Northrop P-61 Black Widow

NORTHROP P-61 AIRCRAFT

Jagriti Srivastava

The Northrop P-61 Black Widow, named for the American spider, was the first operational U.S. military aircraft designed specifically for night interception of opposing aircraft, and was the first aircraft specifically designed to use radar. It was an all-metal, twin-engine, twin-boom design developed during World War II. The first test flight was made on 26 May 1942, with the first production aircraft rolling off the assembly line in October 1944. 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, the Pacific Theater, the China Burma India Theater and the 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. After the war, the P-61 served in the United States Air Force as a long-range, all weather, day/night interceptor for Air Defense Command until 1948, and Fifth Air Force until 1950.

DESIGN

The P-61 featured a crew of three: pilot, gunner, and radar operator. It was armed with four 20 mm (.79 in) Hispano M2 forward firing cannons mounted in the lower fuselage, and four .50 in (12.7 mm) M2 Browning machine guns lined up horizontally with the two middle guns slightly offset upwards in a remotely aimed dorsally mounted turret. The turret was driven by the General Electric GE2CFR12A3 gyroscopic fire control computer, and could be directed by either the gunner or radar operator, who both had aiming control and gyroscopic collimator sight assembly posts attached to their swiveling seats.

The two Pratt & Whitney R-2800-25S Double Wasp engines were each mounted approximately one-sixth out on the wing's span. Two-stage, two-speed mechanical superchargers were fitted. In an effort to save space and weight, no turbo-superchargers were fitted, despite the expected 50 mph (80 km/h) top speed and 10,000 ft (3,048 m) operational ceiling increases.

Main landing gear bays were located at the bottom of each nacelle, directly behind the engine. The two main gear legs were each offset significantly outboard in their nacelles, and retracted towards the tail; oleo scissors faced forwards. Each main wheel was inboard of its gear leg and oleo. Main gear doors were two pieces, split evenly, longitudinally, hinged at inner door's inboard edge and the outer door's outboard edge.

Each engine cowling and nacelle drew back into tail booms that terminated upwards in large vertical stabilizers and their component rudders, each of a shape similar to a rounded right triangle. The leading edge of each vertical stabilizer was faired smoothly from the surface of the tail boom upwards, swept back to 37°. The horizontal stabilizer extended between the inner surfaces of the two vertical stabilizers, and was approximately ¾ the chord of the wing root, including the elevator. The elevator spanned approximately ? of the horizontal stabilizer's width, and in overhead plan view, angled inwards in the horizontal from both corners of leading edge towards the trailing edge approximately 15°, forming the elevator into a wide, short trapezoid. The horizontal stabilizer and elevator assembly possessed a slight airfoil cross-section.

The engines and nacelles were outboard of the wing root and a short "shoulder" section of the wing that possessed a 4° dihedral, and were followed by the remainder of the wing which had a dihedral of 2°. The leading edge of the wing was straight and perpendicular to the aircraft's centerline. The trailing edge was straight and parallel to the leading edge in the shoulder, and tapered forward 15° outboard of the nacelle. Leading edge updraft carburetor intakes were present on the wing shoulder and the root of the outer wing, with a few inches of separation from the engine nacelle itself. They were very similar in appearance to those on the F4U Corsair—thin horizontal rectangles with the ends rounded out to nearly a half-circle, with multiple vertical vanes inside to direct the airstream properly

NORTHROP P-61C BLACK WIDOW

The heavily-armed Black Widow was the United States' first aircraft specifically designed as a night-fighter. The P-61 carried radar equipment in its nose that enabled its crew of two or three to locate enemy aircraft in total darkness and fly into proper position to attack. 

The XP-61 was flight-tested in 1942 and the delivery of production aircraft began in late 1943. The P-61 flew its first operational intercept mission as a night fighter in Europe on July 3, 1944, and later was also used as a night intruder over enemy territory. In the Pacific, a Black Widow claimed its first "kill" on the night of July 6, 1944. As P-61s became available, they replaced interim Douglas P-70s and Bristol Beaufighters in all USAAF night fighter squadrons. 

During World War II, Northrop built approximately 700 P-61s; 41 of these were C models manufactured in the summer of 1945 offering greater speed and capable of operating at higher altitude. The Black Widow on display was presented to the museum by the Tecumseh Council, Boy Scouts of America, Springfield, Ohio, in 1958. It is painted and marked as a P-61B assigned to the 550th Night Fighter Squadron serving in the Pacific in 1945.  

The P-61 Black Widow was the first US aircraft designed specifically for nightfighting.

The Northrop P-61 Black Widow became the United States' first aircraft specifically designed from the outset as a platform dedicated to the fine art of night-fighting. Enabled by its complex through highly-effective nose-mounted radar, a distinct overall black paint scheme, its trained crew of three (though sometimes two) specialists and a heavy base armament made up of cannon and heavy machine guns, the "Widow" made its way into all major theaters encompassing World War 2. The P-61 could operate in total darkness, aided by its onboard systems, and move into position to deliver an enemy aircrew's final moments. The Black Widow appeared in quantity during 1944, then under the command of the US Army Air Force (USAAF) and soldiered on well past the war years into 1952, retiring with the newly-minted United States Air Force. The P-61 became one of Northrop's most successful products of all time and essentially put the corporation on the map. The P-61 (later redesignated to F-61) was no longer in operational service by the time of the Korean War, missing the conflict by small window of opportunity. While replacing the aged Douglas A-20 Havoc and D-70 systems in World War 2, the P-61 was itself replaced by the North American F-82 "Twin Mustang" before the Korean conflict.

