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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.1 The Defiant was designed for specifications (Air Ministry F.9/355) that were released in 1935.2


The turret (Boulton Paul powered5) was electrically operated and located on top of the fuselage.4 The turret contained four machine guns.4


The Defiant prototype first flew on August 11, 1937.1,2,5


Production lasted until February 1943.1

  • Prototypes: 22
  • Defiant Mk I: 7232
    • Production: 19375
  • Defiant Mk II: 2702
    • Production: February 1941 - January 19425
  • Defiant TT.1 / Defiant Mk III5: 1402
    • Production: January 19425
  • Total: 1,0601, 1,0643, 1,0752
    • Manufacturer: Boulton Paul Aircraft Ltd.3


  • Defiant Mk I / Defiant F.I: First flew on July 30, 1939.5 Entered service in December 1939.2
  • Defiant NF.I: Night fighter.2
  • Defiant Mk IA / Defiant NF.IA: Had AI. Mk IV or Mk VI radar for used at night.1
  • Defiant Mk II: First flew on July 20, 1940.5 Was in service when they were converted into night fighters.1 New radiator and cowling.5 Rudder was larger.5
  • Defiant Mk III: Conversion of the Mk I into target towers.1
  • Defiant TT.I: Target tug based on the Mk II.2
  • Defiant TT.III: Target tug converted from Mk Is.2


The Defiant joined the No. 264 Squadron in December 1939.1

Defiants were used as day fighters, night fighters, target towers, air sea rescue, radar calibration, and radar countermeasures.1

Heavy Losses

The first action by six Defiants was in May 1940, and five of these were lost.2

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.2

Dunkirk Evacuation

The Defiants had some success during the evacuation from Dunkirk.1,5 The Germans were initially surprised by the turret as the Defiant had an appearance as a normal fighter.1

Battle of Britain

The Nos 141 and 264 Squadrons suffered horrendous Defiant losses to German pilots who were now used to the Defiant.1

Withdrawn to the Night

In August 1940 the Defiant was withdrawn from day operations.2,3

The Defiants were then moved into the night fighter role with the Mk I flying "blind" at night.1 Thirteen night fighter squadrons were to be equipped with the Defiant.2

Non-combat Duties

The Defiant was relegated to target towing, air-sea rescue, radar calibration, and electronic countermeasures (Mandrel jamming system) after 1941.2


  Boulton Paul Defiant
Type Fighter2, Night fighter4
Crew 22,4
Engine (Type) 1: Rolls-Royce Merlin III4
Cooling Liquid4
HP 1,0304
Propeller blades 32
Span 39' 4"2,4
12 m2
Length 35' 4"2,4
10.77 m2
Height 11' 4"4, 12' 2"2
3.7 m2
Loaded 7,500 lb4
Speed 300 mph4
Rear turret 4: 0.303" MG2
  Boulton Paul Defiant Mk I
Type Fighter3
Crew 23
Engine (Type) Rolls-Royce Merlin III1,2,3,5
Cylinders V 122,3
Cooling Liquid3
HP 1,0301,2,3,5
Span 39' 4"3
Length 35' 4"3
Height 12' 2"3
Loaded 8,350 lb3
Speed @ 16,500' /
5,030 m
303 mph3
Speed @ 17,000' /
5,180 m
303 mph2
487 kph2
Climb 1,900'/minute2
580 m/minute2
Service ceiling 30,350'2,3
9,250 m2
Range 465 miles2,3
748 km2
Rear turret 4: MG3
  Boulton Paul Defiant Mk II
Type Night fighter1
Crew 21
Engine (Type) Rolls-Royce Merlin XX piston1,2,5
Cylinders Inline1
HP 1,2601,2,5
Propeller blades 31
Span 39' 4"1
11.99 m1
Length 35' 4"1
10.77 m1
Height 12' 2"1
3.71 m1
Wing area 250 ft2 1
23.23 m2 1
Empty 6,150 lb1,2
2,790 kg2, 2,892 kg1
Loaded 8,600 lb1,2
3,900 kg2, 3,901 kg1
Speed @ 16,500' /
5,030 m
315 mph1,2
507 kph2, 517 kph1
Climb 2,050'/minute1,2
625 m/minute1,2
Service ceiling 31,800'1,2
9,690 m1,2
Range 480 miles1,2
772 km1,2
Rear turret 4: 7.7 mm Browning MG1


  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
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