Westland Whirlwind (fighter)

The Westland Whirlwind was a British twin-engined heavy fighter developed by Westland Aircraft. It was the Royal Air Force's first single-seat, twin-engined, cannon-armed fighter, and a contemporary of the Supermarine Spitfire and Hawker Hurricane. It was one of the fastest aircraft in service when it flew in the late 1930s, and was much more heavily armed than any other. However, protracted development problems with its Rolls-Royce Peregrine engines delayed the entire project and only a relatively small number were ever built. During the Second World War only two RAF squadrons were equipped with the Whirlwind, and despite successful use as a fighter-bomber it was withdrawn from service in 1943.

Background
The Whirlwind was developed for the RAF in the mid-1930s, following the retirement of biplane fighters. With increased fighter attack speeds creating shorter times for firing on targets, it was decided to improve the weight of fire that could be delivered. Instead of two rifle-calibre machine guns, six or eight were required; studies had shown that eight machine guns could deliver 256 rounds per second. Cannon, such as the French 20mm Hispano-Suiza HS.404, which could fire explosive ammunition, offered another type of heavy firepower, and requirements were made for aircraft designs which could carry four cannon.

A problem for designers in the 1930s was that most agile combat aircraft were generally small. These aircraft had limited fuel storage and only enough flying range for defensive operations. A multi-engined fighter appeared to be the best solution to the problem of range, but a fighter large enough to carry an increased fuel load might be too unwieldy to successfully engage in combat. Germany and the United States pressed ahead with their design programs, resulting in the Messerschmitt Bf 110 and the Lockheed P-38 Lightning.

The first specification for a high performance machine-gun monoplane was F.5/34 but the aircraft produced were overtaken by developments by Hawker and Supermarine.

Design and development
The Air Staff thought that an experimental aircraft armed with the 20mm cannon was needed urgently and Air Ministry specification F.37/35 was issued in 1935. The specification called for a single-seat day and night fighter armed with four cannon. The top speed had to be at least 40 mph greater than that of contemporary bombers - at least 330 mph at 15,000 ft (4,570 m).

Eight aircraft designs from five companies were submitted in response to the specification. Boulton Paul offered the P.88A and P.88B (two related single engine designs); Bristol the single-engined Type 153 and the twin-engined Type 153A; Hawker offered a variant of the Hurricane; the Supermarine 312 was a variant of Spitfire and the Supermarine 313 a twin engined design with four guns in the nose and potentially a further two firing through the propeller hubs; the Westland P.9 had two Rolls-Royce Kestrel K.26 engines and a twin tail.

When the designs were considered in May 1936, there were two issues - concern that two engines would be less manoevrable than a single-engined design and that uneven recoil from cannons set in the wings would give less accurate fire. The conference favoured two engines with the cannon set in the nose and recommended the Supermarine 313.

Although Supermarine's efforts were favoured due to their success previously with fast aircraft and the promise of the Spitfire which was undergoing trials, neither they nor Hawker were in a position to deliver a modified version of their single-engined designs quickly enough. Westland which had less work and was more advanced in the project was chosen along with the P.88 and the Type 313 for construction. A contract for two P.9s was placed in February 1937 which were expected to be flying in mid-1938. The P.88s were ordered in December along with a Supermarine design to F37/35 but both were cancelled in January.

Westland's design team, under the new leadership of Teddy Petter (who later designed the English Electric Canberra, Lightning and Folland Gnat) designed an aircraft that employed state-of-the-art technology. The magnesium monocoque fuselage was a small tube with a T-tail at the end, although as originally conceived, the design featured a twin tail which was discarded when large Fowler flaps were added that caused large areas of turbulence over the tail unit. The horizontal stabilizer (tailplane) was moved up out of the way of the disturbed air flow caused when the flaps were down. The engines were the Kestrel K.26, later renamed Peregrine, with internal exhaust and leading edge radiators to reduce drag. The airframe was built completely of stressed-skin duraluminium, with the pilot sitting high under one of the world's first full bubble canopies, while the low and forward location of the wing made for superb visibility (except for directly over the nose). Four 20 mm cannon were mounted in the nose, making it the most heavily armed fighter aircraft of its era; the clustering of the weapons also meant that there were no convergence problems as with wing-mounted guns. Hopes were so high for the design that it remained "top secret" for much of its development, although it had already been mentioned in the French press.

The first prototype (L6844) flew on 11 October 1938, construction had been delayed chiefly due to the new features and also the late delivery of the engines. Further Service Trials carried out at Martlesham Heath. It exhibited excellent handling and was very easy to fly at all speeds. The only exception was the inadequate directional control during takeoff which necessitated an increased rudder area above the tailplane. Production orders were contingent on the success of the test program; delays caused by over 250 modifications to the two prototypes led to an initial production order for 200 aircraft being held up until January 1939 followed by a second order for a similar number, deliveries to fighter squadrons being scheduled to begin in September 1940. Earlier, due to the lower expected production at Westland, there had been suggestions that production should be by other firms and an early 1939 plan to build them at the Castle Bromwich factory was dropped in favour of Spitfire production.

