The Boulton Paul Defiant was a so-called "turret fighter", designed and built by Boulton Paul Aircraft Ltd. It was a contemporary of the Royal Navy's Blackburn Roc. The concept of a turret fighter was similar to that of the First World War-era Bristol Fighter. In practice, the Defiant was found to be vulnerable to the Luftwaffe's more agile, single-seat Me 109 fighters; crucially, the Defiant had no forward-firing guns.

It was later used as a night fighter before being replaced by the Bristol Beaufighter and de Havilland Mosquito. The Defiant found use in gunnery training, target towing, ECM and air-sea rescue. Among RAF pilots, it had the nickname "Daffy", probably a diminutive of "Defiant".

The concept of a turret-armed defensive fighter emerged in 1935, at a time when the RAF anticipated having to beat off massed formations of unescorted enemy bombers. Advances in aircraft design during the 1920s and 1930s had resulted in a generation of multi-engined bombers that were faster than the single-engined biplane fighters in service. The RAF believed that its turret-armed bombers, such as the Vickers Wellington, would be able to penetrate enemy airspace and defend themselves without fighter escort and also that the German Luftwaffe would be able to do the same.

In theory, turret-armed fighters would approach an enemy bomber from below or from the side and coordinate their fire. The separation of the tasks of flying the aircraft and firing the guns would allow the pilot to concentrate on putting the fighter into the best position while the gunner could engage the enemy. Previously the Hawker Demon had tested the concept with 59 of the biplane fighters (manufactured by Boulton Paul under a sub-contract) equipped with a powered rear turret while the remainder of the series already manufactured were converted.

Air Ministry Specification F.9/35 required a two-seater day and night "turret fighter" capable of 290 mph at 15,000 ft. It followed the earlier F.5/33 which was for a pusher design with a front turret. F.5/33 had been abandoned as it offered little over existing fighters and the Armstrong Whitworth AW.34 design which had been ordered was not completed.

Operational history

In October 1939 No. 264 (Madras Presidency) Squadron was reformed at RAF Sutton Bridge to operate the Defiant. Initial training and development of tactics began with other aircraft as it only received their first Defiants in early December at Martlesham Heath. They began night fighter training in February 1940. The squadron tested their tactics against British medium bombers - Hampdens and Blenheims - and the 264's CO flew against Robert Stanford Tuck in a Spitfire showing the Defiant could defend itself by circling and keeping its speed up. By March, 264 Squadron had two flights operational with Defiants. No. 141 Squadron received its first Defiant.

The first operational sortie came on 12 May 1940. Defiants flew with six Spitfires of 66 Sqn, and a Ju 88 was shot down over Holland. The following day, in a patrol that was a repetition of the first, Defiants claimed four Ju 87s, but were subsequently attacked by Bf 109Es. The escorting Spitfires were unable to prevent five of the six Defiants being shot down by a frontal attack.

During the evacuation of the British Expeditionary Force from Dunkirk, the Squadron was forward based at RAF Manston one of the 16 Squadrons that No. 11 Group had available to cover the evacuation. On the 27th 264 Sqn claimed 3 He 111 and 2 damaged. On the 28th, shortly after take-off ten Defiants were attacked by about 30 Bf 109s - forming a circle, six German fighters were claimed for the loss of three Defiants.

The Defiant was initially successful against enemy aircraft. Its best day was 29 May 1940, when No. 264 Sqn claimed 37 kills in two sorties: 19 Ju 87 Stuka dive bombers mostly picked off as they came out of their dives, nine Me 110 twin-engined heavy fighters, eight Me 109s a Ju 88. One Defiant gunner was lost after he bailed out though the aircraft made base to be repaired.

Initially, Luftwaffe fighters suffered losses when "bouncing" flights of Defiants from the rear, apparently mistaking them for Hurricanes. The German pilots were unaware of the Defiant's rear-firing armament and encountered concentrated defensive fire. 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. According to the book The Turret Fighters by aviation historian Alec Brew, 264 Sqn. developed a counter against single-seat aircraft such as the Me 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.

