Often maligned as a failure, the Boulton Paul Defiant found a
successful niche as a night-fighter during the German 'Blitz' on
London, scoring a significant number of combat kills before being
relegated to training and support roles.
The Boulton Paul company first became interested in powered gun turrets
when it pioneered the use of a pneumatic-powered enclosed nose turret
in the Boulton Paul Overstand biplane bomber. The company subsequently
brought the rights to a French-designed electro-hydraulic powered
turret and soon became the UK leaders in turret design.
On 26 June 1935, the Air Ministry issued Specification F.9/35 calling
for a two-seat fighter with all its armament concentrated in a turret.
Performance was to be similar to that of the single-seat monoplane
fighters then being developed. It was envisioned that the new fighter
would be employed as destroyer of unescorted enemy bomber formations.
Protected from the slipstream, the turret gunner would be able to bring
much greater firepower to bear on rapidly moving targets than was
Boulton Paul tendered the P.82 design, featuring an 4-gun turret
developed from the French design, and was rewarded with an order for
two prototypes. On 28 April 1937, the name Defiant was allocated to the
project and an initial production order for 87 aircraft was placed
before the prototype had even flown.
The first prototype (K8310) made its maiden flight on 11 August 1937,
with the turret position faired over as the first turret wasn't ready
for installation. Without the drag of the turret, the aircraft was
found to handle extremely well in the air. With these promising
results, a further production contract was awarded in February 1938.
Performance with the turret fitted was somewhat disappointing, but
still considered worthwhile. In May 1938, the second prototype
(K8620)was ready for testing. This aircraft was much closer to the
final production standard. Development and testing of the aircraft and
turret combination proved somewhat protracted, and delivery to the
Royal Air Force was delayed until December 1939, when No.264 Squadron
received its first aircraft. Numerous engine and hydraulic problems
were not finally resolved until early in 1940.
The A. Mk IID turret used on the Defiant was a self-contained 'drop-in'
unit with its own hydraulic pump. To reduce drag two aerodynamic
fairings, one fore and one aft of the turret, were included in the
design. Rectraction of these fairings by means of pneumatic jacks
allowed the turret to traverse. Too allow the turret a clear field of
fire, two rather large radio masts were located on the underside of the
fuselage. These masts retracted when the undercarriage was extended.
The overall aircraft was of modern stressed skin construction, designed
in easy-to-build sub-assemblies which greatly facilitated the rapid
build-up in production rates.
Previously, a single-seat fighter unit, 264 Sqn spent some time working
out the new tactics required by the type. Good co-ordination was
required between the pilot and gunner in order to get into the best
position to open fire on a target. A second day fighter unit, 141 Sqn,
began converting to the Defiant in April 1940. The Defiant undertook it
first operational sortie on 12 May 1940, when 264 Sqn flew a patrol
over the beaches of Dunkirk. A Junkers Ju 88 was claimed by the
squadron. However, the unit suffered its first losses the following
day, when five out of six aircraft were shot down by Bf 109s in large
dogfight. The Defiant was never designed to dogfight with single-seat
fighters and losses soon mounted. By the end of May 1940, it had become
very clear that the Defiant was no match for the Bf 109 and the two
squadrons were moved to airfields away from the south coast of England.
At the same time, interception of unescorted German bombers often
proved successful, with several kills being made.
In the summer of 1940, flight testing commenced of an improved version
of the Defiant fitted with a Merlin XX engine featuring a two-speed
supercharger (prototype N1550). The resultant changes included a longer
engine cowling, deeper radiator and increased fuel capacity.
Performance increases were small. Nevertheless, the new version was
ordered into production as the Defiant Mk II.
The limitations on the Defiant's manoeuvrability forced its eventual
withdrawal from daylight operations in late August 1940. 264 and 141
squadrons became dedicated night-fighter units. The Defiant night
fighters were painted all-black and fitted with flame damper exhausts.
