|Type 171 Sycamore|
|Bristol 171 Sycamore in Ansett-ANA service in Australia around 1960. Note possible spraying arm attachments.|
|Role||Rescue and Anti-Submarine Helicopter|
|National origin||United Kingdom|
|Manufacturer||Bristol Aeroplane Company|
|First flight||27 July 1947|
|Primary users||Royal Air Force
Royal Australian Navy
|Produced||1947 - 1959|
The Bristol Type 171 Sycamore was an early helicopter developed and built by the helicopter division of the Bristol Aeroplane Company. The name refers to the seeds of the Sycamore tree, Acer pseudoplatanus, which fall with a rotating motion. It has the distinction of being the first British helicopter to receive a certificate of airworthiness, as well as being the first British-designed helicopter to be introduced by and to serve with the Royal Air Force (RAF).
Typically capable of seating up to three passengers, the type was often used as a transport for both passengers and cargo alike. In RAF service, the Sycamore was normally used in the search and rescue and casualty evacuation roles. The type proved the value of rotorcraft to easily traverse inhospitable or otherwise inaccessible terrain; the Sycamore made valuable contributions to British military activities during the Malayan Emergency, the Cyprus Emergency, and the Aden Emergency, in addition to other operations.
In addition to its British military service, various models of the Sycamore were produced and operated by a number of users, including overseas military operations and civil customers. Civilian operations typically involved transportation, mountain rescue, and aerial survey work. In 1959, production of the Sycamore ended after 180 rotorcraft had been completed.
Design and development
During the Second World War, new methods of aircraft propulsion were devised and experimented with 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 their own work on the development of rotorcraft designs under the noted helicopter pioneer Raoul Hafner; however, the successful use of Horsa and Hamilcar gliders during Operation Overlord had led to helicopter development being recognised as a priority. Hafner was promptly appointed by Bristol as the head of this new helicopter division.
In June 1944, work commenced on the development on a 4 seat helicopter intended for both civil and military use; it was out of this programme that the Sycamore would emerge. During development, particular emphasis was assigned to the producing the necessary level of endurance of the rotorcraft's mechanical components. On 25 July 1947, the first prototype, VL958, which was powered by a 450 horsepower (340 kW) Pratt & Whitney Wasp Junior (there being no suitable engine in the Bristol range), performed the type's maiden flight. In mid-1948, the third prototype, which had been built to the improved Sycamore Mk.2 standard, was completed; this model had been fitted with a 550 horsepower (410 kW) Alvis Leonides engine, the Leonides engine would become the standard powerplant for all subsequent Sycamore production. On 25 April 1949, a certificate of airworthiness was granted for the Sycamore.
During the flight test programme, Bristol's key development pilots for the Type 171 included Charles "Sox" Hosegood and Col. Robert "Bob" Smith. In 1951, a Bristol-owned Sycamore Mk.2 was used during a series of deck landing trials performed onboard the Royal Navy aircraft carrier HMS Triumph. A total of 15 Sycamore Mk.3s were produced for evaluation purposed by the Royal Air Force (RAF), Army Air Corps (AAC), and British European Airways (BEA).
Versions of the Sycamore up to and including the Mk.3A retained the standard two-seat cockpit layout, placing the pilot in the left-hand seat and the co-pilot in the right. However, on the main production model, designated as the Mk.4, this arrangement was switched to the American standard practice of positioning the pilot's seat on the right. There were also a number of other developments that had featured upon the earlier versions, such as a four-door design, that were standardised for the Mk.4. This version entered RAF service as the HR14.
Civil versions were not marketed under the Sycamore name, they were instead known simply as the Bristol Type 171.
The Sycamore HR14 entered service with 275 Squadron of the RAF in April 1953, and went on to serve with nine squadrons in total. It was used during the Malayan Emergency (1948-1960) for deploying Army foot patrols into the jungle. The type was used by the Royal Air Force Central Flying School for pilot training.
A total of 50 Sycamores were delivered to the German Federal Government, and three to the Belgian Government.
The RAFs last Sycamores were officially retired in December 1971, as critical parts had reached the end of their fatigue life. However 32 Squadron continued to operate two Sycamores until August 1972.
- Mk 1
- Prototype; two built.
- Mk 2
- Second prototype; one built.
