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. Manufacturer’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 underside of the fuselage and the tailboom. Machine gun and grenade launcher armament have been tested on the ground and in the air.
The four-place OH-4A in the Army’s LOH competition covered a 700 mile course in 4 hr 27 min for an average speed of 159 mph, powered by a 250 hp T-63 Allison turbine.
The JetRanger was fundamentally the same as the OH-4A (formerly HO-4) prototypes, except for fuselage modifications to provide seat¬ing for five.
After losing the competition the company built a new prototype which it designated as the Model 206A JetRanger.
In 1955 the US Army initiated a design competition to speed the procurement of a new helicopter suitable for casualty evacuation, instrument training, and general utility duties. In June 1955 the US Army selected the Bell Helicopter Company’s proposal, this having the company designation Bell Model 204. The new helicopter was known initially to the US Army as the H-40, changed to HU-1 when it entered service, and given the name Iroquois. It was also the first of the ‘Hueys’, a nickname evolved from the HU-1 designation which, in 1962, was altered to UH-1 under the tri-service rationalisation scheme.
The US Army’s first order was for three prototypes for testing, under the designation XH-40, the type having the H-40 designation allocated to it at that time to identify it in the USAF helicopter category. The first of these prototypes made its first flight on 22 October 1956, and these were used by Bell for test and development. Just before the first flight, six examples of the pre-production YH-40 were ordered, all being delivered by August 1958. The YH-40 evaluation aircraft were essentially the same as the XH-40 prototypes but had their cabin space extended a full 12-inches. One remained with Bell, but the remainder were distributed one each to Eglin AFB and Edwards AFB, and three to Fort Rucker, for trials. Duly ordered into production, nine of the definitive pre-production HU-1A were delivered on 30 June 1959, and were followed into service by 74 production examples, of which 14 went to the Army Aviation School at San Diego. The latter aircraft had dual controls and were used as instrument trainers. First major use overseas was with the 55th Aviation Company in Korea, and HU-1As were among the first US Army helicopters to operate in Vietnam. The 57th Medical Detachment would be the first in Vietnam beginning in March 1962. In all, over 3,300 UH-1 Hueys were lost in Vietnam, from a total of over 5,000 introduced to the region.
The Model 204 had a stabilising bar above and at right angles to the two blades of the main rotor, and also had a small elevator surfaces attached to the rear fuselage. Tubular skid-type landing gear was ideal for utility operations and accommodation was provided for a crew of two and six passengers or two stretchers. Powerplant consisted of a 522kW Avco Lycoming T53-L-1A turboshaft, and this made the Model 204 the first turbine-powered aircraft, rotary- or fixed-wing, to be ordered by the US Army.
In this HU-1 a series of seven speed, distance and rate of climb records was set up in July 1960. The best speed was 158.05 mph and the time to climb to 9843 ft was 3 min 22.4 sec.
Production totalled 182 HU-1A / UH-1A’s. These were followed by four YUH-1B prototypes leading up to the UH-1B production model, of which more than 700 were built, essentially being “improved” A-models. Early production HU-1B having the 716kW Avco Lycoming T53-L-5 engine, and late production models the 820kW T53-L-11 engine. Other improvements in the HU-1B included redesigned main rotor blades, and an enlarged cabin to accommodate a crew of two, plus seven passengers or three stretchers.
In 1963 the USAF first ordered the Iroquois. Twenty-five were ordered for delivery beginning March 1064 to be used by SAC to transport personnel and supplies to remote Minuteman missile sites. The USAF UH-1F have 48 ft rotor, four feet longer than UH-1D, and 1250 hp GE T58/8B engine instead of Lycoming T53/9 of 1100 hp. They can lift one ton payload or pilot and 10 passengers. The DoD had transferred responsibility for military Iroquois procurement from the USAF to the Army. About 70 UH-1’s were being produced each month for US military services.
In the autumn of 1965 the UH-1B was superseded in production by the UH-1C, which had an improved ‘door-hinge’ rotor with wide-chord blades, this new main rotor conferring some increase in speed and improved manoeuvrability. 767 were built.
A few UH-1As operating in Vietnam were equipped with rocket packs and two 7.62mm machine-guns for use in a close-support role, and the success of these resulted in many UH-1Bs serving in a similar capacity, armed mainly with four side-mounted 7.62mm machine-guns, or two similarly-mounted packs, each containing 24 rockets. Other military versions of the Model 204 include the UH-1E for the US Marine Corps (generally similar to the UH-1B, but equipped with a personnel hoist, rotor brake and special avionics). The first being delivered to the Marine Air Group 26 on 21 February 1964, and from October 1965 Bell’s new ‘door-hinge’ rotor being fitted to production aircraft; the UH-1F for the USAF, generally similar to the UH-1B but with a 962kW General Electric T58-GE-3 turboshaft, increased-diameter rotor, and able to accommodate a pilot and 10 passengers; a similar TH-1F training version of the above, for the USAF; the HH-1K SAR version for the US Navy, similar to the UH-1E but with 1044kW T53-L-13 engine; TH-1L and UH-1L training and utility versions respectively of the UH-1E with T53-L-13 engine; and three of the UH-1M with night sensor equipment for evaluation by the US Army.
By the fall of 1962, the Army’s first true gunships began to accompany Army troops carrying helicopters on their airmobile missions. These were UH-1A, Hueys, that were equipped essentially in the field with side mounted .30 calibre machine guns, pods for carrying 2.75in rockets, and door gunners equipped with machine guns. Because of the success of the UH-1As, production of the UH-1B started and this became the Army’s standard gunship and the first armoured helicopter to appear in sizable quantities. The UH-1B was essentially the same as the A model, but did have a more powerful engine and better armament. Starting in 1963, some of the Army Huey gunships rode shotgun for Maron air assault missions. Meanwhile the Marine Corps was beginning to fully realise the potential of the helicopter for the unique fighting conditions found in Vietnam. USMC doctrine called for attack aircraft, naval gunfire, and artillery fire to secure a safe landing zone for helicopter borne assault troops. This was difficult in Vietnam where the bad guys were intermingled with the good guys. Air strikes with almost surgical precision were needed to suppress the enemy without doing harm to the civilian population. The Marines, especially those experienced in the SHUFLY operations, recognised that the armed helicopter was the weapon to do the job. It could fly low and slow and even hover while firing its weapons. The first armed Hueys were delivered to the Marines in February 1964, and a year later they went to work in Vietnam. The Marine’s gunship was essentially identical to the Army’s UH-1B except the UH-1E had its external gun fixed in a forward firing position. The Army version had a flexible gun system. This difference in gun mounting led to different deployment tactics for the Army and Marine Corps, the Army’s being more desirable. To overcome the deficiency in flexibility, later versions of the UH-1E were equipped with a turret below the nose of the helicopter which held two M-60 machine guns. The Marine Hueys also had a rotor brake that was necessary for amphibious operations. For on the flight deck it was necessary to stop the rotors immediately. The Marines purchased a total of 270 UH-1Es which turned out to be very good gunships, perhaps even too good a gunship. The Marines originally intended to use the UH-1E for armed observation and reconnaissance, command and control, liaison, and airborne forward air controllers. But because of the frequent lack of availability of fixed wing close support aircraft, the Huey’s effectiveness, and its ability to fly under conditions that kept fixed wing fighters on the ground, almost two-thirds of the UH-1E missions were as armed gunships to support ground troops. Thus, there was a shortage of Hueys for the role for which they were originally intended.
The Model 204B was built in small numbers by Bell, for civil use and military export. Generally similar to the UH-1B, these were of 10-seat capacity, had the larger-diameter rotors of the UH-1F, and the T53-L-11 engine. Model 204Bs and UH-1s have been built by Fuji in Japan, under sub-licence from Mitsubishi, and in 1967 this company introduced the Fuji-Bell 204B-2, which differs from the Model 204B by having a more powerful engine and a tractor tail rotor.
The Australian Navy bought six UH-1Bs in 1964 to replace Bristol Sycamore for air-sea rescue.
YUH-1B
As part of the US Army’s high-speed helicopter research program, in 1964 a Bell YUH-1B was modified with adjustable stub wings to unload the main rotor. Powered by a 1100 hp T53 and two 630 lb thrust turbojets mounted along the fuselage, it was able to reach 222 mph.
The Italian company Costruzione Aeronautiche Giovanni Agusta built large numbers of the Model 204 under the designation Agusta AB.204 for many customers, some of them (including the Swedish navy version) being powered by a Rolls Royce Gnome turboshaft in place of the usual T53. Production switched from the AB.204 in 1966 to the larger multi role AB.205.
UH-1H
The commercial Model 204B features a two-blade all-metal semi-rigid main rotor with interchangeable blades. Usual Bell stabilising bar above and at right angles to main rotor blades. Underslung feathering axis hub. Two-blade all-metal tail rotor of honeycomb construction. Blades do not fold. Shaft-drive to both main and tail rotors. Main rotor rpm 295 to 324 (294 to 317 in UH-1F only). The main blades built up of extruded aluminium spars and laminates. Blade chord 53.3cm. All-metal tail rotor blades. The fuselage is a conventional all-metal semi-monocoque structure. A small synchronised elevator on rear fuselage is connected to the cyclic control to increase allowable CG travel.
Bell 205A-1
The landing gear is a tubular skid type, with lock-on ground handling wheels available. The 204B is powered by one 820kW Lycoming T5309A turboshaft engine mounted above fuselage aft of cabin. Two fuel tanks on CG, immediately aft of cabin, have a total capacity 916 litres. The cabin holds a crew of two side by side, with dual controls. Standard model has bench seats for eight passengers, three abreast in centre row and five abreast in rear row. Optional layouts include individual chairs with tip-up seats or special interiors to customer’s requirements, with optional settee, cabinet, writing table and glass-panelled dividing wall between crew and passenger compartments. Two doors on each side, front one hinged to open forward, rear one sliding aft. Compartment for 182kg of baggage. Passenger seats removable to provide 3.96cu.m of accessible cargo space for loads of up to 1,360kg weight. Forced air ventilation system. Standard equipment includes hydraulic power boost on cyclic, collective and tail rotor flying controls. Optional equipment includes full all-weather flight instrumentation, multichannel select VHF transceivers, visual omni-range and ILS course indicator with heading and glide slope presentation, ADF, VHF marker beacon receivers, Sperry C-4 navigation compass, Lear VGI 5 in all-attitude flight indicator, and external sling for 1,820kg of freight.
In early 1960 Bell proposed an improved version of the Model 204 design with a longer fuselage, plus additional cabin space resulting from relocation of the fuel cells, thus providing accommodation for a pilot and 14 troops, or space for six stretchers, or up to 1814kg of freight. In July 1960, therefore, the US Army awarded Bell a contract for the supply of seven of these new helicopters for service tests, these having the US Army designation YUH-1D and being identified by the manufacturer as the Bell Model 205. The first of these flew on 16 August 1961, and following successful flight trials was ordered into production for the US Army, the first UH-1D being delivered to the 11th Air Assault Division at Fort Benning, Georgia, on 9 August 1963. The powerplant of these initial aircraft was the (1100shp) 820kW Avco Lycoming T53-L-11 turboshaft, driving a 14.63m rotor, and the standard fuel storage of 832 litres could be supplemented by two internal auxiliary fuel tanks to give a maximum overload capacity of 1968 litres of fuel. Accommodation provided for a pilot and 14 troops, or six stretchers and a medical attendant, or 1815kg of cargo. Large-scale production of the UH-1D followed for the US Army, as well as for the armed forces of other nations, and 352 were built under licence by Dornier in West Germany for service with the German army and air force.
