Army launched a design competition for a new aircraft which it identified as a Light Observation Helicopter (LOH). Perhaps, more truthfully, it was seeking two or three helicopters in just one all-purpose design, for the LOH was required to fulfill casualty evacuation, close support, observation, photo-reconnaissance and transport missions. Previously no one aircraft had been able to embrace such a wide range of duties, and the specification called for four seats, a 181kg payload and cruising speed of around 193km/h. Design proposals were put forward by 12 US helicopter manufacturers from whom Bell, Hiller 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.
If the US Army had some doubts about the capabilities of the Bell HO-4 submission, the company did not share them, and after losing the competition it built a new prototype which it designated as the Model 206A JetRanger. This flew for the first time on 10 January 1966, and on 20 October 1966 this aircraft received FAA certification, after which it entered production for commercial customers, being built also by Agusta in Italy. The JetRanger was fundamentally the same as the OH-4A (formerly HO-4) prototypes, except for fuselage modifications to provide seating for five. It has been built in large numbers since 1966, and continues in production in 1989 in Canada under the designation Model 206B JetRanger III, having been the subject of progressive development and improvement programmes.
The US Army had expected to procure some 4,000 examples of the OH-6A, but became somewhat disenchanted with Hughes when the unit cost began to climb rather steeply, and the production rate to fall off. As a result, the US Army's LOH competition was reopened in 1967 and, on 8 March 1968, Bell's Model 206A was announced as the winner, with production under the designation OH-58 Kiowa starting without delay; some 2,200 of these aircraft were delivered by the end of 1973. The OH-58 differs from the commercial JetRanger by having a larger-diameter main rotor, with detail changes in internal layout and the provision of military avionics. Initial deliveries to the US Army began on 23 May 1969, and within something less than four months the Kiowa was deployed operationally in Vietnam.
Of the original 2,200 ordered for the US Army, 74 were withdrawn from the production line for delivery to the Canadian Armed Forces from December 1971 under the designation COH-58A, subsequently CH-136. An additional US Army contract for 74 aircraft was issued in January 1973 to replace those aircraft supplied to Canada.
In the early months of 1971, Bell began delivery of an improved Model 206B JetRanger II, and this subsequently replaced the Model 206A in production. It differed by having the more powerful 298kW Allison 250-C20 turboshaft engine, the installation of which involved only minor airframe modification, so that it was possible also to provide kits for the upgrading of Model 206As to Model 206B standard. Australia acquired this version under the designation Model 206B-1 Kiowa, 12 being supplied by Bell and 44 produced under a co-production agreement. Commonwealth Aircraft Corporation in Australia was responsible for final assembly and only the powerplant and avionics came from the United States. Under a US Army development contract, a single OH-58A was equipped with a more powerful 313kW Allison T63-A-720 turboshaft engine and an improved flat glass canopy. This modified aircraft has the designation OH-58C, and subsequently two additional OH-58A to OH-58C conversions were carried out to allow more extensive flight testing by Bell and the US Army. As a result of these tests, production modification of 275 OH-58As to a further-improved OH-58C configuration began in March 1978. Other versions include 12 OH-58Bs, similar to the OH-58A, supplied to the Austrian air force in 1976, and the US Navy has 40 TH-57A SeaRangers. These latter aircraft are dual-control trainers, which were ordered on 31 January 1968, to fulfil the requirement for a primary training helicopter for service with Naval Air Training Command at Pensacola, Florida. They are basically civil Model 206A JetRangers with US Navy avionics.
Production of the JetRanger II ended in the summer of 1977, when it was replaced by the Model 206B JetRanger III. This introduced a more powerful version of the Allison turboshaft engine, offering further improvement in performance, and was the current production version in late 1981. This engine is also available as an installation kit to upgrade JetRanger IIs to JetRanger III standard.
The capability and reliability of the JetRanger family resulted in Bell developing a medium-lift version under the designation Model 206L LongRanger.
D.Donald "The Complete Encyclopedia of World Aircraft", 1997
Model 206 originally offered (unsuccessfully) to US Army as OH-4, having first flown on 8 December 1962. Civil version flew 10 January 1966, after extensive redesign, and entered service as 206A JetRanger; followed by 206A-1 and 206B JetRanger II. Delivery of current 206B-3 JetRanger III began Summer 1977; transferred to Mirabel, Canada, 1986. Also built in Italy by Agusta. Upgraded version, under consideration in 1999, would feature improved engine, transmission and dynamic components, with target selling price under US$900,000. However, by late 2001, Bell was weighing possibility of closing JetRanger production line.
