Bristol Sycamore

During the Second World War, new methods of aircraft propulsion were devised and experimented with; in particular, breakthroughs in rotary aircraft, such as gyrocopters and helicopters, were making such aircraft more practical. In 1944, Bristol established a specialised helicopter division shortly after the Allied invasion of Europe, when engineers from the Airborne Forces Experimental Establishment (AFEE) at Beaulieu became available. The AFEE had been conducting its own work on the development of rotorcraft designs under the noted helicopter pioneer Raoul Hafner; however, the successful use of Airspeed Horsa and General Aircraft Hamilcar gliders during Operation Overlord had led to helicopter development being recognised as a priority. Hafner, whose company had been acquired by Bristol was promptly appointed by the company as the head of Bristol's new helicopter division. An improved model of the helicopter, designated as the Sycamore Mk.3, was rapidly developed; it featured an increased capacity for five occupants, a wider fuselage and a shortened nose. ==Design==

, Munich, Germany The Bristol Sycamore was one of the first production helicopters to be developed. The blades of the three-bladed main rotor were attached to the rotor head with lightweight interleaving steel plates while tie-rods carried the centrifugal tension loads. The Sycamore was powered by a single Alvis Leonides piston engine of . The engine was mounted below and to the rear of the main rotor on a flexible mounting to reduce vibrations transmitted to the helicopter structure. It was isolated in a fireproof enclosure which was fitted with fire detection and extinguishing equipment to meet certification requirements. Air was drawn through a forward-facing grill to cool the gearbox before passing through the engine cowling and leaving the fuselage. The engine power was controlled by the collective pitch lever. In order to maintain the rotor speed at its required setting fuel to the engine had to be automatically varied as the rotor pitch setting commanded by the pilot changed the load on the engine; fine adjustment of engine power was achieved by twisting the pitch lever. The Sycamore had a relatively high rotor speed for the era, which was claimed to give a smoother ride and be safer in the event of engine failure. ==Operational history==

From 1952 to 1955 the Sycamore was used for various trials by the Air-Sea Warfare Development Unit RAF which was stationed at RAF St. Mawgan. In April 1953, the Sycamore HR14 entered service with No. 275 Squadron of the RAF and went on to serve with nine squadrons in total. Various marks of Sycamore served with the RAF; they would primarily be used as air ambulances ( Sycamore HC.10 ), for Army communications ( Sycamore HC.11 ) and for search and rescue operations (Sycamore HR.12 to Sycamore HR.14). The Sycamore was heavily used during the Malayan Emergency (1948–1960), typically deploying Army foot patrols into the jungle. Numerous Sycamores were transferred to the Far East Air Force to participate in the conflict; however, the type was involved in a number of crashes in the region which had occurred as a result of tail or main rotor blade problems. In response, a series of blade trials were conducted prior to a modified blade design being adopted and Sycamore operations in the theatre being resumed. Following the end of most combat operations in August 1960, Sycamores remained in the region, including a detachment in Brunei, to support British forces stationed there to deter further aggression by Malayan communist guerrillas. The Sycamore was the second helicopter type to be used by the Australian Defence Force; ten were delivered to the Royal Australian Navy. Sycamores operated by Australian National Airways were routinely available for charter, performing tasks such as the aerial surveying of mining claims, supply missions, and the transporting of equipment across the remote Outback areas of the nation. ==Variants==

Type 171 ;Mk 1 : Prototype; two built. ;Mk 3A : Civilian version with additional freight hold, two built for British European Airways. ;Mk 4 : This was the main production model and similar to the military version called Sycamore with a more powerful engine. 154 built. Sycamore ;Sycamore HC.10 : (=Mk.3) one built for evaluation by the Army Air Corps as an air ambulance. ;Sycamore HC.11 : (=Mk.3) four built for evaluation by the Army Air Corps, as communications aircraft. ;Sycamore HR.12 : (=Mk.3A) four built for the RAF for evaluation as search and rescue aircraft. ;Sycamore HR.13 : (=Mk.3A) two built with rescue winches for the RAF for evaluation as search and rescue aircraft. ;Sycamore HR.14 : (=Mk.4) 85 built for the RAF, as search and rescue aircraft. ;Sycamore Mk.14 : three built for the Belgian Air Force, for use in the Belgian Congo. ;Sycamore Mk.50 : three built for the Royal Australian Navy, for search and rescue, and plane guard duties. ;Sycamore HC.51 : seven built for the Royal Australian Navy, for search and rescue, and plane guard duties. ;Sycamore Mk.52 : 50 built for the German Air Force and Navy. ==Operators==

Civil operators ; • British European Airways ; • Australian National Airways/Ansett-ANA • Jayrow Helicopters ; • Flying Bulls In 2013 the Flying Bulls by Red Bull reinstated one Sycamore Military operators service around 1960 taking off from the flight deck of HMAS Melbourne. ; • Royal Australian Air Force – Only two Sycamores were in service with the RAAF from 1951 to 1965. The two helicopters were used for general support duties at the Woomera Rocket Range in South Australia. • Aircraft Research and Development Unit • No. 1 Air Trials unit • Royal Australian Navy • 723 Squadron RAN • 724 Squadron RAN ; • Belgian Air Force: Belgium used three Mk.14B's (registered as B1/OT-ZKA, B2/OT-ZKB & B3/OT-ZKC) to equip the metropolitan power in the Congo with a rescue flight based at Kamina Air Base, Katanga Province. Used between 1954 and 1960. ; • Luftwaffe • German Navy ; (1977) • Royal Air Force • Air-Sea Warfare Development Unit • Central Flying School • 22 Squadron • 32 Squadron • 84 Squadron • 103 Squadron • 110 Squadron • 118 Squadron • 194 Squadron • 225 Squadron • 228 Squadron • 275 Squadron • 284 Squadron • 651 Squadron • 657 Squadron • No. 1563 (Helicopter) Flight RAF • Army Air Corps ==Surviving aircraft==

in 2010 Australia ;On display • Australian Fleet Air Arm Museum in Nowra ; stored and used for technical training • Bundesfachschule für Flugtechnik, Langenlebarn, ex D-HFUM Belgium ;On display • Sycamore HR.14 XG547 of the Royal Air Force at Royal Museum of the Armed Forces and Military History in Brussels • Sycamore 3 WA576 – Dumfries and Galloway Aviation Museum, Dumfries. • Sycamore 3 WA577 – North East Aircraft Museum, Sunderland. • Sycamore 3 WT933 – Newark Air Museum, Newark. • Sycamore HR.12 WV781 – Caernarfon Airport Airworld Museum, Caernarfon • Sycamore HR.12 WV787 – RAF Museum London. • Sycamore HR.14 XG502 – Museum of Army Flying, Middle Wallop, Hampshire. • Sycamore HR.14 XG518 – Norfolk and Suffolk Aviation Museum, Flixton. • Sycamore HR.14 XJ380 – Boscombe Down Aviation Collection, Old Sarum. • Sycamore HR.14 XJ918 – Royal Air Force Museum Midlands, RAF Cosford. • Sycamore HR.14 XL824 – Aerospace Bristol, Filton. • Sycamore HR.14 XL829 – The Helicopter Museum in Weston-super-Mare • Sycamore HR.14 XE317 – South Yorkshire Aircraft Museum, Doncaster. ;Stored or under restoration • Sycamore HR.14 XJ917 – Aerospace Bristol, Filton. ==Specifications (Mk.4 / HR14)==