Bristol 171 Sycamore

The first British designed helicopter to enter production.
Bristol 171 Sycamore WT933 Bristol 171 Mk3 Sycamore WT933 at Newark Air Museum


The Austrian designer Raoul Hafner produced a nimble Autogyro, the Hafner ARIII, which flew in 1935 and had some notable innovations, including the use of cyclic pitch applied via a compact rotor head.


Blade pitch change took place at the centre of the rotor head controlled by a ‘spider’ mechanism and applied to a torsion bar attachment for each rotor blade. These features were quite novel and continue in use today on Westland’s Lynx helicopter.


In 1944, and after the Allied invasion of Europe, the success of the Horsa and Hamilcar gliders during Operation Overlord resulted in increased priority in helicopter development.  Bristol acquired Hafner’s company and design rights, with Hafner becoming Chief Designer of the Helicopter Division.  The success of the Horsa and Hamilcar gliders during Operation Overlord resulted in increased priority in helicopter development.


The first design was an all-new four seat helicopter, named the Sycamore, in view of the type’s side elevation which resembled a Sycamore seed which, in addition to falling with a rotating motion, bears a striking resemblance with the bulbous forward cabin, seeping up to a slim tailboom and high-mounted tail rotor.


Bristol 171 Sycamore XJ918 Bristol 171 Sycamore HR-14 XJ918 photographed at RAF Cosford


The first prototype (VL958) flew for the first time on 27th July 1947, powered (as was the second aircraft) by a Pratt & Whitney 450hp Wasp Junior engine.


The Sycamore was the first British-designed helicopter to enter production and be granted a civilian Certificate of Airworthiness. It was also the first to serve with the Royal Air Force.


A Mk.2 prototype was flown in September 1949 with a 550 hp Alvis Leonides engine and this became the standard fit for subsequent aircraft.


The Mk.3 had a shorter nose and a wider fuselage, which increased capacity to five occupants; 23 were built.


The main production model was the Sycamore Mk 4, of which 154 were built, seeing long service with the RAF, 85 being operated as the Sycamore HR.14, with smaller numbers of other marks.


The Mk.4 re-positioned the pilot on the right (which is now the standard pilot-in-command position in helicopters) and adopted as standard the four door configuration of the earlier HC.10 version of the Sycamore Mk.3.  


In military service the Sycamore was designated HC whilst in civillian use it was referred to simply as the Bristol Type 171.


Bristol 171 Sycamore XF266 Bristol 171 Sycamore HR.14 XF266 photographed in service in Singapore


The main duties of the RAF Sycamores were as Air Ambulances (HC.10), Army communications (HC.11) and as Search and Rescue (HR.12 to HR.14).


Foreign users included Belgium (3), Royal Australian Navy (10) and German Federal Government (50).   In addition, the Aurtsalian Defence Force operated 7 aircraft and in total (including prototypes and civil demonstrators) 180 were built.

The Sycamore was 'officially' retired in December 1971 when critical parts became fatigue life-expired although 32 Squadron continued to use their pair of aircraft until August 1972.


  Sycamore Mk4                                                                   
Powerplant One 550 hp Alvis Leonides
Rotor diameter 48 ft 7 in
Maximum Weight 5,600 lb
Capacity  Two crew and three passengers 
Maximum Speed 132 mph
Endurance / Range  330 miles

Number built

180               All variants - see table below           


Bristol 171 Mk.1 2 prototypes
Bristol 171 Mk.2 1 prototype
Bristol 171 Mk.3 & 3A 15 civil and military models
Bristol 171 Mk.4 Main production model for UK and export military service
Military Designations  
Sycamore HC.10 1 built air ambulance variant based on Mk 3
Sycamore HC.11 4 built for Army communications based on Mk 3
Sycamore HR.12 4 for RAF SAR trials
Sycamore HR.13 2 for RAF SAR trials
Sycamore HR.14 85 RAF SAR operations
Sycamore Mk.14 3 Belgian Air Force
Sycamore HR.50 3 for RAN SAR / plane guard
Sycamore HR.51 10 for RAN SAR / plane guard
Sycamore HR.52 50 for West German Army / Navy


HR.52 (Flying)
(OE-XSY / XG345)
‘Flying Bulls’ organisation in Salzburg, Austria

RAF Museum Cosford

Museum of Army Flying at Middle Wallop

Newark Air Museum 
RAN Museum at Nowra, NSW

Helicopter Museum Weston-super-Mare

Australian National Aviation Museum, Moorabbin, VIC 
Norfolk & Suffolk Air Museum, Flixton

Roy Museum of Armed Forces and Military History, Brussels
(XJ380) HR14
Boscombe Down Aviation Collection, Old Sarum
Hubschrauber Museum, Buckeburg

Other information