The USMC UH-1E was based on the UH-1B and UH-1C models. 192 of this type were built.
The USAF UH-1F were based on the UH-1B and UH-1C models, using of General Electric T-58-GE-3 turboshaft engines of 1,325shp. 120 total examples of these Hueys were produced.
The UH-1D was followed into production, by the more or less identical UH-1H which differed, however, in the use of the more powerful (1400shp) 1044kW Avco Lycoming T53-L-13 turboshaft engine. Delivery of the UH-1 H to the US Army began in September 1967, and this variant proved to be the final production version. The UH-1H was built extensively for the US Army, nine were supplied to the RNZAF, and under the terms of licence agreement which was negotiated in 1969, the Republic of China (Taiwan) produced a total of 118 of these aircraft for service with the Nationalist Chinese army. Variants of the UH-1H include the CH-118 (originally CUH-1H) built by Bell for the Canadian Armed Force’s Mobile Command, with the first of 10 being delivered on 6 March 1968; and the HH-1H local base rescue helicopter of which 30 were ordered for the USAF on 4 November 1970, deliveries being completed during 1973. By 1976 1242 UH-1H had been built.
UH-1H NZ3801 RNZAF No.3 Sqn
The UH-1D/H was employed extensively on a very wide range of duties in South East Asia, and was regarded by many as the workhorse helicopter par excellence in Vietnam. In particular, the type played a major role in special warfare operations in Laos, Cambodia, and in some of the remote areas of South Vietnam, and USAF historians have commented that in this latter theatre of operations nearly all battlefield casualties were evacuated by UH-1 helicopters.
Specifically the military UH-1H features a two-blade semi-rigid main rotor. Stabilising bar above and at right angles to main rotor blades. Underslung feathering axis head. Two-blade all-metal tail rotor. Shaft drive to both main and tail rotor. Transmission rating 820kW. Main rotor rpm 294 to 324.
A small synchronised elevator on rear fuselage is connected to the cyclic control to increase allowable CG travel. The interchangeable main blades are built up of extruded aluminium spars and laminates. Tail rotor blades of honeycomb construction. Blades do not fold. The fuselage is a conventional all-metal semi-monocoque structure.
The landing gear is tubular skid type. Lock-on ground handling wheels and inflated nylon float bags available. Powered by one 1,044kW Textron Lycoming T53-L-13 turboshaft, mounted aft of the transmission on top of the fuselage and enclosed in cowlings. Five interconnected rubber fuel cells, total capacity 844 litres, of which 799 litres are usable. Overload fuel capacity of 1,935 litres usable, obtained by installation of kit comprising two 568 litre internal auxiliary fuel tanks interconnected with the basic fuel system.
The UH-1H seats a pilot and 11 to 14 troops, or six litters and a medical attendant, or 1,759kg of freight. Crew doors open forward and are jettisonable. Two doors on each side of cargo compartment; front door is hinged to open forward and is removable, rear door slides aft. Forced air ventilation system.
Since that time, a small number of UH-1Hs have been selected to fulfill an electronic counter-measures role under the designation EH-1H, and examples with advanced systems were being delivered from 1981. Under the US Army’s Stand-Off Target Acquisition System (SOTAS) programme, four UH-1Hs were modified for evaluation. Their role was to obtain radar data of battlefield movements, relaying them to commanders on the ground and providing real-time information on the tactical situation.
Bell also produces a commercial version of the UH-1H under the designation Model 205A-1. It is powered by a 1044kW (1250shp) Avco Lycoming T5313B turboshaft, derated to 932kW. Normal fuel capacity of the Model 205A-1 is 814 litres, with an optional fuel capacity of 1495 litres. Because it is intended for a wide range of users, special attention has been given to interior design to permit quick conversion for air freight, ambulance, executive, flying crane and search roles. External load capacity in the flying crane role is 2268kg. Maximum accommodation is for a pilot and 14 passengers.
5,435 UH-1H were built and featured an improved Lycoming T-53-L-13B turboshaft engine of 1,400shp.
The USN utilized the purpose-built HH-1K (based on the Bell Model 204) for Search and Rescue duties. The UH-1M was a dedicated gunship model fitted with the Lycoming T-53-L-13 engine of 1,400shp.
Built by Agusta under license from Bell, the AB.205 is a direct counterpart of the UH-1H Iroquois (Model 205) military helicopter. Production switched from the AB.204 in 1966 to the larger multi role AB.205. In its basic form, the AB.205 is similar to the US Army’s UH-1D and UH-1H, but can be configured for specialist roles such as SAR with a door-mounted rescue hoist. The AB.205 is equipped for all-weather operation in its military utility role, and can be fitted with protective armor as well as any of several arma-mentkits. In l969Agusta started licensed produc¬tion of the Model 205A-1 civil version as the AB.205A-1 and, like its American counterpart, this is powered by the 1,400-shp (l,044-kW) T53 13B civil version of the military turboshaft derated, in this application, to 1,250 shp (932 kW). Production of the AB.205A-1 totalled 290 helicopters.
In Japan the Fuji-Bell Model 205A-1 is available. The UH-1J, built by Fuji of Japan, is a Bell 205B powered by an up-rated 800 shp Kawasaki built Textron Lycoming T53 turboshaft. Versions have also been built under licence in West Germany (Dornier). The UH-1D may be up-graded to a UH-1H by replacing the engine with the T53-L-13.
A US Army Request for Proposal for composite main rotor blades for the UH-1H was issued on 16 November 1981. The army’s schedule called for a qualified blade to be ready for production after 32 months. Procurement of 6,000 blades was anticipated in 1985-89, at a cost of US$20,000 or less per blade in FY81. Bell tendered a joint proposal with Boeing, and this team was awarded a US$19 million development contract during 1982 by the US Army Aviation Research and Development Command. Bell designed the composite blade for the UH-1H, but both companies fabricated test blades and supported laboratory and flight testing to ensure compliance with army requirements. The composite rotor blades provide a 6% improvement in the UH-1H’s hovering capability and a 5 to 8 per cent reduction in fuel flow in forward flight. Bell provided manufacturing tools and fixtures and transferred specific manufacturing knowledge to Boeing, so that both companies were equally capable and qualified to manufacture production blades, for which contracts are expected to exceed US$100 million. The first flight of the composite rotor blades on a UH-1H took place in early 1985. Production deliveries began in January 1988.
Bell 204 Variants: XH-40: Three prototypes, the first of which flew in 1956.
YH-40: Six service test models.
UH-1: Nine preproduction models.
UH-1A Iroquois: initial six-seater production version powered by one Lycoming T53-L-1A turbo-shaft engine, derated to 770shp. Deliveries began to the US Army on 30 June 1959 and were completed March 1961. Thirteen modified to carry 70mm rockets and two 7.62mm machine-guns for service in Vietnam with the Utility tactical Transport Helicopter Company. A total of 14 was delivered for use as helicopter instrument trainers with dual controls and a device for simulated instrument instruction.
UH-1B Iroquois: development of the UH-1A powered initially by one 960shp T53-L-5 turboshaft engine. Subsequent deliveries with 1100shp Lycoming T53-L-11 engine. Crew of two plus seven troops or three stretchers and two sitting casualties. Alternatively 1360kg of freight. Rotor diameter 13.41m. Normal fuel capacity 625 litres; overload capacity 1,250 litres. For armed support missions could be equipped with rocket pack and electrically controlled machine-guns. Delivered from March 1961. This version was superseded by the UH-1C on the Bell assembly line, but production continued by Fuji in Japan in order to fulfil an order of 89 UH-1Bs for the JGSDF.
UH-1C: In September 1965, Bell introduced its Model 540 ‘door hinge’ rotor, with blades of increased 69mm chord, on this developed version of the UH-1B, offering some increase in speed and a substantial increase in manoeuvrability through resistance to blade stall. Through reduced vibration and stress levels, the 540 rotor eliminated previous limitations on maximum level flight speed. T53-L-11 turboshaft, accommodation and armament as for UH-1B. Normal fuel capacity 916 litres; overload 2,241 litres. Superseded UH-1B in production for US Army, but itself superseded by AH-1G.
Bell 211 HueyTug: It was announced on 3 September 1968 that a UH-1C had been retrofitted with a 2,125kW Lycoming T55-L-7C turboshaft and 15.24m ‘door-hinge’ rotor as the prototype of a new flying crane version able to lift a 3 ton external payload. Associated modifications, all of which could be applied retrospectively to existing UH-1s, include substitution of a 1,491kW transmission and larger tail rotor, reinforcement of the airframe and fitment of a larger tailboom, and use of a stability control and augmentation system instead of the normal stabiliser bar.
UH-1E: In March 1962, Bell won a design competition for an assault support helicopter for the US Marine Corps, to replace Cessna O-1B/C fixed-wing aircraft and Kaman OH-43D helicopters. Designated UH-1E, this version is generally similar to the UH-1B/C, but has a personnel hoist, rotor brake and marine electronics. The 540 rotor and increased fuel capacity (as UH-1C) were introduced in 1965.
UH-1F: Following a design competition, it was announced in June 1963 that an initial batch of 25 UH-1F helicopters, based on the UH-1B were to be built for the USAF in 1963-64, and many more later, for missile site support duties. Each has a 948kW General Electric T58-GE-3 turboshaft (derated to 820kW), a 14.63m rotor, normal fuel capacity of 945 litres and overload capacity of 1,552 litres. This version can handle up to 1,815kg of cargo at missile site silos, or carry a pilot and 10 passengers. The first UH-1F flew 20 February 1964. Subsequent contracts for a further 121 aircraft were completed in 1967. First delivery to an operational unit was made to the 4486th Test Squadron at Eglin AFB in September 1964. This model was used for classified psychological warfare missions in Vietnam.
TH-1F Iroquois: training version of UH-1F for USAF.
HH-1K Iroquois: SAR version for US Navy. Twenty-seven ordered and delivered in 1970. Powered by T53-L-13 engine (derated to 820kW), the aircraft has the UH-1E airframe, and revised avionics.
TH-1L Iroquois: training version for US Navy, similar to UH-1E. Powered by T53-L-13 turboshaft, derated to 1100shp. Improved electronics. Contract for 45 received 16 May 1968; the first of these was delivered to the US Navy at Pensacola, Florida, 26 November 1969.
UH-1L: Utility version of TH-1L for US Navy. Eight ordered, and delivered during 1969.
UH-1M: US Army version fitted with Hughes Aircraft Iroquois night fighter and night tracker (Infant) system to detect and acquire ground targets under low ambient lighting conditions, two sensors mounted on nose of cabin serve a low-light level TV system with three cockpit displays and a direct-view system using an image intensifier at cockpit/gunner’s station. Three UH-1Ms deployed with hunter-killer helicopter groups in Vietnam in early 1970 to evaluate system.
