Great Britain (1939)

Twin-engined fighter-bombert Number built: 114 plus two prototypes

In the history of aviation, small production numbers usually indicated that a particular aircraft did not meet the desired results, or was simply a bad design. However, there were designs that performed well in their designated roles, but still built in few numbers. In such cases, external factors were usually to blame for that aircraft’s downfall. These were typically connected to production difficulties, such as the unavailability, or the unreliability of components. This was the case with the UK Westland Whirlwind, a twin-engined fighter that despite its excellent performance, failed due to engine supply issues, and was built in limited numbers.

History

The 1930s saw the United Kingdom Royal Air Force’s extensive adoption of new technologies. Improvements in fuselage design, new materials, heavier armaments, and more powerful engines were key in this period. These allowed for the development of faster, harder-hitting fighters than those previously in service. At that time, the fighter force of the RAF consisted of biplanes such as the Bristol Bulldog, for example. These were becoming obsolete in regard to speed of and offensive armament. In 1934, the development of much better low-wing fighters was initiated by the Air Ministry. These would evolve into the well-known Hurricane and Spitfire fighters. Such aircraft were armed with licensed 7.62 mm (0.3 in) Browning machine guns, but something with a heavier punch was also considered. For this purpose, the French Hispano-Suiza company was contacted. This company produced the well-known 20mm (0.78 in) Hispano cannon. A license was acquired and these cannons would be built by the BSA company. The delivery of new guns was carried out at a slow pace, and it was not produced in great quantities up to 1942. With the acquisition of a sufficiently strong armament and the availability of more powerful engines, the Air Ministry issued a request for more heavily armed twin-engined aircraft designs. This included the single and a two-seat day and night fighter configuration.

The final specifications for such aircraft were issued in 1936. The principal concept of this new aircraft was to focus a strong armament of four 20mm cannons inside of the aircraft nose. Several companies responded to these requests. The Air Ministry was mostly satisfied with the work of the Bristol, Supermarine, and Westland companies.

Westland Aircraft Ltd., was a relatively new, but successful aircraft manufacturer in mid-1930, and they were highly interested in the new twin-engine fighter project. For this, a team was gathered under the leadership of was designed by W.E.W. Petter.  The project was initially designated as P.9, “P” stands for Petter but has nothing to do with its chief designer, and was presented to the Air Ministry. The following year the Westland project was deemed the best design and given the green light. Orders for the construction of two prototypes were issued, initially designated L6844 and L6845, in February 1937.  The first wind-tunnel tests showed that some changes were needed regarding the model tail assembly due to longitudinal control problems. The Whirlwind was initially to have a twin rudder and fins configuration, but this was changed to a high-set tailplane to solve the problem. In May 1937 the first mock-up was completed. As it was deemed sufficient, work on the first prototype began shortly after its unveiling.  Due to delivery problems, this aircraft could not be completed until October 1938.

At that time, the project was officially designated as Whirlwind. The same month, the first ground test was completed, and shortly after that the maiden flight was made. The aircraft was flight-tested by Westland’s own chief pilot Harald Penrose. Following that, it was allocated to the Royal Aircraft Establishment at Farnborough for future testing.

During this early testing stage, numerous problems were encountered. The engine was somewhat problematic as it was prone to overheating. Another major problem was poor directional stability during flight. This was solved by increasing the rudder area at the tailplanes. In addition, the engineers added a concave-shaped surface on the rudders. To further stabilize the aircraft during stall and dives, an oval-shaped extension was added at the connection point of the vertical and horizontal stabilizers.

With these modifications, the flight testing of the first prototype continued into 1939. At that time the work on the second prototype was nearing completion. It would be tested with engines that rotated in the same direction. As this did not affect its overall performance, it made the production slightly easier. As both prototypes performed well, a production order of 200 aircraft was placed at the start of 1939.

However, precise specifications needed for production were not made until May 1939. The delay was caused by the indecisiveness regarding which engine to use, during this period various proposals were made. Further tests showed problems with exhaust systems, which had to be replaced with simpler designs. The overheating problems led to the redesigning of the pressurized cooling system.

As there were no available 20mm cannons, the prototypes were initially not fitted with any offensive armament. Once these were available, they would be fitted on both prototypes. Additional firing trials were to be carried out. These were to test various other proposed armaments

Following the successful testing of the first prototype, it would be allocated to the No.4 School of Technical Training. The second prototype would be allocated to  RAF No. 25 Squadron In June 1940. It would remain there until it was damaged in an accident and removed from service in June 1941.

