North American XB-28

XB-28

Picture - North American XB-28 with engines running.

Role: 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 an aircraft 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, with only two aircraft having been built.

Design and development

The order for a high-altitude medium bomber was put out on 13 February 1940; the XB-28 first flew on 26 April 1942. 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. The XB-28A crashed into the Pacific after crew bail-out on 4 August 1943.

Specifications (XB-28A)

Picture - Side view of the North American XB-28.

Data from

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: 2x— Pratt & Whitney R-2800-27 turbosupercharged radial engines, 2,000 hp (1,500 kW) each

Performance

Maximum speed: 372 mph (599 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 x— .50 in (12.7 mm) machine guns in remote-sighted turrets
Bombs: 4,000 lb (1,814 kg)

Related development

B-25 Mitchell

Comparable aircraft

B-26 Marauder
Martin XB-27
XB-33 Super Marauder

Bibliography

Joe Baugher's Encyclopedia of American Aircraft
USAF Museum

Living Warbirds: The best warbirds DVD series.

Source: WikiPedia