FIRST FLIGHT

First flight of the XP-61 was achieved on May 21st, 1942, with showman test pilot Vance Breeze at the controls and responded quite well considering the project's relatively infant stage. As the General Electric turret was still unavailable, Northrop engineers had to fashion a replica dorsal installation to compliment the completed airframe and achieve realistic flight test results. Post-flight, some other (relatively) slight variations came to the design and included a new horizontal stabilizer and revised engines (via Pratt & Whitney) - adding further delays within the program. The radar had also yet to be installed and properly tested airborne within the airframe with the radar system itself a "top secret" project under careful guard offsite

THE P-61A

The initial production versions - now taking on the full designation name of P-61 "Black Widow" - were P-61A models. Thirty-seven of the first A-models were fitted with the impressive General Electric remotely-controlled dorsal turret housing a battery of 4 x .50 caliber M2 Browning heavy air-cooled machine guns as well as an array of 4 x 20mm Hispano cannons mounted as a fixed forward-firing amendment in a ventral position. It was soon discovered (via wind tunnel tests and, later, with a P-61 airframe test gondola) that the dorsal turret was the cause of an air flow disturbance along the aft portion of the central gondola, occurring just aft of the turret assembly itself. This find forced the removal of the turret from the 38th P-61A production example and onwards. The stability issue developed when the turret was traversed to either side or elevated away from its "at rest" face-forward position causing a disruption to the air flow causing buffeting over the aircraft when at speed. . 

The P-61A was represented by four major sub-variants. The P-61A-1 became the initial production models fitting the R-2800-10 series engines of 2,000 horsepower. Forty-five of these systems were produced in whole though the last seven in the run were delivered without the dorsal turret (as explained above). The P-61A-5 was also produced without the dorsal turret but fitted instead with the R-2800-65 series engines of 2,250 horsepower (Northrop engineers were always trying to get more "punch" out of her engines). Thirty-five such machines were produced in the run. The P-61A-10 were built to the tune of 100 examples and featured water injection for an increased boost to engine output (known as "War Emergency Power" or "WEP", a small burst of power culminating in a short duration of improved performance). The P-61A-11 were given underwing hardpoints (one to a wing, inboard of the engines) for the carrying of fuel tanks or 2 x 1,600lb bombs. Twenty A-11s were ultimately produced. The addition of fuel tanks is noteworthy here for it drastically increased the range of the base Widow, allowing it to be considered for use in the vastness of the Pacific Theater. Comparatively, the addition of bombing capabilities allowed for night-time ground attacks to be added to the Widow's forte, known as a "night intruder" when in this role.

GENERAL INFORMATION:

Type:

    P-61: Three-seat Night Fighter

    F-15: Two-seat strategic reconaissance

Manufacturer: Northrop

Models: P-61A thru C, F-15 (RF-61C) Reporter

First Flight: May 21, 1942 (XP-61)

Service Delivery:

    May 1944 (P-61A)

    1946 (F-15A) 

Final Delivery: N/A

Total Produced: 941 (plus 35 photo-recon versions)

POWERPLANT:

   Model: Pratt & Whitney R-2800 Double Wasp

   Type: 18-Cyl 2-Row Radials

   Horsepower (P-61A): 2,000hp R-2800-10

   Horsepower (P-61B): 2,000hp R-2800-65

   Horsepower (P-61C and F-15): 2,800hp R-2800-73

FUEL:

   Capacity: N/A

   Type: N/A

DIMENSIONS:

   Wing span: 20.12m (66 ft.)

   Length (P-61A): 14.92m (48 ft. 11 in.)

   Length (P-61B & C): 15.1m (49 ft. 7 in.)

   Length (F-15): 15.3m (50 ft. 3 in.)

WEIGHTS:

   Empty (Typical P-61): 10,886kg (24,000 lbs.)

   Empty (F-15): 9,979kg (22,000 lbs.)

   Maximum, Loaded (P-61A): 14,696kg (32,400 lbs.)

   Maximum, Loaded (P-61B): 17,237kg (38,000 lbs.)

   Maximum, Loaded (P-61C): 18,280kg (40,300 lbs.)

   Maximum, Clean (F-15): 12,700kg (28,000 lbs.)

PERFORMANCE:

   Maximum Speed (P-61A & B): 366 mph (590 km/h)

   Maximum Speed (P-61C): 430 mph (692 km/h)

   Maximum Speed (F-15): 440 mph (708 km/h)

   Initial climb (P-61A & B): 2,200 ft. (670 m) per minute

   Initial climb (P-61C & F-15): 3,000 ft. (914 m) per minute

   Service Ceiling (P-61A & B): 33,000 ft. (10,060 m)

   Service Ceiling (P-61C & F-15): 41,000 ft. (12,500 m)

   Range - Max. Fuel (P-61A): 500 Miles (2360 km)

   Range - Max. Fuel (P-61B & C): 2,800 Miles (4500 km)

   Range - Max. Fuel (F-15): 4,000 Miles (6440 km)

ARMAMENTS:

Four 20mm M-2 Cannon in belly, fixed forward.

Plus

Electric Dorsal turret with four .50 machine guns, remotely controlled

from front or rear sight station and fired by pilot.

(in first 37 A's, last 250 B's and all C's)

Plus (B & C Only)

Wing racks for 6,400 lb. ordnance load.

F-15 carried no armament.

   Height: 4.49m (14 ft. 8 in.)

   Wing Surface Area: N/A

Regards,

Jagriti Srivastava [B.Tech ] 

Web Developer / Blog Master 

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