Thursday, November 12, 2009

Convair B-58 Hustler

The Convair B-58 Hustler was the first operational supersonic jet bomber, and the first capable of Mach 2 flight.  The aircraft was developed for the United States Air Force for service in the Strategic Air Command (SAC) during the late 1950s. Originally intended to fly at high altitudes and speeds to avoid Soviet fighters, the introduction of highly accurate Soviet surface-to-air missiles forced the B-58 into a low-level penetration role that severely limited its range and strategic value. This led to a brief operational career between 1960 and 1969. Its specialized role was succeeded by other American supersonic bombers, such as the FB-111A and the later B-1B Lancer.

The B-58 received a great deal of notoriety due to its sonic boom, which was often heard by the public as it passed overhead in supersonic flight.

The genesis of the B-58 program came in February 1949, when a Generalized Bomber Study (GEBO II) had been issued by the Air Research and Development Command (ARDC) at Wright-Patterson AFB, Ohio.[4] A number of contractors submitted bids including Boeing, Convair, Curtiss, Douglas, Martin and North American Aviation.

Building on Convair's experience of earlier delta-wing fighters, beginning with the XF-92A, a series of GEBO II designs were developed, initially studying swept and semi-delta configurations, but settling on the delta wing planform. The final Convair proposal, coded FZP-110, was a radical two-place, delta wing bomber design powered by General Electric J53 engines. The performance estimates included a 1,000 mph (1,609 km/h) speed and a 3,000 mi (4,828 km) range.

The USAF chose Boeing (MX-1712) and Convair to proceed to a Phase 1 study. The Convair MX-1626 evolved further into a more refined proposal redesignated the MX-1964. In December 1952, the Air Force selected the MX-1964 as the winner of the design competition ] to meet the newly proposed SAB-51 (Supersonic Aircraft Bomber) and SAR-51 (Supersonic Aircraft Reconnaissance), the first General Operational Requirement (GOR) worldwide for supersonic bombers. In February 1953, the Air Force issued a contract for development of Convair's design.

The resulting B-58 design was the first "true" USAF supersonic bomber program. The Convair design was based on a delta wing with a leading-edge sweep of 60° with four General Electric J79-GE-1 turbojet engines, capable of flying at twice the speed of sound. Although its large wing made for relatively low wing loading, it proved to be surprisingly well suited for low-altitude, high-speed flight. It seated three (pilot, bombardier/navigator, and defensive systems operator) in separated tandem cockpits. Later versions gave each crew member a novel ejection capsule that made it possible to eject at an altitude of 70,000 ft (21,000 m) at speeds up to Mach 2 (1,320 mph/2,450 km/h). Unlike standard ejection seats of the period, a protective clamshell would enclose the seat and the control stick with an attached oxygen bottle. In an unusual test program, live bears and chimpanzees were successfully used to test the ejection system.  The XB-70 would use a similar system.

Because of heat generated at Mach 2 cruise, not only the crew compartment, but the wheel wells and electronics bay were pressurized and air conditioned. The B-58 utilized one of the first extensive applications of aluminum honeycomb panels, which bonded outer and inner aluminum skins to a honeycomb of aluminum and fiberglass.

The pilot's cockpit was fairly conventional for a large multiengine aircraft.  The electronic controls were ambitious and advanced for the day. The navigator and DSO's cockpits featured wrap around dashboards with warning lights and buttons, and automatic voice messages and warnings from a tape system were audible through the helmet sets. Research during the era of all-male combat aircraft assignments revealed that a woman's voice was more likely to gain the attention of young men in distracting situations. Nortronics Division of Northrop Corporation selected actress and singer Joan Elms to record the automated voice warnings. To the men flying the B-58, the voice was known as "Sexy Sally."

The Sperry AN/ASQ-42 bombing/navigation system combined sophisticated inertial navigation with the KS-39 astro-tracker to provide heading reference, the AN/APN-113 Doppler radar to provide ground velocity and windspeed data, a search radar to provide range data for bomb release and trajectory, and a radio altimeter.  The AN/ASQ-42 was estimated to be 10 times more accurate than any previous bombing/navigation system.

Defensive armament consisted of a single 20 mm (0.79 in) T-171E-3 rotary cannon with 1,200 rounds of ammunition.  It was remotely controlled by the DSO through the Emerson MD-7 fire control radar system.  Offensive armament typically consisted of a single nuclear weapon, along with fuel tanks, in a streamlined MB-1C pod under the fuselage. Incurable difficulties with fuel leakage resulted in the replacement of the MB-1C with the TCP (Two Component Pod), which placed the nuclear weapon in an upper section while the lower fuel component could be independently jettisoned.

From 1961 to 1963, the B-58 was retrofitted with two tandem stub pylons under each wing, inboard of the engine pod, for B43 or B61 nuclear weapons for a total of five nuclear weapons per airplane. Although the USAF explored the possibility of using the B-58 for the conventional strike role, it was never equipped for carrying or dropping conventional bombs in service. A photo reconnaissance pod, the LA-331, was also fielded. Several other specialized pods for ECM or an early cruise missile were considered, but not adopted.

The first prototype, serial number 55-660, was completed in late August 1956.[13] The first flight took place in November 1956.[14] A difficult and protracted flight test program involving 30 aircraft continued until April 1959.[15] The final B-58 was delivered in October 1962.[15]

General characteristics
  • Crew: 3: pilot; observer (navigator, radar operator, bombardier); defense system operator (DSO; electronic countermeasures operator and pilot assistant).
  • Length: 96 ft 9 in (29.5 m)
  • Wingspan: 56 ft 9 in (17.3 m)
  • Height: 29 ft 11 in (8.9 m)
  • Wing area: 1,542 ft² (143.3 m²)
  • Airfoil: NACA 0003.46-64.069 root, NACA 0004.08-63 tip
  • Empty weight: 55,560 lb (25,200 kg)
  • Loaded weight: 67,871 lb (30,786 kg)
  • Max takeoff weight: 176,890 lb (80,240 kg)
  • Powerplant: 4× General Electric J79-GE-5A turbojet
  • * Zero-lift drag coefficient: 0.0068
  • Drag area: 10.49 ft² (0.97 m²)
  • Aspect ratio: 2.09
  • Maximum speed: Mach 2.0 [26] (1,319mph) at 40,000 ft (12,000 m)
  • Cruise speed: 610 mph (530 kn, 985 km/h)
  • Combat radius: 1,740 mi (1,510 nmi, 3,220 km)
  • Ferry range: 4,720 mi (4,100 nmi, 7,590 km)
  • Service ceiling: 63,400 ft (19,300 m)
  • Rate of climb: 17,400 ft/min (5,310 m/min) at gross weight[27]
  • Wing loading: 44.01 lb/ft² (214.9 kg/m²)
  • Thrust/weight: 0.919
  • Lift-to-drag ratio: 11.3 (without weapons/fuel pod)
  • Guns: 1 × 20 mm (0.79 in) T171 cannon
  • Bombs: 4 × B-43 or B61 nuclear bombs; maximum weapons load was 19,450 lb (8,823 kg)