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 Bristol Aeroplane Company had more than a passing interest in rotary aircraft and during the period post World War II, it invested heavily in the development of some iconic British helicopter designs, one of the most famous of which was the Bristol Type 171 Sycamore.

 

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

 

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

 

In 1944, and after the Allied invasion of Europe, the success of the Airspeed Horsa and General Aircraft Ltd (GAL) Hamilcar gliders during Operation Overlord resulted in increased priority in helicopter development.  

 

Bristol Aeroplane Company acquired Hafner’s company and its design rights, with Hafner himself becoming Chief Designer of their Helicopter Division. Their first design was an all-new four seat helicopter, named the Bristol Type 171 Sycamore, the name inspired by the view of the side elevation which resembled a Sycamore seed. It was said that in addition to falling with a rotating motion, it also 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 Bristol Type 171 Sycamore (VL958) flew for the first time on 27th July 1947, powered by a Pratt & Whitney 450hp Wasp Junior engine, as was the second aircraft.

 

The Bristol Type 171 Sycamore was the first British-designed helicopter to enter production and to be granted a civilian Certificate of Airworthiness. It was also the first helicopter to serve with the Royal Air Force.

 

The Bristol Type 171 Sycamore Mk.2 prototype was flown in September 1949, this time with a 550 hp Alvis Leonides engine, this becoming the standard fit for subsequent aircraft. Later, the Bristol Type 171 Sycamore 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 Bristol Type 171 Sycamore Mk 4, of which 154 were built. The aircraft saw long service with the RAF who operated 85 of the type as the Sycamore HR.14, with smaller numbers of other marks.

 

The Bristol Type 171 Sycamore Mk.4 re-positioned the pilot to 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 Bristol Type 171 Sycamore Mk.3.  

 

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

 

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 Australian Defence Force operated 7 aircraft and in total (including prototypes and civil demonstrators) 180 were built.

 
The Bristol Type 171 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.

 

Specification


  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           

Variants

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

 

Survivors


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

www.flyingbulls.at/en/

HR14 (XJ918)
RAF Museum Cosford  

www.rafmuseum.org.uk/cosford/

HR.14 (XG502)
Museum of Army Flying at Middle Wallop 

www.armyflying.com

Mk.3 (WT933)
Newark Air Museum 
HR.50 (XA220)
HR.51 (XD653)
RAN Museum at Nowra, NSW 

www.navy.gov.au/history/museums/fleet-air-arm-museum

Mk.3 (G-ALSX)
HR.14 (XL829)
Helicopter Museum Weston-super-Mare 

www.helicoptermuseum.co.uk

Mk.3 (A91-1)
Australian National Aviation Museum, Moorabbin, VIC 
HR.14 (XG518)
Norfolk & Suffolk Air Museum, Flixton 

www.aviationmuseum.net

Mk.14 (XG547)
Roy Museum of Armed Forces and Military History, Brussels  www.klm-mra.be/D7t/
HR.14 (XJ380)
Boscombe Down Aviation Collection, Old Sarum  www.boscombedownaviationcollection.co.uk
MK.52 (78+20)
Hubschrauber Museum, Buckeburg  www.hubschraubermuseum.de

 

Other information