XB-39 Superfortress

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Boeing XB-39 Superfortress
Type	Test-bed bomber aircraft
Manufacturer	Boeing
Maiden flight	1944
Introduced	n/a
Status	Never mass-produced
Primary user	United States Army Air Forces
Produced	1944
Number built	1

The Boeing XB-39 Superfortress was a prototype bomber aircraft, a single example of the B-29 Superfortress converted to fly with alternative powerplants. It was intended to demonstrate that the B-29 could still be put into service even if the first choice of engine, the Wright R-3350, ran into development or production difficulties.

Starting life as the first YB-29 delivered to the United States Army Air Forces, it was modified by General Motors to use Allison V-3420-17 liquid-cooled inline engines. Testing on it began in early 1944. Since no problems with the R-3350 developed, and most flaws of the B-29 were worked out by the time production began, the XB-39 was never ordered.

[edit] Specifications (XB-39)

General characteristics

Crew: 10: pilot, co-pilot, flight engineer, bombardier, navigator, radio operator, side gunners (two), top gunner, and tail gunner
Length: 99 ft 0 in (30.18 m)
Wingspan: 141 ft 3 in (43.05 m)
Height: 27 ft 9 in (8.46 m)
Wing area: 1736 ft² (161.3 m²)
Empty weight: 74,500 lb (33,800 kg)
Loaded weight: 120,000 lb (54,000 kg)
Max takeoff weight: 133,500 lb (60,560 kg)
Powerplant: 4× Allison V-3420-11 liquid-cooled V24 engines, 2,100 hp (1,600 kW) each

Performance

Maximum speed: 405 mph (351 knots, 648 km/h)
Range: 6,290 mi (5,460 nm, 10,060 km)
Service ceiling: 35,000 ft (11,000 m)
Wing loading: 69.12 lb/ft² (337.5 kg/m²)
Power/mass: 0.073 hp/lb (121 W/kg)

Armament

Guns:
- 8× .50 in (12.7 mm) Browning M2 machine guns in remote controlled turrets
- 2× .50 in (12.7 mm) machine guns in manual turrets
- 1× 20 mm (0.787 in) M2 cannon in tail
Bombs: 20,000 lb (9,000 kg)

[edit] References and external links

XB-39 on USAF Museum site

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