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Great Britain's flag Great Britain's RAF aircraft marking

Great Britain's Boulton Paul Defiant fighter


  • Boulton Paul Defiant Prototype
  • Boulton Paul Defiant
  • Boulton Paul Defiant
  • Boulton Paul Defiant
  • Boulton Paul Defiant
  • Boulton Paul Defiant Mk I
  • Boulton Paul Defiant Mk I Night Fighter
  • Boulton Paul Defiant


The Boulton Paul Defiant was intended to be the smallest aircraft that could carry a two crew members, use the Merlin inline engine, and have a four gun turret that could fire to the flanks of the aircraft. The Defiant was designed for specifications (Air Ministry F.9/35) that were released in 1935.


The turret (Boulton Paul powered) was electrically operated and located on top of the fuselage. The turret contained four machine guns.


The Defiant prototype first flew on August 11, 1937.


Production lasted until February 1943.

  • Prototypes: 2
  • Defiant Mk I: 723
    • Production: 1937
  • Defiant Mk II: 270
    • Production: February 1941 - January 1942
  • Defiant TT.1 / Defiant Mk III: 140
    • Production: January 1942
  • Total: 1,060, 1,064, 1,075
    • Manufacturer: Boulton Paul Aircraft Ltd.


  • Defiant Mk I / Defiant F.I: First flew on July 30, 1939. Entered service in December 1939.
  • Defiant NF.I: Night fighter.
  • Defiant Mk IA / Defiant NF.IA: Had AI. Mk IV or Mk VI radar for used at night.
  • Defiant Mk II: First flew on July 20, 1940. Was in service when they were converted into night fighters. New radiator and cowling. Rudder was larger.
  • Defiant Mk III: Conversion of the Mk I into target towers.
  • Defiant TT.I: Target tug based on the Mk II.
  • Defiant TT.III: Target tug converted from Mk Is.


The Defiant joined the No. 264 Squadron in December 1939.

Defiants were used as day fighters, night fighters, target towers, air sea rescue, radar calibration, and radar countermeasures.

Heavy Losses

The first action by six Defiants was in May 1940, and five of these were lost.

Early Victories

On a single day in the month of May 1940 Defiant crews claimed to have shot down 18 German planes with a loss to themselves.

Dunkirk Evacuation

The Defiants had some success during the evacuation from Dunkirk. The Germans were initially surprised by the turret as the Defiant had an appearance as a normal fighter.

Battle of Britain

The Nos 141 and 264 Squadrons suffered horrendous Defiant losses to German pilots who were now used to the Defiant.

Withdrawn to the Night

In August 1940 the Defiant was withdrawn from day operations.

The Defiants were then moved into the night fighter role with the Mk I flying "blind" at night. Thirteen night fighter squadrons were to be equipped with the Defiant.

The No 307 Squadron was manned by Polish pilots and was the first to be used for night fighting in September 1940. In November 1940 the No 255 and No 256 Squadrons were assigned as night fighters. In December 1940 the No 151 Squadron became night fighters. They became operational in 1941 and had AI Mk VI radars installed when they became available.

In January 1941 the No 85 Squadron flew three operations before being converted to Havocs.

Radar Jammers

No 515 Squadron was used to jam German radar starting in 1942.

Non-combat Duties

The Defiant was relegated to target towing, air-sea rescue, radar calibration, and electronic countermeasures (Mandrel jamming system) after 1941.


  Boulton Paul Defiant
Type Fighter, Night fighter
Crew 2
Engine (Type) 1: Rolls-Royce Merlin III
Cooling Liquid
HP 1,030
Propeller blades 3
Span 39' 4"
12 m
Length 35' 4"
10.77 m
Height 11' 4", 12' 2"
3.7 m
Loaded 7,500 lb
Speed 300 mph
Rear turret 4: 0.303" MG
  Boulton Paul Defiant Mk I
Type Fighter, Night Fighter
Crew 2
Engine (Type) Rolls-Royce Merlin III
Cylinders V 12
Cooling Liquid
HP 1,030
Span 39' 4"
11.99 m
Length 35' 4"
10.77 m
Height 12' 2"
3.71 m
Wing Area 250 sq ft
23.225 sq m
Empty 6,000 lb
2,722 kg
Loaded 8,350 lb
3,788 kg
Speed at 16,500' / 5,030 m 303 mph
488 kph
Speed at 17,000' / 5,180 m 303 mph
487 kph
Climb 1,900'/minute
579 m/minute, 580 m/minute
Service ceiling 30,350', 30,500'
9,250 m, 9,295 m
Range 465 miles, 470 miles
748 km, 756 km
Turret - Rear 4: MG
4: 0.303" / 7.7 mm Browning MG in Boulton Paul powered turret
  Boulton Paul Defiant Mk II
Type Night fighter
Crew 2
Engine (Type) Rolls-Royce Merlin XX piston
Cylinders Inline
HP 1,260
Propeller blades 3
Span 39' 4"
11.99 m
Length 35' 4"
10.77 m
Height 12' 2"
3.71 m
Wing area 250 ft2
23.23 m2
Empty 6,150 lb
2,790 kg, 2,892 kg
Loaded 8,600 lb
3,900 kg, 3,901 kg
Speed @ 16,500' /
5,030 m
315 mph
507 kph, 517 kph
Climb 2,050'/minute
625 m/minute
Service ceiling 31,800'
9,690 m
Range 480 miles
772 km
Rear turret 4: 7.7 mm Browning MG


  1. Fighting Aircraft of World War II, Editor: Karen Leverington, 1995
  2. Aircraft of WWII, Stewart Wilson, 1998
  3. World War II Airplanes Volume 1, Enzo Angelucci, Paolo Matricardi, 1976
  4. Aeronautics Aircraft Spotters' Handbook, Ensign L. C. Guthman, 1943
  5. Jane's Fighting Aircraft of World War II, 1989
  6. The Encyclopedia of Weapons of World War II, Chris Bishop, 1998
20th Century American Military History Crucial Site