Westland Wyvern with Rolls-Royce Clyde Turboprop

[Would you like to see this in-game?]
  • Yes
  • No
0 voters


In early 1944, W.E.W. Petter, the Chief Technical Officer of Westland, submitted a proposal for a single-seat fleet fighter. He aimed to design an aircraft that combined the flying performance of the most advanced piston-engine fighters with a large payload capacity for a “torpedo/attack fighter” to replace the Royal Navy’s Blackburn Firebrand. By April, the proposal had expanded to three design drafts, with the first two utilising the developing Rolls-Royce H-type 24-cylinder engine (later named the Eagle), differing in engine placement; the latter adopted a turboprop engine. At a meeting at the end of April, the Ministry of Aircraft Production believed that a long-range fighter-bomber would be valuable to both the Royal Air Force and Navy, and recommended that Westland continue development based on the design installing the H24 engine in the nose.

In July, the Admiralty showed strong interest in Westland’s proposal, but the RAF was dissatisfied with the estimated performance of the aircraft. The RAF had already tendered for the Hawker Fury and de Havilland Hornet as future short-range and long-range fighters in 1943, and the estimated top speed of 480mph for Westland’s new aircraft (later revised to 463mph) was inferior to both, with a service entry at least two years later. Additionally, its climb rate was worse, with no significant range advantage, its only merit being the ability to carry a 2000-pound bomb load. Consequently, the RAF withdrew from the project.

Nonetheless, the Admiralty decided to proceed with the project, issuing the specification N.11/44 in August 1944 and ordering six prototypes, one of which was planned to use RR’s Clyde turboprop engine. However, RR assessed that they lacked the resources to develop both the Eagle and Clyde simultaneously and decided to abandon the Eagle project. They estimated that the Eagle would need at least two more years of development to achieve 4000 horsepower, suggesting a more compact and promising turboprop engine might be a better choice for Westland. In June 1945, the Royal Aircraft Establishment also reported that the aircraft using the Eagle was too heavy, and using the lighter Clyde turboprop engine would reduce weight and wing loading, improving the take-off and landing performance, and could even increase the sea-level top speed by 50mph and climb rate by 1000 feet/minute. The resulting Clyde-powered version of Westland’s project was called the W.35 and its wings, tail, fin and empennage were all in common to the Eagle-powered W.34, but it introduced a new fuselage to fit the turboprop engine.

However, in early 1946, Rolls-Royce decided to cease the development of the Clyde in the future and instead focus on developing a new jet engine, which later became the Avon. Westland was advised to use the Armstrong Siddeley Python turboprop as the power for the Wyvern. Due to gearbox issues, neither the Clyde nor the Python was ready in 1946. The Python was larger and heavier than the Clyde. However, since the Clyde would not go into production, Westland had to make do with the Python.

The two types of turboprop engines were not ready for installation until August 1948. However, due to being more compact, the Clyde engine was relatively easy to install. In January 1949, the Clyde-powered VP120 made its first flight. VP120 subsequently underwent a total of 50 flight hours of testing, with a primary focus on performance, engine handling, and an examination of surge behaviour. Due to Rolls-Royce’s decision to cease production and development of the Clyde, Westland also proposed replacing the Clyde with Napier’s E.125 Nomad diesel engine. However, due to the complexity of the Nomad engine, this plan never materialised. VP120 was eventually used for crash barrier trials and was destroyed in the process.


  • Type

    • Single-seater fighter-striker
  • Armament

    • 4 x 20mm Hispano Mk.V Cannons (300 rounds per gun)
    • 3 x 1000lb MC bomb
    • 1 x 2000lb AP bomb
    • 8 x 25lb RP
    • 16 x 60lb RP
    • 1 x 18’’ torpedo Mk.15 or Mk.17, 16 x 60lb RP
    • 2 x Uncle Tom rockets
  • Dimensions

    • Length: 42.25 ft
    • Height: 15 ft
    • Wing Span: 44 ft
    • Wing Area: 355 sq. ft
    • Wing Loading (calculated with 17270lb all-up weight): 48.6 lbs/sq. Ft
  • Weight

    • Tare: 13183lb (5979.9kg)
    • All-Up as Short-range naval fighter (340 imp gal internal fuel): 17270lb (7833.5kg)
    • Overload take-off: 20500lb (9298.6kg)
  • Internal fuel capacity

