The Northrop P-61 Black Widow

United States of America
United States of America

Sorry, No ID pictures yet

When the War broke out, not many people understood the importance of night bombings, or night-fighters in the war to come. More countries had tried to develop. or looked at the possibility of aircraft that could perform their task during darkness. Until World War 2, however, the technology was mostly inadequate. The development of long range radio sets in (small) aircraft and even radar enabled pilots for the first time to navigate precisely, or spot an enemy beyond visual range (which is rather short during the night).
The first night fighters were modifications of twin-engined fighters, and were used by the British to counter the night-offensive of the Luftwaffe during the end of 1940 - beginning 1941. In order to succesfully intercept night intruders or night bombers the fighters already had to be airborne, and only twin-engined aircraft had the range and endurance to be up in the air for a long time. Also, when an aircraft was intercepted it could relatively easy escape, so the first burst of the attacking fighter needed to be lethal, or heavily damaging. This was also a strength of twin-engined aircraft, which usually had a nose (in front of the cockpit) where additional or heavy armament could be installed, later together with Air Interception Radar.
So it came that the first nightfighters were modifications of the Bristol Blenheim (fast and light bomber) and the Bristol Beaufighter (twin-engined again). These aircraft were to counter the night-intruder campaign of the Luftwaffe, which was mostly carried out by Dornier Do 17 bombers and Messerschmitt Bf 109 JaBo fighter bombers. A team of officers from the USAAC (later USAAF) visited Great Birtain to learn about the British night fighters at the end of 1940. The USAAC realised that night-fighting would become a major element in the air war and set about the creation of an American night-fighting capability. In the short term the best that could be achieved was an extemporized type, the Douglas P-70 Havoc based on the A-20 attack bomber, but for the longer term the USAAC understood that a purpose-designed type would be necessary. In October 1940 an outline requirement was communicated to John K.Northrop, and a mere two weeks later Northrop and his chief assistant, Walter J.Cerny, visited the USAAC’s Air Material Command headquarters at Wright Field, which was located outside Dayton, Ohio, to present the results of their initial thinking. Discussions with the appropriate USAAC officers proved most stimulating, and in December 1940 Northrop offered a full design to the Air Material Command. This resulted in a January 1941 order for two XP-61 prototypes.

The NS-8A design was singularly advanced, and was based on a twin-engined powerplant and an all-metal airframe that was very large by the fighter standards of the day. The core of the structure was a central nacelle and wing center section. The nacelle was of light alloy semi-monocoque construction and carried the crew, air interception radar and much of the armament, the last consisting of four 20 mm fixed forward-firing cannon in the wing leading edges and six 0.50 inch (12,7 mm) Browning machine guns with 500 rounds per gun in a power-operated dorsal four-gun barbette and power-operated ventral two-gun barbette: the barbettes could be locked to fire directly forward under control of the pilot, or unlocked for use defensively as trainable weapons under the remote control of the gunner. The shoulder/mid-set and slightly dihedraled wing center section was of light alloy stressed-skin construction and of the constant-chord type. Installed under the outer ends of this center section were the nacelles for the two wing-mounted engines and their fuel supply, and these nacelles were extended rearward as light alloy semi-monocoque booms that supported the tail unit of two vertical surfaces, each with a rudder, separated by a constant-chord horizontal surface with a single elevator. The flying surfaces were completed by the outer wing panels, which were set at a less acute dihedral angle than the center section, and were tapered in thickness and chord; virtually the whole of the trailing edges was occupied by small outboard ailerons supplemented by spoilers, and long-span inboard flaps that were originally of the Zap type but later of the slotted type. The airframe was completed by the tricycle landing gear, which comprised a nosewheel unit that retracted rearward into the underside of the central nacelle below the cockpit, and two mainwheel units that retracted rearward into the nacelles behind the engines.
The selected powerplant was 2 × Pratt & Whitney R-2800-A5G (or R-2800-25 in USAAC terminology) radial , rated at 2,000 hp (1491 kW) at optimum altitude each, and intended to drive a four-blade Curtiss Electric metal propeller of the constant-speed type. Pending the availability of this propeller type, a four-blade Hamilton Standard Hydromatic metal propeller of the constant-speed type was selected.
In April 1941 a USAAC team inspected the XP-61 mock-up and asked for several changes, including the relocation of the cannon from the wing leading edges to the underside of the central nacelle, and the elimination of the ventral barbette. The USAAC team’s reasoning for the elimination of the ventral barbette was that it would improve the airflow over this part of the airframe and simplify the night-fighter’s maintenance, but the change meant considerable revision of the central nacelle’s structure. Various other considerations then added further delays, but in September 1941 the USAAF ordered an initial 150 production aircraft and in February 1942, shortly after the USA’s entry into the War as a result of the Japanese attack on Pearl Harbor (and the Philippines) in December 1941, contracted for a further 410 aircraft.
The first XP-61 made its maiden flight in May 1942, and in its subsequent manufacturer’s trials revealed generally good handling characteristics and impressive performance, although considerable concern was expressed about the reliability of the R-2800 engine even in its improved R-2800-10 version. The second XP-61 was completed in November 1942. The SCR-720 radar was installed after the aircraft had been delivered for their official trials, and after a number of additional modifications had been made the XP-61 was accepted as the basis for the production model.

