Category Archives: UK

Westland Whirlwind

UK, WW2,

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.

The Westland Whirlwind twin-engined day and night fighter. Source: Wiki

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.

The first prototype during its early testing phase. Source: M. Ovcacik and K. Susa Westland Whirlwind

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.

The second prototype aircraft. Source: Wiki

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.

With its four 2 cm cannon armament this aircraft possesses quite strong firepower. Source: Wiki
Given their limited numbers, only two squadrons would be ever equipped with this type of aircraft during the war. Source: Wiki

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.

With the addition of bombs the firepower of this aircraft was greatly boosted. Source: www.staplesandvine.com
Close-up view of the bomb release mechanism. Source: Pinterest

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 Whirlwind was designed as a twin-engined low-wing all-metal day and night fighter. Some of the easily recognizable features were the enlarged glazed cockpit and the positions of the tail horizontal stabilizers. Source: Wiki

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).

This aircraft was powered by two Rolls-Royce Peregrine engines. The lack of this engine ultimately leads to the abandonment of the whole project. Source: dingeraviation.net

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.

 

Once the nose cover was removed we can clearly see the arrangement of the four 2 cm Hispano Mk.I type 404 cannons. The ground crew member to the left is holding the 60-round drum magazine. Source: /dingeraviation.net

 

Other experimental proposals included adding 12 machine guns. Source: M. Ovcacik and K. Susa Westland Whirlwind
While this proposal included four horizontally positioned cannons and three more machine guns. In either case, none of these would be adopted. Source: M. Ovcacik and K. Susa Westland Whirlwind

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

The completed pilot cockpit and the armament are located at the Kent Battle of Britain Museum. Source: https://www.whirlwindfp.org/

 

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

Whirlwind in the Battle of Britain era camouflage scheme.
Whirlwind in the 1942/43 livery

 

 

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/

 

Boulton Paul P.105 & P.107

UK, WW2, ,

Great Britain (1944)

Strike Fighter Concept

Side view of the Boulton Paul P.105C. This was the single-seat fighter version of the aircraft, armed with four 20mm cannons. (Boulton Paul Archive Photos)

The Boulton Paul P.105 was a concept for a multi-purpose, single-engine aircraft that was designed to fill a number of carrier based roles. To do so, the P.105 would utilize a unique and innovative method that would use interchangeable fuselage sections and cockpit modules that would allow the aircraft to perform different missions. These modules could be changed quickly to fill a needed role aboard carriers or airbases. The aircraft would not be chosen for production, and The P.105 would be developed further into the P.107, a land-based escort version. The P.107 would have a rear-facing turret and a twin boom tail design to allow greater traverse of the gun. This design wouldn’t be adopted either, and the program would conclude before the war’s end.

History

Late in the Second World War, the Royal Naval Air Arm began seeking out a new aircraft design that would be able to fill both the fighter and bomber roles aboard their carriers. Having one aircraft perform multiple roles would eliminate the need for specialized carrier-borne aircraft to fill the fighter, dive bomber, and torpedo bomber roles that were currently in operation. No official requirements were ever put out to build such an aircraft, but several companies had begun developing aircraft that would fit this role, which had become known as the “Strike Fighter”. Westland, Blackburn, Fairey and Boulton Paul would all develop designs that correspond to the strike fighter role. Boulton Paul’s aircraft design would be known as the P.105.

After the production of their Defiant turret fighter was finished, Boulton Paul began producing the Fairey Barracuda carrier bomber under license. After working extensively with a naval aircraft of this type, lead aircraft designer of Boulton Paul, John North, began to show interest in developing new aircraft to serve the Royal Navy’s carriers. The timing for this interest was beneficial too, as the Royal Air Arm began showing interest in new aircraft that were to be used in the Pacific Theater. He would first design a single engine fighter, dubbed the P.103 which would compete for the Navy’s Specification N.7/43 aircraft project. The P.103 was a heavily reworked Defiant with the turret removed and the design heavily cleaned up to make for a more effective fighter. Two designs existed for the P.103; the A and B, with the A using a Rolls Royce Griffon engine and the B using a Bristol Centaurus engine. The P.103 would utilize a number of innovative features, such as contra-rotating propellers, a low drag wing, specialized landing gear that became shorter when stowed, and elevators with automatic trim tabs. In addition, a more radical design was also submitted, the P.104, which was a twin-boom pusher. Despite both the P.103 and P.104 satisfying the specification, the Navy ultimately would find that a Hawker Tempest variant that was to be produced could easily be adapted to this role. This aircraft would become the Hawker Fury, and naval-ized into the Sea Fury.

While the P.103 wouldn’t be built, there were plans to test many of its design features on an existing aircraft. A Defiant was chosen to be extensively modified with most of the features found on the P.103, including the contra-rotating “dive-brake” propellers driven by a Centaurus engine, electric trim tabs, specialized shortening landing gear, and automatically closing landing gear doors. This aircraft, known as the Special Features Defiant, would also go unbuilt, with only a Defiant being modified with the elevator trim tabs. Boulton Paul wouldn’t yield any aircraft from this specification, but a new design would soon come from John North, who would continue working on Naval aircraft projects, looking to create an aircraft that would replace the Fairey Barracuda. Using design aspects intended for the P.103, and newer features found on the Special Features Defiant, he would design the P.105.

Static model of the standard P.105A. (British Secret Projects 1935-1950)

The P.105 was a small, high-performing aircraft that was meant to perform a number of duties aboard carriers. To achieve this the P.105 would have a unique design feature. To fill the variety of carrier-borne roles, the P.105 would have modular cockpit and bomb bay sections. Each of these modules would pertain to a particular role and would include necessary equipment to operate for the given task. The interchangeable modules included a two-seat torpedo-bomber with the necessary modifications to carry a torpedo (P.105A), a two-seat reconnaissance aircraft with an extended cockpit with changes to improve visibility (P.105B), a single-seat fighter armed with four 20mm cannons (P.105C) and a dive-bomber (P.105D). All aircraft aside from the C would be armed with four 12.7mm machine guns. With this system, it was thought more P.105 airframes could be stored inside hangars and carriers, while the unused modules could easily be stored and would take up less space, compared to having a number of different aircraft specified for specific roles, in theory, increasing the combat capacity of the carrier the P.105 would be stationed on. Boulton Paul expected the aircraft to be very high performance, and the P.105C fighter version, would be thought to serve as an excellent penetration fighter. Like its predecessors, the P.105 was originally going to utilize a Griffon 61 engine, but before performance predictions were done on the design, it would change to a Centaurus with counter-rotating propellers. The brochure on the details of the aircraft was submitted to the RNAA, but no order for production came about.While no particular reason was given for the design not being chosen, the modularity concept may have been less convenient in practice then on paper. Another reason could be that current aircraft at the time were deemed to have been performing adequately and didn’t need such an extensive replacement.

A side view plan drawing showing the layout of the Boulton Paul P.107. (Boulton Paul Archive Photos)

Although the P.105 wasn’t granted production, the design was further reworked into the Boulton Paul P.107. The P.107 was a return to basics for Boulton Paul, being a single-engine two-seat fighter with a turret. It can be assumed the P.107 began development during or shortly after the P.105 had been created. John North expressed many concerns with aircraft meant to operate in the Pacific War, with the biggest issue being the extreme range an aircraft would need in order to operate efficiently in this conflict. While details are sparse on its development, the P.107 extended range escort fighter appears to be his own attempt to create an aircraft meant to amend this issue. Overall, the P.107 shared many aspects of the P.105C, continuing to use the same overall design, Centaurus engine with contra-rotating propellers, and the same armament of four 20mm cannons. However, the P.107 wasn’t meant to operate from carriers, instead being designed as a land-based aircraft. Changes done to the design for this reason include the lack of folding wings and the removal of the torpedo blister. The aircraft would also benefit with the addition of a turret housing two 12.7mm machine guns. To improve the firing efficiency of the turret, the single fin of the P.105 was changed in favor of a twin fin design, which improved the firing range of the guns. The P.107 could also be configured for different roles, such as a dive bomber and for reconnaissance, but it is unknown if it used the same modular system the P.105 used. As was the case with his earlier designs, the P.107 wasn’t selected for production either.