RH-2: one UH-1A used as flying laboratory for new instrument and control systems. Installations included an electronic control system and high-resolution radar in a large fairing above the flight deck, enabling the pilot to detect obstacles ahead of the aircraft in bad visibility.
Model 204B: Commercial and military export version of UH-1B, with 10 seats, 820kW T5311A turboshaft and 14.63m rotor. Tailboom incorporates a 0.99cu.m baggage compartment, cabin doors with jettisonable emergency exits, passenger steps on each side of cabin, improved outside lights, commercial radio equipment, fire detection and extinguishing systems. First flight 8 March 1962; received FAA certification 4 April 1963.
UH-1P Iroquois: Similar to UH-1F but used for special missions.
Agusta-Bell 204B: utility helicopter, similar to Iroquois, produced under licence in Italy by Agusta from 1961 to 1974 and sold to military and civil customers. By end of 1973 about 250 delivered, including the AB 204AS version for the Italian and Spanish navies, armed with two Mk.44 homing torpedoes or AS.12 air-to-surface missiles depending on anti-submarine search and attack or anti-fast surface vessel role.
Bell 205 Variants:
CH-118: Similar to UH-1H, for Mobile Command, Canadian Forces. First of 10 delivered on 6 March 1968. Originally designated CUH-1H.
EH-1H: Electronic countermeasures configuration, with the Quick Fix I airborne communications interception, emitter locating and jamming system, including an AN/APR-39(V)2 radar warning receiver, XM130 chaff/flare dispenser and AN/ALQ-144 infra-red jammer. The FY81 budget added US$5.1 million to convert initial Quick Fix IA systems in the EH-1H to Phase IB configuration, plus survivability equipment to protect the aircraft against known and postulated threats, including hot metal/plume suppression. However, the Quick Fix mission has been taken over by the much larger Sikorsky EH-60A version of the Black Hawk utility transport helicopter.
HH-1H: It was announced on 4 November 1970 that a fixed price contract worth more than US$9.5 million had been received from the USAF for 30 HH-1H aircraft (generally similar to the UH-1H) for use as local base rescue helicopters. Deliveries were completed during 1973.
UH-1D: This US Army version of the Model 205 Iroquois has an 820kW Lycoming T53-L-11 turboshaft, 14.63m rotor, normal fuel capacity of 832 litres and overload capacity of 1,968 litres. Relocation of the fuel cells increased cabin space to 6.23m3, providing sufficient room for a pilot and 12 troops, or six litters and a medical attendant, or 1,815kg of freight. A contract for a service test batch of seven YUH-1Ds was announced in July 1960 and was followed by further very large production orders from the US Army and from many other nations of the non-Communist world. First YUH-1D flew on 16 August 1961 and delivery to US Army field units began on 9 August 1963. The UH-1D was superseded in production for the US Army by the UH-1H, but 352 UH-1Ds were built subsequently under licence in Germany for the German Army and Air Force. Prime contractor was Dornier.
UH-1H: Following replacement of the original T53-L-11 turboshaft by the 1,044kW T53-L-13, the version of the Model 205 for the US Army was designated UH-1H. Deliveries of an initial series of 319 aircraft for the US Army began in September 1967. Another 914 ordered subsequently in several batches, with delivery extending into 1976. Under a licensing agreement concluded in 1969, the Republic of China produced UH-1Hs for the Nationalist Chinese Army, with much of the manufacturing and assembly process carried out at Taichung, Taiwan. Total procurement 118.
UH-1V: Approximately 220 UH-1Hs converted by US Army as a medevac version. Avionics and equipment in this version include a radio altimeter, AEL AN/ARN-124 DME, glide slope and rescue hoist. The 7,000th Model 205/205A helicopter was completed in 1973.
Model 205A-1: Civil and export designation of UH-1H. Also built in Italy by Agusta, Japan by Fuji and Taiwan by AIDC. First flight 22 March 1967; FAA certification 25 October 1968. A total of 332 produced by Bell at Fort Worth, Texas between 1968 and 1980.
AB 205A: Agusta-built version of the Bell 205 UH-1D. Also built in Germany by Dornier.
AB 205A-1: Agusta-built Bell Model 205A-1 (UH-1H).
Specifications:
XH-40 Engine: 1 x Lycoming T53, 620/640 shp. MTOW: 5800 lb / 2631 kg Useful load: 1000 lb / 454 kg
Model 204 Engine: 522kW Avco Lycoming T53-L-1A turboshaft Vne: 120 kt Crew: 2 Accommodation: six passengers or two stretchers
Model 204B Similar to the UH-1B Engine: 820kW T53-11A turboshaft Rotor diameter: 14.63m Vne: 120 kt Baggage compartment: 0.99cu.m Seats: 10
Model 204B Engine: one 820kW Lycoming T53-09A turboshaft engine Main rotor: two-blade all-metal semi-rigid Rotor dia: 48 ft / 14.63m Main rotor rpm: 295 to 324 Tail rotor: Two-blade all-metal Fuel capacity: 916 litres. Vne: 120 kt Crew: two side by side Passengers: eight Baggage Compartment: 182kg Freight: 1,360kg External sling capacity: 1,820kg
Bell 205A-1 Engine: Lycoming T5313A turboshaft, 1400shp derated to 1250shp. Main rotor diameter: 48 ft 0 in / 14.63 m Fselage length: 41 ft 6 in / 12.65 m Empty weight, equipped: 5197 lb / 2357 kg Normal TO weight: 9500 lb / 4309 kg MTOW, external load: 10,500 lb / 4763 kg Max cruise SL normal TOW: 110 kt / 127 mph / 204 kph Max ROC SL normal TOW: 1680 fpm / 512 m/min Service ceiling normal TOW: 14,700 ft / 4480 m Range, SL, max cruise, normal TOW: 270 nm / 311 mi / 500 km Range 8000ft/ 2440m max cruise, no res, normal TOW: 298 nm / 344 mi / 553 km Cargo caacty: 248 cu.ft / 7.02 cu.m External load: 5000 lb / 2268 kg Seats: 15
Bell 205A-1 Commercial version of the UH-1H Engine: 1044kW (1250shp) Avco Lycoming T5313B turboshaft, derated to 932kW. Seats: 15 Disc loading: 5.25 lb/sq.ft Pwr loading: 6.8 lb/hp Max TO wt: 9500 lb Empty wt: 5199 lb Equipped useful load: 4266 lb Payload max fuel: 1645 lb Range max fuel/ cruise: 437 nm/ 4 hr Range max fuel / range: 482 nm/ 4.6 hr Service ceiling: 14,500 ft Max cruise: 110 kt Vne: 120 kt Max range cruise: 106 kt ROC: 1680 fpm HIGE: 10,400 ft HOGE: 6000 ft Max sling load: 5000 lb / 2268kg Normal fuel capacity: 814 litres Optional fuel capacity: 1495 litres. Maximum accommodation: Pilot + 14 passengers.
CUH-1H / CH-118 Similar to UH-1H Vne: 120 kt
HH-1H: Generally similar to the UH-1H Vne: 120 kt
HH-1K Similar to the UH-1E Engine: 1044kW T53-L-13 (derated to 820kW) Vne: 120 kt
UH-1D Engine: 1 x Lycoming T53-L-11, 1100 shp / 820kW Max speed: 124 kt Std fuel cap: 832 lt (+560 lt aux) Maximum overload fuel capacity: 1968 lt Range std fuel: 370 km Rotor dia: 48 ft (14.63m) Length: 41.503 ft / 12.65 m Height: 14.6 ft / 4.45 m Vne: 120 kt HIGE: 13,600 ft Service ceiling : 21982 ft / 6700 m Empty wt: 2363 kg MTOW: 9500 lb / 4309.0 kg Range: 281 nm / 520 km Crew: 2 Accommodation: 14 troops, or six stretchers and a medical attendant Cargo capacity: 1815kg
UH-1E Generally similar to the UH-1B/C The 540 rotor and increased fuel capacity (as UH-1C) were introduced in 1965. Vne: 120 kt
UH-1F Similar to the UH-1B Engine: 962kW General Electric T58-GE-3 turboshaft Vne: 120 kt Accommodation: Pilot and 10 passengers
UH-1F Based on UH-1B Engine: General Electric T58-GE-3 turboshaft 1272 shp / 948kW (derated to 820kW) Rotor dia: 48 ft / 14.63m Main rotor rpm: 294 to 317 Vne: 120 kt Normal fuel capacity: 945 lt Overload capacity: 1,552 lt Cargo capacity: 1,815kg Passenger capacity; 10
Model 205 / UH-IH Engine: 1 x 1044-kW (1,400-shp) Avco Lycoming T53-L-13 turboshaft Maximum speed 204km/h (127 mph) Cruise: 110 kts ROC: 488 m/min Hovering ceiling in ground effect 4145m (13,600ft) Service ceiling 3840m (12,600ft) Vne: 120 kt Fuel capacity: 844 litres Usable fuel: 799 litres Overload fuel capacity: 1,935 litres usable Range with maximum fuel at sea level 511 km (318 miles) Empty equipped weight: 2363 kg (5,210 lb) Mission take-off weight: 4100kg (9,039 lb) Maximum take-off weight: 4309 kg (9,500 lb) Max underslung load: 1045kg Freight capacity: 1,759kg Main rotor diameter: 14.63m (48ft) Main rotor: two-blade semi-rigid Transmission rating 820kW. Main rotor rpm: 294 to 324. Tail rotor diameter: 2.59m (8ft 6 in) Tail rotor: Two-blade all-metal Length, rotors turning: 17.62m (57ft 9.75in) Height, tail rotor turning: 4.43m (14ft 5½ in) Width: 2.8m Main rotor disc area 168.06 sq.m (1,809 sq.ft) Passengers: 9 passengers or 5 troops (full pack) or 7 troops (light) or six litters and a medical attendant
UH-1J Engine: Lycoming T53, 1800 shp. Vne: 120 kt
Fuji UH-1J Similar to Bell 205B Engine: 1800 shp Kawasaki built Textron Lycoming T53 turboshaft. Vne: 120 kt
UH-1L Similar to the UH-1E Engine: T53-L-13 engine Vne: 120 kt
UH-1P Iroquois Similar to UH-1F Vne: 120 kt
UH-1V Converted UH-1H Vne: 120 kt
YUH-1B Engines: Lycoming T-53, 1100 hp / 2 x thrust toubojets, 630 lb Max speed: 333 mph
AB 204AS Armament: two Mk.44 homing torpedoes or AS.12 air-to-surface missiles
AB 205A / Bell 205 UH-1D
Fuji/Bell Model 204B-2 Engine: 1 x Avco Lycoming T53-13B turboshaft, 1044kW (1,400-shp) derated to 1,250 shp (932 kW). Main rotor diameter: 14.63m / 48 ft Main rotor disc area 168.1 sq.m (1,809.5sq.ft) Fuselage length: 12.31 m (40ft 4.75 in) Height: 3.77m (12 ft 4.5 in) Maximum take-off 3856 kg (8,500 lb) Empty weight: 2177 kg (4,8001b) Max speed: 204km/h (127 mph) Hovering ceiling, IGE: 4635m (15,200ft) Service ceiling: 5790m (19,000ft) Range at sea level: 383km (238 miles)
AB.205A-1 / UH-1H Engine: one 1,400-shp (l,044-kW) Lycoming T53-L-13 turboshaft derated to 1,100 shp (820 kW) Maximum speed: 138 mph (222 kph) at sea level Initial climb rate: 1,680 ft (512 m) per minute Service ceiling: 15,010 ft (4,575 m) Range: 360 miles (580 km) Empty weight: 4,800 lb (2,177 kg) Maximum take-off weight: 9,500 lb (4,309 kg) Main rotor diameter: 48 ft 3.25 in (14.71 m) Length overall, rotors turning: 57 ft 0.75 in (17.39 m) Height: 14 ft 8.5 in (4.48 m) Main rotor disc area: 1,829.36 sq ft (169.95 sq.m) Payload: 14 troops, or six litters and one attendant, or freight.
