BRISTOL 171 SYCAMORE

Avanzado el año 1944, Bristol Aeroplane Company, constituyó un departamento de helicópteros en Filton y llevó allí a Raoul Hafner, del Establecimiento Experimental de Fuerzas Aerotransportadas, donde había dirigido un equipo para el desarrollo de giraviones. Utilizando su experiencia preguerra con el A.R.III Gyroplane, Hafner comenzó a trabajar en un helicóptero monomotor de cuatro plazas para aplicaciones tanto militares como civiles. La ausencia de un motor británico de la potencia requerida y suficientemente desarrollado llevó a la adopción del Pratt & Whitney Wap Junior de 450 HP – de muy amplio uso- para los primeros prototipos Tipo 171 Mk1, desarrollados de acuerdo con las especificaciones E 20/45 del Ministerio de Abastecimientos.

El diseño mostraba una cabina de aleación ligera y un larguero de cola de revestimiento resistente, con un motor central y caja de transmisión, mientras que la cabeza del rotor se completaba con tres palas monocoque de madera. Tras largas pruebas de sus diversos elementos, el 9 de mayo de 1947 comenzaron las pruebas en tierra de la célula completa, y el 27 de julio H.A. Marsh realizaba el vuelo de prueba. El segundo aparato comenzó el programa de pruebas en febrero de 1948 y el 25 de abril de 1949, a fin de facilitar su vuelo al Salón de París, se convirtió en el primer helicóptero británico que recibió un certificado civil de aptitud para el vuelo.

En la tercera célula. Se instaló un motor radial Alvis Leonides. Este helicóptero, con la denominación tipo 171 Mk2, realizó su vuelo inaugural el 3 de septiembre de 1949, con todo éxito, pero el segundo intento de despegue terminó bruscamente con la desintegración del rotor. Los vuelos de desarrollo recomenzaron con un rotor reforzado, al tiempo que continuaban el montaje de 15 Mk3 de serie.

Austrian-born Raoul Hafner, who had devoted himself to rotary wing research in the thirties, moved to England before the Second World War and took charge of the helicopter division of the Bristol Aeroplane Co. in 1944. His first aircraft, the Bristol 171 Sycamore, flew on 27 July 1947 with an American Pratt & Whitney R-985 Wasp engine, no suitable British engine being available at the time. It was of metal construction with a three-blade main rotor and was designed as an air taxi (four-five seats) and for military tasks such as air observation and casualty evacuation.

In September 1949 the Mk.2 variant flew, powered by a 550hp Alvis Leonides 71 engine. This helicopter was put into production for the British armed forces and among the first 25 built, one (HC Mk.10) was fitted out as an air ambulance, four (HC Mk.11) were intended for Army communications, four (HC Mk.12) for the RAF (liaison, and rescue services) and three (Mk.50) for the Royal Australian Navy (search and rescue). All of these were completed to Mk.3 standard with a Leonides 173 engine.

The Bristol 171 Mk.3 civil version, whose capacity was increased to six seats, was also adopted by BEA, which began an experimental service with these helicopters between Eastleigh and Heathrow airport in 1954, which lasted for about two years. In 1950, Bristol produced another civil version, the Mk.4 with four access doors, a longer-stroke landing gear, a bigger baggage compartment and an hydraulic winch. This was primarily intended for search and rescue and air ambulance duties, and was supplied to the RAF (Mk.14), Belgian Air Force (Mk.14B), Royal Australian Navy (Mk.51) and West German Government (Mk.52).

Finally, in the mid fifties, the British company began work on development of a turbine-engined Sycamore. This was the Bristol 203 with capacity increased to 11 seats and a larger tail. But this project, using the last two airframes of the Bristol 171, was abandoned when the company was taken over by Westland, although some of its finer points were later incorporated in the Lynx.

When production of the Sycamore ended in 1959, 177 had been built. Apart from the RAF, the biggest operator of this helicopter was the German government, which used 50 for the Army and Navy. RAF Sycamores were deployed in various parts of the world where British troops were operating, and in particular played an active part in Malaysia in 1954 and during the trouble in Cyprus towards the end of 1956.

Variantes

171 MK 3: Trompa mas corta y cabina 0,20 m mas ancha a fin de permitir el acceso de 3 pasajeros.

177 MK 4: Versión principal de serie, con un tren de aterrizaje mas alto y cuatro puertas de cabina y el puesto de piloto resituado de la izquierda a la derecha

Characteristics Características	Information Información	Characteristics Características	Information Información
First Flight Primer Vuelo	1947	Engine Motor	1 Radial Alvis Leonides 73
Seating Capacity Plazas	2 / 3	Power Potencia	550 HP
Empty Weight Peso Vacío	1738 Kg	Hover Ceiling O.G.E. Estacionario O.G.E	Ft
Maximum Weight Peso Máximo	2540 Kg	Hover Ceiling I.G.E. Estacionario I.G.E	3330 Ft
Vel. Cruise Vel. crucero	90 Kts	Service Ceiling Techo de Servicio	Ft
V.N.E. V.N.E	110 Kts	Maximum Range (Std) Alcance (Std)	3 Hrs