Design

3-Way drawing of the P.105B. This was the reconnaissance version. (British Secret Projects 1935-1950)

The Boulton Paul P.105 had a conventional monoplane fighter layout. In the front, it would utilize a 6-bladed contra-rotating propeller that had reversible pitch. Originally, the design would have mounted a Griffon 61 V-12 inline engine but was changed in favor of the Centaurus 18-cylinder radial CE.12.SM engine instead. The wings on the P.105 were inverted gull wings, much like those on the Vought F4U Corsair or Junkers Ju 87 Stuka, which allowed the mounting of a larger propeller. To allow for easy storage aboard carriers, the wings were able to fold inwards. The fuselage had the most interesting aspect of the design overall, and that was its interchangeable cockpit and lower fuselage modules. Each variant of the P.105 would use different modules that would pertain to the intended role it served. The P.105A was a torpedo bomber and would use the torpedo blister present under the tail, and provisions for carrying another crewmember. The P.105B was a reconnaissance aircraft, and its cockpit would be lengthened to sit a pilot and observer. It would use a glass hull beneath the observer to assist in spotting. The P.105C was an escort fighter and would be a one-man aircraft. The last was a dive-bomber version, which only has very sparse details available. The dive bomber would carry up to two 1,000 lb (450 kg) bombs, most likely in an internal bomb bay module. The tail of the aircraft would be a conventional single rudder and tailplane arrangement. The armament of the P.105 was a standard two to four 12.7mm machine-guns in the wings of the aircraft, with the only deviation being the P.105C, which would use four 20mm cannons instead.

3-Way view of the P.107. Notice the turret and twin tail. (British Secret Projects 1935-1950)

The P.107 borrowed many aspects of the P.105 design, but changed some details to better fit its role. The engine and front sections would stay the same, keeping the contra-rotating propellers and Centaurus engine. Reference materials refer to the aircraft as being able to convert from an escort fighter to either a fighter-bomber, or photo reconnaissance aircraft. However, whether it was a conventional conversion, or via the module system the P.105 used is unknown, the latter being most likely. The wing design would stay the same, with the inverted gull wing style. Given its land-based nature, the wings no longer needed to be folded to conserve space, and the torpedo blister under the tail was removed. Behind the pilot, a gunner would sit and remotely control two 12.7mm machine guns. The machine-guns would be housed within the aircraft, with only the ends of the barrel protruding out. To give the gunner a better firing arc, the single tailfin was switched to a double tailfin. The turret and twin tail design are the most obvious differences between the P.107 and P.105. The aircraft’s fuel would be stored in a main tank beneath the crew members and two smaller drop tanks. The fuel amount was expected to give the aircraft a 3,000 mi (4,827 km) range, with up to 30 minutes of combat. The drop tanks could be switched for 2,000 Ib (900 Kg) of bombs. For offensive armament, the P.107 would use four 20m cannons mounted in the wings.

Conclusion

While no P.105 or P.107 would be constructed, the designs do attempt to amend issues that were present at the time. The Strike Fighter designation would eventually become a standard type of aircraft aboard carriers, and aircraft meant to fulfill multiple roles would also eventually be developed, but none would ever use such a unique system as the interchangeable fuselage of the P.105. It is interesting to note that the P.105 and P.107 appear to be the last military propeller aircraft that Boulton Paul would design before their switch to trainers and jet powered research aircraft, the aircraft themselves being distantly related to their Defiant fighter that they became known for during the war.

Variants

 

  • Boulton Paul P.105A– Two-seat torpedo bomber version of the P.105.
  • Boulton Paul P.105B– Two-seat reconnaissance version of the P.105. This version would have a glazed hull for the observer.
  • Boulton Paul P.105C– Single-seat Fighter version of the P.105.
  • Boulton Paul P.105 Dive bomber– Dive bomber version of the P.105. No designation was given to this design. (P.105D?)
  • Boulton Paul P.107– Land-based escort fighter derived from the P.105. The P.107 shared many design aspects with the P.105 but would remove features that would be needed for carrier use, such as the lack of folding wings. The P.107 would also have a turret and the tailplane would be switched to a double rudder design to accommodate the turret’s firing arc. Photo reconnaissance and fighter bomber versions of the P.107 are also mentioned.

Operators

 

  • Great Britain – Had they been built, the P.105 and P.107 would have been used by the Royal Fleet Air Arm, with a focus of being used in the Pacific Theatre aboard carriers and from land.

Boulton Paul P.105 Specifications
Wingspan 38 ft / 11.6 m
Length 34 ft 5 in / 10.5 m
Folded Width 15 ft 4 in / 4.67 m
Wing Area 250 ft² / 23.3 m²
Engine 3,000 hp ( 2,200 kW ) Centaurus CE.12.SM engine
Fuel Capacity 260 gal (1,180 lit)
Weights 12,285 Ib / 5,572 kg with torpedo

12,509 Ib / 5,674 kg with bombs
Climb Rate 3,660 ft/min / 1,110 m/min
Maximum Speed 469 mph / 755 km/h at 20,000 ft / 6,000 m
Cruising Speed 407 mph / 655 km/h
Range 1,300 mi / 2100 km – 3,320 mi / 5340 km
Crew Pilot

Other crew member (Depending on the variant)
Armament
  • 2-4 12.7mm machine guns (All versions)
  • 1x Torpedo (P.105A)
  • 2x 1,000 Ib (454 kg) bombs (Dive Bomber)
  • 4x 20mm cannons (P.105C)

Boulton Paul P.107 Specifications
Wingspan 38 ft / 11.6 m
Length 34 ft 8 in / 10.6 m
Wing Area 250 ft² / 23.3 m²
Engine 3,000 hp ( 2,200 kW ) Centaurus CE.12.SM engine
Fuel Capacity Main: 495 gal (2,250 lit)

Drop Tanks: 140 gal (640 lit)
Weight 15,900 Ib / 7,200 kg
Max Speed 470 mph / 755 km/h at 22,000 ft / 6,700 m
Range With Drop Tanks: 3,000 mi / 4,800 km

Without: 2,200 mi / 3,540 km

Fighter-Bomber: 700 mi / 1,120 km
Crew 1 Pilot

1 Gunner
Armament
  • 4x 20 mm guns
  • 2 x 12.7mm machine guns in rear facing turret
  • 2,000 Ib (907 kg) of bombs

Illustrations

Boulton-Paul P.107
Boulton-Paul P.105 Reconnaissance Variant

Credits

  • Article written by Medicman11
  • Edited by  Henry H.
  • Ported by Henry H.
  • Illustrated by Haryo Panji

Sources

Boulton Paul P.75 Overstrand

UK, WW2, ,

United Kingdom (1933)

Medium Bomber – 28 Built

A flight of five No.101 Squadron Overstrands. (Boulton Paul Aircraft Since 1915)

The Boulton Paul P.75 Overstrand was a two-engined biplane that became the RAF’s mainstay bomber aircraft in the early to mid 1930s. The Overstrand was an improvement upon the earlier P.29 Sidestrand biplane bombers after the type recieved several criticisms regarding the frontal gunner position being exposed to the elements on such a high speed aircraft. To amend the complaints, Boulton Paul would design a modified version of the Sidestrand that would use a fully-enclosed powered turret, which would be revolutionary for the time. To test the design, three Sidestrands would be converted into Overstrands. The Overstrand would equip No.101 squadron and 25 newly built Overstrands would be constructed. Aside from mainline service, a number were experimentally modified by Boulton Paul, such as receiving different turret arrangements and more powerful engines. By the time of the Second World War, the aircraft had become obsolete, as new monoplane bombers entered production and replaced it. The type would continually fly in limited numbers for training and auxiliary purposes, but by 1941 would be considered obsolete and grounded.

