The Defiant was a conventionally constructed aircraft of similar size and design to the Hawker Hurricane. The most unusual feature was the method of attaching light alloy skins to stringers and ribs, before these were attached to the fuselage frame and wing spars. This avoided the need to preform the skins, which were riveted while flat and using countersunk holes, creating an exceptional surface finish. The fuselage was built on two sections. The forward part was built up of four L section longerons and several bulkheads, while the rear part consisted of two side panels and the top decking.
The Deﬁant was an aircraft of exceptional qualities and an excellent ﬂying machine, and as the world’s ﬁrst ﬁghter to have an enclosed power-driven turret it made its mark on history. It was hardly to be expected that the Deﬁant, penalised by the weight and high drag of even such a compact turret as that evolved by Boulton Paul and possessing a motor of only the same power as that of the very much lighter Hurricanes and Spitﬁres, would compete in performance and agility with contemporary single-seaters, and it was not the fault of the design team that their product was born of an outmoded philosophy. The Deﬁant failed by day, but when the Luftwaffe turned to night operations, presenting the R.A.F. with a formidable problem, it found its forte, ﬁlling a gap in Britain’s defences until more advanced night interceptors became available.
Development of the Defiant began in 1935, when the British Air Ministry issued Specification F.9/35 to meet the requirement for a two-seat fighter which concentrated the main armament in a revolving powered turret, and possessed a speed capability similar to the single seat fighters then beginning to enter service.
Five manufacturers submitted proposals to meet F.9/35, with two of them being selected in the Autumn of 1935 to build one prototype each - Boulton Paul Aircraft with the Defiant, and Hawker Aircraft Ltd with the Henley derived Hotspur. However, due to their Hurricane commitments, Hawker were unable to build the Hotspur prototype until 1937, which also made it impossible to spare any effort to bring the Hotspur prototype up to service standard. This eventually led to development of the Hotspur being discontinued in favor of the Defiant.[N 3]
The First Defiant prototype - K8310 - was flown by Boulton Paul's chief test pilot Cecil Feather on August 11, 1937. Due to delays with the turret, the Defiant was initially flown as a single seater, with the turret well faired over and carrying ballast in place of the turret and second crew member. [N 4]
When tested at Martesham against the Hotspur - with both types carrying similar ballast loads and a wooden mock up of the turret - the Defiant was found to be heavier and slower than the Hawker aircraft.
Air Sea Rescue
As Deﬁants were released from the night ﬁghter role they were handed over to R.A.F. Fighter Command air-sea rescue units, largely supplanting the Lysander. Two “M”-type rescue dinghies were carried in containers beneath the wings, and the ﬁfty or so Deﬁants converted for the air-sea rescue role served with Nos. 275, 276, 277, 278 and 281 Squadrons. Their suitability for the role was questionable as their wide turning circle and high stalling speed were distinct disadvantages on A.S.R. operations. However, maintenance problems necessitated their withdrawal after some six months.
Deﬁant production ended with a run of 140 examples of a target-towing variant ordered in July 1941 as the T.T.Mk.I. The turret was removed and replaced by a ﬁxed canopy over the winch operator’s cockpit, and a “B” or “E” type winch was attached to the side of the fuselage and driven by a “windmill” on the fuselage starboard side, and target sleeves were carried in a pack under the rear fuselage. Based on the Deﬁant II, the ﬁrst T.T.Mk.I (DR863) was completed at the end of 1941, and deliveries occupied most of 1942. The last forty Mk. II ﬁghters were also converted as T.T.Mk. Is and, subsequently, 150 Deﬁant Is with Merlin III engines were converted as target tugs following a successful trial conversion of N3488 in mid-1942, and designated T.T.Mk. III. The designation T.T.Mk. II was reserved for a proposed production variant with a 1,620 h.p. Merlin 24 engine. The Deﬁant performed the unglamorous but vital task of target tug throughout the remainder of the war years, serving at air gunnery training schools and many ﬁghter and bomber O.T.U.s. Some sixty Deﬁant target tugs were transferred to the Royal Navy, while two others, including DR945, were flown in mixed RAF/US Insignia by the 11th Combat Crew Replacement Centre, United States Army Air Force 326th Bombardment Squadron, based at Bovingdon.
- Some were later modified for Target Towing, while others were used for Air/Sea Rescue work, with inflatable dingy packs under the wings.
- Additional Information;
*Height 11 ft. 4 in.,
*Wing area, 250 sq. ft.
*Internal fuel capacity: 104 Imp. gal. (125 U.S. gal.)
*Endurance, 1.78 hrs.
*Initial climb rate, 1,900 fl./min.
*Time to 15,750 ft., 8.5 min.
*Service ceiling, 30,350 ft.
- A plan for Avro to produce the Hotspur had to be dropped due to their own existing commitments.
- This single seat configuration was briefly restored in 1940, as part of a proposal to build some Defiants as single seat fixed gun fighters.
- Green, William - Fighters. 1975. Page 223.
- Green, William - Fighters. 1975. Page 229.
- Green, William. Famous Fighters of the Second World War. Purnell Book Services. 1975. Page 221.
- Green, William and Gordon Swanborough. 2001. Page 287.
- Green, William - Fighters. 1975. Pages 222-223.
- Green, William - Fighters. 1975. Page 220.
- Green, William - Fighters. 1975. Page 228.
- Green, William - Fighters. 1975. Pages 228-229.
- Green, William. Famous Fighters of the Second World War. Book Club Associates. 1975.
- Green, William and Gordon Swanborough. Complete Book of Fighters. Salamander Books. 2001. ISBN 1-84065-269-1