Hawker Henley

The Hawker Henley was a British two-seat target tug derived from the Hawker Hurricane that was operated by the Royal Air Force during the Second World War.

Henley
Role Target tug
National origin United Kingdom
Manufacturer Hawker Aircraft
First flight 10 March 1937
Introduction 1938
Retired 1945
Primary user Royal Air Force
Number built 202
Developed from Hawker Hurricane
Developed into Hawker Hotspur

Design and development

In 1934 Air Ministry Specification P.4/34 was issued which called for a light bomber that could also be deployed in a close-support role as a dive-bomber.

Fairey, Gloster and Hawker attempted to fulfil this need and competition was tight to attain the highest performance possible. As the aircraft required only a modest bomb load and with performance being paramount, the Hawker design team chose to focus its efforts on developing an aircraft similar in size to their Hurricane fighter.

The Hurricane was then in an advanced design stage and there would be economies of scale if some assemblies were common to both aircraft. This resulted in the Henley, as it was to become known, sharing identical outer wing panel and tailplane jigs with the Hurricane. Both were equipped with the Rolls-Royce Merlin engine as it offered the best power-weight ratio as well as a minimal frontal area. The Henley's cantilever fabric-covered monoplane wing was mid-set, a retractable tail wheel landing gear was selected and accommodation provided for a pilot and observer/air gunner, which differed from the Hurricane's single-seat cockpit.

Although construction of a Henley prototype began as early as mid-1935, with priority given to Hurricane development, it was not until 10 March 1937 that, powered by a Merlin "F" engine, it was first flown at Brooklands, shortly after the competing Fairey P.4/34. Subsequently, the aircraft was refitted with light alloy stressed-skin wings and a Merlin I engine (production version of the F) and further test flights confirmed the excellence of its performance. It could reach a top speed of 300 mph (480 km/h).

By this time the Air Ministry had, however, decided that it no longer required a light bomber (probably because it was felt that this role was adequately filled by the Fairey Battle). Accordingly, the Henley, which in line with RAF policy had not been fitted with dive brakes; bomb crutches; or specialised bomb sights and thus limited to attack angles of no greater than 70° (and consequently far less accurate than specialised German dive bombers of the same period, notably the Ju 87 Stuka, fitted with all of the foregoing and a semi-automatic bomb release and dive termination system and thus capable of near-vertical dives of pin-point accuracy) was relegated to target-towing duty.

Henley production was subcontracted to Gloster Aircraft and 200 were ordered into production.

The second prototype was fitted with a propeller-driven winch to haul in drogue cable after air-to-air firing sorties. This was first flown on 26 May 1938.

Operational history
Hawker Henley deploying drogue target

Production Henley III aircraft, entered service with Nos. 1, 5 and 10 Bombing and Gunnery Schools, as well as with the Air Gunnery Schools at Barrow, Millom and Squires Gate. Unfortunately, it was soon discovered that unless the aircraft were restricted to an unrealistically low towing speed of 220 mph (350 km/h), the rate of engine failures was unacceptably high, attributed to a cooling system matched to the Henley's original missions but inadequate when towing a target at high engine speed but low airspeed.[1] Henleys were relegated to towing larger drogue targets with anti-aircraft co-operation units, predictably proving themselves even less well-suited to this role; the number of engine failures increased and problems with engines were compounded by difficulties releasing drogue targets. Several Henleys were lost after the engine cut out and the drogue could not be released quickly enough. A solution was never found to this problem and in mid-1942, the Henley was withdrawn from service, in favour of adapted Boulton Paul Defiants and specialised Miles Martinet aircraft.[2]

Variants
Henley I
Prototype.
Henley II
Second prototype.
Henley III
Two-seat target tug aircraft for the RAF, 200 built.
Hawker Hotspur
Prototype two seater fighter variant of the Henley with a four-gun power-driven turret. This did not reach production, the requirement being met by the Defiant.

Operators
 United Kingdom

Specifications (Henley Mk III)

Data from Hawker aircraft since 1920[3]

General characteristics

  • Crew: 2
  • Length: 36 ft 5 in (11.10 m)
  • Wingspan: 47 ft 10.5 in (14.592 m)
  • Height: 14 ft 7.5 in (4.458 m)
  • Wing area: 342 sq ft (31.8 m2)
  • Airfoil: root: Clark YH mod (20%) ; tip: Clark YH mod (12%)[4]
  • Empty weight: 6,010 lb (2,726 kg)
  • Max takeoff weight: 8,840 lb (4,010 kg)
  • Powerplant: 1 × Rolls-Royce Merlin II V-12 liquid-cooled piston engine, 1,030 hp (770 kW)
  • Propellers: 3-bladed de Havilland two-pitch propeller

Performance

  • Cruise speed: 235 mph (378 km/h, 204 kn) at 15,000 ft (4,572 m)
  • Target-towing speed: 272 mph (236 kn; 438 km/h) at 17,500 ft (5,334 m)
  • Range: 950 mi (1,530 km, 830 nmi)
  • Service ceiling: 27,000 ft (8,200 m)
  • Rate of climb: 1,150 ft/min (5.8 m/s)
  • Wing loading: 25.9 lb/sq ft (126 kg/m2)
  • Power/mass: 0.121 hp/lb (0.199 kW/kg)

See also

Related development

Aircraft of comparable role, configuration, and era

References
Notes
  1. Mondey, Mondey (1982). Hamlyn Concise Guide to British Aircraft of World War II. Chancellor. p. 145. ISBN 1851526684.
  2. Gunston 1995
  3. Mason, Francis K. (1991). Hawker aircraft since 1920 (3rd, rev. ed.). London: Putnam. pp. 302–307. ISBN 0-85177-839-9.
  4. Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.
Bibliography
  • Cooper, H.J.,O.G. Thetford and C.B. Maycock. Aircraft of the Fighting Powers – Volume II. Leicester, UK: Harborough Publishing, 1942.
  • Gunston, Bill. Classic World War II Aircraft Cutaways. London: Osprey, 1995. ISBN 1-85532-526-8.
  • Hannah, Donald. Hawker FlyPast Reference Library. Stamford, Lincolnshire, UK: Key Publishing Ltd., 1982. ISBN 0-946219-01-X.
  • James, Derek N. Hawker, an Aircraft Album No. 5. New York: Arco Publishing Company, 1973. ISBN 0-668-02699-5. (First published in the UK by Ian Allan in 1972)
  • Mason, Francis K. Hawker Aircraft since 1920. London: Putnam, 1991. ISBN 0-85177-839-9.
  • Mondey, David. The Hamyln Concise guide to British aircraft of World War II. London: Hamlyn/Aerospace, 1982. ISBN 0-600-34951-9.
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