Version list:

Further pictures:

Northrop P-61 Black Widow in full flight. The central fuselage is clearly visible with it's barbette.
Northrop P-61 Black Widow in full flight. The central fuselage is clearly visible with it's barbette.

Northrop P-61 Black Widow in full flight. This time the underside is more visible.
Northrop P-61 Black Widow in full flight. This time the underside is more visible.

 

Technical data on the Northrop P-61A Black Widow
Powerplant 2 × Pratt & Whitney R-2800-10 Double Wasp 18-cylinder radial, rated at 2,000 hp (1.491 kW) each (45 first aircraft), or 2 × Pratt & Whitney R-2800-65 Double Wasp 18-cylinder radial, rated at 2250 hp (1677.35 kW) each Role during war
  • Fighter-bomber
  • Night-Fighter
  • Reconnaissance Aircraft
Length 48 ft 11 inch Height 14 ft 8 inch
Empty weight 20965 lb Operational weight 27600 lb typical,
34200 lb max
Wing Span 66 ft 0.75 inch Wing Aspect ratio 6.59
Wing Area 662.36 sq ft Service ceiling 33100 ft
Maximum speed 369 mph at 20000 ft Cruising speed 319 mph at 20000 ft
Initial climb rate Climb to 15,000 ft in 7 min 36 sec Range 1010 miles typical,
1900 miles max
Fuel capacity internal 550 Imp gal (660 US gal) Fuel capacity external Up to 516 Imp gal (620 US gal) in two 258 Imp gal (310 US gal) drop tanks (late production batch aircraft)
Machine guns
  • 4 × 0.50 inch Browing M2 trainable in the remotely controlled power-operated dorsal barbette, 560 rounds each.
Cannons
  • 4 × 20 mm Hispano M2 fixed forward-firing in the underside of the forward fuselage, 200 rounds each.
Bomb load Up to 6,400 lb, carried on four underwing hardpoints, rated at 1,600 lb each (late production aircraft). General disposables load consisted of:
  • 4 × 1,600, 1,000, 500, 325, 250 or 100 lb bombs
Torpedoes/rockets -
Crew 2: pilot, radar operator/radio operator (late production aircraft had the same crew as the P-61B) Naval or ground based Ground
First flight (prototype) 26 May 1942 Operational Service march 1944 - 1952
Manufacturer Northrop Corporation/Northrop Aircraft Inc. Number produced 742 total, 200 this version
Metric system
Length 14.91 m Height 4.47 m
Empty weight 9510 kg Operational weight 12519 kg typical,
15513 kg max
Wing Span 20.14 m Wing Aspect ratio 6.59
Wing Area 61.53 m² Service ceiling 10089 m
Maximum speed 594 km/h at 6096 m Cruising speed 513 km/h at 6096 m
Initial climb rate Climb to 4.570 m in 7 min 36 sec Range 1625 km typical,
3058 km max
Fuel capacity internal 2.498 liters Fuel capacity external Up to 2.347 liters in two 1.173 liters drop tanks (late production batch aircraft)
Machine guns
  • 4 × 12,7 mm Browing M2 trainable in the remotely controlled power-operated dorsal barbette, 560 rounds each.
Cannons
  • 4 × 20 mm Hispano M2 fixed forward-firing in the underside of the forward fuselage, 200 rounds each.
Bomb load Up to 2.903 kg, carried on four underwing hardpoints, rated at 726 kg each (late production aircraft). General disposables load consisted of:
  • 4 × 726, 454, 227, 147, 113 or 45 lb bombs
Torpedoes/rockets -

