page_title: Northrop P-61 Black Widow
section_title: Origins
hierarchical_section_title: Northrop P-61 Black Widow / Development / Origins
caption_attribution_description: English: Good view of the P-61 night fighter's radar operators compartment in the rear of the fuselage. Photo was taken on Saipan,Marianas Islands on July 20,1944.
context_page_description: The Northrop P-61 Black Widow, named for the North American spider, was the first operational U.S. warplane designed as a night fighter, and the first aircraft designed to use radar. The P-61 had a crew of three: pilot, gunner, and radar operator. It was armed with four 20 mm Hispano M2 forward-firing cannon mounted in the lower fuselage, and four .50 in M2 Browning machine guns mounted in a remote-controlled dorsal gun turret.
  It was an all-metal, twin-engine, twin-boom design developed during World War II. The first test flight was made on May 26, 1942, with the first production aircraft rolling off the assembly line in October 1943. The last aircraft was retired from government service in 1954.
  Although not produced in the large numbers of its contemporaries, the Black Widow was effectively operated as a night-fighter by United States Army Air Forces squadrons in the European Theater, Pacific Theater, China Burma India Theater, and Mediterranean Theater during World War II. It replaced earlier British-designed night-fighter aircraft that had been updated to incorporate radar when it became available.
context_section_description: In August 1940, 16 months before the United States entered the war, the U.S. Air Officer in London, Lieutenant General Delos C. Emmons, was briefed on British research in radar (RAdio Detection And Ranging), which had been underway since 1935 and had played an important role in the nation's defense against the Luftwaffe during the Battle of Britain. General Emmons was informed of the new Airborne Intercept radar (AI for short), a self-contained unit that could be installed in an aircraft and allow it to operate independently of ground stations. In September 1940, the Tizard Mission traded British research, including the cavity magnetron that would make self-contained interception radar installations practicable, for American production.
  Simultaneously, the British Purchasing Commission evaluating US aircraft declared their urgent need for a high-altitude, high-speed aircraft to intercept the Luftwaffe bombers attacking London at night. The aircraft would need to patrol continuously over the city throughout the night, requiring at least an eight-hour loiter capability. The aircraft would carry one of the early (and heavy) AI radar units, and mount its specified armament in "multiple-gun turrets". The British conveyed the requirements for a new fighter to all the aircraft designers and manufacturers they were working with. Jack Northrop was among them, and he realized that the speed, altitude, fuel load and multiple-turret requirements demanded a large aircraft with multiple engines.
  General Emmons returned to the U.S. with details of the British night-fighter requirements, and in his report said that the design departments of the Americans' aviation industry's firms possibly could produce such an aircraft. The Emmons Board developed basic requirements and specifications, handing them over towards the end of 1940 to Air Technical Service Command (ATSC) at Wright Field, Ohio. After considering the two biggest challenges—the high weight of the AI radar and the very long (by fighter standards) loiter time of eight hours minimum—the board, including Jack Northrop, realized the aircraft would need the considerable power and resulting size of twin engines, and recommended such parameters.  The United States had two twin-row radials of at least 46 liters displacement in development since the late 1930s; the Double Wasp and the Duplex Cyclone.  These engines had been airborne for their initial flight tests by the 1940/41 timeframe, and were each capable, with more development, of exceeding 2,000 hp (1,491 kW).
  Vladimir H. Pavlecka, Northrop Chief of Research, was present on unrelated business at Wright Field. On 21 October 1940, Colonel Laurence Craigie of the ATSC phoned Pavlecka, explaining the U.S. Army Air Corps' specifications, but told him to "not take any notes, 'Just try and keep this in your memory!'" What Pavlecka did not learn was radar's part in the aircraft; Craigie described the then super-secret radar as a "device which would locate enemy aircraft in the dark" and which had the capability to "see and distinguish other airplanes." The mission, Craigie explained, was "the interception and destruction of hostile aircraft in flight during periods of darkness or under conditions of poor visibility."
  Pavlecka met with Jack Northrop the next day, and gave him the USAAC specification. Northrop compared his notes with those of Pavlecka, saw the similarity between the USAAC's requirements and those issued by the RAF, and pulled out the work he had been doing on the British aircraft's requirements. He was already a month along, and a week later, Northrop pounced on the USAAC proposal.
  On 5 November, Northrop and Pavlecka met at Wright Field with Air Material Command officers and presented them with Northrop's preliminary design. Douglas' XA-26A night fighter proposal was the only competition, but Northrop's design was selected and the Black Widow was conceived.
caption: Close-up view of the P-61 radar operator's compartment in the rear of the fuselage, East Field, Saipan, Mariana Islands, 20 July 1944.
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