One Bell Model 47G was fitted experimentally with a Turbomeca Artouste turbine built under license by Continental as the Model 200-T51T-3; it delivered 425shp. As the XH-13F, it was built at the beginning of 1955 to test some components for the Bell 204.
Bell’s first turbine helicopter, the XH-13F, first flew on October 20, 1954, with test pilot Bill Quinlan at the controls. Project engineer for this joint Army/USAF research program was J. R. “Bob” Duppstadt.
The engine weighed so little that it had to be mounted behind the helicopter’s fuel tanks and rotor mast for weight-and-balance reasons.
Pleased with the prototype during its Phase I (factory) testing, Quinlan called the XH-13F the “smoothest Model 47 ever built”. At the start of April 1955, the prototype was handed over to USAF Major Jones P. Seigler and First Lieutenant Donald A. Wooley. The two officers, attached to Edwards Air Force Base in California, conducted the Phase II test program at Fort Worth to ensure good coordination with Bell.
At the end of the 1940s, it became apparent that the helicopters in the Navy’s inventory were not of the size to accomplish anti-submarine warfare (ASW) missions and in 1950 the US Navy launched an industrywide competition for a new helicopter to be designed specifically for the ASW role. Bell’s only twin-rotor helicopter, the HSL-1 was the largest US helicopter of the day and was the first helicopter designed from the outset for the submarine hunter/killer role with the Fairchild Petrel air-to-underwater missile. In June 1941, Bell won this competition in June 1950, and was awarded a contract calling for the building of three prototypes of its Model 61, to be designated XHSL-1 (BuNos 129133/129135). The two rotors were of the basic Bell two blades and automatic stabilising bar. The fore and aft rotors were interconnected and could be folded for carrier operations but the HSL was too large even with its rotors folded, to fit on the elevators of the aircraft carriers. The Model 61 was powered by a single 2.400hp Pratt & Whitney R-2800-50 engine installed in the centre fuselage and driving a transmission shaft to the front pylon, and total fuel capacity was 425 US gal providing a flight endurance of nearly four hours. Armament was intended to include air-to-surface missiles such as the Fairchild AUM-2 Petrel, as well as a dipping ASDIC. The HSL-1 was equipped with a Bell-developed autopilot which permitted motionless hovering for long periods. For the development and production, the Bell Helicopter Division was moved from Buffalo to Fort Worth.
Powered by a 2400hp Pratt & Whitney R-2800-50 engine, the first of three prototypes flew on 4 March 1953. After the vibration had been cured, carrier tests were made aboard the escort carrier USS Kula Gulf (CVE-108) in March 1955. Even if the HSL performed well in the air, its large size, even with rotor blades folded, was not compatible with the carrier’s elevator. Even worse, was its very high level of noise while in stationary flight and this limited the sonar operator’s capability of identifying contacts. Due to these shortcomings the first production contract calling for seventy-eight HSL-1s, including eighteen machines under MAP destined for Britain’s Fleet Air Arm, was cut back to fifty (BuNo 129154/129168, 129843/129877) in July 1955. A follow-on contract for sixteen more (BuNo 140414/140429) was cancelled. The Navy ordered the Sikorsky HSS-1 “Sea Bat” instead. Deliveries to Squadron HU-1 began in January 1957. Production models differed from the prototypes in having stabilising fins at the rear of the fuselage. The HSL-1 programme was not a complete failure because the Bell helicopter demonstrated interesting capabilities in the mine-sweeping role. Six HSL-1s were modified to do this and were operated by the Navy Mine Defense Laboratory in Panama City (Florida), until the end of 1960. The remaining aircraft were used for training or as spares.
HSL-1
The HO4S, which the HSL-1 had been intended to replace, remained in service until the appearance of the HSS-1 antisubmarine version of the Sikorsky S-58.
A civil variant, the D-116, and two derivatives of the HSL-1 were considered under design numbers D-216 and D-238 but they remained as projects.
No HSL-1 seems to have survived.
HSL-1
HSL-1 Engine: 1 x Pratt & Whitney R-2800-50, 1415kW Rotor diameter: 15.70m Fuselage length: 11.90m Height: 4.40m Width (rotors folded): 3.5m Loaded weight: 12020kg Maximum speed: 185km/h Cruising speed: 155km/h Range: 563km Fuel capacity: 425 US gal Warload: 800 kg Payload: 1814 kg
By February 1946 the USAAF issued a to specification for a liaison and observation aircraft. This called for a two-seat, single main rotor type of about 1360kg gross weight and to be powered by a supercharged engine of approximately 260hp. G & A Aircraft Co (Firestone) of Willow Grove, Pennsylvania, won first place and was awarded a contract for three examples of its 100hp Continental A100 powered XR-14-GA (s/n 46-527/529) which were never built. Bell, with its Model 54 proposal, won only second place in this design competition. But at that time, some AAF personnel advocated a contract with Bell and in May 1946 action was initiated for the building and development of three examples of the Model 54 under the designation XR-15-BE (to be redesignated XH-15-BE in 1948). The formal contract was signed a few weeks later. The XR-15 was to be developed both for the Air Force and Army Ground Forces. The Model 54 was an all-metal four-seat helicopter using the same basic rotor system employed in other Bell models, featuring a two-blade rotor with stabilising bar. Power was provided by one 275hp Continental XO-47-5 engine located at the bottom of the rear cabin. Accommodation was provided for a crew of two seated side-by-side in a largely glazed cabin. It had a semi-monocoque fuselage reinforced with stiffeners and fitted with a horizontal stabiliser, and a tricycle (later quadricycle) non-retractable undercarriage. The two-bladed anti-torque rotor was fitted on the starboard side. The aircraft were initially designated XR-15, but this had been changed to XH-15 by the time the first example made its maiden flight in March 1948. Three aircraft were built (s/n 46-530-532) and tested but no production contracts followed. Though funded by the Army Ground Forces (AGF) the XH-15 was evaluated almost exclusively by the Air Force, the latter service having taken control of several AGF aviation projects following the 1947 creation of the USAF. All three examples acquired were used by the Army as high altitude research vehicles until development of the Model 54 came to a halt at the end of 1950. They were stricken from the inventory in the early 1950s. No XH-15 has survived.
In 1946, Bell developed a new general utility helicopter of larger dimensions than the Model 47, as the Model 42, and a military version, the Model 48. The general configuration was a two-blade rotor with stabilising bar, three-wheel non-retractable undercarriage and five-seat cabin with car-like windscreen and doors. The engine was a 540hp Pratt & Whitney R-1340-AN-1 Wasp radial mounted horizontally in the rear fuselage with radiator air intake on top. Alternative equipment included flotation gear for water operation (which was tested on aircraft s/n 46-215), rescue hatch and hoist, litters and life rafts. The USAAF ordered two prototypes of a military derivative, the Model 48, designated XR-12-BE (s/n 46-214/215) as well as a static test airframe. A first production batch of thirty-four examples (R-12A-BE, s/n 47-491/524) was ordered but never built. This order was cancelled in 1947. Meanwhile, the USAAF had ordered a prototype of an enlarged variant, designated XR-12B-BE (s/n 46-216), able to carry up to ten people. This prototype, known as the Model 48A, was followed by a batch of ten similar service trials YR-12B-BE (s/n 46-217/226) with the more powerful 600hp Pratt & Whitney R-1340-5 5 Wasp. The YH-12B was different in shape and the undercarriage had four wheels (wheel base 3.30m; wheel track 2.13m). The wider cabin had separate doors for the crew and passengers and the nose was nearly all-glazed. Horizontal stabilisers were fitted each side of the tail boom. The anti-torque rotor was now located on the port side of the tail-boom end. At the time, the approximate cost of the YR-12, less government-furnished equipment, was estimated at $175,000. Initial deliveries of the YR-12 were scheduled for the summer of 1946. However, Bell was faced with serious engineering difficulties with the prototype. Serious blade weaving and rotor governor trouble were encountered in the main rotor system. In April 1946, Bell accepted the assistance of the Propeller Laboratory at Wright Field to overcome these problems. In May 1946, the USAAF considered that the YR-12 ‘was going to require considerable development and time delay before it was a successful ship’ and procurement of the heavier Sikorsky S-51 was then considered. Delivery of the first YR-12 was in September 1946. Flight tests went smoothly but no production batches of the H-12 were ordered. In 1948, the Bell Model 48 and 48A were respectively re-designated XH-12-BE, XH-12B-BE and YH-12B-BE. They were used for a variety of test programmes before being withdrawn from use. None of them is known to have survived.
Developed from the Model 30 (third prototype configuration), the Bell Model 47 was ordered for the US Army and Navy towards the end of World War II and first flew in 1945. The pre-production model had a 178 hp Franklin engine driving a two-blade wooden main rotor, two side-by-side seats, open cockpit (but later removable transparent bubble), four-leg wheel u/c, open frame rear fuselage with tail skid (later tubular tail rotor protector), ventral fin and and a car-type. The prototype (NC41962/NC1H) first flew on 8 December 1945. Only ten were built.
On 8 March 1946 this was awarded the first Approved Type Certificate issued for a civil helicopter anywhere in the world. Licensed by the Federal Government and manufactured under Helicopter Type Certificate One. The A and B models used the enclosed body In 1947 the USAAF procured 28 of the improved Model 47A, powered by 117kW (157-hp) Franklin O-335-1 piston engines, for service evaluation: 15 were designated YR-13, three YR-13As were winterised for cold-weather trials in Alaska, and the balance of 10 went to the US Navy for evaluation as HTL-1 trainers. Little time was lost by either service in deciding that the Model 47 was an excellent machine, and the orders began to flow in. The US Army’s first order was issued in 1948, 65 being accepted under the designation H-13B; all US Army versions were later named Sioux. Fifteen of these were converted in 1952 to carry external stretchers, with the designation H-13C. Two-seat H-13Ds with skid landing gear, stretcher carriers, and Franklin O-335-5 engines followed, and generally similar three-seat dual control H-13Es. The H-13G differed by introducing a small elevator, and the H-13H introduced the 186kW Lycoming VO-435 engine. Some of the H-13Hs were used also by the USAF, as were two H-13Js with 179kW Lycoming VO-435s acquired for the use of the US President. Two H-13Hs converted for trial purposes, with an increased-diameter rotor and 168kW Franklin 6VS-335 engine, were designated H-13K. In 1962 US Army H-13E, -G, -H and -K aircraft were redesignated with the prefix letter O, for observation. US Air Force H-13Hs and H-13Js were given the U prefix as utility helicopters. Later acquisitions were the three-seat OH-13S to supersede the OH-13H, and the TH-13T two-seat instrument trainer. US Navy procurement began with 12 HTL-2s and nine HTL-3s, but the first major version was the HTL-4, followed by the HTL-5 with an O-335-5 engine. HTL-6 trainers incorporated the small movable elevator. The HUL-1 was acquired for service on board ice-breaking ships, and the final HTL-7 version for the US Navy was a two-seat dual-control instrument trainer with all-weather instrumentation. In 1962 the HTL-4, HTL-6, HTL-7 and HUL-1 were redesignated respectively TH-13L, TH-13M, TH-13N and UH-13P The 47B-3, a utility and agricultural model, had an open sports-car style body and it was from this design that the goldfish bowl moulded canopy was derived.
