Westland Welkin

Westland Aircraft Company

Industry	Aerospace
Founded	1935
Headquarters	Yeovil , United Kingdom
Products	Aircraft, including the Westland Welkin

The Westland Welkin was a British twin-engine heavy fighter developed by the Westland Aircraft Company, engineered specifically for operations at very high altitudes within the stratosphere. The term welkin refers to "the vault of heaven" or upper atmosphere. Initiated in 1940, this aircraft was created in reaction to the deployment of modified Junkers Ju 86P bombers conducting reconnaissance missions, which raised concerns that the Luftwaffe might resume high-altitude bombing raids over Britain. Production took place between 1942 and 1943. However, as the anticipated threat did not emerge, only a limited number of Welkin aircraft were manufactured, with few entering active service.

Design and development

Westland proposed the P.14, essentially an evolution of their Whirlwind fighter design (alongside the more experimental P.13 twin), to satisfy Air Ministry Specification F.4 of 1940 for a high-altitude fighter. The most distinctive characteristic was its very large high-aspect-ratio wing, spanning 70 feet on production models. For reference, the Avro Lancaster heavy bomber featured a wingspan of 102 feet, while the de Havilland Mosquito had a wingspan of 54 feet. The original Whirlwind’s compact but problematic Rolls-Royce Peregrine engines were replaced by more powerful two-stage Rolls-Royce Merlin Mk.76/77 engines. A major innovation was the pressurised cockpit, which demanded significant design effort. After extensive development, a new cockpit structure was created using thick duralumin plates bolted directly to the main spar's front. The canopy consisted of an inner thick perspex layer to maintain pressure and an outer thin layer to streamline aerodynamics, with heated air circulated between them to prevent frost accumulation.

In January 1941, the Ministry of Aircraft Production approved construction of two P.14 prototypes, DG558 and DG562. That same year, Specification F.4/40 was revised to F.7/41, positioning the Welkin against competitors like Vickers Type 432 equipped with Merlin 61 engines.

The pressurisation was supplied by a Rotol supercharger linked to the left-hand engine (the key difference between Merlin 76 and 77 variants), maintaining a constant pressure approximately 3.5 psi above ambient atmospheric pressure. This system resulted in a cabin altitude equivalent to about 24,000 feet when flying at its operational ceiling near 45,000 feet. Since this cabin altitude remained too high for unassisted breathing, pilots were required to wear oxygen masks during flights. A rubber gasket inflated with pressurised air sealed the canopy when activated, and an automatic valve regulated cabin pressure. Additionally, pilots wore specialised high-altitude suits due to potential bailout scenarios at extreme altitudes.

The Welkin featured an advanced electrical system designed to reduce cockpit seal penetrations for controls and instruments; pre-flight checks of this system required about four hours by skilled electricians familiar with its intricacies. Due to its expansive wingspan, the Welkin did not employ the Whirlwind’s Fowler flaps but instead used simpler split flaps for lift control. The enlarged wing area necessitated a longer tail section to enhance stability by increasing moment arm length. Armament consisted of four Hispano 20 mm cannons housed in a belly-mounted tray that simplified reloading and minimized muzzle flash interference with pilot vision.

However, the Welkin faced significant challenges with compressibility effects caused by its elongated high-aspect-ratio wing, which had a root thickness-to-chord ratio near 19% for structural strength. This led to a drastically narrowed flight envelope at high altitudes between stall due to excessive angle of attack and shock stall from approaching critical Mach number speeds—a common limitation among subsonic high-altitude aircraft also observed in later designs like the Lockheed U-2. When W.E.W. Petter designed his subsequent high-altitude aircraft—the English Electric Canberra jet bomber—he opted for noticeably shorter wings with a root thickness-to-chord ratio around 12%, delaying compressibility onset until approximately Mach 0.85.

Details regarding the Welkin remained classified until after World War II concluded.

A radar-equipped two-seat night fighter variant called the Welkin NF.Mk.II was developed under Specification F.9/43; however, only one prototype was built as it did not proceed into production.

Operational history

When the Welkin Mk.I reached completion and entered production, it had become clear that the Luftwaffe had largely ceased conducting high-altitude sorties. This shift was primarily due to effective interceptions by specially adapted Supermarine Spitfires. In total, only 77 fully assembled Welkins were manufactured, alongside an additional 26 airframes delivered without engines. Although two Welkins were assigned to the Fighter Interception Unit at RAF Wittering between May and November 1944, where they contributed to tactical development and pilot training for high-altitude engagements, the RAF never deployed the Welkin in active combat operations.

Variants

• P.14: Prototype pair constructed to fulfill Air Ministry Specification F.7/41.
• Welkin Mk.I: High-altitude, single-seat twin-engine fighter; 75 units completed with an extra 26 airframes produced without engines.
• Welkin NF.Mk.II: Night fighter variant featuring two seats, converted from a Mark I prototype.

Operators

Template:UK

• Royal Air Force
  • Fighter Interception Unit – RAF Wittering (utilized two aircraft for evaluation purposes)

External links

• Westland Welkin – British Aircraft Directory