Despite the whole project being undertaken in secrecy, both Germany and France were aware of its existence. The French even published technical papers mentioning this aircraft, with the Germans publishing their own in 1940. However, in Britain, the existence of this aircraft was only publicly announced in 1942.

Production

The production of the Whirlwind was delayed due to a lack of engines up to May 1940. The fighter versions that slowly began to be issued for operational use were designated Whirlwind  MK. I. The production version was slightly different from the prototypes. The mudguards on the landing wheels were removed and the exhaust was modified. Some other changes would be implemented during its production, such as moving the position of the radio mast. Initially, it was positioned on the sliding hood but later it would be moved further forward. Beyond that, the cockpit underwent a minor redesign. There were plans to adopt this fighter for service in other parts of the British Empire, but this request was never implemented.

As the production was slowly going on, another order for 200 more aircraft was placed in 1939. But this production quota would be canceled at the end of 1940. The Air Ministry limited the production of this aircraft to only 114 examples. The reasons for these limited production numbers were a general lack of Peregrine engines. These engines were actually being phased out of production in favor of more powerful engines, namely the Rolls Royce Merlin. The last aircraft was completed in December of 1941 or January 1942 depending on the source. Production was carried out at the newly built factories at Yeovil.

Service

Given their small production numbers, it should not come as a surprise that the distribution of this aircraft to frontline units was limited. The first three operational aircraft were allocated to No.25 Squadron stationed at North Weald. These were only briefly used by this unit from June to mid-July 1940. It was decided to instead re-equip the unit with the Beaufighter Mk. IF. The RAF’s No.263 squadron stationed at Grangemouth was next to be supplied with the Whirlwinds. The deliveries of the first aircraft were scheduled to arrive in July 1940. On the 7th of August, an accident occurred where one aircraft was lost. During a take-off, one of the tires blew out damaging the loading gear. Despite this, the pilot managed to retain control and fly off the aircraft away from the airstrip. Once in the air, he was informed of the damage sustained during the take-off. The pilot at that point had two options, either to try a hard landing and hope to survive or to simply bail out of  the aircraft and use his parachute. The pilot chose the latter option, while the aircraft was completely lost, the pilot was unharmed. Due to slow delivery, only 8 aircraft were received by this unit by October 1940. At the end of that year, the unit was repositioned to Exeter. The first combat action occurred on the 12th of January 1941. One aircraft took off and tried to engage returning German bombers. After a brief skirmish, one German Ju 88 was reported to be damaged.  The first air victory was achieved a month later when a Whirlwind managed to shoot down an Arado 196 near Dodman Point.

In March, some 9 out of 12 operational Whirlwinds would be damaged in one of many German air raids. For this reason, the unit was moved to Portreath and then to Filton. During this period the unit suffered further casualties, of which three were in action while the majority were lost during accidents.

On the 14th of June, some 6 aircraft were used in ground attack operations against German airfields at the Cherbourg peninsula. Due to bad weather, the attack was rather unsuccessful. In August, this squadron was repositioned to Charmy Down. From this base it flaw several escort missions. The same month several air raids against enemy air bases were also undertaken. These were successful, with the Whirlwinds managing to destroy many enemy aircraft on the ground. These included: three Ju 88s, possibly up to eight Ju 87s, and a few Bf 109s. Interestingly, even one German submarine was reportedly destroyed.

On a few occasions, enemy aircraft were engaged in the air. During one air clash, some 20 Bf 109s engaged a group of four Whirlwinds. In the following skirmish, the Germans lost two fighters. The British had two damaged aircraft, with one more being lost after a forced landing due to damage sustained during this fight.

No.137 squadron was another operational unit that had some Whirlwinds in its inventory. It was fully operational starting from October 1941 when it was stationed at Charmy Down. This unit was formed with the assistance of the previously mentioned squadron which provided experienced pilots and ground crew. One of the first combat actions of this unit occurred in February 1942. During an engagement with German Bf 109 fighters, this unit lost four Whirlwinds. Both units would continue to operate the Whirlwinds in various combat missions, which usually involved attacking ground targets and facilities, either along the English Channel or in Western parts of occupied Europe.