Boulton & Paul and the Sidestrand

The Boulton & Paul P.29 Sidestrand was a modern and aerodynamic aircraft of the time. But while it was fast it had several glaring flaws, the biggest being the open front turret which exposed the gunner to high speed winds and cold air. (Boulton Paul Aircraft Since 1915)

In the mid 1920s, the Boulton & Aircraft company was beset by hard times. The company was surviving off of small orders for prototype aircraft and was in a rough financial state. The company had, up to this point, focused on creating twin-engine biplane bombers, starting with the Bourges in the First World War and going to their latest of the time, the P.25 Bugle. In late 1925, their savior would be their newest twin bomber design; the P.29 Sidestrand. It was an all-metal, twin-engine biplane bomber with extensive work done into designing its aerodynamic fuselage, creating an innovative and sleek-looking aircraft for the time. Production was soon ordered and 18 were built. This new bomber would populate the No.101 squadron, the only bomber squadron the RAF was operating at the time. Despite its success, a problem began to arise with the forward gunners of the aircraft. The Sidestrand, thanks to its aerodynamic design and powerful Bristol Jupiter engines, was able to achieve a top speed of 140 mph (225 km/h). While this speed made the twin engine bomber quite a fast aircraft for the time, this luxury was not so appreciated by the front gunners of the aircraft, who had no means of protection against the strong slipstream in their open cockpits. The strong winds made aiming the Lewis gun difficult, as it was blown around, and even reports of the propellers being hit by drum magazines thrown from the position were growing to be common. This was not to mention the extreme cold the gunner had to endure as well. Frozen fingers were another common complaint from Sidestrand gunners. While the Sidestrands began to take to the air (and torment their front gunners), Boulton & Paul set to procure more production orders of the type over the 18 that were built, but no further production was ordered, mostly due to the worldwide recession. In the early 1930s, many current fighters of the time were experiencing the same slipstream issues as the Sidestrand was. The Air Ministry put out an order on December 28th, 1932 to seek design reworks that would fix this now commonplace issue with the Sidestrand. While many of the other aircraft would seek simple means, the issue with the gunner position on the Sidestrand was more complex and would require more work put into redesigning the aircraft. Ultimately, Boulton & Paul would decide the answer was a completely covered turret. The company had been working on such a design with their P.70 aircraft concept.

The P.70 was a concept aircraft that was based off the P.64 mailplane and used components of the Sidestrand. While it was never built, it had an innovative enclosed nose turret that the Overstrand would use. (Boulton Paul Aircraft Since 1915)

The P.70 was a twin-engine biplane bomber design based on their earlier P.64 mailplane and incorporated aspects of the Sidestrand. In the nose of the P.70 was a fully enclosed, cylindrical turret that was fully powered via compressed air. The turret would have a single gun mounted that elevated and depressed down a vertical split in the design. It would also have 360 degrees of rotation as long as the gun was elevated 70 degrees to allow it to lift over the nose of the aircraft. Ultimately, the P.70 was not selected for the competition it took part in, but the innovative turret design was chosen to be used on the reworked Sidestrand. In addition to making the front gunner more comfortable, other additions were made for the rest of the crew. The rear gunner had a new windshield installed behind his back to protect him from the fast winds, and the pilot now sat in a fully enclosed cockpit. Even further, the aircraft would implement an onboard heating system, taking off excess heat from the engine intakes. Other planned changes to the design were the wings being swept at the outer edges to compensate for the weight of the front turret, and structurally integrity was also improved in the hull of the aircraft to allow for a bigger bomb load. With the improved design finalized, it was chosen that the first aircraft to test this new design, at this point called the Sidestrand V, would be created by modifying a Sidestrand III; J9186. The order for the creation of the prototype would be 29/33.

The mockup of the powered turret design. (Boulton Paul Aircraft)

Design

The Boulton Paul P.75 Overstrand was a twin-engined biplane bomber designed to improve the performance and crew comfort of the Boulton Paul P.29 Sidestrand. The airframe of the aircraft was of all-metal construction. The fuselage had a length of 46ft 11in (14.3 m). The wings of the aircraft were all-metal, 3-bay biplane wings. The wings themselves had an additional outer edge sweep to them, a design choice not found on the Sidestrand. This was to counter the increased weight of the nose due to the powered turret. The aircraft would have a wingspan of 71ft 11 in (29.2 m). Both the upper and lower wings would be built with ailerons. Mounted between the wings were two 580 hp Pegasus II.M.3 engines connected to two 4-bladed metal propellers. The engines were housed in nacelles that also carried a 17 gallon fuel tank, priming pumps, hand-stating magnetos and a gas starter. The very first Overstrand, which was converted from a Sidestrand, was equipped with 555 hp Pegasus I.M.3 engines. Covering the engine cowlings were 9-sided Townend rings. These assisted with improving the airflow of radial engines, reducing drag and increasing the overall speed of the aircraft. Connected to the engine nacelles on each side were the main connectors for the landing gear, which were each supported by struts. The Overstrand had large, rubber wheels that were bigger than those on the Sidestrand. The cockpit was located in front of where the wings connected to the main body. The cockpit itself was fully-enclosed with a sliding hood, a feature not present on the Sidestrand. The cockpit was glazed with anti-glare perspex. For the pilot, an autopilot was equipped, a feature also found in the Sidestrand. This was located directly behind the pilot’s seat. Behind the cockpit were two gunner positions near the middle of the airframe, one ventral and one dorsal. The dorsal firing position had a windshield installed to protect the gunner from the high speeds the aircraft would encounter. The ventral position would not have to deal with the rough winds due to the way it was positioned within the fuselage. The ventral gunner would also operate several pieces of equipment, including an F.8 camera, and a wireless set consisting of a T.1083 wireless transmitter, a R.1082 wireless receiver and a T.R.11 wireless transmitter/receiver. On the converted Sidestrands, they would continue to use the T.73 transmitter and R.74 receiver they came standard equipped with. Extra ammo magazines were availablefor all gunners. For crew communication, there was a telephone system installed that connected each of the crew members. For crew comfort, a heating system was equipped in the interior of the aircraft. Each crew member was able to appreciate the benefits of this system, no matter where they were located. Heat was siphoned from the Townend rings and engine cowlings through a series of ducts into the interior of the aircraft. Care was taken to make sure these ducts were clear of objects or debris when the system was activated, otherwise they would be forcefully ejected from the vents. At the tail end of the aircraft was a 9 inch by 5 inch tail-wheel, which replaced the landing skid of the Sidestrand. The vertical and horizontal stabilizers remained largely the same as how they were on the Sidestrand, but the rudder of the aircraft was lengthened. The Overstand also retained a rudder extension that was present on the Sidestrand. The horizontal stabilizers were supported by two struts on each side that connected to the fuselage.

