Northrop B-2 Spirit

Development of the B-2 was begun in 1978 and the US Air Force originally wanted 133 examples, but by 1991 successive budget cuts had reduced this to 21 aircraft. The prototype flew on 17 July 1989, and the first production B-2 was delivered to the 393rd Bomb Squadron of the 509th Bomb Wing at Whiteman AFB, Missouri, on 17 December 1993.

In designing the Advanced Technology Bomber (ATB), as the B-2 project was originally known, the Northrop Company decided on an all-wing configuration from the outset. Flying-wing devotees such as Hugo Junkers and Jack Northrop have existed as long as aviation itself, arguing that a flying wing will carry the same payload as a conventional aircraft while weighing less and using less fuel. The weight and drag of the tail surfaces are absent, as is the weight of the structure that supports them. The wing structure itself is far more efficient because the weight of the aircraft is spread across the wing, rather than concentrated in the centre.

Northrop's experimental piston-engined flying-wing bomber of the 1940s, from which ideas for the B-2 were drawn, was designed to equal the range and carry the same warload as the Convair B-36, but at two-thirds the gross weight and also at two-thirds the power. The company produced a prototype flying-wing jet bomber, the YB-49, in 1947; however, this had little influence on the decision to pursue an all-wing solution for the B-2; the all-wing approach was selected because it promised to result in an exceptionally clean configuration for minimizing radar cross-section, including the elimination of vertical tail surfaces, with added benefits such as span-loading structural efficiency and high lift/drag ratio for efficient cruise. Outboard wing panels were added for longitudinal balance to increase lift/drag ratio and to provide sufficient span for pitch, roll and yaw control. Leading-edge sweep was selected for balance and trans-sonic aerodynamics, while the overall planform was designed for neutral longitudinal (pitch) static stability. Because of its short length, the aircraft had to produce stabilizing pitchdown moments beyond the stall for positive recovery. The original ATB design had elevons on the outboard wing panels only but, as the design progressed, additional elevons were added inboard, giving the B-2 its distinctive 'double-W trailing edge. The wing leading edge is so designed that air is channelled into the engine intakes from all directions, allowing the engines to operate at high power and zero airspeed. In trans-sonic cruise, air is slowed from supersonic speed before it enters the hidden compressor faces of the GE F118 engines.

A stores management processor is in place to hande the B-2's 22,730kg weapons load. A separate processor controls the Hughes APQ-181 synthetic-aperture radar and its input to the display processor. The Ku-band radar has 21 operational modes, including high-resolution ground mapping. The B-2 lifts off at 260km/h, the speed independent of take-off weight. Normal operating speed is in the high subsonic range and maximum altitude around 15,240m. The aircraft is highly manoeuvrable, with fighter-like handling characteristics.

Robert Jackson "The Encyclopedia of Aircraft", 2004

External links

• Wikipedia

3-View

A three-view drawing (767 x 440)