- Mk 3
- Production model with five seats in a widened fuselages and a shortened nose to improve visibility. Fifteen 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.
- Sycamore HC10
- (=Mk.3) one built for evaluation by the Army Air Corps as an air ambulance.
- Sycamore HC11
- (=Mk.3) four built for evaluation by the Army Air Corps, as communications aircraft.
- Sycamore HR12
- (=Mk.3A) four built for the RAF for evaluation as search and rescue aircraft.
- Sycamore HR13
- (=Mk.3A) two built with rescue winches for the RAF for evaluation as search and rescue aircraft.
- Sycamore HR14
- (=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 HC51
- seven built for the Royal Australian Navy, for search and rescue, and plane guard duties.
- Sycamore Mk 52
- 50 built for the German Army and Navy.
- Flying Bulls In 2013 the Flying Bulls by Red Bull reinstated one Sycamore
- 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
- 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.
- Royal Air Force
- Central Flying School
- No. 22 Squadron RAF
- No. 32 Squadron RAF
- No. 84 Squadron RAF
- No. 103 Squadron RAF
- No. 110 Squadron RAF
- No. 118 Squadron RAF
- No. 194 Squadron RAF
- No. 225 Squadron RAF
- No. 228 Squadron RAF
- No. 275 Squadron RAF
- No. 284 Squadron RAF
- No. 651 Squadron RAF
- No. 657 Squadron RAF
- Army Air Corps
The RAF Museum Cosford displays Sycamore XJ918. This aircraft saw active service during the Malayan Emergency and was one of the last four Sycamores to be officially retired from RAF service in 1971. It went to the RAF Museum Cosford in 1983.
Other Sycamores are at the Hubschraubermuseum Bückeburg (Bückeburg Helicopter Museum), in Bückeburg, Germany, the Fleet Air Arm Museum in the United Kingdom, the Royal Museum of the Armed Forces and Military History in Brussels, Belgium, the The Helicopter Museum in Weston-super-Mare, the Museum of Army Flying (Middle Wallop, Hampshire) and the Australian Fleet Air Arm Museum in Nowra, Australia.
Specifications (Mk.4 / HR14)
Data from 
- Crew: two
- Capacity: accommodation for three passengers
- Payload: 1,000 lb (454 kg)
- Length: 61 ft 1¼ in (18.62 m)
- Rotor diameter: 48 ft 7 in (14.8 m)
- Height: 13 ft 10.6 in (4.23 m)
- Empty weight: 3,810 lb (1,728 kg)
- Loaded weight: 5,600 lb (2,540 kg)
- Powerplant: 1 × Alvis Leonides piston engine, 550 hp (410 kW)
- Aircraft of comparable role, configuration and era
- Related lists
- "Aircraft of the Month: Bristol Sycamore." Tangmere Military Aviation Museum, Retrieved: 2 January 2017.
- Myall, Eric. Sycamore Seeds: Background and Development of the Bristol Type 171. Air Enthusiast, #77, September/October 1998. pp. 14-19.
- "Bristol Aircraft Company." The Helicopter Museum, Retrieved: 2 January 2017.
- Simpson, Andrew. "INDIVIDUAL HISTORY BRISTOL SYCAMORE HR. 14 XJ918/8190M MUSEUM ACCESSION NUMBER 84/A/1168" (PDF). RAF Museum. Retrieved 18 June 2015.
- "Bristol 171 Sycamore Mk.14, XG547 / G-HAPR". Brussels Air Museum Fund. Retrieved 11 October 2015.
- Jefford 1988, p. 139.
- "Bristol 171 Sycamore". Flugzeug. Retrieved 11 October 2015.
- Barnes, C. H. (1964). Bristol aircraft since 1910. Putnam. ISBN 0-85177-823-2.
- Bowyer, Chaz. The Encyclopedia of British Military Aircraft. Bison Books Limited. ISBN 0-86124-258-0.
- Bridgman, Leonard, ed. Jane's All The World's Aircraft 1951–1952. London: Samson Low, Marston & Company, Ltd 1951.
- Jefford MBE, Wg Cdr C G (1988). RAF Squadrons. A comprehensive record of the movement and equipment of all RAF squadrons and their antecedents since 1912. Shrewsbury: Airlife. ISBN 1-85310-053-6.
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