A view of the prototype’s nose. On later models, the turret would be widened for increased crew comfort. (Boulton Paul Aircraft Since 1915)

The most innovative technical feature of the Overstrand was the powered turret at the nose of the aircraft. The turret design was created by H A Hughes, head of Armaments Section for Boulton & Paul. The design itself was originally part of the P.70 aircraft design, but with that project being canceled, the turret was reused on the Overstrand. The turret was cylindrical in shape, with the top and bottom being rounded. The majority of the turret was covered in Perspex to allow optimal viewing for the gunner, with the rest of the turret and frame being made of metal. The powered aspect of the turret came from pneumatic power from compressed air that was held in bottles. Each bottle was held at 200 Ib/sq and fed into the turret by an engine-powered air compressor at 40 Ib/sq. These bottles were rechargeable via the compressor and, at their full, could allow a total of 20 complete rotations of the turret before being exhausted. The turret itself was capable of 240 degrees of rotation with the gun pointing forward, and a complete 360 degrees if the gun was raised by 70 degrees. The turret was held on ball-bearings with brackets connected to the bottom and top longerons of the airframe. The top longerons in particular ended in a circular design that allowed rollers to rotate. The air was fed into the base of the turret, which was the main mechanism that rotated the turret. The armament of the turret was a single .303 Lewis machine gun, mounted to a mechanism that the gunner would use. The gun would protrude from a vertical slit at the front of the turret that allowed it to elevate. To protect this slit, a zip fastener canvas was put in place, but this was only found on the prototype Overstrand and was quickly replaced by a simple canvas strip held in place by clips. While the horizontal movement of the turret was done via pneumatic power, elevating the gun was manual. To assist the gunner in this regard, his seat and the gun mount remained balanced with one another and would raise and lower with the gun. Turning the turret was done via applying pressure to plungers on each side of the gun. To prevent the gunner from damaging the aircraft or turret, if rotated with the gun lowered more than 70 degrees to the rear, it would release the pressure from the plunger and stop the turret before the barrel could hit the body. The seat could also be adjusted manually by the gunner. For emergencies, the top dome of the turret could be removed to allow the gunner to exit. The top was held onto the turret via 3 pins, which were locked via pins with finger rings. Removing these three and pushing the top off allowed the gunner to escape. At the rear of the turret was a door that could be opened to enter the airframe of the aircraft. In addition to holding the gunner, the turret also served as the bombardier’s position. The bottom of the turret was heavily glazed to allow downwards visibility. Bomb controls were located to the left of the gun and were also duplicated in the cockpit for the pilot. The bomb sight could not be used in normal use and was stowed away. For bombing, the turret was locked forward into position and the gun moved so the bomb sight could be used.

Front and interior views of the powered turret. (Boulton Paul Aircraft Since 1915)

Aside from the frontal turret, there were two other gunner positions on the aircraft’s rear; one ventral and one dorsal. Both would use the same .303 Lewis gun as the main turret. Many improvements were done over the basic Sidestrand to allow the Overstrand to carry much more weight, including an enlarged bomb load of 1500 Ibs. Two 500 Ibs bombs could be carried internall,y with two additional 250 Ibs bombs on external racks on the fuselage, Additional racks could be installed at the front and rear of the fuselage, each carrying either 4 20 Ibs bombs or 2 20 Ibs bombs and two flares.

The Overstrand Takes Flight

A side view of the completed prototype J9186. This aircraft was converted from a Sidestrand III. (Boulton Paul Aircraft)

The modifications to Sidestrand J1896 would be completed around August of 1933. On its maiden flight, the aircraft would seemingly catch fire, as smoke poured from one of the inner wings. The craft would land immediately, the culprit being found to be caused by fresh varnish on the heating system ducts. Despite this incident happening on the first flight, testing continued on the aircraft. The early days of testing the aircraft yielded two incidents which could be considered quite humorous. After a test flight not long after the first, J1896 would have one of its wheels fall into a hole on the airfield, causing the aircraft to fall forward. One of the propellers would be destroyed and the nose turret would hit the ground. The current occupant of the turret was a member of the armaments section, someone who personally helped with the creation of the turret itself. When the turret dug into the ground, he began to panic and called out for help from the ground crew as he attempted to escape the turret. Due to his panicked state, he had forgotten how to operate the emergency pins that held the top of the turret on. The ground crew found his situation ironic, one of the men who had helped create the turret had forgotten how to operate it in his panicked state. He was in no danger whatsoever and the crew eventually helped the man out. Sometime later, the Air Ministry was intrigued in seeing the progress of the innovative powered turret system and thus sent an official to inspect it. The official was allowed to enter the cockpit to try out the new device. While trying the controls, he accidentally pushed on one of the plungers and began spinning. The gun itself had also been raised over 70 degrees, allowing a full 360 degrees of rotation. In a vain attempt to stop, the official leaned against the gun, and unknowingly onto the plunger; making the turret spin continuously against the intentions of the man. Humored by the situation, the design team that was showcasing the turret simply let him exhaust the air supply and finally let him out once the turret stopped spinning. The Overstrand would make its first debut to the public in late 1933, where it was part of the “Parade and Fly Past of Experimental Types” at the Hendon Air Display. On February 22nd, 1934, the prototype flew to be tested firsthand with the 101 squadron at Andover, who had been operating the Sidestrand up to this point. The main goal was to receive feedback on the changes to the Sidestrand’s design by its would-be operators, if the new additions were at all effective in increasing crew comfort. Aerial tests began and the crews liked the new design for a number of reasons, but they also had their criticisms. Being February, the heating system was very appreciated by the crews. Thanks to its Pegasus engines, the aircraft could attain a top speed of 153 mph (246.2 km/h) while still being as maneuverable as its predecessor. Despite all of this praise, pilots noted that the aircraft felt sluggish on the controls longitudinally and that the engines caused excessive vibrations. Gunners enjoyed not being subjected to harsh winds in the newly enclosed turret, but many felt it was currently too claustrophobic. With the necessary information received, the prototype would leave Andover and return on March 19th. Revisions began immediately to fix the criticisms of the design. A second Sidestrand was converted into this new design (J9770), and the new revisions were input into the modifications of this aircraft. The turret was widened to give the gunner’s more space. The zip-fastened canvas that protected the open slit of the turret was removed in favor of a simple canvas strip that was held on by strips. To accommodate the widened turret, the fuselage nose was widened to a slight degree. Changes were done to improve the autopilot, elevators, and fins to fix the vibration issues. The two-bladed propellers of the Sidestrand were replaced with four-bladed metal ones. Work was also done to make it easier to work on the engine’s compressors. The engines were replaced by the newer Pegasus II.M3 to increase performance and all would be equipped with this engine after this point. By this point in development, the aircraft design would receive a new official name, the Overstrand, named after a town near the city of Sidestrand, the namesake of its base design. Work began on converting two more Sidestrands (J9179 and J9185) into Overstrands not long after the second was completed. Further testing of the types revealed that the aircraft was still having issues with engine vibration. This would plague the converted Sidestrands but was noticeably more tame on the later production versions.

A side view of J9770. This was the 2nd converted Sidestrand and would evenutally be equipped with Pegasus IV engines. (https://www . destinationsjourney . com/)

While Boulton & Paul was in the midst of developing their new bomber, financial issues finally caught up to the company. With the failure to procure production contracts on several aircraft in the past and the Sidestrand itself not performing as well as had previously hoped, Boulton & Paul made the decision that of their four divisions of the company, the Aircraft Division had been the weakest. The Aircraft Division was completely sold off to a financial group, Electric and General Industries Trust Ltd, who would reformat the division into its own dedicated company that would be simply named Boulton Paul Ltd. Despite this drastic change happening with the development team, Boulton Paul would continue their work on the Overstrand starting on June 30th, 1934.

With the early success of the converted Sidestrands, the RAF put out an order (Specification 23/24) to Boulton Paul, which requisitioned the production of 19 newly-built Overstrands to begin replacing the Sidestrands in service.

In Service

A production Overstrand with a Sidestrand in the background. (Boulton Paul Aircraft Since 1915)

On January 24th, 1935, the very first Overstrand would enter service with the 101st Squadron. The squadron itself was already quite familiar with the design, thanks to the testing done the year before, as well as an Overstrand being flown by No.101 squadron members at the 1934 Hendon Air Display. Here, the Overstrand would participate in a mock dogfight against 3 Bristol Bulldog fighters (This display and the rest of the air show can be viewed at the Imperial War Museum’s website, found here.). The plan was to introduce the Overstrand slowly into the squadron, at first forming a third C flight and eventually replacing the Sidestrands in A and B flights. In late May, the Overstrands participated in a bombing demonstration to officials and students of the Imperial Defense College. The target was 200 yards by 300 yards and was meant to represent a bridge. All three bombing runs hit the target and impressed the students with their accuracy. Many however were not so impressed, as the demonstration did not represent accurate combat conditions the bombers would face in battle against a target that would no doubt be defended. Further showcasing of the new bomber continued as on July 6th, No.101 would fly to Mildenhall for the King’s Jubilee Air Review. While there, King George VI would personally inspect Overstrand J9185, and he was particularly interested in the powered turret.

