Boulton Paul Defiant

Boulton Paul Defiant

Infobox Aircraft
name= P.82 Defiant
type= Two-seat fighter, night fighter, trainer, target tug
manufacturer= Boulton Paul Aircraft

caption= Defiant Mk.I "N1585", PS-A of No. 264 Sqn., RAF Kirton in Lindsey, July 1940.
designer= John Dudley North
first flight= 11 August 1937
introduced= December 1939
status= Retired
primary user= Royal Air Force
more users= Royal Australian Air Force Royal Canadian Air Force Polish Air Force
number built= 1,064
unit cost=
variants with their own articles=

The Boulton Paul Defiant was a British fighter aircraft and bomber interceptor used early in the Second World War. The Defiant was designed and built by Boulton Paul Aircraft as a "turret fighter " and served with the Royal Air Force (RAF). Contemporary with the Royal Navy's Blackburn Roc, the concept of a turret fighter was somewhat similar to the World War I-era Bristol Fighter. In practice, the Defiant was found to be vulnerable to the Luftwaffe's more agile, single-seat Messerschmitt Bf 109 fighters; crucially, the Defiant did not have any forward-firing guns. It was later used successfully in the night fighter role, before it was phased out of combat service in favour of the Bristol Beaufighter and de Havilland Mosquito. The Defiant finally found use in gunnery training, target towing, ECM and air sea rescue. Among RAF pilots it had the irreverent nickname "Daffy."

Design and development


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 would do the same. 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 inch (7.7 mm) Browning guns. In theory, the Defiant would approach an enemy bomber from below or beside and destroy it with a concentrated burst of fire.


Designed to meet the Air Ministry Specification F.9/35, which specified a "turret fighter" with a powered turret as the sole armament. Boulton Paul, who had considerable experience with turrets from their earlier Overstrand bomber, submitted their P.82 project. This design was selected as the most promising of seven initial proposals and one of only two prototypes constructed. The other competing design was the Hotspur from Hawker Aircraft.

The central feature of the P.82 was the four-gun turret based on a design by French aviation company SAMM which had been licensed by Boulton Paul for use in the earlier Boulton Paul Sidestrand bomber but eventually installed in the "follow-up" design, the Boulton Paul Overstrand and Blackburn Roc naval fighter. Bowyer 1970, p. 270.] The turret, the Type A, was an electro-hydraulically powered "drop-in" unit with a crank-operated mechanical backup. The fuselage was fitted with aerodynamic 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 Browning guns were electrically fired, and insulated cut-off points in the turret ring prevented the guns from being activated when they were pointing at the propeller 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 first P.82 prototype ("K8310") was rolled out in 1937 without its turret, looking superficially like the Hawker Hurricane although it was at least 1,500 pounds heavier. A clean, simple and compact monoplane structure had been achieved with main landing gear retracting into a broad mainplane section. The pilot's cockpit and rear turret were faired into a streamlined upper fuselage section. Fuel was carried in the wing centre section along with a large ventral radiator that completed the resemblance to the Hawker fighter. With a 1,030 hp Rolls-Royce Merlin I installed, the newly named "Defiant" prototype first flew on 11 August 1937, nearly a year ahead of the Hotspur. A second prototype, "K8620", equipped with a turret, was modified with telescopic radio masts, revision to the canopy and changes to the undercarriage fairing plates.

Completing its acceptance tests with the turret installed, the Defiant reached a top speed of 302 mph and subsequently was declared the victor of the turret fighter competition. Apart from detail changes, the production Defiant Mk I looked similar to the two Defiant prototypes. However, its service entry was delayed to such an extent 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 (1,030 / 1,160 hp) The normal rating used for Battle of Britain Hurricane Mk.Is, Spitfire Mk.Is and Defiants was 1,030 hp; however, from June 1940 supplies of 100 octane fuels from America became available, increasing the available power.] with a total of 713 aircraft built.


The P.85 was a version of the Defiant for Fleet Air Arm (FAA) use, but the Blackburn Roc was selected and the only FAA use was to be the target tug version of the Defiant.


The first Defiant prototype had not been initially fitted with a turret, and therefore had an impressive top speed. Consequently, in 1940, Boulton Paul developed a conventional, single-seat, turret-less version of the Defiant called the P.94, armed with 12 Browning .303 machine guns (six per wing). By that time, the RAF had sufficient quantities of Hawker Hurricanes and Supermarine Spitfire and did not require a new single-seat fighter. With a top speed of about 360 mph, the P.94 was almost as fast as a contemporary Spitfire, although less manoeuvrable.