Bell 47B
In parallel with production of military aircraft, by both Bell and its licencees, there were civil versions for a wide variety of purposes. These have included the Model 47B (equivalent to the military YR-13/HTL-1), and the agricultural/utility Model 47B-3 with open crew positions. Available in 1948, this model was the crop-dusting variant featuring a fully open cockpit and bins were affixed aft of the cabin and could carry 180kg of dust. The 47B was powered by a vertically mounted 175hp Franklin 6ALV-335 six-cylinder engine. The enclosed cabin, seating two side-by-side, featured two car-like doors. A total of 78 Model 47Bs (including 47B-3) were produced.
Two Bell 47B-3’s used by B.E.A. had plexiglass cabin, covered fuselage, and 178 hp Franklin 6V4-178-B32 engines.
Bell 47B-3
Early in 1948, the Model 47B was superseded by the Model 47D (FAA certified in February 1948) which incorporated improvements, including the plastic bubble-like cabin, the top of which could be removed to provide an open cockpit. In 1949, a new sub-variant appeared, the Model 47D-1 utility helicopter with an openwork tail boom capable of carrying three people or 225kg of payload. The same year, Bell helicopters began to be used on air mail services in Chicago and a Bell 47 set a new altitude record with 5654m as well as a new speed record with 215.45km/h. In 1950, a Bell 47D-1 became the first helicopter to fly over the Alps, and in Belgium the first European postal service by helicopter was set up by Sabena on 21 August, 1950. At the end of the same year, Bell 47s were used to take precise measurements over the Niagara Falls. On 17 September, 1952, Bell pilot, Eiton J. Smith set the world’s straight line distance record for helicopters without payload (Class-E) at the controls of a Model 47D-1 registered N167B, flying nonstop from Hurst (Texas) to Buffalo (New York): 1958.37km in 12hr 57min. On 2 September, 1956, at the National Aircraft Show in Oklahoma City, an H-13H flown by an Army pilot stayed in the air for 57hr and 50min, an unofficial world’s record. The introduction of the Model 47G (granted an FAA certificate in 1953) combined the three-seat capacity of the Model 47D-1 with a 149kW Franklin engine which, through a two-stage planetary transmission system, drove a main rotor of laminated wooden blades with steel leading edges, a tail rotor and a cooling fan. This helicopter had a synchronized elevator directly linked to the cyclic pitch control lever, an improvement which gave better stability and an increased margin of centre-of-gravity travel. The landing gear consisted of two skis 2.88 metres apart, and, if needed, quick-change flotation gear could be fitted. In the former case, two small wheels assisted handling on the ground. The service designations were H-13G in the United States Air Force, HTL-6 in the United States Navy. The designation 47G-1 is that given to the prototype of the 47J equipped with a Lycoming 250hp derated engine.
A Bell 47G-2 landed on the summit of Mt.Blanc (15,770 ft) with two occupants.
Bell 47G-3B-1
Substitution of the similarly powered Avco Lycoming VO-435 resulted in the Model 47G-2 (H-13H). A 179kW VO-435 engine brought the changed designation Model 47G-2A, followed in 1963 by the wider cabin Model 47G-2A-1 with improved rotor blades and increased fuel capacity. Other engine installations included a 168kW supercharged Franklin 6VS-335-A (Model 47G-3); 209kW turbocharged Avco Lycoming TVO-435 (47G-3B); and normally aspirated Avco Lycoming VO-540 and VO-435 engines in the three-seat utility Model 47G-4 and Model 47G-5 respectively. A two-seat agricultural version of the latter was known as the Ag-5, and a civil version of the USAF’s H-13J VIP transport was marketed as the Model 47G-4 and Model 47G-5 respectively.
Bell 47G-2 Wing Ding
The Model 47G-2 registered N6723D and nicknamed “Wing Ding” was converted under the leadership of Jan Drees and flown by Floyd Carlson and Lou Hartwig in 1963. The purpose of the Wing Ding programme was to develop an aircraft which would lift very large payloads in excess of its hover capability, taking advantage of running take-offs and landings. In addition to the wing the rotor’s mast angle could be varied in flight.
Bell 47H
Introduced in 1955, the Model 47H was a deluxe version of the Model 47G. It had an enclosed sound-proofed, 3 seat cabin. The cabin had leather upholstery throughout as well as a leather covered dashboard grouping all electrical switches and carburettor controls. The metal monocoque tail boom contained a luggage compartment. The cabin’s width has been increased to 1.52 metres, so that motor vehicle-size seats can be used. With a 200hp engine, the Bell 47H was not a commercial success.
Bell 47J-2A
First proposed in 1956, the Model 47J was a four-seat utility version of the Model 47G civil version of the USAF’s H-13J VIP transport, powered by a 220hp derated Lycoming VO-435. The enclosed cabin sat the pilot centrally in front and three passengers on a cross bench behind. This bench could be removed to allow the installation of two stretchers. The left door could also be removed for an internal electrically-powered hoist. Alternative skid or pontoon landing gear could be fitted and metal rotor blades were optional permitting a loaded weight of 1290kg. Larger capacity fuel tanks (182 litres) could also be installed providing an extended range of 400km. All the mechanical parts were the same as in the 47G-2. The soldered-tube tail is replaced in the 47J by a monocoque beam. The central section was still made of tubes, but was streamlined. This model was also built under licence by Agusta with 152 aircraft built. Sub-variants were:
Model 47J-1 – this sub-variant was similar to the Model 47J but was powererd by a Lycoming VO-435A.
Model 47J-2 and J-2A “Ranger” – introduced in 1960, this sub-variant was similar to Model 47J but had a 305hp (derated to 240hp) Lycoming VO-540-B1B, metal rotor blades, hydraulic power controls and a gross weight of 1290kg. The Model 47J-2A of 1964 was produced in Italy by Agusta.
Model 47J-3 “Super Ranger” – this variant, produced by Agusta, was powered by a Lycoming VO-540 derated to 260hp. It differed from the standard J-2A in having a modified main transmission able to absorb greater power input. A special ASW version was designed for the Italian Navy with new instrumentation, high efficiency rotor brake and armed with a single Mk.44 torpedo.
Model 47J-3B-1 – this sub-variant produced by Agusta was a high-altitude version powered by a 270hp Lycoming TVO-435-B1A and equipped with an exhaust-driven supercharger which maintained sea level conditions up to 4260m. This model also had a high-inertia rotor and servo-control on the pitch control systems.
1959 Bell 47J
The 1959 version of the Bell 47J Ranger had a modified tail-rotor control to simplify maintenance. Larger drag-links are required for the metal blades of the main rotor. B 1959, over 2000 Bell 47s had been built.
The 47J “Ranger” is the first helicopter to have crossed the Andes by way of the Christo Paso. This flight was made at a height of 5180m, with a total weight of approximately 68kg below the helicopter’s own maximum gross weight. HUL-1 is the U.S. Navy designation. Experimental versions have been numerous. Perhaps the two most important were the turbine Bell Model 201 (service designation XH-13F) and the armed Bell Model 207 Sioux Scout. Bell’s production of Model 47s eventually came to an end in late 1973, versions of the Model 47G-5 being the last to be built. 4,018 were built in 24 different basic configurations. Of the many different models built only two of the commercial versions, the Bell 47G-2 and the Bell 47G-3B-l, had production runs in excess of 300 (334 and 337 respectively).
In 1952 Agusta SpA of Italy was granted a licence to build the Bell 47 and produced its first 47G in 1954. Since then Agusta has built over 1000 G (from 1954 to 1976) and J marks. Agusta produced a three-seat version as the EMA 124.
Agusta-Meridionali EMA.124
The Agusta-Meridionali EMA.124 Bell 47 derivative had three-seats, an open frame rear fuselage, skid u/c and one 305hp Textron Lycoming VO-540-B1B3 piston engine. Intended for production by Elicotteri Meridionali SpA, one prototype, I-EMAF, was built, first flown on 28 May 1970.
Kawasaki in Japan received a licence in 1953, and the Kawasaki-Bell 47G3B-KH-4 first flew as a type in 1962. Being a development of the Bell 47 G3B by Kawasaki, the type features a four-seat cabin layout, modified instrument and control systems, and a 260 hp Lycoming.
Kawasaki KH-4
In August 1964 it was reported that the British Army was buying 150 Bell 47G three-seat, similiar to the US Army OH-13S Sioux, but with 270 hp Lycoming TVO-435 engines. The first 50 were to be built in Italy by Agusta, and the next 100 by Westland Aircraft in Britain. The unit cost was about $50,000.
The Model 47 was built under licence by Westland in the UK (the 47G-2 for the British Army) with the name Sioux.
In addition there have been specialised conversions by at least two American companies, including a high-performance Carson Super C-4, and a number of El Tomcat agricultural aircraft developed by Continental Copters Inc. Turboshaft conversions of several models have been produced by Soloy in the USA.
47 Initial prototype, 10 built. Car-type cabin Engine: Franklin, 178 hp Main rotor: two-blade wooden, Seats: two side-by-side
47A / YR-13 / YH-13 / HTL-1 USAF version of Model 47 as YR-13 with enclosed rear fuselage and tail boom, powered by one 175hp Engine: Franklin O-335-1, 175hp 28 built.
47A / YH-13A Three YH-13 modified for cold weather operations. Engine: Franklin O-335-1, 117kW (157-hp)
47B Two-seat commercial Model 47 with enclosed tailboom, fully enclosed fuselage with stepped windshield, under-nose transparencies and two car-type doors, four-leg u/c. Prot NX41967. Engine: Franklin 6V4-178-B3, 178hp Rotor diameter: 10.26m Gross weight: 992kg Empty weight: 626kg Cruising speed: 128km/h Rate of climb: 290m/min Service ceiling: 2960m Range: 320km Seats: two side-by-side
47B-3 Model 47 for crop dusting with modified open cockpit, engine compartment fairing, and externally mounted dusting hoppers. Engine: Franklin 6V4-178-B32, 178hp Payload: 180kg of dust.
