Originally designed as a bomber destroyer the Defiant was pressed into service as a day fighter over the beaches of Dunkirk and during the Battle of Britain. Despite early successes ever
increasing losses saw the Boulton Paul Defiant moved to night fighting where it excelled.
First flight 11th August 1937
Entered service December 1939
Total built 1,065
In 1935 a new tactical concept was conceived, this proposed the idea that fighters would have a gun turret mounted on them as opposed to forward firing guns. This appeared to have two advantages,
firstly, it meant the pilot could concentrate on flying the aircraft and not have to worry about finding and hitting a target. Secondly the guns could be used over a greater area than before and
could be used for both offence and defence.
When the Air Ministry issued Specification F.9/35 for a two-seater fighter plane with a power operated gun turret Hawker and Boulton Paul both made submissions. Hawker's prototype was called the
Hotspur, however this aircraft was not to compete against the two which were ordered from Boulton Paul. This was mainly because there was no producing capacity left in the Hawker factories meaning
the prototype was abandoned.
The first prototype of Boulton Paul's, now called the Defiant, made its initial flight on the 11th August 1937. A two seater low-wing cantilever monoplane fighter of all metal construction with
retractable tail wheel type landing gear and powered by a Rolls-Royce Merlin I inline engine (the second prototype had a Merlin II engine). Both of the prototypes had the large heavy four gun
turret mounted within the fuselage just behind the cockpit. However the weight and high degree of drag caused by the protruding section of the turret was to limit both the manoeuvrability and
speed of the Defiant.
The first production Boulton Paul Defiant was flown on the 30th July 1939 and would orginally operate as a day fighter. The first deliveries of this new aircraft were made to No. 264 Squadron
during December 1939. The following year saw the squadron move to RAF Duxford on the 10th May. Two days later on the 12th May 264 Squadron took the Defiant into battle for the first time over
Holland. In its first operations it achieved complete surprise as Luftwaffe pilots either mistook the Defiant for a Hawker Hurricane or assumed it was armed with forward
firing guns like most conventional fighters. By the end of May 1940 they had claimed a total of 65 enemy aircraft destroyed. This air superiority was only brief for it did not take long for the
Luftwaffe pilots to work out that if they attacked the Defiant head on they could do so with complete immunity. This saw the aircraft suffer huge losses and as a result they were removed from
daylight operations in August 1940.
The Boulton Paul Defiant was instead moved into a new night fighter role which lead to the Defiant NF Mk IA and a number of aircraft were installed with a comparatively new and secret Airbourne Interception (AI) Mk. IV radar. It was in the
night fighter role that the Defiant was to have success as part of Britain's night defences in the winter of 1940-41. During this period they were to shoot down more enemy aircraft than any other
contemporary night fighter.
The aircraft would be involved in one of the more mysterious episodes of the Second World War when on the 10th May 1941 a pair of Defiants from No. 141 Squadron, Ayr were sent to intercept an
aircraft. Despite pursing the aircraft they were unable to catch it. It would later transpire that the aircraft was a Messerschmitt Bf 110 flown by Rudolf Hess, the Deputy Fuhrer to Adolf Hitler.
To try to improve the performance of the Defiant two Mk Is served as prototypes for the new Mk II version. Fitted with a more powerful Merlin XX engine whilst other changes to the aircraft saw the
rudder improved with a greater area, modifications to the fuel systems, engine cooling and an increased fuel capacity. This new Defiant was first flown in June 1940 and over 200 were
built, although many were converted to target tugs later on, and a number were built as dedicated target tugs. In this role they were used both at home and in the Middle and Far East. Also serving
in other roles Defiants were used for air sea rescue, carrying air dropped dinghies, and some also carried the Mandrel noise jammer to co combat the German early warning radar.
A sole Defiant TT Mk I would be sent to Martin-Baker on the 11th December 1944 so it could be used by the company to test their ejection seats. The first dummy trials started on the 11th May 1945.
The Air Ministry would also conduct their own trials using a Defiant until March 1947.
During its peak as a night fighter 13 RAF squadrons were using Defiants. Its removal from combat duties in 1942 was followed a year later by production being ceased. In total 1,065 had been built.