Operational history

In December 1939, No. 264 Squadron at RAF Manston was the first to be equipped with the Defiant Mk I. The first operational sortie came on 12 May 1940 during the evacuation of the British Expeditionary Force from Dunkirk. The Defiant was initially successful against enemy aircraft. Its high-water mark was on 29 May 1940, when No. 264 Sqn claimed 65 kills, mostly Ju 87 Stukas and Messerschmitt Bf 110 twin-engined heavy fighters.

Initially, Luftwaffe fighters suffered losses when "bouncing" flights of Defiants from the rear, apparently mistaking them for Hurricane fighters. [ Green 1961, p. 12.] The German pilots were unaware of the Defiant's rear-firing armament and encountered concentrated defensive fire. However with a change in Luftwaffe tactics, opposing fighters were able to out-manoeuvre the Defiant and attack it from below or dead ahead, where the turret offered no defence. Defiant losses quickly mounted, particularly among the gunners, who were often unable to leave stricken aircraft. The additional weight of the turret and the second crewman plus the aerodynamic drag, gave the Defiant lower performance than conventional fighter aircraft. [ Winchester 2005, p. 16. ] On 13 May, a flight of six Defiants was attacked by Bf 109Es; five of the Defiants were shot down from a frontal attack.

According to the book "The Turret Fighters" by aviation historian Alec Brew, 264 Sqn. developed effective countermeasures against single-seat aircraft such as the Bf 109. By flying in an ever-descending "Lufberry" circle, Defiant crews sacrificed the advantage of height but eliminated the possibility of attack from underneath, while giving 360° of defensive fire. [ Brew 2002, p. 56. ] This tactic was used successfully by 264 Sqn. but when the Defiants of 141 Sqn. were committed to combat a few months later during the Battle of Britain, 141 Sqn. chose to ignore their advice, with devastating consequences. On 19 July 1940, six out of nine Defiants of 141 Sqn. were shot down and the remaining three only survived due to the intervention of Hurricanes of 111 Sqn. [Brew 2002, pp. 65–66. Note: This action is sometimes called "slaughter of the innocents."] Although 264 Sqn. claimed an astonishing 48 kills in eight days over Dunkirk (recent research suggests no more than 12 to 15 enemy aircraft were actually destroyed; the turret's wide angle of fire meant that several Defiants could engage the same target at one time), the cost was high at 14 Defiants lost.

264 Squadron lost two aircraft on 26 August, then another five on 28 August with the deaths of nine crew members. With these prevailing losses, the Defiant was quickly transferred from daylight operations to night fighting duties and, as a night fighter, the Defiant achieved some success. Defiant night fighters typically attacked enemy bombers from below, in a similar manoeuvre to the later successful German Schräge Musik methods. Defiants attacked more often from slightly ahead or to one side, rather than from directly under the tail. During the winter "Blitz" on London of 1940–41, the Defiant equipped four squadrons, shooting down more enemy aircraft than any other type. [Taylor 1969, p. 326.] The turret-fighter concept was not immediately discarded and the fitting of Defiant-style turrets to Beaufighter and Mosquito night fighters was trialled to enable these aircraft to duplicate these methods, but the effect on performance proved drastic, and the idea was abandoned. [Brew 2002, p. 105.] 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.

After trials in 1940 with the School of Army Co-operation to assess its capabilities in that role, the Defiant was re-evaluated as a high-speed gunnery trainer with the Air Ministry agreeing to keep the production lines open. The Defiant was removed from combat duties in 1942 and, thereafter, used for training, target towing, ECM and air sea rescue. The Defiant was used to carry the Mandrel noise jammer to combat the German Freya early warning radar. Bowyer 1970, p. 270.] Further deployments occurred to Canada where the Defiant fulfilled a role as both a target tug and trainer with the British Commonwealth Air Training Plan.

Defiants were also utilized for "special" work including tactical evaluations with the RAF Gunnery Research Unit and Air Fighter Development Unit (AFDU) at Farnborough. On 11 May 1945, Martin-Baker used a Defiant, "DR944", to test their first ejection seat with dummy launches. Bowyer 1970, p. 270.]

The last operational use of Defiants was in India, where they were used as target tugs. [ Aircraft of the Indian Air Force - Boulton-Paul Defiant TT I & TT III] ]


;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 I:Defiant Mk I converted into night fighters

;Defiant NF Mk IA:NF Mk I with Airborne Interception radar.

;Defiant ASR Mk I:Mk I carrying air-dropped dingies for air-sea rescue.