47C / H-13G U.S.A.F. version
47D Model 47B-3 with improved plexiglass, bubble canopy, new wheel installation with brakes, 24 volt electrical system, modified fuel system, optional float u/c (47D-S) and 178hp Franklin 6V4-178-B32 engine.
47D / H-13B Sioux / HTL-2 Military model similar to civil 47D with four-leg u/c, bubble canopy with removable top, covered rear fuselage and dual controls. 61 built. Engine: Franklin O-335-3, 200hp
47D / H-13C Sioux H-13B with uncovered rear fuselage and skid u/c with external medevac litter fittings. 16 built.
47D / H-13D Sioux H-13C with single pilot controls. 88 built. Engine: 200hp Franklin O-335-5 Rotor dia.: 35 ft. 11 in. Weight: 2,350 lb Max speed: 100 mph Seats: 2
47D / H-13E Sioux / OH-13E H-13D with dual controls, modified main and tail gearboxes and main transmission. 49 built. Engine: Franklin O-335-5B, 178hp Seats: 3
47D-1 Three-seat Model 47D with open frame fuselage, new canopy, gravity-feed fuel system, ventral fin, roller-bearing transmission, 29-USG fuel capacity, reduced equipment and increased useful load. 937kg TOGW.
47D-1 / HTL-4 / TH-13L US Navy version of Model 47D-1. Later TH-13L. 46 built. Rotor diameter: 10.72m Overall length: 12.56m Fuselage length: 8.33m Height: 2.79m Loaded weight: 943kg Empty weight: 626kg Maximum cruising speed SL: 147km/h Rate of climb: 313m/min Service ceiling: 3965m Hover ceiling in ground effect: 1920m Range (75% power): 342km Seats: 3 Fuel capacity: 29-USG
47D-1 / HTL-5 HTL-4 with 200hp Franklin O-335-5 engine. Payload: 225kg Seats: 3
Bell 47D-S Engine: Franklin 6V4-178-B32, 178hp Undercarriage: floats
47E / HTL-3 Two-seat Model 47D with 200hp Franklin 6V4-200-C32 engine, 1060kg TOGW, 33-USG fuel capacity, optional open cockpit.
47G Three-seat Model 47D with 200hp Franklin 6V4-200-C32AB engine, skid u/c, small tailplane with endplates, relocated battery, revised tail rotor gearbox, synchronised elevator and relocated 43-USG ‘saddle’ fuel tanks 1060kg TOGW. Entered production 1953
47G-2 Model 47G with 200hp Lycoming VO435-A1A engine, relocated cyclic hydraulic boost controls, bonded metal rotor blades and 1105kg TOGW. Also built by Kawasaki.
Bell 47G / H-13G Sioux / HTL-6 / TH-13M / OH-13G US Navy dual control training version of H-13G. Later TH-13M. Military model similar to 47G-2 with increased fuel and external stretcher fittings. 265 built. Engine: Franklin, 200 hp / 149kW Rotor diameter: 10.72m Overall length: 12.62m Fuselage length: 8.33m Height: 2.87m Loaded weight: 1067kg Empty weight: 651kg Maximum speed: 138km/h Cruising speed: 113km/h Initial rate of climb: 238m/min Service ceiling: 2718m Hover ceiling in ground effect: 1098m Range: 341km Seats: 3 landing gear two skis Skid width: 2.88 m
Bell 47G-1 Engine: Lycoming 250hp derated
Bell 47G-2 / H-13H Sioux / UH-13H H-13G with 250hp Lycoming VO-435-23 engine, improved skid u/c and all-metal bonded rotor blades. 468 built. Engine: Avco Lycoming VO-435-23, 250hp
47G-2A Three-seat Model 47G with 240hp Lycoming VO-435-A1E engine, 1285kg TOGW. Also Kawasaki model.
47G-2A-1 47G-2A with fuel capacity inc. from 43-USG to 61.6-USG.
Bell 47G-2 Wing Ding
Bell 47G-3 / H-13K Sioux Civil and military model 47G with 225hp Franklin 6VS-335-A engine, longer rotor blades and 14-inch longer tailboom. 1195kg TOGW. Engine: 225hp Franklin 6VS-335-A supercharged TOGW: 1195kg
47G-3B / OH-13S Sioux Civil and military Model 47G-3 with turbocharged 260hp Lycoming TVO-435-A1A and 1285kg TOGW. 576 built. Engine: 260hp Lycoming TVO-435-A1A Length : 31.562 ft / 9.62 m Height : 9.285 ft / 2.83 m Rotor diameter : 37.238 ft / 11.35 m Max take off weight : 2954.7 lb / 1340.0 kg Max. speed : 91 kt / 169 km/h Service ceiling : 17487 ft / 5330 m Range : 274 nm / 507 km Seats: 3
47G-3B1 Model 47G-3B with 270hp turbocharged Lycoming TVO-435-B1A engine, 8-inch wider 3-seat cabin, 61.6-USG fuel capacity. 1330kg TOGW. Built also by Westland and Agusta. Engine: Lycoming TVO-435-B1A, 260 hp Max speed: 105 mph Range: 273 sm Rotor: 2-blade, 11.32-rn (37 ft 2 in) Cruise @ 65%: 80 mph Endurance: 3 hr TOGW: 1330 kg Useful load: 470 lb Seats: 3 Fuel capacity: 61.6-USG
47G-3B2 Model 47G-3B1 with turbocharged 280hp Lycoming TVO-435-G1A. 1330kg TOGW. Engine: Lycoming TVO-435-G1B, 280 hp Rotor: 2-blade, 11.32-rn (37 ft 2 in) Max speed: 91 kt Cruise: 73 kt Range: 215 nm Empty wt: 858 kg MTOW: 1340 kg
47G-3B-2A Engine: Lycoming TVO-435-F1A, 280 hp Rotor dia: 37 ft 1.5 in / 11.32 m Fuselage length: 37 ft 7 in / 9.63 m Empty weight equipped: 1893 lb / 858 kg MTOW: 2950 lb / 1338 kg Cruise 5000 ft / 1525m: 73 kt / 84 mph / 135 kph ROC SL: 990 fpm / 302 m/min Service ceiling: 19,000 ft / 5790 m Range max fuel 6000ft / 1830m, no res: 214 nm / 247 mi / 397 km Seats: 3 side by side External cargo: 1000 lb / 454 kg
47G-3B2 / TH-13T Two/three seat military instrument trainer with extra IFR equipment. 417 built.
47G-3B2A Model 47G-3B2 with TVO-435-F1A engine and 11-inch wider cabin
47G-4 Model 47G with 260hp Lycoming VO-540-B1 B3 engine, 61.6-USG fuel, hydraulically assisted controls and 1330kg TOGW. Engine: Lycoming VO-540-B1 B3, 260hp TOGW: 1330 kg Fuel capacity: 61.6 USG Seats: 3
47G-4A Model 47G-4 with engine uprated to 280hp.
Bell 47G-4 Ag-5 agricultural version Engine: Lycoming VO-540-B1 B3, 260hp Fuel capacity: 61.6 USG Seats: 2
47G-5 / H-13J Economy 2-seat version of 47G-4 with 12 volt electrical system. 1285kg TOGW, 28-USG fuel capacity. Can be upgraded to 3-seat configuration with synchronised elevator mod. Engine: Avco Lycoming VO-435, 260 hp TOGW: 1285 kg Fuel capacity: 28 USG Seats: 2-3
47G-5A 3-seat Model 47G-5 with 61.6-USG fuel tanks and 11-inch wider cabin. Engine: Avco Lycoming VO-435-B1A, 198-kW (265-hp) Max speed at sea level: 196 km/h (105 mph) Cruise: 137 km/h (85 mph) at 1525m (5,000ft) Service ceiling: 3200m (10,500ft) Range max fuel: 412 km (256 miles) Empty equipped weight: 786 kg (1,732 lb) MTOW: 1293 kg (2,850 lb) Main rotor dia: 11.32m (37ft 1½ in) Tail rotor diameter: 1.78m (5ft 10in) Length, rotors turning 13.3m (43ft 7½in) Height: 2.84m (9ft 3¾ in) Main rotor disc area: 100.61 sq.m (1,083 sq ft). Seats: 3 Fuel capacity: 61.6 USG
Bell 47H Engine: 200 h.p. Franklin 6V4-200-C32 Rotor diameter: 35 ft. 1.5 in. Rotors: 2-blade main; 2-blade tail Fuselage length: 31 ft. 4 in Loaded weight: 2,350 lb. Max. speed: over 100 m.p.h. Ceiling: 10,600 ft. Typical range: over 200 miles at 95 mph with full load. Cabin width: 1.52 m Seats: 3.
47H-1 Model 47G with fully clad fuselage, wider three-seat deluxe cabin and rear baggage stowage locker, contoured 35-USG fuel tanks, modified skid u/c. 1060kg TOGW. Rotor diameter: 10.72m Overall length: 12.62m Fuselage length: 8.33m Height: 2.82m MTOW: 1067kg Empty weight: 681kg Fuel capacity: 35 USG Maximum speed: 161km/h Cruising speed: 142km/h Initial rate of climb: 250m/min Service ceiling: 3660m Hover ceiling in ground effect: 1310m Range: 339km Number of seats: 3
47J Formerly 47G-1 Four-seat development of Model 47H with single pilot seat and rear 3-place passenger seat. Powered by one 220hp Lycoming VO-435-A1B, 1157kg TOGW and 35-USG fuel capacity.
47J / H-13J Model 47J for USAF with 240hp Lycoming VO-435-21.
47J / HUL-1 Model 47J for US Navy with 260hp Lycoming VO-435-B1B. Later UH-13P. Also HUL-1G (HH-13Q) for USCG. 25 built.
Bell 47J / H-13J / UH-13J Engine: Lycoming VO-435-21, 240hp
47J-1 Model 47J with VO-435A engine. Engine: Lycoming VO-435-A1B, 220hp Fuel capacity: 35 USG Opt fuel tanks: 182 lt Length : 31.562 ft / 9.62 m Height: 9.285 ft / 2.830 m Rotor diameter: 37.238 ft / 11.35 m Max take off weight: 1157kg Metal rotor blades option MTOW: 1290kg Max. speed: 91 kt / 169 km/h Service ceiling: 17487 ft / 5330 m Range: 274 nm / 507 km Seats: 4
47J-2 Ranger Model 47J with 240hp VO-540-B IB engine, metal rotor blades, fixed stabiliser, hydraulic controls, blue tinted bubble and windows, 48-USG fuel capacity and 1285kg TOGW. Originally 47G-1 Engine: Lycoming VO-540-B1B, 305hp (derated to 240hp) Gross weight: 1290kg Fuel capacity: 48 USG Seats: 4
47J-2A Model 47J-2 with 260hp Lycoming VO-540-B 1 B3 engine, collective boost system and 1330kg TOGW. Built by Agusta.
47J-3 Naval Model 47J-2A with strengthened transmission, improved rotor brake and underslung torpedo. Agusta built.
