The main rotor system was originally based upon the rigid rotor technology developed by Messerschmitt-Bölkow-Blohm for the MBB Bo 105; however, due to control problems experienced while at high speeds upon prototype aircraft, the rigid rotor was replaced with a semi-articulated one on production aircraft. The difficulties experienced with the early design of the main rotor was one of the factors contributing to the lengthy development time of the Gazelle.^[13] The individual rotor blades were crafted out of composite materials, primarily composed of fiberglass, and had been designed for an extremely long operational lifespan; composite rotor blades would become a common feature of later helicopters.^[11][14] The main rotor maintains a constant speed in normal flight, and is described as having a "wide range of tolerance" for autorotation.^[15]

The Gazelle is capable of transporting up to five passengers and up to 1,320 pounds of cargo on the underside cargo hook, or alternatively up to 1,100 pounds of freight in 80 cubic feet of internal space in the rear of the cabin. Armed variants would carry up to four HOT (Haut subsonique Optiquement Téléguidé Tiré d'un Tube) wire-guided anti-tank missiles, or a forward firing 20mm cannon mounted to the fuselage sides with its ammunition supply placed in the cabin.^[16] Various optional equipment can be installed upon the Gazelle, such as fittings for engine noise suppression, 53 gallon ferry tanks, a rescue winch capable of lifting up to 390 pounds, emergency flotation gear, particle filter, high landing skids, cabin heater, adjustable landing lights, and engine anti-icing systems.^[17] While the Gazelle had been developed under a military-orientated design programme, following the type's entry to service increasing attention to the commercial market was paid as well.^[18] The type was marketed to civil customers; notably, civilian operator Vought Helicopters at one point had a fleet of at least 70 Gazelles.^[6][19] Civil-orientated Gazelles often included an external baggage access door mounted beneath the main cabin.^[20]

Civil SA 341G Gazelle

The Gazelle was the first helicopter to be adapted for single-pilot operations under instrument flight rules. An advanced duplex autopilot system was developed by Honeywell in order to allow the pilot to not be overworked during solo flights; the Gazelle was chosen as the platform to develop this capability as it was one of the faster and more stable helicopters in service at that point and had a reputation for being easy to fly.^[21] The docile flying abilities of the Gazelle are such that it has been reported as being capable of comfortably flying without its main hydraulic system operation at speeds of up to 100 knots.^[22] The flight controls are highly responsive; unusually, the Gazelle lacks a throttle or a trimming system. Hydraulic servo boosters are present on all flight control circuits to mitigate control difficulties in the event of equipment failure.^[19][22]

The Gazelle was designed to be easy to maintain, all bearings were life-rated without need for continuous application of lubrication and most fluid reservoirs to be rapidly inspected.^[22] The emphasis in the design stage of achieving minimal maintenance requirements contributed towards the helicopter's low running costs; many of the components were designed to have a service life in excess of 700 flying hours, and in some cases 1,200 flight hours, before requiring replacement.^[23] Due to the performance of many of the Gazelle's subsystems, features pioneered upon the Gazelle such as the fenestron would appear upon later Aerospatiale designs.^[13][24]

As the Gazelle continued to serve into the 21st century, several major modernisation and upgrade programs were undertaken, commonly adding new avionics to increase the aircraft's capabilities. Aerotec group offered an overhaul package to existing operators, which comprised upgraded ballistic protection, night vision goggles, new munitions including rockets and machine guns, and 3D navigational displays; as of 2013, Egypt is said to be interested in upgrading their domestically built Gazelles.^[25] QinetiQ developed a Direct Voice Input (DVI) system for the Gazelle, the DVI system enables voice control over many aspects of the aircraft, lowering the demands placed upon the crew.^[26] In September 2011, QinetiQ and Northrop Grumman proposed outfitting former British Gazelles with autonomous flight management systems derived from the Northrop Grumman MQ-8 Fire Scout, converting them into unmanned aerial vehicles (UAV)s to meet a Royal Navy requirement for an unmanned maritime aerial platform.^[27]

The "Hotel" model Huey was produced in larger numbers than any other model, with 4,850 delivered to the US Army alone.^[4] The "Hotel" model was widely exported and was also built under license in Germany, Italy, Japan and Taiwan.^[3]