The Whirlwind was quite small, only slightly larger than the Hurricane in overall size, but smaller in terms of frontal area. The landing gear was fully retractable and the entire aircraft was very "clean" with few openings or protuberances. Radiators were in the leading edge on the inner wings rather than below the engines. This careful attention to streamlining and two 885 hp Peregrine engines powered it to over 360 mph (580 km/h), the same speed as the latest single-engine fighters.

But there were problems as well. The aircraft had limited range, under 300 miles combat radius, which made it marginal as an escort. More troublesome were the continued failures of the Peregrine engine. It was originally intended to be one of Rolls' main designs, but the Merlin had become much more important to the war effort and the Peregrine was relegated to a secondary status and development cancelled (there being no other aircraft needing the engine); the first deliveries of Peregrine engines did not reach Westland until January 1940.

By 1940, the Supermarine Spitfire was mounting 20 mm cannons, so the "cannon-armed" requirement was also being met, and by this time the role of escort fighter was becoming less important as RAF Bomber Command turned to night bomber missions. The main qualities the RAF were looking for in a twin-engine fighter were range and carrying capacity (to allow the large radar apparatus of the time to be carried), in which requirements the Bristol Beaufighter could perform just as well as or even better than the Whirlwind.

Development and delivery problems with the Peregrine engines, along with a number of flying accidents and the aircraft’s high landing speed (which restricted the number of airfields from which it could operate), resulted in Whirlwind production being ended in January 1942, after the completion of just 112 production aircraft. Westland campaigned for the creation of a Mk II model, initially designed around a more powerful 1,010 hp Peregrine which was aborted owing to Rolls-Royce's cancellation of further development of the engine. Additional proposals by Petter similarly remained as "paper projects" and included re-engining with Bristol Hercules, American radials and even using two 1,400 hp Merlin XX engines, each concept being rejected by the Air Ministry. Westland were aware that their design - which had been built around the Peregrine - was incapable of being re-engined with anything larger.

Operational history
The first squadron to receive the Whirlwind was No. 25 Squadron, then based at North Weald. The squadron was fully equipped with radar-equipped Bristol Blenheim IF night fighters when Squadron Leader K. A. K. MacEwen flew prototype Whirlwind L6845 from Boscombe Down to North Weald on 30 May 1940. The following day it was flown and inspected by four of the squadron's pilots, and the next day was inspected by the Secretary of State for Air, Sir Archibald Sinclair, and Lord Trenchard. The first two production Whirlwinds were delivered in June to 25 Squadron for night-flying trials. It was then decided, however, to re-equip No. 25 Squadron with the two-seat Bristol Beaufighter night fighter, as it was already an operational night fighter squadron.

It was instead decided that the first Whirlwind squadron would be 263 Squadron, which was reforming at Grangemouth, Scotland after disastrous losses in the Norwegian Campaign. The first production Whirlwind was delivered to No. 263 Squadron by its commander, Squadron Leader H. Eeles on 6 July. Deliveries were slow, with only five on strength with 263 Squadron on 17 August 1940, with none serviceable. (The squadron supplemented its strength with Hawker Hurricanes to allow the Squadron's pilots to fly in the meantime. ) Despite the Battle of Britain and the consequent urgent need for fighters, 263 Squadron remained in Scotland - Air Chief Marshall Hugh Dowding, in charge of RAF Fighter Command, stated on 17 October that 263 could not be deployed to the south because "there was no room for 'passengers' in that part of the world".

The first Whirlwind was written off on 7 August when Pilot Officer McDermott had a tyre blow out while taking off in P6966. In spite of this he managed to get the aircraft airborne. Flying Control advised him of the dangerous condition of his undercarriage, and to land the aircraft in such condition was extremely hazardous. PO McDermott bailed out of the aircraft between Grangemouth and Stirling. The aircraft dived in and buried itself 30 feet into the ground (see Survivors).

No. 263 Squadron moved south to RAF Exeter and was declared operational with the Whirlwind on 7 December 1940. Initial operations consisted of convoy patrols and anti E-boat missions. The Whirlwind’s first confirmed kill occurred on 8 February 1941, when an Arado Ar 196 floatplane was shot down; the Whirlwind responsible also crashed into the sea and the pilot was killed. From then on the Squadron was to have considerable success with the Whirlwind while flying against enemy Junkers Ju 88s, Dornier Do 217s, Bf 109s and Fw 190s.