With the necessary modifications made to the designs from actual criticisms of the prototype, the Overstrand and its many accommodations made the aircraft very well liked by the crews who flew them. The Overstrand was a comfortable aircraft to be in, but was also a well performing aircraft no less. At the start of its service, bomb aiming accuracy went up from only 15% accuracy to 85% thanks to the well thought out turret design which factored in bomb-aiming equipment. On top of bomb-aiming, the No.101 Squadron won the Sassoon Trophy of 1935 for photo-reconnaissance with a score of 89.5% accuracy. Gunner accuracy is also noted as having improved considerably thanks to the turret design.

Starting in September, newly produced Overstrands would begin entering service with the No.101 squadron. The first accident with an Overstrand occurred on September 9th, when J9185 crashed at the North Coates Range. Despite this accident, newly built Overstrands would continue to enter service through January of 1936. Before the year would close, an order for five more Overstrands (K8173-K8177) was placed, to serve as replacements in the event any were lost. This would bring aircraft production up to a total of 28 aircraft. While most of the Overstrands would be delivered to the No.101 squadron, K4552 would be sent to the Air Armament School at East-Church, where it would serve as a training aircraft for recruits to become familiar with the type and turret. 1936 was a largely uneventful year for the Sidestrand aside from 3 separate accidents. J9197 would lose an engine shortly after takeoff, K4556 would be forced down in a bog and K4562 would have its brakes seize up on landing.

The aftermath of the crash of K4556. (Boulton Paul Aircraft)

In January of 1937, the RAF began expanding its forces, and creating new squadrons. The No.144 Squadron was formed in support of No.101 and would borrow four Overstrands until new aircraft were made available. The Overstrands would serve for only a month until new Bristol Blenheim bombers could be supplied, after which the Overstrands were returned. Also in January, K4564 would crash while flying in thick fog from Midenhall to Bicester. Unfortunately, the aircraft would be destroyed and the crew was killed. Another aircraft would crash in June. A notice was put out to modify all Overstrands by reinforcing the nose to reduce vibration. Overstrands would once again appear at the Hendon Air Display, however, this would be the last year it was held. An Overstrand would perform a mid-air refuel with a Vickers Viriginia and yet again a mock dog fight would be held, this time an Overstrand would go against three Hawker Demon fighters.

The modified nose of K1785 with the de Buysson turret. (Boulton Paul Defiant: A Technical Guide)

In 1935, Boulton Paul purchased the rights to build the de Buysson electric turret from the Societe d’Applications des Machines Motrices (SAMM) in France. De Buysson was an engineer in the organization and had designed a four-gun electrically powered turret for use on aircraft. The French government was not interested in pursuing it, but de Buysson had caught wind of Boulton Paul’s work on turrets with the Overstrand. SAMM approached the company with their turret design and John North, lead aircraft designer at Boulton Paul, found their turret design superior and purchased the rights to its patent. In 1937, Overstrand K8175, one of the reserve aircraft, was experimentally modified with a de Buysson turret. The turret heavily increased the firepower of the Overstrand from a single Lewis gun to four Barne guns in the nose. Despite the increase in firepower, K8175 would be the only Overstrand to be equipped with this turret. The de Buysson turret would serve as the basis for the turret used in the developing P.82 turret fighter, which would be soon to be renamed the Defiant. Another Overstrand, K8176, would have its turret heavily modified to house a 20mm Hispano cannon. The nose of this aircraft had to be changed drastically to equip this weapon, and the turret was now built into the fuselage. The weapon itself was now on a mount that rotated and most of the glazing of the nose was removed, while what was necessary for bomb-aiming remained.

The modified nose of K1786 with its 20mm Hispano cannon. (Boulton Paul Aircraft Since 1915)

The P.80 Superstrand: A Bomber Behind the Times

Aside from the various modifications done to the Overstrand, there are two known variants that were proposed:

Early in development, Boulton Paul pitched an idea of a variant of an Overstrand that would be converted for coastal reconnaissance, designated P.77. While this idea was pitched, it was found to be largely unnecessary, as the Avro Anson could easily fill this role, and it was a modern monoplane design.

The P.80 Superstrand was meant to be the final evolution of the design, using Pegasus IV engines, retractable landing gear and a redesigned cockpit. While expected performance was much better than the Overstrand, the design was already outdated as it was being made, as newer and more advanced monoplane bombers were entering production, the need for further refining the type was made unnecessary. (Boulton Paul Aircraft Since 1915)

At some point during its service, the second Overstrand built (J9770) was re-equipped with much stronger Pegasus IV engines to increase performance of the aircraft. Plans were further done to modernize the design with retractable landing gear. The development continued with further refinements to the design, eventually becoming a new design entirely. The P.80 Superstrand was meant to be the final step in the bomber’s design, incorporating many modern aspects that were not found on the Overstrand. Aside from the previously mentioned Pegasus IV engines and retractable landing gear, the aircraft would also use variable-pitch propellers. The cockpit section was also redesigned, now connecting the pilot’s position with the rear dorsal gunner’s. The dorsal gunner position was also now fully enclosed. The front turret had many changes done to the design as well. Only the upper section of the turret would now be transparent, and it appears that the front section was now part of the fuselage, with accommodations in the nose for a bomb sight. It was expected these changes to the Overstrand would increase the top speed to 191 mph (307 km/h), give it a maximum ceiling of 27,500 ft and an increase bomb load. The Superstrand was never built, as the aircraft was obsolete even as it was being designed. While the Overstrand was performing well, aircraft development had continued and was now pushing towards more modern monoplane aircraft designs, the opposite of what the Superstrand was. Even Boulton Paul itself, by this point, was beginning to design monoplane bombers. The previous numeric design, the P.79, was a monoplane twin-engine bomber that, while never built, incorporated many elements found in the Overstrand but now adapted onto a more modern airframe. No further work was done on bringing the P.80 to reality.

End of the Line

Direct front view of an Overstrand. (Boulton Paul Aircraft Since 1915)

By 1938, the Overstrand was beginning to show its age. Modern bombers, like the Bristol Blenheim and even larger aircraft, such as the Vickers Wellington, had already, or were soon to enter production and replace the biplanes that remained in service. The Overstrand was no exception. On August 27th, No.101 squadron began gradually replacing their Overstrand bombers with Blenheims. By summer of next year, the Overstrand would be completely removed from frontline service. Despite this, the aircraft still continued to fly in various training schools and serve auxiliary roles. 5 Overstrands were sent to the No.2 Air Observer School in 1938 for training. K4552 would be sent to the No.1 Air Observer school in Lincolnshire, where it would continue its training mission until it was deemed non-airworthy and repurposed to a ground instructional frame. Despite not being in the air, the airframe was still the victim of accidents and, on April 28th, 1940, would be damaged and scrapped after a Gloster Gauntlet trainer overshot and hit it. The final nail in the coffin for most Overstrands came in July, when K1873 would break up mid air, killing the crew. After this incident, all Overstrands were ordered to remain in training as ground instructional air frames only.

K8175 parked in front of the aircraft hangar at the Boulton Paul factory at Wolverhampton. (Boulton Paul Aircraft Since 1915)

Despite this order, a handful of Overstrands would continue flying as part of rather unorthodox missions. K8176 would be sent to be used by the Special Duty Flight at Christchurch. Eventually, this aircraft would be sent to the Army Cooperation Development unit. K4559 would be operated by the Balloon Development Unit at Cardington. There, the aircraft would provide a slipstream for barrage balloons and would test the fatigue of the cables to the balloons. By 1941, the aircraft type was deemed obsolete and it is believed the previously mentioned aircraft were returned to Boulton Paul for turret development. Not long after, K1876 would be involved in an accident due to bad weather. While flying to Edinburgh, the aircraft would attempt to land at Blackpool but would undershoot the runway and crash. This is known to be the last time an Overstrand flew. It is interesting to note that K1876 had just been painted with camouflage, which would make it possibly the only Overstrand that was not in the standard bare metal finish aside from the prototype. It is unlikely any Overstrands saw any combat by happenstance during their short period of operation in the Second World War.