Success came quickly, with the first night kill being claimed on 15
September 1940. From November 1940, an increasing number of new night
fighter squadrons were formed on the Defiant. Units operating the
Defiant shot down more enemy aircraft than any other night-fighter
during the German 'Blitz' on London in the winter of 1940-41. Initial
operations were conducted without the benefit of radar. From the Autumn
of 1941, AI Mk 4 radar units began to be fitted to the Defiant. An
arrow type aerial was fitted on each wing, and a small H-shaped aerial
added on the starboard fuselage side, just in front of the cockpit. The
transmitter unit was located behind the turret, with the receiver and
display screen in the pilot's cockpit. The addition of radar brought a
change in designation for the Mk I to N.F. Mk IA, but the designation
of the Mk II version did not change. By February 1942, the Defiant was
obviously too slow to catch the latest German night intruders and the
night fighter units completely re-equipped in the period
From March 1942 many of the remaining aircraft were transferred to
Air-Sea Rescue (ASR) units. The aircraft was modified to carry a M-type
dinghy in a cylindrical container under each wing. Both Mk I and Mk II
versions were used for this task, but the Defiant proved less useful
than originally anticipated, and all examples were replaced in this
role during the first half of 1943.
A specialised Target-tug version of the Defiant was first ordered in
July 1941, designated the T.T. Mk I. The new version was based on the
Mk II airframe, with the Merlin XX engine, but with space formerly
occupied by the turret now taken up with an observers station with a
small canopy. A fairing under the rear fuselage housed the target
banner, and a large windmill was fitted on the starboard fuselage side
to power the winch. The first prototype Target-tug aircraft (DR863) was
delivered on 31 January 1942. 150 Mk II aircraft were also converted to
Target-tugs, under the designation T.T. Mk I. A similar conversion of
the Mk I was carried out by Reid & Sigrist from early 1942 under the
designated T.T. Mk III. Nearly all the Target-tugs were withdrawn from
service during 1945, although one example lasted until 27 February
Boulton Paul Defiant TT.Mk I of an RAF fighter Operational Training
Unit based in the Middle East 1945. The Black and Yellow
scheme was adopted for high conspicuity as a Target Tug
publicised, task of the Defiant was in the radar jamming role. 515
Squadron operated at least nine Defiants fitted with 'Moonshine' or
'Mandrel' radar jamming equipment in support of USAAF 8th Air Force
daylight bombing raids on Germany between May 1942 and July 1943,
before replacing them with larger aircraft types.
One Defiant T.T. Mk I (DR944) was seconded to Martin Baker on 11
December 1944. It was fitted with the first ever Martin Baker ejection
seat in the observers station, and commenced dummy ejection trials on
11 May 1945. Another Defiant (AA292) was later used for similar trials
by the Air Ministry until March 1947. Martin Baker retained their
Defiant until 31 May 1948.
The lack of forward firing armament presented a great handicap to a
fighter which lacked the manoeuvrability to match single-seat fighters
in combat, but as an interim night-fighter the Defiant met with a great
deal of success.
Paul Defiant Mk II)
Type: Two Seat
Paul Design Team
Bolton Paul Aircraft, Wolverhampton.
II) One 1,280 hp (954 kW) Rolls-Royce Merlin XX inline piston engine.
(Mk I) One 1,030 hp (768 kW) Rolls-Royce Merlin III Vee 12-cylinder
Maximum speed 313 mph (504 km/h) at 19,000 ft (5790 m); cruising speed
260 mph (418 km/h); service ceiling 30,350 ft (9250 m); initial climb
rate 1,900 ft (579 m) per minute.
Range: 465 miles
(748 km) on internal fuel.
Weight: (Mk II)
Empty 6,282 lbs (2849 kg) with a maximum take-off weight of 8,424 lbs
(3821 kg). (Mk I) Empty 6,078 lbs (2757 kg) with a maximum take-off
weight of 8,350 lbs (3787 kg).
39 ft 4 in (11.99 m); length 35 ft 4 in (10.77 m); height 11 ft 4 in
(3.45 m); wing area 250.0 sq ft (23.23 sq m).
Armament: Four 7.7 mm (0.303 in) Browning machine-guns in a
hydraulically operated dorsal turret with 600 rounds per gun.
Boulton Paul P.82 Defiant (prototype), Defiant F.Mk I, Defiant NF.Mk IA,
Defiant Mk II, Defiant TT.MK I, Defiant TT.MK III.
Avionics: AI Mk
IV or Mk VI radar, Mandrel jamming system.
flight (prototype) 11 August 1937; (production Mk 1) 30 July 1939;
first delivery December 1939.