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North American XB-28
| XB-28 | |
|---|---|
 | |
| North American XB-28 with engines running. | |
| Type | High-altitude medium bomber |
| Manufacturer | North American Aviation |
| Status | Design only |
| Primary user | U.S. Army Air Force |
| Number built | 2 |
| Developed from | B-25 Mitchell |
The North American XB-28 (NA-63) was a plane proposed by the North American Aviation to fill a strong need in the United States Army Air Corps for a high-altitude medium bomber. It never entered into full production and only two aircraft were built.
Contents
Design and development
The order for a high-altitude medium bomber was put out on 1940 February 13; the XB-28 first flew on 1942 April 26. The XB-28 was based on North American Aviation's highly successful B-25 Mitchell, but as it evolved it became a completely new design, much more reminiscent of the Martin B-26 Marauder. The overall configuration of the B-25 and XB-28 were fairly similar; the most important distinction was that the twin tail of the B-25 was changed to a single tail on the XB-28. It was among the first planes with a pressurised cabin.
The XB-28 proved an excellent design, with significantly better performance than the B-25, but it was never put into production. High-altitude bombing was hampered significantly by factors such as clouds and wind, which were frequent occurrences in the Pacific. At the same time, medium bombers were becoming much more able at lower altitudes. The models being used at these levels had been used successfully in combat for months and even years. The gains in aircraft performance that came with high altitude flight were not significant enough to justify switching from low-altitude bombing.
Testing and evaluation
Even though the Army Air Force rejected the XB-28 as a bomber, they ordered another prototype. Designated XB-28A, it was meant to explore the possibility of use as a reconnaissance aircraft. This design never progressed past the prototype stage either.
Specifications (XB-28)
General characteristics
- Crew: five
- Length: 56 ft 5 in (17.20 m)
- Wingspan: 72 ft 7 in (22.12 m)
- Height: 14 ft 0 in (4.27 m)
- Wing area: 676 ft² (62.8 m²)
- Empty weight: 25,575 lb (11,600 kg)
- Loaded weight: 35,740 lb (16,210 kg)
- Max takeoff weight: 37,200 lb (16,874 kg)
- Powerplant: 2× Pratt & Whitney R-2800-27 turbosupercharged radial engines, 2,000 hp (1,500 kW) each
Performance
- Maximum speed: 372 mph (446 km/h) at 25,000 ft (7,600 m)
- Cruise speed: 255 mph (410 km/h)
- Range: 2,040 mi (3,280 km)
- Service ceiling: 33,500 ft (10,213 m)
- Rate of climb: 1,111 ft/min (6 m/s)
- Wing loading: 52.87 lb/ft² (258.14 kg/m²)
- Power/mass: 0.112 hp/lb (184 W/kg)
Armament
- Guns: 6× .50 in (12.7 mm) machine guns in remote-sighted turrets
- Bombs: 4,000 lb (1,800 kg)
References
External links
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