Boulton Paul Defiant

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Boulton Paul P.82 Defiant

A pair of 264 Squadron Defiants.
Type	Two-seat fighter aircraft
Manufacturer	Boulton Paul Aircraft
Maiden flight	1937-08-11
Introduced	December 1939
Status	Retired
Primary user	Royal Air Force
Number built	1,064

The Boulton Paul Defiant was an early World War II fighter aircraft and bomber interceptor of the Royal Air Force, built by Boulton Paul Aircraft Ltd. Amongst pilots it had the informal nickname "Daffy".

The Defiant emerged at a time when the RAF anticipated having to defend Great Britain against unescorted enemy bombers. Advances in aircraft design during the 1920s and 1930s resulted in a generation of multi-engined bombers that were faster than the single-engined biplane fighters then in service. The RAF believed that its own turret-armed bombers, such as the Vickers Wellington, would be able to penetrate enemy airspace and defend itself without fighter escort, and that the German Luftwaffe - its most obvious future enemy - would do the same in return. A turret-armed fighter would be able to engage enemy bombers from angles that would defeat the bomber gunners. Thus, the Defiant was armed with a powered dorsal turret, equipped with four 0.303 in (7.7 mm) Browning machine guns. In theory, the Defiant would approach an enemy bomber from below or beside and destroy it with a concentrated burst of fire.

The concept was similar to the successful World War I Bristol Fighter, and the Fleet Air Arm's contemporary Blackburn Roc, but in practice the Defiant was highly vulnerable to the more agile Luftwaffe Bf 109 escort fighters. It was later used in the night fighter role where it proved successful against Luftwaffe bombers, before it was phased out of combat operations in favour of heavily-armed aircraft such as the Bristol Beaufighter and de Havilland Mosquito

1 Development
2 Operational history
3 P94
4 Variants
5 Operators
6 Specifications (Mk.I)
7 Related content

[edit] Development

The Defiant was designed to Air Ministry Specification F.9/35, which required a powered turret as the sole armament. The Boulton Paul design was selected ahead of the Hotspur submitted by Hawker Aviation. The Defiant prototype first flew on August 11, 1937, and immediately went into production as the Defiant Mk.I, although its entry into service was delayed such that only three aircraft had reached the RAF by the start of the war. The Mk.I was powered by the Rolls Royce Merlin III and a total of 713 aircraft were built.

The turret was based on a design by French aviation company SAMM, and had been licensed by Boulton Paul for use in the Blackburn Roc naval aircraft. The turret was a hydraulically powered "drop-in" unit with a crank-operated mechanical backup. The Defiant's fuselage was fitted with aerodyamic fairings that helped alleviate the drag of the turret; they were pneumatically powered, and could be lowered into the fuselage so that the turret could rotate freely. The turret was armed with four .303 Browning machine guns, which were electrically fired. Insulated cut-off points in the turret ring prevented the guns from being activated when they were pointing at the propellor disc or tailplane. The gunner entered and exited via a hatch in the rear of the turret, although there was a smaller exit in the lower fuselage that was more often used to load ammunition. As a consequence of this arrangement the gunner could not exit the Defiant quickly if the turret was rotated to point to the rear. There was not enough space in the turret for the gunner to wear a parachute, which was instead stowed in the Defiant's fuselage. In case of emergency the gunner could transfer firing control of the guns to the pilot. In practice this was rarely done, as the turret's minimum forward elevation was 19°, and the pilot did not have a gunsight.

The Defiant was initially successful against enemy aircraft. Its high water mark was on May 29, 1940, on which date 264 Sqn claimed 65 kills, mostly Ju 87 Stukas and Messerschmitt Bf 110 twin-engined heavy fighters. The German pilots were apparently unaware of the Defiant's rear-firing armament. However, Defiant losses quickly mounted, particularly amongst the gunners, who were often unable to leave the stricken aircraft. The additional weight of the turret and the second crewman, plus the aerodynamic drag, gave the Defiant much poorer performance than conventional fighter aircraft. Opposing fighters were able to out-maneouvre the Defiant and attack it from below or dead ahead, where the turret offered no defence.

According to the recent book The Turret Fighters by aviation historian Alec Brew, 264 Sqn developed effective countermeasures against single seat aircraft such as the Bf109. By flying in an ever-descending circle, Defiant crews sacrificed the advantage of height but eliminated the possibility of attack from underneath, while giving 360° of defensive fire. This tactic was used successfully against Bf109s in action, but 141 Sqn chose to ignore their advice, with devastating consequences.

[edit] Operational history

No. 264 Squadron was the first to be equipped with the Defiant Mk.I in December 1939. The first operational sortie came on May 12, 1940. On May 13, a flight of six Defiants was attacked by Bf 109Es. Five of the Defiants were shot down from a frontal attack.

In late May, during the evacuation of the BEF from Dunkirk, the Defiant had some success. Being visually similar to the Hawker Hurricane, it was initially able to surprise fighters attacking it from the rear. By the time of the Battle of Britain, a few months later, its weaknesses were known and exploited. On July 19 six out of nine Defiants of No. 141 Squadron were shot down and the remaining three only survived due to the intervention of Hurricanes of No. 111 Squadron.

The Defiant was quickly moved to night fighting duties, and as a night fighter the Defiant achieved some success. The Defiant Mk.II model was fitted with the AI Mk IV airborne interception radar and a Merlin XX engine. A total of 207 Mk.II Defiants were built. During the winter Blitz on London of 1940-41, the Defiant equipped four Squadrons.

The Defiant was removed from combat duties in 1942 and thereafter used for training, target towing, ECM, and air sea rescue. In this latter role the Defiant was equipped with a pair of underwing pods that contained dinghies. A further 140 Defiant Mk.III aircraft were built; this model lacked the dorsal turret and was used as a target tug. Many of the surviving Mk.I and Mk.II Defiants also had their turrets removed.

In May 1945, Martin-Baker used a Defiant to test their first ejection seat.

The single surviving Defiant, a nightfighter, is on display at the Royal Air Force museum in Hendon, London.

[edit] P94

The very first Defiant prototype had not been fitted with a turret, and in 1940 Boulton Paul developed a conventional, single-seat version of the Defiant called the P94, which was armed with twelve .303 Browning machine guns, six per wing. By that time the RAF had sufficient quantities of Hurricanes and Spitfires, and did not require a new single-seat fighter. With a top speed of about 360mph the P94 was almost as fast as a contemporary Spitfire, although less manoeuvrable.

[edit] Variants

Defiant Mk I : Two-seat turret fighter for the RAF. Powered by a 1,030-hp (768-kW) Rolls-Royce Merlin III piston engine. 723 built.
Defiant NF.Mk IA : Defiant Mk I converted into night fighters.
Defiant Mk II : Two-seat night fighter for the RAF. Powered by a 1,280-hp (954-kW) Roll-Royce Merlin XX piston engine, and fitted with the AI Mk IV airborne interception radar. 210 built.
Defiant TT.Mk I : Defiant Mk IIs were converted into target tugs, 140 built from new.
Defiant TT.Mk III : Defiant Mk Is were converted into target tugs, 150 conversions.