Technical data on the Northrop P-61B Black Widow
Powerplant 2 × Pratt & Whitney R-2800-65 Double Wasp 18-cylinder radial, rated at 2250 hp (1677.35 kW) each Role during war
  • Fighter-bomber
  • Night-Fighter
  • Reconnaissance Aircraft
Length 49 ft 7 inch Height 14 ft 8 inch
Empty weight 22000 lb Operational weight 29700 lb typical,
38000 lb max
Wing Span 66 ft 0.75 inch Wing Aspect ratio 6.59
Wing Area 662.36 sq ft Service ceiling 33100 ft
Maximum speed 366 mph at 20000 ft Cruising speed 300 mph at 10000 ft
Initial climb rate 2,550 ft per min
Climb to 20,000 ft in 12 min 0 sec
Range 1350 miles typical,
3000 miles max
Fuel capacity internal 550 Imp gal (660 US gal) Fuel capacity external Up to 516 Imp gal (620 US gal) in two 258 Imp gal (310 US gal) drop tanks
Machine guns
  • 4 × 0.50 inch Browing M2 trainable in the remotely controlled power-operated dorsal barbette, 560 rounds each.
Cannons
  • 4 × 20 mm Hispano M2 fixed forward-firing in the underside of the forward fuselage, 200 rounds each.
Bomb load Up to 6,400 lb, carried on four underwing hardpoints, rated at 1,600 lb each. General disposables load consisted of:
  • 4 × 1,600, 1,000, 500, 325, 250 or 100 lb bombs
Torpedoes/rockets -
Crew 3: pilot, radar operator, radio operator/gunner Naval or ground based Ground
First flight (prototype) 26 May 1942 Operational Service march 1944 - 1952
Manufacturer Northrop Corporation/Northrop Aircraft Inc. Number produced 742 total, 450 this version
Metric system
Length 15.11 m Height 4.47 m
Empty weight 9979 kg Operational weight 13472 kg typical,
17237 kg max
Wing Span 20.14 m Wing Aspect ratio 6.59
Wing Area 61.53 m² Service ceiling 10089 m
Maximum speed 589 km/h at 6096 m Cruising speed 483 km/h at 3048 m
Initial climb rate 777 m per min
Climb to 6.095 m in 12 min 0 sec
Range 2173 km typical,
4828 km max
Fuel capacity internal 2.498 liters Fuel capacity external Up to 2.347 liters in two 1.173 liters drop tanks
Machine guns
  • 4 × 12,7 mm Browing M2 trainable in the remotely controlled power-operated dorsal barbette, 560 rounds each.
Cannons
  • 4 × 20 mm Hispano M2 fixed forward-firing in the underside of the forward fuselage, 200 rounds each.
Bomb load Up to 2.903 kg, carried on four underwing hardpoints, rated at 726 kg each. General disposables load consisted of:
  • 4 × 726, 454, 227, 147, 113 or 45 lb bombs
Torpedoes/rockets -

Here is a quick overview of all different versions, without the full technical specifications:

Different versions of the Northrop P-61  Black Widow
Northrop P-61 Black Widow prototypes The first protoype, designated XP-61, was the direct result of an American visit to Great Britain in the end of 1940. Similarities to the British night-fighters can clearly be discerned, but the twin-boom and pod construction was reasonably novell. The more or less only problem was the reliability of the engine, which could be a reason for concern. Later aircraft would be fitted with a more reliable engine as a result of this concern.
Number built: 2 XP-61, 13 YP-61 Service Trials aircraft.
Northrop P-61A Black Widow The YP-61 trials aircraft revealed that the barbettes caused considerable buffeting problems when the guns were elevated or traversed. As a stopgap measure pending a definite solution the two inner guns were removed, and the construction was reinforced. Because production was well underway when the problems were identified, the first 37 P-61A's were delivered with a barbette that was locked to fire straight ahead, and fitted with 4 guns. The rest of the batch, 163 aircraft, were delivered as a two-seat aircraft without the barbette. Some of these were later re-engineered with the barbette when the problem was solved.
Also the P-61A series distinguished themselves in the field of different powerplants. The first 45 examples had a powerplant of 2 × Pratt & Whitney R-2800-10 radial, rated at 2,000 hp (1.491 kW) each, next came a batch of 35 aircraft powered by 2 × Pratt & Whitney R-2800-65 radial rated at 2,250 hp (1.667 kW) at War Emergency Power/Combat Contingency Power each. the other aircraft were fitted with 2 × Pratt & Whitney R-2800-65 Double Wasp 18-cylinder radial modified with a water injection system.
Number built: 200
Northrop P-61B Black Widow Before the P-61A Black Widow entered operational service, Northrop had started deliveries in July 1944 of the P-61B with a number of improvements including an 8 in (0.203 m) lengthening of the nose. Deliveries amounted to 450 aircraft, and progressive improvements effected during the course of the P-61B’s production run resulted in a number of production blocks:

P-61B-10 Four underwing hardpoints fitted, each rated at 1,600 lb (726 kg), and able to carry a bombs or a drop tank (like some aircraft in the P-61A series).
P-61B-15 This block saw the reinstallment of the dorsal barbette with four guns.
P-61B-20 These aircraft were fitted with a new General Electric barbettewith a revised fire-control system.


Number built: 450
Northrop P-61C Black Widow Experienceunder War conditions with the P-61 showed that although the Black Widow posessed a good general performance, agility and firepower, the speed and climb rate were insufficient. Therefor Northrop installed a powerplant consisting of 2 × Pratt & Whitney R-2800-73 Double Wasp radial, rated at 2,800 hp (2.088 kW) each, with General Electric CH-5 turbochargers and driving Curtiss Electric propellers with four hollow blades. This uprated powerplant resulted in a maximum level speed of 430 mph (692 km/h) at 30,000 ft (9.145 m) and a service ceiling of 41,000 ft (12.495 m) even though the normal and maximum take-off weights had increased to 32,200 and 40,300 lb (14.606 and 18.280 kg) respectively. The increase in maximum speed was particularly notable, and raised fears that the P-61C would overhaul its targets too quickly and therefore be unable to fire before it had passed the enemy aircraft, so the type was fitted with air brakes above and below the wings. Some 41 of this version had been completed by the time of Japan’s defeat. The remaining 476 of the same order were canceled.
Number built: 41
Northrop P-61G Black Widow The P-61C was the last version of the P-61 to enter production, but several other versions were in the prototype stage or in project stage. The XP-61D was powered with 2 × R-2800-77 turbocharged radials, the XP-61E version of the P-61B had it's nose radar replaced by 4 × 0.5 inch (12,7 mm) Browning machine guns in place of the (then deleted) dorsal barbette, the XP-61F version of the P-61C to XP-61E standard (armament of the XP-61E, powerplant of the P-61C).
The P-61G was a conversion of the P-61C that was meant for unarmed weather reconnaissance duties.
Number converted: 12
Northrop F2T-1N 12 P-61B Black Widows were transferred to the US Marine Corps, which used them as night-fighter trainers with the revised designation F2T-1N
Number transferred: 12
Northrop F-15A Reporter This was the unarmed photo-reconnaissance version of the Black Widow. The type was evaluated in the form of the single XF-15 and XF-15A prototype conversions from XP-61E and P-61C standards with six cameras in a modified nose, and the success of these two machines paved the way for the F-15A production model, of which 36 were completed and 139 more were canceled.
Number built: 36

Operational remarks:

The P-61A entered service in the middle of 1944 in Florida, where the 481st Night-Fighter Group was established as the parent of the 348th, 349th and 420th Night-Fighter Squadrons, and in Great Britain where the 422nd and 425th Night-Fighter Squadrons re-formed in the type. The first sorties were flown from Britain in July 1944, but it was in the Pacific that the first kill of the P-61 was scored in the same month when a P-61A of the 6th Night-Fighter Squadron claimed a Mitsubishi G4M ‘Betty’ bomber of the Imperial Japanese Navy Air Force in the central Pacific. A steady increase in the number of operational squadrons was possible as teething problems with the P-61A fighter and its temperamental radar were eliminated, and soon the type was operational in Europe, the Pacific, New Guinea and China.
Regretfully I lack further interresting information on this fascinating aircraft.

Strengths:

Weaknesses:

 

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© by Frans Bonné, 2000
Last revision: 9/23/01