Fighter-Bomber Adaptation 

While the armament of four cannons offered strong offensive capabilities, a bomb load would expand the air-to-ground capabilities of the plane even further. Such rearmament was proposed in September 1941 by T. Pugh, one of the squadron leaders. Given their limited number and the urgency of other projects, the first tests were not carried out until July 1942. One aircraft was modified at the Aeroplane and Armament Experimental Establishment to be able to carry either 113 kg (250 lb) or 226kg (500 lb) bombs placed beneath the outer wings. The results were positive and mechanics from the No.263 squadron began adding the bomb bracket on the wings starting from August 1942. No.137 squadron followed up soon with the same modifications. While no official designations were issued for these modifications, the units that used them referred to them as Whirlibombers. In total, some 67 such modifications would be carried out.

The first combat action of these modified aircraft occurred on the 9th of September 1942. The British launched an attack on German trawler ships near Cherbourg. These aircraft would see extensive use up to 1943 against various ground targets. Trains were a common target, with some 67 being destroyed.

Whirlwind Mk.II Project

While having a good overall design, the Whirlwinds had a few shortcomings. While having excellent flight performance at low altitudes, at greater heights its performance dropped sharply. The main reason for this was that its Peregrine engines used a small, single-stage, single-gear supercharger, and the small engine lost a considerable amount of power in thinner air. But there were some attempts made to further improve its performance, designated as Mk.II. The main drawback of the whole design was the engines, which while good had the potential to be further improved, and they were quite underpowered compared to the Rolls Royce Merlin engines. In 1940 it was proposed to use stronger Peregrine engines, a modified armament, and an increased fuel load. The armament would have consisted of four 2 cm Hispano Mk.II cannons which were belt-fed. While the fuel load would be increased by 42 gallons. Given that the main producer of engines, Rolls-Royce, was focusing all available resources on Merlin engine production there was simply no room for other projects. Thus the Air Ministry would simply abandon plans to further improve this aircraft.

Final Fate

All produced aircraft would be only used by these two units. Eventually, due to limited production numbers, and the wear of equipment, they were relegated to limited service. No.137 squadron retained its Whirlwinds up to June 1943 before they were replaced with  Hurricane Mk.IVs. The other unit operated them a bit longer, until the end of the year. These would be replaced with the Hawker Typhoon. The surviving aircraft were gathered at various maintenance depots before finally being declared obsolete and scrapped in late 1944. Only one aircraft survived the war. It remained in service up to 1947 before it too was scrapped.

Limited Export Service

As very few aircraft were produced, there was little prospect of them being exported to other Allied nations. An exception would be one aircraft (P6994) which was shipped to America in June 1942. There it was likely used for evaluation and testing, but its history or fate is unknown.

Technical characteristics

The Whirlwind was designed as a twin-engined low-wing, all-metal, day and night fighter. Despite being originally intended for this double role, it was never used in night operations.  The fuselage was oval-shaped and consisted of 17 metal formers that were connected together. The front sections were built using aluminum while the rear part used magnesium alloy. The nose is where the main armament was located, along with a 9 mm thick armor plate to protect the pilot.

The tail assembly had the same construction. Which consisted of a metal frame covered in duralumin sheeting. But if in need of repairs, the whole rear section could be removed. As mentioned the horizontal stabilizers had to be moved further up the fin. An interesting feature of this aircraft was the two-part rudder. Initial testing showed that they were quite ineffective during take-off. For this reason, they were replaced with new ones that were concave,on both sides, in shape.

The wings were constructed using metal frame ribs. These were then covered with duralumin sheeting which was flush riveted. Several various sizes of access panels were added to help the ground repair crew during the maintenance or replacement of damaged parts of the wings. The ailerons were also covered in metal. These were provided with trimming tabs which could be adjusted when the aircraft was on the ground. The wings on this aircraft incorporated the two-engine nacelles. These fairly large, but aerodynamically well-shaped nacelles were used to store the engine, fuel, and oil pumps that the front landing gear units. A highly interesting design decision was to add coolant radiators which were located on the central part of the wing trailing edges. This allows them to reduce the drag as much as possible.

Behind the aircraft’s nose, the cockpit was located. It had a large canopy which provided an excellent all-around view for the pilot. Given the offensive role of the aircraft, the pilot was fairly well protected. To the front, a 9 mm armor plate was positioned. While on the rear and lower parts of the seat were protected by a 6 and 4-mm thick armor plate. The cockpit itself was connected to the main fuselage by using bolts. The front part of the canopy was protected by bullet-resistant laminated glass. Under and behind the cockpit various equipment was stored. This included a radio unit,  de-icing tanks, accumulators, exigent tanks, etc.  To have easy access to some of these a small hatch was installed on the right side of the rear fuselage.