;Defiant TT Mk I:Defiant Mk IIs converted to target tugs; 150 conversions.

;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 III:Dedicated turret-less target tug; 140 built from new.


;AUS;flagicon|India|British British India;flag|Canada|1921;POL;UK;USA


The single surviving complete example of the type is a Defiant I, "N1671", on display as a night fighter at the Royal Air Force Museum in Hendon, London.Bowyer 1970, p. 270.] [ [ "Boulton Paul Defiant 1."] Royal Air Force Museum. Retrieved: 12 January 2008.] It was delivered to No. 307 Polish Night Fighter Squadron at RAF Kirton in Lindsey, Lincolnshire, England on 17 September 1940 with three other Defiants. Major parts of at least two other Defiants survive; "N1766" and "N3378", both Mk Is.Simpson, Andrew. [ "Boulton Paul Defiant I N1671/837OM: museum accession no. 74/A/16."] Royal Air Force Museum. Retrieved: 12 January 2008.]

pecifications (Mk I)

aircraft specifications
plane or copter?=plane
jet or prop?=prop

crew=2: pilot, gunner
length main=35 ft 4 in
length alt=10.77 m
span main=39 ft 4 in
span alt=11.99 m
height main=12 ft 2 in
height alt=3.71 m
area main= 250 ft²
area alt= 23 m²
empty weight main=6,078 lb
empty weight alt=2,755 kg
loaded weight main=8,318 lb
loaded weight alt=3,773 kg
max takeoff weight main=
max takeoff weight alt=

engine (prop)=Rolls-Royce Merlin III
type of prop=liquid-cooled V12 engine
number of props=1
power main=1,030 hp
power alt=780 kW

max speed main=304 mph
max speed alt=264 knots, 489 km/h
range main=465 mi
range alt=404 nm, 748 km
ceiling main=30,350 ft
ceiling alt=9,250 m
climb rate main=1,900 ft/min
climb rate alt=9.65 m/s
loading main=
loading alt=
power/mass main=0.124 hp/lb
power/mass alt=204 W/kg

guns=4 × 0.303 in (7.7 mm) Browning machine guns in hydraulically-powered dorsal turret (600 rounds per gun, 2,400 rounds total)

ee also


similar aircraft=
* Blackburn Roc
* Hawker Hotspur

* List of aircraft of the RAF

see also=
* YFM Airacuda
* Boulton Paul P.92




* Ansell, Mark. "Boulton Paul Defiant". Redbourn, Herts, UK: Mushroom Model Publications, 2005. ISBN 83-89450-19-4.
* Bowyer, Michael J.F. "The Boulton Paul Defiant." "Aircraft in Profile, Vol. 5". London, Profile Publications Ltd., 1966.
* Brew, Alex. "The Turret Fighters - Defiant and Roc". Ramsbury, Marlborough, Wiltshire, UK: Crowood Press, 2002. ISBN 1-86126-497-6.
* Brew, Alex. "The Defiant File". Tunbridge Wells, Kent, UK: Air-Britain (Historians) Ltd., 1996. ISBN 0-85130-226-2.
* Green, William. "War Planes of the Second World War: Fighters, Vol. 2". London: Macdonald & Co., 1961. No ISBN.
* Green, William and Gordon Swanborough. "WW2 Aircraft Fact Files: RAF Fighters, Part 1". London: Macdonald and Jane's Publishing Ltd., 1978. ISBN 0-354-01090-5.
* Hall, Alan W. and Thomas, Andrew. "Boulton Paul Defiant" (Warpaint Series No.42). Luton, Bedfordshire, UK: Warpaint Books Ltd., 2003. ISBN X-9999-0042-X.
* Price, Alfred. "Instruments of Darkness: The History of Electronic Warfare". St Albans, UK: Granada, 1979. ISBN 0-586-04834-0.
* Taylor, John W.R. "Boulton Paul Defiant." "Combat Aircraft of the World from 1909 to the present". New York: G.P. Putnam's Sons, 1969. ISBN 0-425-03633-2.
* Whitehouse, Les. "The Disappointing Defiant." "AirEnthusiast Five", November 1977-February 1978. Bromley, Kent, UK: Pilot Press Ltd., 1977.
* Winchester, Jim. "Boulton Paul Defiant." "The World's Worst Aircraft: From Pioneering Failures to Multimillion Dollar Disasters". London: Amber Books Ltd., 2005. ISBN 1-904687-34-2.

External links

* [ Fleet Air Arm Archive]
* []
* [ The Boulton Paul Association]

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