Bell 47J-3 Super Ranger Engine: Lycoming VO-540 derated to 260hp
47J-3B1 Model 47J with turbocharged Lycoming TVO-435-B1A engine for high altitude operation and modified servo control system 1330kg TOGW. Lycoming TVO-435-B1A 270hp @ 4260m Rotor diameter: 11.32m Fuselage length: 9.87m Height: 2.83m Take-off weight: 1340kg Empty weight: 845kg Maximum speed at sea level: 169km/h Cruising speed at 1525m: 138km/h Initial rate of climb: 276m/min Service ceiling: 5340m Hover ceiling in ground effect: 5030m Hover ceiling out of ground effect: 3720m Range: 338km Seats: 4
47K / HTL-7 / TH-13N US Navy 2-seat trainer based on HUL-1 with modified cockpit and IFR instrumentation. 240hp Lycoming O-435-6 engine. 1157kg TOGW, 35-USG fuel capacity. Later TH-13N. 18 built. Engine: Lycoming O-435-6, 240hp TOGW: 1157kg Fuel capacity: 35 USG Seats: 2
47L / HUL-1M / UH-13R Experimental Model 47J with 250shp Allison YT-63-A-3 turboshaft and 1285kg TOGW. First a/c Bu. 149838 FF 6 Jan, 1961. Later UH-13R. 2 built.
Kawasaki-Bell 47G3B-KH-4 Engine: Lycoming TVO-435-D1A, 270 hp Main rotor diameter: 37 ft 1.5 in / 11.32 m Fuselage length: 32 ft 7.25 in / 9.93 m Empty weight: 1890 lb / 757 kg MTOW: 2850 lb / 1292 kg Cruise speed: 76 kt / 87 mph / 140 kph ROC S/L: 850 fpm / 260 m/min Range max fuel: 186 nm / 214 mi / 345 km Seats: 4
Continental Copters 47G-2 El Tomcat Agricultural conversion by Continental Copters with single seat cockpit and two large external hoppers plus underslung spray bars. Seats: 1
Texas Helicopters M-74 Wasp Conversion by Texas Helicopters
Texas Helicopters M-79T Hornet Conversion by Texas Helicopters
Agusta EMA 124 3 seat development of 46G Engine: VO-540, 250 hp Seats: 3
With the Model 47 in production Bell concluded that there was a market for a larger helicopter with seating for five or six people. The Model 42 was a streamlined all-metal helicopter which could carry five people: the pilot’s and co-pilot’s seat were situated in the front of the cabin, and a bench seat for three passengers was located in the rear. The Model 42 had a completely enclosed fuselage pod and boom and a fixed tricycle undercarriage, and a stabilising bar on the main rotor. It was powered by one 450hp Pratt & Whitney R-985 Wasp Junior engine, mounted horizontally behind the cabin driving a two-blade symmetrical aerofoil wooden rotor. Cooling was assured by a large airscoop located at the root of the main rotor mast. The rotor had a reduction gear ratio of 8.987:1. In addition to the free-wheeling coupling, the transmission included a rotor brake. A three-bladed anti-torque tail rotor, also made of laminated wood, was on the starboard side of the semi-monocoque tail boom. Access to the cabin was via two car-like doors. The undercarriage was of the fixed tricycle type and fuel capacity was 65 US gal. The Model 42 design was a monstrous tangle of cables winding around drums and full of unexpected difficulties, and responsibility of the development was transfered to the Gardenville team. After much work and re-design, Arthur Young and Bartram Kelley got most of the bugs out of the prototype (c/n 1, NX33540) and made it fly properly. In December 1946, the Model 42 was displayed at the Cleveland Air Show. Two more examples were assembled and tested (c/n 2, NX42063; and c/n 3) but no firm orders were placed and the development of the Model 42 came to a halt. Nevertheless, the characteristic silhouette of the Model 42 would re-appear months later with the military Model 48. None of the Model 42 seem to have survived.
Model 42 Engine: one 450hp Pratt & Whitney R-985 Wasp Junior Rotor diameter: 14.48m Maximum weight: 2315kg Useful load: 656kg Maximum speed at sea level: 200km/h Cruising speed 75% pwr: 160km/h Service ceiling: 3965m Range: 480km
By the autumn of 1941, Arthur M Young had been testing helicopter scale-models on his farm in Pennsylvania for some thirteen years. After this period of research, many failures and his big breakthrough with the invention of the stabiliser bar, Young had perfected a design that would appeal to a manufacturer. Young’s first attempts at interesting aircraft companies in his machine met with little enthusiasm until one of his friends visited Bell’s factory. This led to an appointment for a demonstration on 3 September, 1941. Larry Bell and Arthur Young reached an agreement and, on 24 November, 1941, Young and his assistant, Bart Kelley, arrived at Bell to supervise the initial building of two prototypes as specified in the contract. On 23 June, 1942, Young and his team (some fifteen people) were installed in an old Chrysler agency and garage in Gardenville, a suburb of Buffalo. Dave Forman was assigned to supervise the project. The Model 30 structure was made of welded tubes with a four-legged undercarriage made of 3in aluminium tubing. The 160hp Franklin six-cylinder horizontally-opposed air-cooled engine was mounted vertically behind the cockpit within a steel-tube framework. The main two-blade rotor hub was mounted on a transmission mast by universal joint and was provided with a stabilising bar below and at right angles to the blades which were rigidly connected to the hub. This bar acted as a flywheel on a hinge. It kept the rotor blades level and independent from the movements of the fuselage, solving the problem of stability. The main rotor drive was done through a centrifugal clutch and a two-stage planetary transmission with a 9:1 reduction ratio. The blades, of symmetrical aerofoil section, were made of solid wood with a steel insert in the leading edge. The two-blade tail rotor (also made of solid wood) was mounted on a thin tube at the end of the fuselage. The roll-out of the first Model 30 (c/n 1, later to be registered NX41867) took place on 24 December, 1942; a secretary broke a bottle of champagne on the fuselage and the aircraft was named Genevieve. That day, the engine was run up at 150rpm. The first flight occurred on 29 December when Young flew the tethered Model 30 at an altitude of 1.5m; the same day Floyd Carlson also flew the aircraft. Early in January 1943, the prototype suffered an accident and its pilot, Bob Stanley, was badly hurt. The aircraft was repaired and on 26 June, 1943, the cable was removed and Carlson took Genevieve on its first free flight. The aircraft performed well and by July 1943 was flying at speeds of over 110km/h. At this time, a three-wheeled undercarriage was installed, the fuselage was covered and the aircraft was painted blue overall, so that it could be used for demonstration flights. While flights of the Model 30 No.1 were underway, aircraft No.2 was being built. Several modifications were introduced in this machine: new undercarriage, semi-monocoque fuselage and new tail rotor mounting, and an enclosed cockpit, with car-like doors, for the pilot and one passenger. Unfortunately a setback occurred in September 1943 when the No.1 crashed with Carlson at the controls. Carlson was unhurt but the badly damaged aircraft had to be rebuilt. It was flying again within six months. In late September 1943, aircraft No.2 (registered NX41868) replaced No.1 as the test vehicle. One of the first passengers to fly in this aircraft was Larry Bell. In 1944, Bell began a demonstration programme with aircraft No.2 which made its public debut in March 1944. On 10 May, Floyd Carlson flew the aircraft indoors in a Buffalo armoury before Civil Air Patrol pilots and cadets. By the spring of 1944, aircraft No.1 had been rebuilt and was designated No.1A. This helicopter was the star attraction at a soldier’s benefit show, staged at Buffalo’s Civil Stadium on 4 July 1944. On 5 January, 1945 the first rescue mission ever made by a Bell helicopter took place when Jack Woolams baled out of a P-59 Airacomet in trouble near Lockport. Floyd Carlson and Dr. Thomas C. Marriott took off in one of the Model 30s and, guided by Joe Masham flying a P-59, rescued the unfortunate pilot. But the first publicised rescue mission took place two months later, on 14 March, when two ice fishermen were rescued on Lake Erie. Carlson received the Treasury Department Silver Medal for this feat. The construction of a third aircraft introduced several improvements including a four-wheel undercarriage, an advanced instrument panel and a tubular tailboom, but it retained the open cockpit of No.1. This helicopter (c/n 3, registered NX41869) flew for the first time on 25 April, 1945, and performed well, so well that it proved to be the best of the trio to demonstrate, but the open cockpit was a real handicap. To overcome this Young had the idea of covering the cockpit with a Plexiglass bubble thus providing both comfort and outstanding visibility for pilot and passenger. The shape of this aircraft was now very near to that of the Model 47. Two of the Model 30s are still in existence: c/n 1A (NX41867) is on display at the National Air and Space Museum and c/n 3 (NX41869) is owned by Buffalo and Erie County Historical Society Museum, Amhurst, New York.
Model 30 Engine: 1 x Franklin 6-cylinder, 110.4kW / 160hp Main rotor diameter: 9.75m Main rotor: 2-blade wooden Length: 8.22m Height: 2.59m Empty weight: 518kg Crew: 1 Passengers: 1
In August 1950, the Air Force and Army announced an official Tilt Rotor design competition. Bell’s proposal for their Model 200 won the competition for the XV-3 (originally designated the XH-33), and Bell was awarded a contract in May 1951. The XV-3 was built and initially flight tested at Bell’s Ft. Worth, Texas, facility. Two prototypes were built, carrying tail numbers 4147 and 4148. The basic configuration was a metal fuselage with the metal wing mounted mid fuselage. A helicopter-like rotor was mounted on each wing tip. The rotor shafts were oriented in a vertical position for take-off, landing and hover like a helicopter, and moved to the horizontal position for forward flight like a conventional aircraft. A single Pratt & Whitney R-985-AN-1 Wasp Junior piston engine, producing 400hp for flight and 450hp for take-off, was located in the fuselage just behind the wing. A series of gearboxes and drive shafts transferred power to the rotors. Fuel was stored in a 380 litres tank located in the fuselage just under the wing. The fuselage length was 9.25m, the wing span was 9.53m, the height was 4.14m, and the wing area was 10.8 sq.m. The maximum speed was predicted to be 252km/h. Three-bladed, fully articulated, 7.63m-diameter rotors were used initially. They were driven through a two speed transmission that could be shifted to a lower gear to allow the rotors to turn at a lower speed while the engine maintained a higher speed for greater cruise efficiency. The rotor tilt was controlled by an electric motor enclosed in a fairing at each wing tip. Each rotor could rotate through a 90-degree arc from vertical to horizontal in 10 to 15 seconds. The pilot could stop or reverse the rotor motion at any point. Steady, stable flight could be maintained with the rotors in any intermediate position. The XV-3 was intended as a research vehicle to evaluate the Tilt Rotor concept and to provide design and test data, but the military contracting rules at the time required that it also be designed and demonstrated with a military mission capability. The XV-3’s military mission was observation, reconnaissance, and medical evacuation. It had mounting points for two litters. Tests confirmed that good propulsive efficiencies for cruise could be obtained using helicopter rotors as propellers by reducing the rotational speed to about half of that used for hover. Only minor design changes were recommended as a result of tests. What the wind tunnel tests did not look at was the impact of the large, slow turning rotors on the aeroelastic and longitudinal stability of the aircraft at cruise speeds. Aeroelastic effects, which are the coupling of the bending motions of various flexible components on the aircraft, plagued the XV-3 throughout its early life. The first XV-3 (serial 54-147) was constructed between January 1952 and December 1954. The aircraft rolled out on February 10, 1955, and following roll out, airframe and control system proof load tests, vibration surveys, and system functional tests were performed. Then, with the XV-3 mounted on a tie down stand, full conversions and operation in helicopter and airplane modes were tested. Ground runs included a rotor stability survey and ten hours of full power operation. These ground tests were completed by August. No major difficulties were noted, and rotor stability checks showed the aircraft to be free of any resonance tendencies.