Ten were sold to Canada for use under the designation CUH-1H with the first one was delivered on 6 March 1968. These were evaluated by the Canadian Forces and found unsuitable for Canadian tactical use, which resulted in the Canadian government sponsoring the development of the twin-engined version of the "Hotel", the UH-1N Twin Huey. The ten CUH-1Hs were re-equipped for search and rescue use, redesignated CH-118 and served until 1995.^[3][4]

Bell developed a certified version of the UH-1H for the civil market. The aircraft incorporated minor changes for safety, such as dual sliding door locks and a baggage compartment in the tailboom. It was marketed by Bell as the Model 205A and later the improved 205A-1.^[3]

The "Hotel" model Huey was also the basis for a number of sub-variants:

• HH-1H was a UH-1H equipped for base rescue duties. Thirty were delivered to the USAF between 1970-73.^[3][4]
• EH-1H was a UH-1H modified under Project Quick Fix in 1976 and used as communications jamming aircraft with the US Army. Twenty-two aircraft were modified to this configuration beginning in 1976. Initial aircraft were fielded to the 82nd Airborne Division and the 2nd Armored Division. The 82nd fielded the type during the invasion of Grenada (Operation Urgent Fury)in 1983.^[3][4]
• UH-1J an improved Japanese version of the UH-1H built under license in Japan by Fuji Heavy Industries. It was locally designated as the UH-1J.^[6]
• EH-1X was an improved EH-1H communications jammer and DF aircraft.^[3]
• JUH-1 was a UH-1H equipped with retractable skid gear and an AN/APS 94 radar boom mounted on the belly.^[3]
• UH-1V was a MEDEVAC version of the "Hotel", with upgraded avionics.^[3]
• TH-1H: Modified UH-1Hs for use as basic helicopter flight trainers by the USAF.

A UAV version of UH-1H is being developed by Aurora Flight Sciences using the Tactical Autonomous Aerial Logistics System platform for the Autonomous Aerial Cargo Utility System (AACUS) program.^[7]

The latest model, the OH-58D Kiowa Warrior, is primarily operated in an armed reconnaissance role in support of ground troops. The OH-58 has been exported to Austria, Canada, Croatia, the Dominican Republic, Taiwan, Saudi Arabia, and Greece. It has also been produced under license in Australia.

https://en.wikipedia.org/wiki/Bell_OH-58_Kiowa

General characteristics

• Crew: 2 pilots
• Length: 42 ft 2 in (12.85 m)
• Height: 12 ft 10 in (3.93 m)
• Empty weight: 3,829 lb (1,737 kg)
• Gross weight: 5,500 lb (2,495 kg)
• Powerplant: 1 × Rolls-Royce T703-AD-700A turboshaft, 650 hp (485 kW)
• Main rotor diameter: 35 ft 0 in (10.67 m)
• Main rotor area: 962.11 sq ft (89.42 m²)

Performance

• Maximum speed: 149 mph (240 km/h, 129 kn)
• Cruise speed: 127 mph (204 km/h, 110 kn)
• Range: 161 mi (556 km, 140 nmi)
• Service ceiling: 15,000 ft (4,575 m)

Armament

• Hardpoints: 2 pylons with provisions to carry combinations of:
  • Rockets: 1x LAU-68 rocket launcher with seven 2.75" Hydra 70 rockets
  • Missiles: 2x AGM-114 Hellfire missiles
  • Other: 1x .50 cal (12.7 mm) M3P (or M296) heavy machine gun^[124]

The U.S. Army is the primary operator of the AH-64. It has also become the primary attack helicopter of multiple nations, including Greece, Japan, Israel, the Netherlands, Singapore, and the United Arab Emirates. It has been built under license in the United Kingdom as the AgustaWestland Apache. American AH-64s have served in conflicts in Panama, the Persian Gulf, Kosovo, Afghanistan, and Iraq. Israel used the Apache in its military conflicts in Lebanon and the Gaza Strip. British and Dutch Apaches have seen deployments in wars in Afghanistan and Iraq.