Boulton Paul Defiant
The Boulton Paul Defiant was a British two-seat turret fighter of the Second World War. Designed in the mid-1930s to destroy unescorted bombers, it carried all four of its machine guns in a powered turret behind the pilot and had no forward-firing armament. Its squadrons claimed heavily over Dunkirk in May 1940, but the claims far exceeded the actual losses, and once German fighters learned to attack where the turret could not bear, the type was withdrawn from daylight operations. It then served as a night fighter during the Blitz, and later in gunnery training, target towing, electronic countermeasures and air-sea rescue. Of 1,064 built, one complete aircraft survives, at the RAF Museum Cosford.
Why It Mattered
The Defiant was the only turret fighter to reach front-line service with the RAF: a two-seat fighter whose entire armament sat in a powered turret behind the pilot, leaving nothing that fired ahead. It had been designed for the war the Air Ministry expected in the mid-1930s, when German bombers were assumed to reach Britain without fighter escorts and a gunner able to fire in almost any direction seemed the answer to them. By 1940 that assumption had failed, as bombers came escorted by fighters based in northern France. Withdrawn from daylight fighting within months, the Defiant found a second career as a night fighter during the Blitz.
Design Notes
Outwardly the Defiant resembled the Hawker Hurricane: a low-wing monoplane of similar size, powered in production Mk I form by a Rolls-Royce Merlin III. Behind the pilot sat the reason for the design, a Boulton Paul Type A turret, electro-hydraulically powered, carrying four 0.303-inch Browning machine guns aimed by a second crewman. The turret could fire over the whole upper hemisphere, and the aircraft was designed to destroy unescorted bombers by beam or ventral attacks, flying alongside or beneath them while the gunner shot. There were no fixed forward-firing guns at all, so the pilot could not shoot where he was pointing. The turret and gunner cost weight and drag, and gave the Defiant lower performance than the single-seat fighters it would meet. The Mk II added a Merlin XX engine and AI Mk IV airborne interception radar, fitting the type for its night role.
Operational History
The prototype, K8310, flew for the first time on 11 August 1937, initially without its turret fitted. No. 264 Squadron received its first Defiants in early December 1939 and spent the following months testing tactics against British medium bombers. The first operational sortie came on 12 May 1940, when Defiants flying with Spitfires over the Dutch coast shot down a Ju 88 that had been attacking a destroyer. Over Dunkirk the type had its famous day: on 29 May, 264 Squadron claimed 37 German aircraft destroyed in two sorties. The claims far outran the reality: across eight days over Dunkirk the squadron claimed 48 victories, but actual German losses were no more than 12 to 15 aircraft, and several Defiants engaging the same target produced multiple claims for one aircraft. German pilots soon learned to attack from below or dead ahead, where the turret guns could not bear, and losses mounted. On 19 July, seven of nine Defiants of No. 141 Squadron sent to cover a convoy off Folkestone were shot down by Bf 109s. After further heavy losses, the Defiant was withdrawn from daytime use before the end of August 1940 and switched to night operations. At night the concept worked better: aviation author John Taylor noted that during the Blitz on London of 1940–41, the four Defiant-equipped squadrons shot down more enemy aircraft than any other type in the theatre. In mid-1942 the night role passed to the Beaufighter and Mosquito, and the Defiant continued in gunnery training, target towing, electronic countermeasures and air-sea rescue. Production of all marks totalled 1,064 aircraft.
Afterlife
A single complete Defiant survives: N1671, taken on RAF charge in August 1940 and operated by the Polish No. 307 Squadron from that September. Its last operational user was No. 285 Squadron, an anti-aircraft co-operation unit, from June 1942. In September 1944 the aircraft was set aside for preservation, and it appeared from its packing crate for museum display in 1960. After many years on display at the RAF Museum at Hendon, it was completely restored by the Medway Aircraft Preservation Society at Rochester Airport and returned to Hendon for further display in 2012. It has since moved to the RAF Museum at Cosford, where it is fully reassembled and on display. Major parts of at least two other Defiants survive, and a full-scale replica built at Wolverhampton by ex-Boulton Paul engineer Jack Holmes and the Boulton Paul Heritage Society is on permanent display at the Kent Battle of Britain Museum.