With the type obsolete, all remaining Overstrands were scrapped. While no surviving aircraft remain to this day, a reproduction of the nose section of Overstrand K4556 was built and currently resides in the Norfolk and Suffolk Aviation Museum, in the Boulton Paul Hangar.

 

Conclusion

The reproduction of the nose of an Overstrand at the Norfolk and Suffolk Aviation Musuem. (https://www . aviationmuseum . net/index . html)

Ultimately, the reason the Boulton Paul Overstrand existed was to improve the pre-existing Sidestrand’s nose gunner position and create a faster platform, which it would successfully accomplish with its reworks. The Overstrand served for only a few years before more advanced aircraft would replace it, but in that time it became a well respected aircraft that was liked by its crews for the various comforts incorporated into the design and which increased the performance.

The Overstrand was a very interesting aircraft, as it seems to be in an area between eras. On one hand, it represents the last of the biplane bombers that can trace their lineage back to the First World War for Britain and for Boulton & Paul. But on the other hand, it had features that were soon to become commonplace. The powered turret design was a game-changer not only for British aviation, but the company that built it as well. Boulton Paul, under H.A.Hughes, would become one of the most prolific turret designers for British aviation in the Second World War, not only designing turrets for use on other bombers, but also with their own upcoming turret fighter design, the Defiant.

Variants

 

  • Sidestrand Mk V -The name given to the design at the start of its development.
  • Prototype Overstrand (J9186) – The very first Overstrand was a converted Sidestrand. This had a smaller turret, two-bladed propellers and a narrower nose.
  • Converted Sidestrands (J9770, J9179, J9185)– The next three Overstrands built were modified from existing Sidestrands. However, these would be further improved over the prototype by having their turrets widened, four-bladed propellers installed and a wider nose to accommodate the bigger turret.
  • Boulton Paul P.75 Overstrand – Production version. 24 built in total.
  • Boulton Paul P.77 – Variant of the Overstrand redesigned for coastal reconnaissance. None were built.
  • Boulton Paul P.80 Superstrand – The final design of the “Strand” family, the P.80 Superstrand was drawn up in the mid 1930s as to further refine the Overtrand’s design with more modern components, including retractable landing gear, Pegasus IV engines, a reworked turret, lengthened cockpit and further streamlined airframe. Due to monoplane bombers now becoming mainstream, the P.80 was seen as obsolete and none of the type were built.

Modifications

  • Overstrand K8175 – Production Overstrand that was experimentally modified to test the du Boysson 4-gun turret.
  • Overstrand K8176 – Production Overstrand that was experimentally modified to house a 20 mm Hispano cannon in its nose turret via pedestal mount.
  • Overstrand J9770 – The second converted Sidestrand, this aircraft was later experimentally modified to house Pegasus IV engines. This was done as part of the development that would lead to the P.80 Superstrand.

Operators

 

  • United Kingdom – The Royal Air Force would operate the Boulton Paul Overstrand from 1935 to 1941 in various squadrons. Most of these would fly operationally with the 101 squadron from 1935 to 1938. The type would also briefly serve with 114 squadron for only a month, until it would be replaced by Blenheim bombers. During WWII, the remaining Overstrands would be relegated to training duties and other special tasks, such as working with barrage balloons.

Boulton Paul P.75 Overstrand Specifications
Wingspan 71 ft 11 in / 29.2 m
Length 46 ft 1 in / 14.3 m
Height 15 ft 9 in / 4.8 m
Wing Area 979.5 ft² / 91 m²
Engine 2x 580 hp ( 426 kW ) Pegasus II.M.3 9-cylinder radial engines
Propeller 2x 4-blade metal propellers
Weights
Empty 8004 lbs / 3630.6 kg
Loaded 11392 lbs / 5167.3 kg
Climb Rate
Time to 6500 ft / 1981 m 5 minutes 24 seconds
Maximum Speed 153 mph / 246.2 km/h at 6,500 ft / 1981 m
Range 545 mi / 877 km
Maximum Service Ceiling 21,300 ft / 6490 m
Crew Crew of 4

1x Pilot

3x Gunners (2 would also serve as the Bombardier and Radioman)
Armament
  • 1x .303 Lewis gun in powered nose turret
  • 1x .303 Lewis gun in dorsal gunner position
  • 1x .303 Lewis gun in ventral turret position
  • 1,500 Ib (680.4 kg) bomb load (2x 500 Ib and 2x 250Ib bombs)

Credits

  • Article written by Medicman11
  • Edited by  Henry H. and Stan L.
  • Ported by Henry H.
  • Illustrated by Esteban P.

Illustrations

 

Overstrand J9186: The first Overstrand built, converted from a Sidestrand
Overstrand K4546: A production Sidestrand that was operated by the No.101 Squadron in their C Flight.
Overstrand K1785: A later Overstrand that was experimentally modified with a quad-gun de Buysson turret for testing

Sources

Boulton Paul Aircraft. Chalford, 1996.

Brew, Alec. Boulton Paul Aircraft since 1915. Fonthill Media, 2020.

Mason, Francis K. The British Bomber since 1914. Naval Inst. Press, 1994.

Boulton-Paul P.105 & P.107

UK, WW2

UK Union Jack United Kingdom (1944)
Strike Fighter – None Built

Static model of the standard P.105. [British Secret Projects]
The Boulton-Paul P.105 is a little known single-engine aircraft meant to fill a variety of carrier-based roles. To do so, the P.105 would utilize a unique and innovative design that involved having interchangeable fuselage and cockpit modules that would pertain to a certain mission, and could be changed quickly to fill a needed role aboard carriers or other airbases. The design was not picked up for unknown reasons but its story doesn’t end there. The design would develop further into the P.107, a land-based escort version of the P.105. The P.107 would have a rear-facing turret and a twin boom tail design to allow greater traverse of the gun. This design wouldn’t be adopted either and the program would conclude before the war’s end.

History

Late in the Second World War, the Royal Naval Air Arm began seeking out an aircraft design that would be able to fill both the fighter and bomber roles. Having one aircraft perform multiple roles would eliminate the specialization of carrier-borne aircraft needed to fill the fighter, dive bomber, and torpedo bomber roles. No official requirement was ever put out to build such an aircraft, but several companies had begun developing aircraft that would fit this role, which had become known as the “Strike Fighter”. Westland, Blackburn, Fairey and Boulton-Paul would all develop designs that correspond to the strike fighter role. Boulton-Paul’s aircraft design would be known as the P.105.

Boulton-Paul is a lesser-known aircraft company which only had a single major type of aircraft enter mass production during the Second World War: the Defiant. The Defiant reflected a lot of their aircraft designs, which were all somewhat unorthodox. . In the Defiant’s case, it was a fighter with a rear turret. Boulton-Paul were much more successful in developing turrets for use on other aircraft, such as the Handley-Page Halifax, Blackburn Roc (which they co-developed alongside Blackburn), Lockheed Hudson and the late war Avro Lincoln. Despite having only one combat aircraft enter production, Boulton-Paul had a very active development section, although most of their designs would stay on the drawing board, with a few being lucky enough to receive prototypes. The designs came from an engineer named J. D. North, who was the main aircraft designer for Boulton-Paul. Before work started on their Strike Fighter design, North had been working on their P.103 and P.104 designs for the Naval Air Arm. The P.103 was an ultra-fast fighter design that utilized a contra-rotating propeller and a Griffon 61 or Centaurus engine. The P.103 wasn’t picked up for production, but North would use many aspects of the P.103 in the P.105. The contra-rotating propeller would once again be used, while the engine would start as a Griffon 61 but shift over to a Centaurus engine later.

