helicopter

helicopter, type of aircraft in which lift is obtained by means of one or more power-driven horizontal propellers called rotors. When the rotor of a helicopter turns it produces reaction torque which tends to make the craft spin also. On most helicopters a small rotor near the tail compensates for this torque. On twin-rotor craft the rotors spin in opposite directions, so their reactions cancel each other. The helicopter is propelled in a given direction by inclining the axis of the main rotor in that direction. The helicopter's speed is limited by the fact that if the blades rotate too fast they will produce compressibility effects on the blade moving forward and stall effects on the rearward-moving blade, at the same time. This method of flight was considered by Leonardo da Vinci, in the 16th cent., who described its possibilities but could not provide a propulsion system. Best known among its developers are the French inventor Louis Breguet and the engineers Igor Sikorsky of the United States and Juan de la Cierva of Spain. The helicopter has become very popular for short-distance transportation, because of its maneuverability and ability to land and take off in small areas; it has been adopted for a wide range of services, including air-sea rescue, fire fighting, traffic control, oil platform resupply, and business transportation. Helicopters have been widely adopted by the military since their first appearance during the Korean War. During the Vietnam War, they became the preferred platforms for transporting troops and evacuating wounded; in the Persian Gulf conflict helicopter gunships provided air cover for advancing tanks.

Aircraft with one or more power-driven horizontal rotors that enable it to take off and land vertically, move in any direction, or remain stationary in the air. Since a rotor is essentially a rotating airfoil, a helicopter is often described as a rotary-wing aircraft, in contrast to a conventional fixed-wing airplane. One of the earliest ideas for flying, it appeared in China and Renaissance Europe as a toy and in Leonardo da Vinci's designs. The Frenchman Paul Cornu made the first manned flight in 1907. Igor Sikorsky produced the first successful prototype in 1939, which was followed by rapid development in the U.S. and Europe. It is widely used for civilian transport, rescue work, and various commercial purposes. It has been used by military forces since the Korean War (1950–53) for transporting material, moving assault troops, and directly attacking other forces.

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The Westland Whirlwind helicopter was a British-built version of the U.S. Sikorsky S-55/H-19 Chickasaw. It primarily served with the Royal Navy's Fleet Air Arm in anti-submarine and search-and rescue roles.

Design and development

The first prototype British Whirlwind HAR.1 flew in August 1953, with the 600 hp Pratt & Whitney R-1340-40 Wasp, and it entered service shortly afterwards. They served in non-combat roles, including search and rescue and communications functions. The HAR.3 had a larger 700 hp Wright R-1300-3 Cyclone 7 engine. It was not until 1955 that the HAR.5 flew for the first time with a British power plant, the Alvis Leonides Major.

The HAS.7 became the first British helicopter designed for anti-submarine work in the front-line when it entered service in 1956. It was equipped with radar and dipping ASDIC for submarine detection and designed to be equipped with a torpedo, but could not carry both simultaneously.The HAS.7 was powered by a 750 hp (560 kW) Alvis Leonides Major 755/1 radial engine. It had a hovering ceiling at 9,400 ft and a range of 334 miles at 86 mph.

Later in their lives, some HAR.9s were converted to use the Rolls-Royce Gnome turboshaft engine.

From its start with the Navy, the Whirlwind came to be used by the British Army and RAF. More than 400 Whirlwinds were built, of which nearly 100 were exported to the foreign customers.

Variants

WS-55 Series 1 : 44 built; American engines (Pratt & Whitney Wasp R-1340-40), transport helicopters for military and civilian useWS-55 Series 2 : 19 built; Alvis engines (Alvis Leonides Major 755), civilian useWS-55 Series 3 : 5 built; Gnome turboshaft (Bristol Siddeley Gnome 101), civilian useHAR.1 : 10 built; RN service; Search and rescueHAR.2 : 33 built; RAF service from 1955HAR.3 : 25 built; RN service; Wright Cyclone engineHAR.4 : 24 built; Improved HAR.2 for hot and high conditions HAR.5 : 3 built; Alvis engines; RN serviceHAS.7 : 129 built; RN anti-submarine duties - 1 torpedo; 12 used as Royal Marine transportsHCC.8 : 2 built; Royal Flight transport, VVIPHAR.9 : RN serviceHC.10 : RAF serviceHAR.10 : 68 built; RAF, transport and air-sea rescueHCC.12 : 2 built; Royal Flight,

The model numbers for the US-built evaluation models were HAR.21 : 44 built; rescueHAS.22 : 44 built; anti-submarine

Operators

Survivors

Over 20 aircraft are preserved in the UK in museums including the RAF Museum and the Fleet Air Arm Museum as well as being the current gate guardian at RAF Odiham.

Whirlwind Series 3 G-APWN, Midland Air Museum, Coventry, England. Sometimes open for viewing

Specifications (Whirlwind HAS7)

See also

External links

• Navy News
• Helicopter museum
• RAF museum
• British Aircraft Directory
• Westland Whirlwind page at helis.com database