The squadron also occasionally carried out day bomber escort missions with the Whirlwinds, one example was when they formed part of the escort of 54 Blenheims on a low-level raid against power stations near Cologne on 12 August 1941. Owing to the relatively short range of the escorts, including the Whirlwinds, the fighters turned back near Antwerp, with the bombers continuing on without escort. Ten Blenheims were lost.

The major role for the squadron's Whirlwinds, however, became low-level attack, flying cross-channel "Rhubarb" sweeps against ground targets and "Roadstead" attacks against shipping. The Whirlwind proved a match for German fighters at low level, as demonstrated on 6 August 1941, when four Whirlwinds on an anti-shipping strike were intercepted by a large formation of Messerschmitt Bf 109s, claiming three Bf 109s destroyed for no losses. A second Whirlwind squadron, No. 137, formed in September 1941, specialising in attacks against railway targets. In the summer of 1942, both squadrons' Whirlwinds were fitted with racks to carry two 250 lb or 500 lb bombs, and nicknamed Whirlibombers. These undertook low-level cross-channel "Rhubarb" sweeps, attacking locomotives, bridges, shipping and other targets.

Channel Dash
No. 137 Squadron's worst losses were to be on 12 February 1942 during the Channel Dash, when they were sent to escort five British destroyers, unaware of the escaping German warships Scharnhorst and Gneisenau. Four Whirlwinds took off at 13:10 hours, and soon sighted warships through the clouds about 20 miles from the Belgian coast. They descended to investigate and were immediately jumped by about 20 Bf 109s of Jagdgeschwader 2. The Whirlwinds shot at anything they got in their sights, but the battle was against odds. While this was going on, at 13:40 two additional Whirlwinds were sent up to relieve the first four, two more Whirlwinds took off at 14:25. Four of the eight Whirlwinds failed to return.

Münsterland
From 24 October until 26 November 1943, Whirlwinds of 263 Squadron made several large attacks against the German blockade runner Münsterland, in dry dock at Cherbourg. As many as 12 Whirlwinds participated at a time in dive bombing attacks carried out from 12,000 to 5,000 ft using 250 lb bombs. The attacks were met by very heavy anti-aircraft fire, but virtually all bombs fell within 500 yards of the target. Only one Whirlwind was lost during the attacks.

Retirement
The last Whirlwind mission to be flown by 137 Squadron occurred on 21 June 1943, when five Whirlwinds took off on a "rhubarb" attack against the German airfield at Poix. One (P6993) was unable to locate the target and instead bombed a supply train north of Rue. While returning, the starboard throttle jammed in the fully open position and the engine eventually lost power. It made a forced landing in a field next to RAF Manston, but the aircraft was a complete write-off, although, as in many other crash landings in the type, the pilot walked away unhurt.

No. 263 Squadron, the first and last squadron to operate the Whirlwind, flew its last Whirlwind mission on 29 November 1943 and turned in their aeroplanes and converted to the Hawker Typhoon in December that year. On 1 January 1944, the type was officially declared obsolescent. The remaining serviceable aircraft were transferred to No. 18 Maintenance Unit, while those undergoing repairs or overhaul were only allowed to be repaired if they were in near-flyable condition, an official letter forbidding aircraft needing repair to be worked on.

Experimental conversions
One Whirlwind was tested as a night fighter in 1940 with No. 25 Squadron, while the first prototype was tested with an armament configuration of twelve 0.303 machine guns. Another Whirlwind had a single 37 mm cannon fitted. The Whirlwind was built with "muffs" to hide flames from the exhausts and landing lights suitable for night flying.

Evaluation
The performance of the Peregrine engine fell off at altitude, so the Whirlwind was used almost exclusively at low level, where it could hold its own against the Bf 109. Though the Peregrine is a much-maligned powerplant, it actually proved to be more reliable than the troublesome Napier Sabre engine used in the Hawker Typhoon, the Whirlwind's successor.

In the ground-attack role the Whirlwind excelled, proving to be both an excellent bombing platform and highly durable. The presence of a second engine meant that many seriously damaged aircraft were able to return from dangerous bombing missions over occupied France and Belgium with one engine knocked out.

The Whirlwind's four 20mm cannon proved extremely effective. From 1941 until 1943, the aircraft was a frequent unwelcome sight over German airfields, marshaling yards, and locomotives. The Whirlwind was used to particularly good effect as a gun platform for destroying German supply trains. Pilots were often credited with several trains damaged or destroyed in a single mission. The aircraft was also very successful in hunting and destroying German E-boats which operated in the English Channel.

The Whirlwind became distinguished for its survivability during crash landings and ground accidents. The placement of the wings and engines ahead of the cockpit allowed the aircraft to absorb a great deal of damage while the cockpit area remained largely intact. As a result, many pilots were able to walk away unhurt from aircraft that were totally written off, a rare occurrence in 1930s era aircraft.

