Tag Archives: Northrop XP-61 Black Widow

26 May 1942

Northrop Corporation XP-61 Black Widow at Hawthorne.
Northrop Corporation XP-61 prototype 41-19509 at Northrop Field, 1942. (U.S. Air Force)

26 May 1942: The prototype Northrop XP-61-NO Black Widow, 41-19509, made its first flight at Northrop Field, Hawthorne, California, with free-lance test pilot Vance Breese at the controls. (Breese had taken the North American Aviation NA-73X, prototype of the Mustang, for its first flight, 20 October 1940.)

Northrop XP-61 41-19509 taking off from Northrop Field. (U.S. Air Force)

The first American airplane designed specifically as a night fighter, the XP-61 was the same size as a medium bomber: 48 feet, 11.2 inches (14.915 meters) long with a wingspan of 66 feet (20.117 meters) and overall height of 14 feet, 8.2 inches (4.475 meters). The prototype was equipped with a mockup of the top turret. Its empty weight was 22,392 pounds (10,157 kilograms), gross weight of 25,150 pounds (11,408 kilograms) and maximum takeoff weight of 29,673 pounds (13,459 kilograms).

Northrop XP-61 41-19509 retracts its landing gear after takeoff. (U.S. Air Force)

The XP-61 was powered by two air-cooled, supercharged, 2,804.4-cubic-inch-displacement (45.956 liter) Pratt & Whitney Double Wasp SSB2-G (R-2800-10) two-row, 18-cylinder radial engines with a compression ratio of 6.65:1. The R-2800-10 had a Normal Power rating of 1,550 horsepower at 2,550 r.p.m. at 21,500 feet (6,553 meters), and 2,000 horsepower at 2,700 r.p.m. for takeoff, burning 100-octane gasoline. The R-2800-10 had a 2:1 gear reduction and drove four-bladed Curtiss Electric constant-speed propellers which had a 12 foot, 2 inch (3.708 meter) diameter. The R-2800-10 was 4 feet, 4.50 inches (1.334 meters) in diameter, 7 feet, 4.47 inches (2.247 meters) long, and weighed 2,480 pounds (1,125 kilograms), each.

The prototype Black Widow had a top speed of 370 miles per hour (595 kilometers per hour) at 29,900 feet (9,114 meters) and a service ceiling of 33,100 feet (10,089 meters). The maximum range was 1,450 miles (2,334 kilometers).

Prototype Northrop XP-61 Black Widow 41-19509 in camouflage. (U.S. Air Force)

The night fighter was crewed by a pilot, a gunner and a radar operator. A large Bell Laboratories-developed, Western Electric-built SCR-720 air search radar was mounted in the airplane’s nose. The gunner sat above and behind the pilot and the radar operator was in the rear fuselage.

SCR-720 Air Search Radar mounted in nose of a Northrop P-61 Black Widow night fighter. (NOAA)

The Black Widow was armed with four Browning AN-M2 .50-caliber machine guns in a remotely-operated upper turret, and four AN-M2 20 mm aircraft automatic cannons, grouped close together in the lower fuselage and aimed directly ahead. This was a superior arrangement to the convergent aiming required for guns mounted in the wings. The fire control system was similar to that used by the B-29 Superfortress. The guns could be fired by either the gunner or the radar operator. The Black Widow carried 200 rounds of ammunition for each cannon,

Northrop P-61A-1-NO Black Widow 42-5507 in olive green camouflage. (U.S. Air Force)
Northrop P-61A-1-NO Black Widow 42-5507 in olive green camouflage. (U.S. Air Force)

The XP-61 was built with a center “gondola” for the crew, radar and weapons, with the engines outboard in a twin-boom configuration, similar the the Lockheed P-38 Lightning. The Black Widow did not use ailerons. Instead, it had spoilers mounted on the upper wing surface outboard of the engines. Roll control was achieved by raising a spoiler, decreasing lift on that wing and causing it to drop. A similar system was employed on the Boeing B-52 Stratofortress ten years later.

Northrop P-61A three-view illustration with dimensions. (U.S. Army Air Forces)

The P-61 got its nickname, Black Widow, from the glossy black paint scheme that scientists at the Massachusetts Institute of Technology (M.I.T.) had determined was the best camouflage for a night fighter. Over 700 P-61s were built, with 36 built as the F-15 photo reconnaissance variant. They served in both the Pacific and European Theaters during World War II, and were also used during the Korean War. After the war, the radar-equipped fighter was used for thunderstorm penetration research.

Northrop P-61C-1-NO Black Widow 43-8353 at the National Museum of the United States Air Force. (U.S. Air Force)
Northrop P-61C-1-NO Black Widow 43-8353 at the National Museum of the United States Air Force. (U.S. Air Force)
Northrop P-61C-1-NO Black Widow 43-8353 at the National Museum of the United States Air Force. (U.S. Air Force)

© 2018, Bryan R. Swopes

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