The first hover flight was made on August 11, 1955, by a Bell test pilot, but limited progress was made in flight testing during the next three years due to continuing problems with wing/pylon/rotor instabilities during flight. The first of these occurred after only one week and 1.2 hours of flight time, during an air taxi test. It resulted in a hard landing, and the XV-3 sustained rotor and airframe damage. While the damage was not extensive, the discovery of the instability raised major concerns. Repairs were made, and several modifications also were made which were felt would eliminate the elastic coupling problem. These included stiffening the rotor controls and adding external struts to make the wing more rigid. The trailing 25 percent of the wing was made to droop during hover to reduce disturbance to the rotor airflow during hover, and also to reduce stall speed to 85 knots, making transitions at a lower speed possible. 200 hours of ground runs and tie down tests were made to evaluate these modifications before clearing the XV-3 to fly again. The next hover flight finally occurred on March 24, 1956. Bell finally began envelope expansion flights in June 1956 and performed a nacelle tilt of 5 degrees on July 11. By July 25, they reached 70 degrees tilt and 150km/h forward speed when another rotor instability was encountered. Flight testing resumed on September 26 after more modifications were made to the rotor system and ground run evaluations were completed. On October 25, during another test flight, 4147 encountered another very severe inflight rotor instability and crashed. The pilot was seriously injured, but survived. Bell took a serious look at the entire rotor system, and decided that the basic design and characteristics of the three-bladed articulating rotor system were unsatisfactory for the XV-3. Prior to resuming flight testing with the second prototype, 4148, Bell made numerous changes. They kept the R-985 engine, despite its limited power, because of its very good reliability record. The flush engine cooling air inlet was replaced with a scoop that spanned across the top of the fuselage, from one wing root to the other. As had been done with 4147, the rotor controls were stiffened and the wing was braced with external struts on the bottom. The number 2 XV-3 was shipped to NASA’s Ames Research Center, where it flew in their 12m x 24m wind tunnel in September and October 1957. Serious flutter problems with the original three blade rotors were confirmed, and Bell decided to replace them with two-bladed, semi-rigid type rotors of 7.3m diameter, mounted on shorter masts. The semi-rigid, versus the fully articulated design, in itself further increased rigidity, which would decrease the possibility of aeroelastic coupling. While in the wind tunnel, pilots were able to practice conversion procedures and gear changes. Further changes to the two bladed rotor/pylon design were still required to eliminate pylon oscillations, but these changes were tested while still in the tunnel, and again appeared to eliminate the problem in all conditions that were tested. The pilots found conversion to be quite easy, but engine gearbox shifting proved to be difficult, requiring considerable manipulation of the pitch controller and throttle throughout the twenty second process. Flight testing of 4148 (serial 54-148) began at Bell on January 21, 1958. Conversions to 30 degree pylon angle and speeds up to 205km/h were accomplished by April 1, 1958. Pilots also demonstrated autorotation to a landing following a simulated engine failure. Helicopter characteristics were rated as good, especially in high speed forward flight, and vibration levels were lower than expected. By May 6, another rotor oscillation was encountered in flight at a 40 degree pylon angle, and the aircraft again was grounded. Bell, the Army, and NACA decided that another series of wind tunnel tests was in order. The 12m x 24m tunnel at Ames Research Center was heavily scheduled through the summer, and the XV-3 sat grounded until being shipped to Ames in September. During this time, Bell conducted analog computer simulations to further analyze the instability problem and recommend configuration changes prior to beginning the wind tunnel tests. During October 1958, the XV-3 finally went into the 12m x 24m foot wind tunnel at NASA Ames, and more refinements resulted. Changes included increasing the control system stiffness to three times greater than original, adding counterweights in to the rotor collective control mechanism, and increasing the blade sweep angle. Flying resumed on December 11, and on December 17, the XV-3 achieved 30 degrees tilt, and on December 18 achieved 70 degrees tilt. After making a few minor rigging corrections, a second flight was made and a full conversion to 90 degrees finally was achieved. The conversion was made in steps, starting at 167km/h in full helicopter mode and finishing at 213km/h in full airplane mode. A second full conversion was made the next day. This was three years after the date projected for full transition at the time of the XV-3’s roll out. Over the next ten weeks, final aerodynamic and control system refinements were made, including adding a large plywood ventral fin to improve the poor directional stability. With all the changes that were made to the rotors and pylons, Bell tried something new to see if the wing really was contributing to the instability. The strut attachments were modified with locking devices that allowed the XV-3 to fly with the supporting struts either locked in place to maintain wing rigidity or loose to provide no support to the wing. They were hydraulically actuated, and the pilot could switch between the two settings in flight. Bell assumed that if the instability resumed with the struts unlocked, then the wing indeed did contribute to the problem. The new device was tested on January 16, 1 959, at rotor angles up to 85 degrees from vertical with no instability problems. On the January 22, the struts were removed and the XV-3 flew up to 220km/h with the rotors 50 degrees from vertical, again with no instability noted. A wheeled landing gear was added to the landing skids, and short take-offs were made on April 13, 1959, using less than 60m of runway, and using only two thirds power. Optimum rotor tilt angle was found to be ten degrees forward of vertical. The first in-flight gear change was made on April 14, 1959, and a forward speed of 220km/h was achieved at a much lower engine speed with an accompanying lower vibration level. The gear change took about ten seconds to accomplish. The process was very similar to shifting a manual transmission in a car, requiring manipulation of the aircraft’s collective control, throttle, and clutch.
By April 24, 1959, the XV-3 was ready for formal evaluation by the military. It was shipped to Edwards AFB for a two month flight evaluation that began on May 14, 1959. The joint Air Force and Army evaluation consisted of 38 flights and a total of 29.6 hours. Forty conversions were made, as were twenty gear shifts to lower the rotor speed while in airplane mode. Also demonstrated were power-off conversions from airplane mode to helicopter mode followed by autorotation to a safe landing. Flights up to 3660m were performed. Air Force and Army evaluators concluded that conversions could be performed easily at all airspeed and fuselage attitudes that were tested. They considered the concept to be operationally practical because of low down wash velocity and temperature, low vibration, reasonable noise levels, and excellent reliability. The XV-3 demonstrated good behavior during stalls, good rolling take-off performance, and good basic controllability without electronic or mechanical stability augmentation. On the negative side, items related to the prop rotor concept included an erratic lateral darting tendency and roll oscillations during hovering in ground effect. A large increase in power was needed as hovering flight was approached. Weak longitudinal and lateral-directional stability was also observed at low speed in helicopter mode, as was excessive blade flapping during longitudinal and directional maneuvering in airplane mode. There was high parasite drag in all configurations at high speeds. And last, the XV-3 displayed a fore/aft surging motion, especially severe in rough air, attributed partly to the use of large, lightly loaded rotors as propellers. Performance was significantly less than predicted and weight had grown. The design empty weight was 1580kg and grew to 1895kg, before the Air Force added 72kg of instrumentation. At a gross weight of 2165kg, only the test pilot and about 190 litres of fuel (half the fuel tank capacity) could be carried. This gave a maximum endurance of one hour. In airplane mode in high gear and full power at 1220m of altitude, cruise speed was 189km/h true airspeed and wing stall was 185km/h. In low gear and full throttle, cruise increased to 213km/h and wing stall was reduced to 174km/h. The XV-3 was dived to 287km/h, which was the top speed due to limits of collective pitch. Short period longitudinal dynamic stability began to deteriorate at 222km/h, and was considered unacceptable at 240km/h. At the completion of Air Force testing, the XV-3 was shipped to NASA Ames where it remained on flight status through July 1962. By the time its flying career ended, the XV-3 had been flown 270 times by 11 pilots for a total of 125 hours. 110 full conversions were made by nine different pilots, six of whom performed the conversion on their first flight.
Flight testing of the XV-3 clearly demonstrated that technology had not yet developed an understanding of the aeroelastic coupling that could occur between the wing and a large, slow-turning rotor located at the wing tips. It wasn’t until the mid-1960s that engineers finally had a relatively complete understanding of the coupling problem, following the development of sophisticated analytical tools and more capable computers. Although the XV-3 demonstrated the feasibility of the Tilt Rotor concept, it was limited because of low power, an unsophisiticated flight control system, and relatively low twist, helicopter-like rotor blades. Several times Bell proposed replacing the powerplant with a Lycoming T-53 turboshaft engine of 600hp and making rotor and control modifications to eliminate the concept-related deficiencies identified during the Air Force evaluation, but the XV-3 never flew again. However, the XV-3’s career was not over yet. Under a NASA contract, Bell continued studying the phenomena of aeroelastic coupling and ways to improve high speed flight. Two additional sets of wind tunnel tests using the XV-3 were performed. The first was done in July 1962, evaluating several changes aimed at increasing maximum speed, improving high-speed flight characteristics, and decreasing the rotor flapping that occurred during maneuvering. The tunnel was run at 240km/h before instabilities set in. Following modifications, the instabilities did not return until 295km/h. Using these results, Bell felt that they finally had a good understanding of the problem. In May 1965, the XV-3 returned to Bell, where further study, modifications, and ground runs were performed between July 1965 and March 1966. It then returned to Ames and again entered the 12m x 24m tunnel for the fourth, and last, time in May 1966. This time, the XV-3 was tested to 365km/h, the limit of the wind tunnel, without encountering any of the oscillations that had plagued the aircraft throughout its career. However, on May 20, while running at maximum tunnel speed and taking the last planned data point, both rotors tore loose following a wingtip fatigue failure, damaging the aircraft and permanently ending the XV-3’s career. Following these events, the XV-3 was placed in storage for many years, spending time at Wright-Patterson AFB and Davis-Monthan AFB. Eventually the U.S. Army Aviation Museum at Fort Rucker, Alabama, acquired it for display. Small size and lack of capital of Platt-LePage Aircraft, along with lack of orders for military aircraft caused the Platt-LePage Aircraft Co. to shut down in August of 1946. The McDonnell Aircraft Co. obtained most of the helicopter patents from Platt-LePage during the liquidation of the company, along with the personnel responsible for the twin engine project. Robert Lichten an ex-Platt-LePage engineer went to Bell Helicopter and developed the Tilt-Rotor idea into the XV-3, an examination of the original patent by Haviland Platt shows a remarkable similarity between the two ideas, and Bell Aircraft eventually paid Haviland Platt for the use of his patent.
Bell XV-3 Engine: 1 x Pratt & Whitney R-985, 330kW / 450hp Type of rotors: 2 x 3-blade combined rotor-propellers Propeller diameter: 7.32m Wingspan: 9.15m / 30 ft Length: 30 ft Take-off weight: 2177kg Empty weight: 1633kg Max speed: 280km/h Ceiling: 3600m Seats: 4
