The Bristol Type 173 was a British twin-engine,
tandem rotor
Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction.
The original use of the term in English was in ''tandem harness'', which is used for two ...
transport
helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
built by the
Bristol Aeroplane Company.
[Jackson 1973, pp. 260–263] It was designed by
Raoul Hafner as a civil transport helicopter but evoked interest from the military. It did not enter production but was developed into the
Bristol Belvedere which was operated by the
Royal Air Force
The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...
from 1961 to 1969.
Design and development
![XF785-Bristol173-2006](https://upload.wikimedia.org/wikipedia/commons/7/7c/XF785-Bristol173-2006.jpg)
The Type 173 was a tandem rotor development of the earlier
Type 171 Sycamore single-rotor helicopter. It used two Sycamore
Leonides Major engine and rotor installations with a new fuselage.
The rotor gearboxes were connected by a shaft which enabled one engine to drive both rotors if an engine failed.
The first Type 173 Mk 1
registered ''G-ALBN'' made its first hovering flight on 3 January 1952 but it tended to fly backwards. After landing from a second hovering flight ground resonance developed.
Modifications to the aircraft to correct these shortcomings delayed the first flight out of the hover, which occurred on 24 August 1952.
During 1953 it was evaluated by the Royal Air Force (using
serial number ''XF785'') and also carried out sea trials for the Royal Navy on the aircraft carrier
HMS ''Eagle''.
To overcome resonance in the fuselage it was later fitted with four-bladed rotors.
The second Type 173 was designated Type 173 Mk 2 and allocated military serial ''XH379'', and had a revised landing gear, with castoring front wheels and fixed rear wheels.
It was also fitted with small stub wings at the front and rear to improve the cruise speed, the stub wings being removed after a few flights when the helicopter was used for Naval trials, and a horizontal tailplane was added.
As a result of the trials the Royal Navy showed an interest in ordering the type for carrier duties.
In August 1956 the second prototype was leased to
British European Airways
British European Airways (BEA), formally British European Airways Corporation, was a British airline which existed from 1946 until 1974.
BEA operated to Europe, North Africa and the Middle East from airports around the United Kingdom. The a ...
for evaluation.
[Jackson 1973, p. 528] The Mk 2 aircraft was destroyed in an accident during an
air show at Filton in September 1956. The helicopter crashed into the ground nose first while making the transition from hover to forward flight. The crew escaped unharmed but the aircraft was written off. After the crash the tailplane was salvaged from the Mk 2 and fitted to the Mk 1 to investigate the best configuration for stability.
The Mk 1 and Mk 2 prototypes were fitted with two 9-cylinder
Alvis Leonides
The Alvis Leonides was a British air-cooled nine-cylinder radial aero engine first developed by Alvis Car and Engineering Company in 1936.
Design and development
Development of the nine-cylinder engine was led by Capt. George Thomas Smith-Cla ...
73 engines, each rated at 550hp (410 kW)
The company received a contract for three evaluation helicopters from the
Ministry of Supply, these improved Type 173 Mk 3 had four-bladed rotors, a taller aft pylon for improved efficiency in gusty air, stronger airframes and were powered by 14-cylinder 850 hp
Alvis Leonides Major engines.
They were to be used for evaluation by the Royal Air Force and Royal Navy which has both issued specifications in 1953 for tandem helicopters.
The Royal Navy requirement (Specification HR.146) was for a Leonides Major-powered aircraft for a shipborne helicopter for anti-submarine, rescue and transport duties, Specification HR.149 was for a similar aircraft for the Royal Canadian Navy.
The Royal Air Force issued specification H.150 for a general-purpose transport helicopter with the ability to lift bulky external loads. Bristol produced three designs, the Type 191 to meet the Royal Navy requirement, Type 192 for the Royal Air Force and the Type 193 to be built in Canada for the
Royal Canadian Navy
The Royal Canadian Navy (RCN; french: Marine royale canadienne, ''MRC'') is the naval force of Canada. The RCN is one of three environmental commands within the Canadian Armed Forces. As of 2021, the RCN operates 12 frigates, four attack submar ...
.
In April 1956 orders were placed for 94 helicopters of all three types, prototypes with Leonides Major engines and production aircraft to use
Napier Gazelle
The Napier Gazelle is a turboshaft helicopter engine that was manufactured by D. Napier & Son in the mid-1950s. In 1961 production was nominally transferred to a joint venture with Rolls-Royce called Napier Aero Engines Limited."ENGLISH ELEC ...
turboshafts.
The third Type 173 was first hovered on 9 November 1956 but further flights were stopped when engine overheating and transmission failures were experienced during ground rig trials.
Although these problems were not severe they were used by the Admiralty as part of the case to cancel the British naval order and place an alternate order for
the Westland-built variant of the US
Sikorsky S-58.
Soon afterwards Canada cancelled the Type 193 in an economy drive.
The company concentrated on the Gazelle-engined Type 192 for the Royal Air Force and the first two of the cancelled Type 191s were used as Gazelle ground test rigs, the third being used as a control fatigue rig.
The original Royal Air Force order for 22 was increased to 26, and the first Type 192 (later given the service name
Belvedere Belvedere (from Italian, meaning "beautiful sight") may refer to:
Places
Australia
*Belvedere, Queensland, a locality in the Cassowary Coast Region
Africa
* Belvedere (Casablanca), a neighborhood in Casablanca, Morocco
*Belvedere, Harare, Zi ...
) flew on 5 July 1958.
Variants
;Type 173 Mk 1
:First prototype.
;Type 173 Mk 2
:Second prototype.
;Type 173 Mk 3
:Three more prototypes for military evaluation with four-bladed rotors.
;Type 191: Projected naval version. Never flown; first two aircraft used as Gazelle ground test rigs for Type 192.
;
Type 192
:Military transport helicopter for the Royal Air Force, named Belvedere.
;Type 193
:Variant of the Type 191 for the Royal Canadian Navy, not built.
Operators
;
*
British European Airways
British European Airways (BEA), formally British European Airways Corporation, was a British airline which existed from 1946 until 1974.
BEA operated to Europe, North Africa and the Middle East from airports around the United Kingdom. The a ...
for evaluation
*
Royal Air Force
The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...
for evaluation
*
Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...
for evaluation
Aircraft on display
The prototype Type 173 ''XF785'' was stored at the
RAF Museum Cosford
The Royal Air Force Museum Cosford, located in Cosford in Shropshire, is a free (currently, 2022) museum dedicated to the history of aviation and the Royal Air Force in particular. The museum is part of the Royal Air Force Museum, a non-departme ...
until 2002, when it was moved to
Kemble for display at the Bristol Aero Collection, until that site closed in May 2012.
It was subsequently moved to
Aerospace Bristol.
Specifications (Type 173 Mk 2)
References
Citations
Bibliography
*
*
{{Bristol aircraft
1950s British helicopters
173
Year 173 ( CLXXIII) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Severus and Pompeianus (or, less frequently, year 926 ''Ab urbe c ...
Tandem rotor helicopters
Aircraft first flown in 1952
Twin-engined piston helicopters