General characteristics Crew: 2-3 (pilot, radar operator, optional gunner) Length: 49 ft 7 in (15.11 m) Wingspan: 66 ft 0 in (20.12 m) Height: 14 ft 8 in (4.47 m) Wing area: 662.36 ft² (61.53 m²) Empty weight: 23,450 lb (10,637 kg) Loaded weight: 29,700 lb (13,471 kg) Max takeoff weight: 36,200 lb (16,420 kg) Powerplant: 2× Pratt & Whitney R-2800-65W Double Wasp radial engines, 2,250 hp (1,680 kW) each Propellers: four-bladed Curtiss Electric propeller, 1 per engine Propeller diameter: 146 in (3.72 m)   Fuel capacity: Internal: 640 US gal (2,423 L) of AN-F-48 100/130-octane rating gasoline External: Up to four 165 US gal (625 L) or 310 US gal (1,173 L) tanks under the wings Performance Maximum speed: 318 knots (366 mph, 589 km/h) at 20,000 ft (6,095 m) Combat range: 530 nm (610 mi, 982 km) Ferry range: 1,650 nm (1,900 mi, 3,060 km) with four external fuel tanks Service ceiling 33,100 ft (10,600 m) Rate of climb: 2,540 ft/min (12.9 m/s) Wing loading: 45 lb/ft² (219 kg/m²) Power/mass: 0.15 hp/lb (25 W/kg) Time to altitude: 12 min to 20,000 ft (6,100 m) (1,667fpm) Armament Guns: 4× 20 mm Hispano M2 cannon in ventral fuselage, 200 rounds per gun 4× 0.50 cal (12.7 mm) Browning M2 machine guns in upper turret, 560 rounds per gun Bombs: for ground attack, four bombs of up to 1,600 lb (726 kg) each or six 5 inch (127 mm) HVAR unguided rockets could be carried under the wings. Some aircraft could also carry one 1,000 lb (454 kg) bomb under the fuselage.     Note: 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 barbette with a revised fire-control system. Avionics SCR-720 (AI Mk.X) search radar SCR-695 tail warning radar     SCR-720 Radar   The production model of the SCR-720A mounted a scanning radio transmitter in the aircraft nose; in Airborne Intercept mode, it had a range of nearly five miles. The unit could also function as an airborne beacon / homing device, navigational aid, or in concert with interrogator-responder IFF units. The XP-61's radar operator located targets on his scope and steered the unit to track them, vectoring and steering the pilot to the radar target via oral instruction and correction. Once within range, the pilot used a smaller scope integrated into the main instrument panel to track and close on the target.