CUSTOMERS: TH-206 (TH-67 Creek) declared winner of US Army NTH competition March 1993; initial 102 ordered in IFR configuration; second batch of 35 VFR helicopters ordered February 1994; deliveries began 15 October 1993 with N67001 and N67014 (all TH-67s have civilian registrations); 45 aircraft (and six procedures trainer) delivered in time for first training course to open 5 May 1994; initial orders 137 TH-67s and nine cockpit procedures trainers; all delivered by late 1995. Additional orders placed on behalf of Taiwanese Army, which received 30 TH-67s in 1997-99. Deliveries in 1999 included six to the Bulgarian Air Force. Further 50 ordered for US Army for delivery between September 2001 and November 2003.
Over 7,750 JetRangers produced by Bell and licensees, including 4,400 Bell 206Bs and 2,200 military OH-58 series; and 900 in Italy. Bell Canada delivered 28 206Bs in 1999; 14 in both 2000 and 2001; and 20 in 2002 (including 10 TH-67s).
COSTS: US Army initial NTH contract US$84.9 million.
DESIGN FEATURES: Typical light utility helicopter with skid landing gear, high-mounted tailboom and horizontal stabiliser. Two-blade teetering main rotor with preconed and underblung bearings; blades retained by grip, pitch change bearing and torsion-tension strap assembly; two-blade tail rotor; main rotor rpm 374 to 394.
FLYING CONTROLS: Hydraulic fully powered cyclic and collective controls and foot-powered tail rotor control; tailplane with highly cambered inverted aerofoil section and stall strip produces appropriate nose-up and nose-down attitude during climb and descent; optional autostabiliser, autopilot and IFR systems.
STRUCTURE: Conventional light alloy structure with two floor beams and bonded honeycomb sandwich floor; transmission mounted on two beams and deck joined to floor by three fuselage frames; main rotor blades have extruded aluminium D-section leading-edge with honeycomb core behind, covered by bonded skin; tail rotor blades have bonded skin without honeycomb core.
LANDING GEAR: Aluminium alloy tubular skids bolted to extruded cross-tubes. Tubular steel skid on ventral fin to protect tail rotor in tail-down landing. Special high skid gear (0.25m greater ground clearance) available for use in areas with high brush. Pontoons or stowed floats, capable of in-flight inflation, available as optional kits.
POWER PLANT: One Rolls-Royce 250-C20J turboshaft, rated at 313kW for T-O; 276kW max continuous. Optionally, one Rolls-Royce 250-C20R/4 rated at 336kW for T-O. Transmission rating 236kW for T-O; 201kW continuous. Rupture-resistant fuel tank below and behind rear passenger seat, usable capacity 344 litres. Refuelling point on starboard side of fuselage, aft of cabin. Oil capacity 5.68 litres.
ACCOMMODATION: Two seats side by side in front and three-seat rear bench. Dual controls optional. Two forward-hinged doors on each side, made of formed aluminium alloy with transparent panels (bulged on rear pair). Baggage compartment aft of rear seats, capacity 113kg, with external door on port side.
SYSTEMS: Hydraulic system, pressure 41.5 bar, for cyclic, collective and directional controls. Maximum flow rate 7.57 litres/min. Open reservoir. Electrical supply from 150A starter/generator. One 28V 17Ah Ni/Cd battery; auxiliary 13Ah battery optional. Optional ECS.
AVIONICS: Comms: VHF communications, intercom and speaker system. Flight: VOR, ADF, DME and R/Nav optional.
EQUIPMENT: Standard equipment includes cabin fire extinguisher, first aid kit, door locks, night lighting, and dynamic flapping restraints. Optional items include clock, engine hour meter, turn and slip indicator, custom seating, internal stretcher kit, rescue hoist, cabin heater, camera access door, high-intensity night lights, engine fire detection system, and external cargo hook of 680kg capacity.
Jane's All the World's Aircraft, 2004-2005
Technical data for Bell Model 206B "Jet Ranger III
Engine: 1 x Allison 250-C20B turboshaft, rated at 236kW, main rotor diameter: 10.16m, length with rotors turning: 11.82m, height: 2.91m, take-off weight: 1454kg, empty weight: 730kg, cruising speed: 216km/h, service ceiling: 4115m, range with max take-off weight: 608km