All pilots who flew this aircraft enthused about it in the air. If the Whirlwind had a fault, it was its high approach and landing speed. Because of the low production level, based on the number of Peregrines available, no redesign of the wing was contemplated, although Westland did test the effectiveness of leading-edge slats to reduce speeds. When the slats were activated with such force that they were ripped off the wings, the slats were wired shut.

Philip J.R. Moyes noted in Aircraft in Profile 191: The Westland Whirlwind: "The basic feature of the Whirlwind was its concentration of firepower: its four closely- [sic]grouped heavy cannon in the nose had a rate of fire of 600 lb./minute – which, until the introduction of the Beaufighter, placed it ahead of any fighter in the world. Hand in hand with this dense firepower went a first-rate speed and climb performance, excellent manoeuvrability, and a fighting view hitherto unsurpassed. The Whirlwind was, in its day, faster than the Spitfire down low and, with lighter lateral control, was considered to be one of the nicest 'twins' ever built… From the flying viewpoint, the Whirlwind was considered magnificent."

Bruce Robertson, in The Westland Whirlwind Described, quotes a 263 Squadron pilot as saying, "It was regarded with absolute confidence and affection.”

The aircraft is well summed up by Francis K. Mason’s comments in Royal Air Force Fighters of World War Two, Vol. One: Bearing in mind the relatively small number of Whirlwinds that reached the RAF, the type remained in combat service, virtually unmodified, for a remarkably long time…The Whirlwind, once mastered, certainly shouldered extensive responsibilities and the two squadrons were called upon to attack enemy targets from one end of the Channel to the other, by day and night, moving from airfield to airfield within southern England.

The last words on the subject were perhaps best stated by Dr. G. Buckwell who, as a young Sergeant Pilot with 263 Squadron, was shot down in a Whirlwind over Cherbourg. "The Whirlwind was great to fly - we were a privileged few":

In retrospect the lesson of the Whirlwind is clear… A radical aircraft requires either prolonged development or widespread service to exploit its concept and eliminate its weaknesses, Too often in World War II, such aircraft suffered accelerated development or limited service, with the result that teething difficulties came to be regarded as permanent limitations.

Variants

 * P.9 prototype
 * Single-seat twin-engine fighter aircraft prototype. Two built (L6844 and L6845), can be distinguished from later production samples by the mudguards above the wheels (Though the first production sample (P6966) had them as well), the exhaust system and the so-called 'acorn' on the joint between fin and rudder. L6844 had a distinctive downward kink to the front of its pitot tube, atop the tail not seen again in following models. L6844's colour was dark grey and not red, as is often stated. L6844 had opposite rotation engines, L6845 had the same rotation engines as per production machines.


 * Whirlwind I
 * Single-seat twin-engine fighter aircraft, 400 ordered, 2 prototype & 114 production aircraft, total aircraft built 116


 * Whirlwind II
 * Single-seat twin-engine fighter-bomber aircraft, fitted with underwing bomb racks, were nicknamed "Whirlibombers". At least 67 conversions made from the original Mk I fighter.

Operators

 * Royal Air Force
 * No. 25 Squadron RAF tested three aircraft between May and July 1940. ( might have carried code letters "ZK" )
 * No. 263 Squadron RAF operated Whirlwinds between July 1940 and December 1943. Aircraft had applied Squadron's "HE" code letters.
 * No. 137 Squadron RAF operated Whirlwinds between September 1941 and June 1943. Aircraft had applied Squadron's "SF" code letters.
 * No. 137 Squadron RAF operated Whirlwinds between September 1941 and June 1943. Aircraft had applied Squadron's "SF" code letters.

US Navy, one aircraft P6994 was sent to the USA for trials in June 1942 and survived there until at least late 1944.

Survivors
After retirement in December 1943, all but one of the surviving Whirlwinds were sent to 18 Maintenance Unit at Dumfries, Scotland, where they were scrapped. The sole exception, P7048 was retained by Westland, and was granted a civil certificate of airworthiness on 10 October 1946, with the registration G-AGOI. It was used as a company hack for a short time before being withdrawn in 1947 and scrapped.

In October 1979, the remains of Whirlwind P6966, the first Whirlwind to be lost, were recovered near Grangemouth by enthusiasts in a dig group. The two Peregrine engines were recovered, as well as many pieces of the airframe.

The Whirlwind Fighter Project began building a full-scale replica Whirlwind in 2011, with the intention to have it ground running in approximately four years.

Plans for a 2/3 scale replica were marketed for home building in the late 1970s and early 1980s as the Butterworth Westland Whirlwind.