Tag Archives: naval

Boulton-Paul P.105 & P.107

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