    • 282 imp gal in three fuselage tanks, 51 imp gal in two inner wing tanks (Protected fuel tanks)
    • 210 imp gal in two outer wing tanks (Unprotected fuel tanks)
  • Engine

    • Type: Rolls-Royce Clyde Turboprop
    • Bare weight: 2900 lb
    • Max RPM: 6000
    • Power
      • 3440 E.H.P. at S.L. (Some source claiming 4030 S.H.P. + 6.89 kN during the trials of VP120)
      • 2815 E.H.P. At 25000 ft.
  • Propeller

    • Blades: 2 x 3
    • Gear ratio: 0.20
    • Diameter: 13 ft
  • Drag in lb. at 100 F.S. (Clean condition)

    • Wings: 25.0
    • Fuselage: 19.5
    • Tail: 11.5
    • Power Plant: 7.5
    • Guns, bombs, drop tanks: 2.0
    • Radio: 1.5
    • Roughness: 1.5
    • Miscellaneous: 9.5
    • Leaks ETC: 2.5
    • Total: 80.5
    • CD0: 0.0191
  • Performance (Clean condition)

    • Max speed (3440 Equivalent B.H.P at sea level at 6000 RPM, 18000 lb)
      • 436 mph at sea level
      • 443 mph at 5000 ft
      • 451 mph at 10000 ft
      • 460 mph at 15000 ft
      • 464 mph at 20000 ft
      • 465 mph at 25000 ft
      • 460 mph at 30000 ft
    • Rate of Climb (All-Up Weight of 17270lb/6000 RPM)
      • 4600 ft/min at sea level
      • 3550 ft/min at 10000 ft
      • 2000 ft/min at 25000 ft
      • 1470 ft/min at 30000 ft
    • Time to Height (All-Up Weight of 17270lb/6000 RPM)
      • 5000 ft: 1.4 mins
      • 15000 ft: 5 mins
      • 25000 ft: 10.4 mins
    • Stalling Speed
      • 93 mph (Engine on)

Major distinctions between the Wyvern S.4 and the Clyde-powered Wyvern VP120

  • To address the Python-powered prototypes’ poorer handling, the S.4 was fitted with a larger fin and tailplane, complemented by auxiliary fins on the tailplane, resulting in increased drag. While the Clyde-powered VP120 retained the tailplane and fin design of the Eagle-powered Wyvern TF.1.
  • The S.4 featured a dihedral angle on its tailplane, which was absent in the VP120.
  • Due to the bulkier Python turboprop engine, the S.4 was equipped with a broader engine cowling. Additionally, its cowling was cut back to ease the loading of starter cartridges.
  • The S.4 was designed with a flat windscreen, in contrast to the VP120’s curved windscreen.
  • The canopy of the S.4 incorporated a composite framing structure, while the VP120 had a one-piece stiffened unit.
  • The S.4’s oil cooler was integrated into the wing root, whereas the VP120 had its oil cooler positioned beneath the engine.
  • The propeller of the S.4 was an 8-blade contra-rotating type while VP120 had a 6-blade type
  • On the S.4, the pilot’s seat was raised further above the fuselage centreline to preserve the original field of view, accommodating the installation of the larger Python engine.
  • The S.4 featured an auxiliary fin adjacent to the aileron on each side of the wing.
  • The S.4 had a different airbrake system.


Clyde-Wyvern VP120


  • ‘Wyvern’ Naval Fighter-Striker - Technical Folder B.114 Issue II., The National Archive Reference: ADM 213/944
  • Westland Wyvern TF Mks.1, 2, T Mk.3, S Mk.4 by 4 + publication, ISBN: 80-902559-9-X
  • Propeller Twilight: The Last Generation of British Piston Engine Fighters by Tony Butler, ISBN: 9781800352735
  • British Secret Projects 3: Fighters 1935-1950 by Tony Butler, ISBN: 9781910809174

This would have been much better to see in the Premium section than the S.4, but that bridge has already been crossed, so +1 for the tech tree


Yeah pity, but +1 for this cause turbo props are neat.

1 Like

+1 for the TT

1 Like

+1 for TT.

1 Like