The landing gear consisted of two wing-mounted retractable wheels. With one smaller tailwheel placed. To provide a smoother landing, the front landing gear units used a pair of heavy shock absorbers. These use 790 x 270  mm (31 in x 10 in) Dunlop-type wheels. All three landing gear units retracted to the rear. The two larger wheels retracted into the engine nacelles. The lowering or retracting of the landing gear was controlled by the pilot by using a lever.

This aircraft was powered by two compact, 880 hp Rolls-Royce Peregrine I engines. These were actually fairly underpowered, they weighed about as much as a Merlin but were significantly less powerful. It’s a major reason this plane wasn’t retained, they simply couldn’t upgrade it with a better, but larger engine. These two engines were provided with a 25 cm  (10 in) diameter thick de Havilland three-bladed with variable pitch propellers. This engine was electrically started. The engine was seated on a specially designed mount which consisted of two bearers and bracing tubes. The engine, while enclosed, was provided with several small hatch access points for repair and maintenance. Fuel was supplied to the engine using two separate systems of power by pumps. The fuel was stored inside two tanks located in each wing. These were encased in a duralumin shell. To avoid spilling the fuel inside the aircraft, a self-sealing covering was also used. The total fuel capacity was 609 liters (134 gallons).

The main armament of this type consisted of four 2 cm Hispano Mk.I type 404 cannons. These were mounted in pairs and located in the front aircraft nose. Its ammunition load consisted of 60 rounds per gun set in large drum magazines. Before the aircraft was to fly into action the Hispano cannons had to be manually cocked while still on the ground. Initially, a hydraulic firing mechanism was used. It would be replaced later in the production by a pneumatic firing system.

Besides the use of four cannons various other armament installations were also proposed or tested. For example, a redesigned nose mounting that consisted of 12 Browning machine guns was tested. Another experimental mount consisted of four vertically positioned cannons and three machine guns.  Additional tests were carried out with larger 3.7 cm and 4 cm guns. The plans of using two 4 cm guns were quickly discarded as it would require extensive rework of the aircraft design. In 1942 attempts were made to add two machine guns for self-defense but this was abandoned too.

 

 

Production Versions

• • Two Prototypes – Both used for varius testing and evaluation with one being lost in an accident
    
  • Mk. I Fighter-bomber – over 60 aircraft were armed with bombs
  • Mk.II – Proposed improved versions, none built

Operators

• • UK – The only operator of these aircraft
  • USA – One Aircraft was shipped to America for testing and evaluation, but its fate is unknown

 

Westland Whirlwind Reconstruction

 

Conclusion

The Westland Whirlwind was a quite advanced twin-engined fighter design for its day. Although initially designed as a day and night fighter, it would never fully be used in this role due to problems with the acquisition of stronger engines and limited production run. Thanks to its strong armament it saw combat service as a ground attack aircraft with good results.

But despite its performance, the lack of sufficiently strong engines and general lack of vision for this aircraft ultimately killed the project. It was more a case that the aircraft was built around an engine that just wasn’t very good, and it couldn’t accept the larger, but much more powerful Merlin engine.

 

Westland Whirlwind  Specifications
Wingspans	13.7 m / 45 ft
Length	9.8 m / 32 ft 3 in
Height	4.9 m / 16 ft 3 in
Wing Area	23.23 m² / 250 ft²
Engine	Two 880 hp Rolls Royce Peregrine inline piston engine
Empty Weight	3.770 kg /8.310 lb
Maximum Takeoff Weight	5.180 kg /11.410 lb
Climb Rate to 6.1 km	In 8 minutes
Maximum Speed	580  km/h / 360 mph
Diving speed	645 km/h / 400 mph
Range	1,115 km / 630 miles
Maximum Service Ceiling	9.240 m / 30.300 ft
Crew	1 pilot
Armament	Four 2 cm ( 0.78in) cannons Payload of 454 kg (1,000 lb kg) bombs

Credits

• Article written by Marko P.
• Edited by  Henry H.
• Ported by Marko P.
• Illustrated By Godzilla

Illustrations

 

 

Source:

• M. Ovcacik and K. Susa (2002) Westland Whirlwind, 4+ Publication
• D. Monday (1994) British Aircraft Of World War II, Chancellor Press
• Duško N. (2008)  Naoružanje Drugog Svetsko Rata-.Beograd
• P. J. R. Moyes  The Westland Whirlwind, Profile Publication
• https://www.whirlwindfp.org/