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Development of the P-70 Night Fighter

Background and Initiation

The success of the RAF’s Havoc I as night interceptors prompted the US Army Air Forces (AAF) to develop its own version, designated the P-70. Initial development challenges of the standard A-20 halted in early 1941 due to issues with turbocharger installations. However, inspired by the RAF’s modifications of the DB-7s into night fighters starting in early 1941, the AAF quickly pursued a similar path.

Key Features and Modifications

• Radar Installation: The P-70 and Havoc I both utilized the British AI Mark IV radar, the first practical airborne-intercept radar. Initially, American equivalents (AI-10) were used, followed by the SCR-540 built by General Electric.
• Airframe Conversion: The AAF tasked Douglas to convert sixty A-20 airframes into radar-equipped night fighters under the new specification DS-434.
• Engines: The P-70 used Wright R-2600-11 engines, replacing the earlier R-2600-7 to mitigate turbocharger issues and due to less emphasis on high-altitude capability.

Specific Modifications

1. Radar and Armament Adjustments:
   • The radar unit was mounted in a modified, unglazed nose section with a transmitting antenna extending forward and receiving dipole antennas on the sides.
   • The nose crewmember position and nose armament were removed, and the rear gunner’s position was adapted for the radar operator.
   • The bomb bay was reconfigured to house a 250-gallon fuel tank and a tray with four 20mm cannons (each with 120 rounds).
   • The aircraft’s electrical system was upgraded from 12 volts to 24 volts.
2. Camouflage and Delivery:
   • P-70s were delivered in an overall matte black finish with standard Air Corps markings and red serial numbers.
   • By September 1942, all sixty P-70s had been delivered, with early deliveries used for training at Orlando, Florida, and later deliveries deployed to operational units in the South Pacific.

Subsequent Variants

1. P-70A:
   • Included sub-variants P-70A-1 and P-70A-2 based on whether modifications were done at the factory or a modification center.
   • Armament shifted to six .50-caliber guns in an A-20G gun nose, with additional flexible .50-caliber guns.
   • The radar installation and antennae configuration followed the original P-70 setup.
   • Thirteen A-20Cs and fifty-one A-20Gs were converted into P-70As, primarily used for stateside training.
2. P-70B:
   • Used the SCR-720B radar with a 10cm wavelength microwave beam and a higher-power transmitter, reducing ground clutter and extending range to about 6 miles.
   • Advanced transmitting antenna behind a radome in the nose, necessitating the relocation of nose guns to fuselage blisters.
   • Sixty-eight A-20Gs were converted into P-70B-1-DOs or P-70B-2-DOs at modification centers.

Known Serial Numbers

• P-70: 39-735 to 39-797.
• P-70A:
  • A-20C: 42-33135, 42-33137, 42-33141 to 42-33221.
  • A-20G: 42-53543, 42-54057 to 42-54274.
• P-70B: 42-54053, 42-86893 to 43-21551.

The P-70 series represented an essential step in the development of radar-equipped night fighters, transitioning from adaptations of existing airframes to more specialized designs. Despite limitations, these aircraft played a crucial role in early night combat operations and training, paving the way for more advanced night fighters like the Northrop P-61 and Douglas XA-26A. Fighter has proven its usefulness in training crews unversed in the use of radar (who would later fly the P-61 when it went into service) and some were also used, at a time when the U.S.A. was desperately short of planes, in the Pacific, at Guadalcanal and in New Guinea in particular, flown by the 6th Fighter Squadron and by 418th, 419th and 421st Squadrons.

Source:
Garry R. Pape: Queen of the Midnight Skies – The Story of America’s Air Force Night Fighters – Schiffer Military History
American Nightfighter Aces of World War 2 – Osprey Aircraft of the Aces 84
Enzo Angelucci: The American Fighter: The Definitive Guide to American Fighter Aircraft from 1917 to the Present