3 way drawing of the P.105. Note the spotter’s lower window. [British Secret Projects]
The P.105 was meant to be a small, high-performing aircraft that could easily be converted to fill other roles, even carrier duties. To do so, it would use a unique idea. To fill the variety of carrier-borne roles, the P.105 would have modular cockpit and bomb bay sections. The interchangable modules included a torpedo-bomber (P.105A), reconnaissance aircraft (P.105B), fighter (P.105C) and dive-bomber (No designation given). Each section would have minor differences between them that fit their respective roles. With this system, more P.105 airframes could be stored in hangars and carriers, while the additional modules would take up less space than other aircraft specified for specific roles, thus increasing the combat capacity of the carrier the P.105 would be stationed on. Boulton Paul expected the aircraft to be very high performance and the P.105C version would be an excellent penetration fighter. Before any specifications were estimated, it was decided to switch from a Griffon 61 engine to the Centaurus inline engine. The brochure on the details of the aircraft was submitted to the RNAA, but no order for production came about. Exactly why it wasn’t adopted is unknown. The reasoning may come from the module system, as it could have been novel in concept, but complex in reality. Another reason could be that current aircraft at the time were deemed to have been performing adequately and didn’t need such a replacement.

3 way drawing of the P.107. Note the sliding aft canopy and smaller profile of the twin tail rudders. [British Secret Projects]
Although the P.105 wasn’t granted production, its story continues in the Boulton-Paul P.107. The P.107 is an intriguing design since very little information pertaining to its development history is available, but its design and specifications has been found. It can be assumed the P.107 began development during or shortly after the P.105 had been created. The P.107 wouldn’t be operated by the RNAA, but instead by the Royal Air Force as a long-range escort fighter. Major differences between the P.107 and P.105 include the lack of folding wings, the removal of the torpedo blister, the addition of a turret and the switch from a single rudder to a twin tail design to improve the firing angle of the turret. The P.107 could also be configured for different roles, but it is unknown if it used the same module system the P.105 used. The P.107 wasn’t selected for production either.

Design

The Boulton-Paul P.105 had a conventional fighter layout. In the front, it would utilize a contra-rotating propeller that had reversible pitch. Originally, the design would have mounted a Griffon 61 engine but was changed in favor of the Centaurus engine instead. The wings on the P.105 were inverted gull wings, much like those on the Vought F4U Corsair or Junkers Ju 87 Stuka. To conserve space in carriers, the wings would be able to fold. The fuselage had the most interesting aspect of the P.105 overall and that was its interchangeable cockpit and lower fuselage modules. Each variant of the P.105 would use different modules that would pertain to the intended role it served. The P.105A was a torpedo bomber and would use the torpedo blister present under the tail. The P.105B was a reconnaissance aircraft, and its cockpit would sit a pilot and observer. It would use a glass hull beneath the observer to assist in spotting. The P.105C was an escort fighter and would be a one-man aircraft. The last was a dive-bomber version, which only has very sparse details available. The dive bomber would carry two 1,000 lb (450 kg) bombs, most likely in an internal bomb bay module. The tail of the aircraft would be a conventional rudder and tailplane arrangement. The armament of the P.105 was a standard two to four 12.7mm machine-guns in the wings of the aircraft, with the only deviation being the P.105C, which would use four 20mm cannons instead.

Papercraft model of the P.107 [Kartonbau.de]
The P.107 borrowed many aspects of the P.105 design, but changed some details to better fit its role. The engine and frontal section would stay the same, keeping the contra-rotating propellers and Centaurus engine. Reference materials refer to the aircraft as being able to convert from an escort fighter to either a fighter-bomber or photo reconnaissance aircraft. However, whether it was conventional conversion or via the module system the P.105 used is unknown, the latter being most likely. The wing design would stay the same, with the inverted gull wing style. Given its land-based nature, the wings no longer folded to conserve space and the torpedo blister under the tail was removed. Behind the pilot, a gunner would sit and remotely control two 12.7mm machine guns. The machine-guns would be housed within the aircraft, with only the ends of the barrel protruding out. To give the gunner a better firing arc, the single tailfin was switched to a double tailfin. The turret and twin tail design are the most obvious differences between the P.107 and P.105. The aircraft’s fuel would be stored in a main tank and two smaller drop tanks. Fuel amount was expected to give the aircraft a 3,000 mi (4,827 km) range, with up to 30 minutes of combat. The drop tanks could be switched for 2,000 Ib (900 Kg) of bombs. For offensive armament, the P.107 would use four 20m cannons mounted in the wings.

Papercraft model of the P.107 [Kartonbau.de]

Variants

 

  • Boulton Paul P.105A– Torpedo bomber version of the P.105.
  • Boulton Paul P.105B– Reconnaissance version of the P.105. This version would have a glazed hull for the observer.
  • Boulton Paul P.105C– Fighter version of the P.105.
  • Boulton Paul P.105 Dive bomber– Dive bomber version of the P.105. No designation was given to this design.
  • Boulton Paul P.107– Land-based escort fighter derived from the P.105. The P.107 was near identical to the P.105 but had a twin boom tail to allow better vision and turn radius for a rear mounted turret. Photo reconnaissance and fighter bomber versions of the P.107 are also mentioned.

Operators

 

  • Great Britain – Had it been built, the P.105 would have been used by the Royal Fleet Air Arm. The P.107 would have been used by the RAF for escort duty had it been built.

Boulton-Paul P.105 Specifications
Wingspan 38 ft / 11.6 m
Length 34 ft 5 in / 10.5 m
Folded Width 15 ft 4 in / 4.67 m
Wing Area 250 ft² / 23.3 m²
Engine 3,000 hp ( 2,200 kW ) Centaurus CE.12.SM engine
Fuel Capacity 260 gal (1,180 lit)
Weights 12,285 Ib / 5,572 kg with torpedo

12,509 Ib / 5,674 kg with bombs
Climb Rate 3,660 ft/min / 1,110 m/min
Maximum Speed 469 mph / 755 km/h at 20,000 ft / 6,000 m
Cruising Speed 407 mph / 655 km/h
Range 1,300 mi / 2100 km – 3,320 mi / 5340 km
Crew Pilot

Other crew member (Depending on the variant)
Armament
  • 2-4 12.7mm machine guns (All versions)
  • 1x Torpedo (P.105A)
  • 2x 1,000 Ib (454 kg) bombs (Dive Bomber)
  • 4x 20mm cannons (P.105C)

Boulton-Paul P.107 Specifications
Wingspan 38 ft / 11.6 m
Length 34 ft 8 in / 10.6 m
Wing Area 250 ft² / 23.3 m²
Engine 3,000 hp ( 2,200 kW ) Centaurus CE.12.SM engine
Fuel Capacity Main: 495 gal (2,250 lit)

Drop Tanks: 140 gal (640 lit)
Weight 15,900 Ib / 7,200 kg
Max Speed 470 mph / 755 km/h at 22,000 ft / 6,700 m
Range With Drop Tanks: 3,000 mi / 4,800 km

Without: 2,200 mi / 3,540 km

Fighter-Bomber: 700 mi / 1,120 km
Crew 1 Pilot

1 Gunner
Armament
  • 4x 20 mm guns + 2x 12.7mm machine guns
  • 2,000 Ib (907 kg) of bombs

Gallery

Illustrations by Haryo Panji

Boulton-Paul P.107 Illustration by Haryo Panji
Boulton-Paul P.105 Reconnaissance Illustration by Haryo Panji

Credits

Martin-Baker Tankbuster

UK, WW2, ,

UK Union Jack United Kingdom (1942)
Anti-Tank Aircraft Design – None Built

3D artist impression of the Tankbuster in flight [candymountain.jp]
The Martin-Baker Tankbuster was a concept British anti-tank aircraft that was designed according to an order in 1942 for a specialized ground attacker. The aircraft had a twin-boom, pusher design and was only armed with a 6-pounder (57mm) cannon, most likely a Molins M-Class Gun. Compared to its competitors, the Tankbuster was strictly limited to exactly what it was named for; busting tanks, and would find itself having trouble against other ground targets or even defending itself. With the program being canceled in early 1943 and Martin-Baker working on more important projects, all work stopped on developing the Tankbuster any further.

