utorak, 30. ožujka 2010.

B-52 Stratofortress

The Boeing B-52 Stratofortress is a long-range, subsonic, jet-powered strategic bomber operated by the United States Air Force (USAF) since 1955.

Beginning with the successful contract bid on 5 June 1946, the B-52 design evolved from a straight-wing aircraft powered by six turboprop engines to the final prototype YB-52 with eight turbojet engines. The aircraft first flew on 15 April 1952 with "Tex" Johnston as pilot.

Built to carry nuclear weapons for Cold War-era deterrence missions, the B-52 Stratofortress replaced the Convair B-36. Although a veteran of a number of wars, the Stratofortress has dropped only conventional munitions in combat. The B-52 carries up to 70,000 pounds (32,000 kg) of weapons.

The USAF has possessed B-52s in active service since 1955. The bombers flew under the Strategic Air Command until SAC was disestablished in 1992 and its aircraft absorbed into the Air Combat Command (ACC), until February 2010 becoming part of Air Force Global Strike Command (AFGSC). Superior performance at high subsonic speeds and relatively low operating costs have kept the B-52 in service despite the advent of later aircraft, including the Mach-3XB-70 Valkyrie, the supersonic B-1B Lancer, and the B-2 Spirit. In January 2005, the B-52 became the second aircraft, after the English Electric Canberra, to mark 50 years of continuous service with its original primary operator. (As of 2009, the list has added the Tupolev Tu-95, the C-130 Hercules, the KC-135 Stratotanker, and the Lockheed U-2.)

On 23 November 1945, Air Materiel Command (AMC) issued desired performance characteristics for a new strategic bomber "capable of carrying out the strategic mission without dependence upon advanced and intermediate bases controlled by other countries". The aircraft was to have a crew of five plus turret gunners, and a six-man relief crew. It was required to cruise at 300 mph (240 kn, 480 km/h) at 34,000 feet (10,400 m) with a combat radius of 5,000 miles (4,300 nmi, 8,000 km). The armament was to consist of an unspecified number of 20 mm cannon and 10,000 pounds (4,500 kg) of bombs. On 13 February 1946, the Air Force issued bid invitations for these specifications, with Boeing, Consolidated Aircraft, and Glenn L. Martin Company submitting proposals.

Only three of the 13 B-52As ordered were built. All were returned to Boeing, and used in their test program. On 9 June 1952 the February 1951 contract was updated to order the aircraft under new specifications. The final 10, the first aircraft to enter active service, were completed as B-52Bs.

Even while the Air Force works on new bombers scheduled for 2037 it intends to keep the B-52H in service until at least 2040, nearly 80 years after production ended. This will be an unprecedented length of service for a military aircraft. B-52s are periodically refurbished at the USAF maintenance depots such as Tinker Air Force Base,Oklahoma.

The USAF continues to rely on the B-52 because it remains an effective and economical heavy bomber, particularly in the type of missions that have been conducted since the end of the Cold War against nations that have limited air defense capabilities. The B-52's capacity to "loiter" for extended periods over (or even well outside) the battlefield, while delivering precision standoff and direct fire munitions, has been a valuable asset in conflicts such as Operation Iraqi Freedom.

The speed of the B-1 Lancer and the stealth of the B-2 Spirit have only been useful until enemy air defenses were destroyed, a task that has been swiftly achieved in recent conflicts. The B-52 boasts the highest mission capable rate of the three types of heavy bombers operated by the USAF. Whereas the B-1 averages a 53% ready rate, and the B-2 achieved a 26%, the B-52 averages 80% as of 2001.

Additionally, a proposed variant of the B-52H was the EB-52. This version would have modified and augmented 16 B-52H airframes with additional electronic jamming capabilities. This new aircraft would have given the USAF an airborne jamming capability that it has lacked since retiring the EF-111 Raven. The program was cancelled in 2005 following removal of funding for the stand-off jammer. The program was revived in 2007 but funding was again canceled in early 2009.

Specifications (B-52H)

General characteristics

Performance

Armament

  • Guns: 1× 20 mm (0.787 in) M61 Vulcan cannon in a remote controlled tail turret, removed from all current operational aircraft
  • Bombs: Approximately 70,000 pounds (31,500 kg) mixed ordnance -- bombs, mines, missiles, in various configurations[6]

Avionics

  • Electro-optical viewing system that uses platinum silicide forward-looking infrared and high resolution low-light-level television sensors
  • Sniper Advanced Targeting Pod

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