This tactic was used relatively successfully by No. 264 Sqn. but when the Defiants of No. 141 Sqn. were committed to combat a few months later during the Battle of Britain, it chose to ignore their advice with devastating consequences. On 19 July 1940, six out of nine Defiants of 141 Sqn. sent to cover a convoy off Folkestone were shot down and the remaining three only survived due to the intervention of Hurricanes of 111 Sqn.

The Hurricanes reported that the Defiants had shot down four Bf 109s. Although 264 Sqn. claimed 48 kills in eight days over Dunkirk, the cost was high with 14 Defiants lost. The actual German losses were no more than 12 to 15 enemy aircraft; the turret's wide angle of fire meant that several Defiants could engage the same target at one time leading to multiple claims.

No. 264 Squadron lost two aircraft on 26 August and five on 28 August with the deaths of nine crew members. With these losses, the Defiant - which had been intended from the start as a day and night fighter - was transferred to night fighting. There, the Defiant achieved some success. Defiant night fighters typically attacked enemy bombers from below, in a similar manoeuvre to the later successful German Schr├Ąge Musik methods.

During the winter Blitz on London of 1940-1, the Defiant equipped four squadrons, shooting down more enemy aircraft than any other type. The turret-fighter concept was not immediately discarded and the fitting of Defiant-type turrets to Beaufighter and Mosquito night fighters was tried to enable these aircraft to duplicate these methods. The effect on performance proved drastic and the idea was abandoned. The Defiant Mk II was fitted with the AI Mk IV airborne interception radar and a Merlin XX engine. A total of 207 of this mark were built.

After trials in 1940 with the School of Army Co-operation to assess its capabilities in that role, the Defiant was tested as a high-speed gunnery trainer with the Air Ministry agreeing to continue production. The Defiant was removed from combat duties in 1942 and used for training, target towing, electronic countermeasures and air-sea rescue.

Two types of Electronic Countermeasures equipment were carried by the Defiant, both countering the German Freya early warning radar. The first system to be deployed was "Moonshine" which re-transmitted the radar's signals to simulate large formations of aircraft. As each "Moonshine" transmitter only covered part of the Freya's frequency, a formation of eight Defiants were needed, giving the appearance of over 100 aircraft.

As the system required formation flying, it could only be used in daylight, where it could draw German fighters onto British fighters leaving another area relatively free for a British bombing raid. A "Special Duties Flight" was set up in May 1942 to use the new countermeasures equipment, with "Moonshine" being used for its first live test on 6 August 1942. Subsequently it was used operationally as part of "Circuses" against coastal targets and on 19th August in support of the Dieppe Raid. The Flight became No. 515 Squadron RAF on 1 October 1942, operations with "Moonshine" continuing until November 1942.

515 Squadron continued operations with the second countermeasures system, "Mandrel", a noise jammer which overwhelmed the signals from Freya. Individual Defiants were sent to orbit positions 50 miles (80 km) off the enemy coast. By using nine aircraft a 200 mile (320 kg) gap could be made in the German's radar coverage. No. 515 Squadron flew its first mission using Mandrel on the night of 5/6 December 1942, continuing to use its Defiants for jamming operations until the spring of 1943, when it began to receive twin-engined Bristol Beaufighters which had longer range and could carry more electronic equipment. The Defiant flew its last jamming mission on 17 July 1943, with one aircraft being lost out of four sent out that night.

In air-sea rescue the Defiant was equipped with a pair of under-wing 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 this final target towing variant, the Defiant ended up with a number of overseas assignments with both the RAF and Fleet Air Arm in the Middle East, Africa and India. Further deployments occurred to Canada, where the Defiant was used as both a target tug and trainer with the British Commonwealth Air Training Plan.

Defiants were also used for "special" work including tactical evaluations with the RAF Gunnery Research Unit and Air Fighter Development Unit (AFDU) at Farnborough. Two Defiants were issued for ejection seat development work; to R Malcolm Ltd and Martin-Baker. On 11 May 1945, Martin-Baker used Defiant, DR944, to test their first ejection seat with dummy launches. The last operational use of Defiants was in India, where they were used as target tugs.

(Source Wikipedia)