History

Drawing of the Martin-Baker Tankbuster [British Secret Projects]
In early 1942, the Royal Air Force began seeking a new ground-attack aircraft that would replace the 40mm-armed Hawker Hurricane Mk.IID. An order was officially placed on March 7th for a specialized ground attacker that would be used against a multitude of targets including ground units, enemy aircraft, transports/shipping, and a main focus on destroying tanks. To accomplish the destruction of the aforementioned targets, the aircraft was meant to use more heavier guns than the Hurricane Mk.IID. Alternative weapon arrangements included: three 40mm Vickers S cannons, four 20mm Hispano Mk.V cannons, a combination of two 20mm with two 40mm cannons, six unguided rocket (RP) racks with two 20mm cannons or one 47mm Vickers gun with two 20mm cannons. Two 500Ibs bombs could also be added. The expected speed for the design had to reach at least 280mph (450 km/h) at 3,000ft (900 m). Visibility was also a necessity and forward view had to be unobstructed and clear. Full production was to be expected by 1944. The programs would be overseen by the Air Staff.

Over 10 different designs by several aircraft companies were subsequently created for this program. A majority of them were of unorthodox design. Armstrong-Whitworth (AW.49) and Boulton-Paul (P.99) both created twin boom designs. Boulton-Paul also submitted a canard design labelled P.100 and a biplane design labelled P.101, the latter being seen as a safe alternative to the radical canard and twin boom designs prevalent through the program. Perhaps the most interesting of the designs was the submission by Martin-Baker.

3D artist impression of the Tankbuster [candymountain.jp]
At the time of its submission, Martin Baker had been working steadily on their MB.5 project, which would eventually become one of the best performing piston aircraft built by Britain, but this wouldn’t be completed until 1944. Their design for the ground attacker was submitted several months after the order was given by the Air Staff and was only named the “Tankbuster”. Martin Baker’s concept was for a twin boom design that deviated extensively from the given requirements. The aircraft was armed with a single 6-pounder (57mm) cannon, and the aircraft would be completely encased in 1/2-inch armor. The armor itself weighed 4,900Ibs (2,200kg).

The project wasn’t very impressive nor reasonable in the eyes of the Air Staff, especially compared to the other designs in the program. Its single large-caliber gun extremely limited its target range and it would only have been able to attack one of six predicted target types the program requested. The aircraft lacked any other offensive or defensive armament and would rely on its armor alone to protect itself, a gambit that other designs in the program resolved by following the armaments listed by the Air Staff. Attempts to add more ordnance such as additional guns, rockets or bombs to the wings would have added too much stress on the airframe. The main feature of the aircraft was the root of its problems, its gun. The gun itself couldn’t be removed from the airframe and an aircraft going into battle with a single weapon would be inefficient for resources. The Tankbuster didn’t meet the armament expectations and fell under the expected speed by 10mph (16 km a h). On April 15th, 1943, Air Marshall F J Linnell (who was a good friend of James Martin, a founder of the company) advised Martin-Baker to drop development of the Tankbuster in favor of continuing work on the more successful MB.5 project going on at the same time.

Near the later days of April 1943, the Air Staff brought the program the Tankbuster was designed for to an end. They concluded that, at the time, developing and producing an entirely new ground attack aircraft would impede the current war programs and that the submissions were too specialized in design compared to modifying aircraft already being produced for ground attack duties. One such aircraft they pointed to was the Hawker Hurricane Mk IV, a ground attacker version of the famous fighter which was performing successfully in the role and had started production in March of 1943. Later additions to the ground attack role would be the Hawker Typhoon, which became a scourge to German ground troops. Even if the program had continued towards production, it was significantly unlikely the Tankbuster would have been chosen for the role. The aircraft was way too specialized and disliked by the Air Staff, and Martin Baker was working on an aircraft that would yield much better results. Although the Tankbuster may have been the runt of a doomed program, it still proves to be an interesting, albeit flawed solution in the name of destroying enemy armor.

Design

The Martin-Baker Tankbuster was a twin-boom single-engine design. The aircraft would have been constructed entirely of metal. The airframe itself would be covered in an additional 1/2-inch (12.7mm) armor. This armor would weigh 4,900Ibs (2,223kg) on its own. The armor covered the entire body and also the engine cowling. What’s interesting to note is that the aircraft had two engine intakes, one facing forward and one facing the rear. The radiator and oil tank were mounted in the frontal fuselage. The radiator itself was armored by offset plates that would prevent bullets from ricocheting inside. The cockpit area had clear forward visibility, and would seat a single pilot. The canopy would most likely have had bulletproof glass to complement the rest of the armored body. For it’s engine, the Tankbuster would have mounted a Griffon II engine in pusher configuration. This is relevant to Martin-Baker’s other project, the MB.5, as this aircraft also used the Griffon. The reason the aircraft utilized a pusher configuration was it gave the pilot clear visibility in the front and the gun could be placed directly forward. The pusher configuration isn’t common because of the fact that it leaves the engine open to enemies that are chasing the aircraft. This would have been especially deadly for the Tankbuster, given it has no defensive armament. The tail section and wings would also be constructed of metal. The wings were wide to improve low level flight. There was an attempt to diversify the targets by adding additional weapons to the wings, but this would only overload them. The Tankbuster had a fixed tricycle landing gear. This decision was made to conserve interior space but would have slowed the aircraft considerably. The only armament the aircraft would have been armed with would be a 6-pounder cannon (57mm) that would be frontally mounted, supplied with 30 rounds of ammunition. The aircraft would only be allowed to target heavily armored targets. To assist in aiming, the gun was placed towards on horizontal axis. This would prevent the aircraft from pitching when the gun was fired.

Role

The Tankbuster’s design might seem odd by conventional aircraft standards, but every single feature the aircraft had was to assist in it’s role of attacking enemy armor. Long, flat wings would give the aircraft an edge in low-level flight. The pusher engine would give the aircraft a clear view and nothing to obstruct the cannon. The entire airframe being heavily armored would protect against AA fire and enemy aircraft. Going into battle, the Tankbuster would need escort fighters to protect against opposing interceptors. Once in the combat zone, the Tankbuster would begin its assault on enemy tanks. The De Havilland Mosquito also mounted the 6-pounder Molins gun and was also used in the ground-attack role, but only for a short time before switching to an anti-shipping role. It is likely the Tankbuster would have also undergone this change had it entered production.

Variants

  • Martin-Baker “Tankbuster” – The only version of the Tankbuster drawn was the original design with a single cannon.

Operators

  • United Kingdom – This aircraft would have been operated by the Royal Air Force had it been produced.

Martin-Baker Tankbuster Specifications
Wingspan 47 ft 10.8 in / 14.6 m
Length 41 ft / 12.5 m
Wing Area 471.5 ft² / 43.8 m²
Engine 1x 1,730 hp ( 1,290 kW ) Griffon II Inline-Engine
Weights 12,000 Ibs / 5,440 kg
Climb Rate 2,250 feet/min / 686 meters/min
Maximum Speed 270 mph / 434 km/h
Minimum Speed 75 mph / 122 km/h
Crew 1 pilot
Armament
  • 1x 6-pounder (57mm) Molins M-Class cannon

Gallery

Illustration by Haryo Panji https://www.deviantart.com/haryopanji

Scale model of the Tankbuster [modelingmadness.com]

Sources