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United States of America B-2 Spirit

B-2 Spirit

The B-2 Spirit is a multi-role heavy bomber capable of delivering both conventional and nuclear munitions. The aircraft is a giant leap forward in technology and the bomber represents a milestone in the United States bomber modernization program.
The first B-2 was publicly displayed on 22 November 1988 when it was rolled out of its hangar at Air Force Plant 42, Palmdale, CA. Its first flight was on 17 July 1989.


Like the B-52 Stratofortress and B-1B Lancer, the B-2 has the penetrating flexibility and effectiveness essential to manned bombers. Its stealth characteristics give the B-2 the ability to penetrate the most sophisticated enemy defenses and threaten its most valued and heavily defended targets, like the F-117 did in Bagdad, during the first and second war in Iraq.

The B-2 Spirit

The B-2 is organic in appearance, a simple flying wing, with absolutely no vertical control surfaces. It has very smooth contours and few features that could "catch" radar waves and reflect them. It has a sweepback of 55 degrees and a "W"-shaped trailing edge. The aircraft is aerodynamically unstable, kept in the air with a quadruple-redundant fly-by-wire (FBW) system, under the control of a General Electric Flight Control Computer (FCC).

The B-2 was designed to be survivable, not merely in penetrating enemy airspace and performing attacks, but in riding out enemy nuclear attacks or counterstrikes. The B-2 is thoroughly radiation hardened; Waaland commented that about all that isn't radiation hardened is the antiskid braking system. It can also operate from dispersed bases, one of the design criteria being the capability to use any airstrip capable of supporting a Boeing 727 airliner.

The B-2 makes heavy use of titanium for structural elements, with much of the rest of the aircraft built of carbon-reinforced plastic (CRP) material. Large CRP skin assemblies were used to make the aircraft as "seamless" as possible, reducing radar reflections. The B-2 is painted in a bluish-gray anti-reflective paint to reduce its visual signature. It is not painted black, as is the F-117, since the B-2 is expected to perform both daylight and night attacks, and black is a high-visibility color for daylight flight operations.

Engine

The B-2's four General Electric F118-GE-110 non-afterburning turbofans, providing 77 kN (8,620 kg / 19,000 lbs) of thrust each, are derived from the popular GE F110 engine. The F118s are buried in the wings, with two engines clustered together inboard on each wing. The engine intakes and exhausts are on the top of the wings for concealment. The intakes have a zigzag lip to scatter radar reflections, and there is a zigzag slot just before each intake to act as a "boundary layer splitter", breaking up the stagnant turbulent airflow that tends to collect on the surface of an aircraft. The inlet ducts are built as an s-curve and lined with RAM to keep radar from picking up the compressor blades.
As with the F-117, the B-2's engines have an exhaust temperature control system, to minimise the aircraft's thermal signature. The B-2 can fly more than 6,000 nautical miles before refueling, and more than 10,000 nautical miles with just one refueling, while carrying 40,000 pounds of weapons.

Weapons

The B-2 stealth bomber is fitted with two side-by-side weapons bays that can accommodate a total of 22,680 kilograms (50,000 pounds) of stores. The leading and trailing edges of the weapons bay doors have the classic stealthy zigag pattern. When the doors are open, twin grilles pop out into the airstream at the front of the weapons bay to ensure proper stores separation. Each of the two weapons bays can be fitted with a Boeing Advanced Rotary Launcher (ARL), each capable of carrying eight 1,000 kilogram (2,200 pound) class munitions, or a Bomb Rack Assembly (BRA) for carriage of smaller munitions.

The B-2 was originally designed for the strategic bombing role, and is therefore qualified for nuclear stores such as the B83 strategic nuclear bomb, with selectable yield in the megatonne range, and the smaller B61 "Silver Bullet" nuclear bomb, with selectable yield in the range of hundreds of kilotonnes. The bomber was later qualified for the penetrating B61-11 penetrating nuclear weapon. A B-2 can carry 16 nuclear stores.

B-2 in Service

Although the Air Force had accepted their first B-2 in late 1993, the B-2 remained in service test for several more years, not reaching formal initial operational capability until 1997. The USAF only obtained a total of 20 operational aircraft. The small production buy meant that the high development costs were spread over a handful of aircraft, and since the program costs were about $48 billion USD, that came to about $2.4 billion USD per aircraft. Had more B-2s been built, of course their incremental cost would have been much less, though still clearly in the hundreds of millions of dollars.

The first ten B-2s delivered to the Air Force, from December 1993 to late 1995, were "Block 10" machines, intended for service evaluation and training. They couldn't fly at full flight loads, lacked precision weapons guidance and terrain following capability, and had a limited DMS. Eight "Block 20" machines were delivered in 1996 and 1997, which were up to operational specification, along with some improvements such as a Global Positioning System (GPS) satellite navigation receiver. The GPS receiver system was integrated into a "GPS Aided Targeting System (GATS)" to support the GAM GPS-guided bomb, and later the JDAM and other GPS-guided weapons. The ten Block 10s were brought up to Block 20 specification.

The Block 20s were followed by two final new-build "Block 30" aircraft, with the older machines brought up to the same specification. The Block 30s have avionics improvements, including a satellite communications (SATCOM) link; the lidar contrail-detection system; support for new GPS-guided weapons; and in particular have substantial modifications to improve their stealthiness. Adding the new stealth features require stripping off all the aircraft's paint and RAM and performing some airframe changes.

The B-2 went into combat for the first time on the night of 24 March 1999, at the very start of Operation Allied Force, the NATO air campaign against Serbia. The B-2 dropped JDAM GPS-guided bombs in the opening phases of the campaign to cripple Serbian air defenses so that conventional strike aircraft could operate with greater safety. The B-2 continued to fly strikes against well-defended targets during the rest of the campaign, unfortunately acquiring a bit of notoriety on 7 May 1999 when a B-2 dropped JDAM's on the Chinese embassy in Belgrade. The Chinese government protested loudly and angrily. The blunder was due to bad intelligence and mission planning, not a technical failure or crew error.

Six B-2s were committed to Operation Enduring Freedom, the American intervention in Afghanistan in 2001/2002, performing strikes in the early phases of the conflict. One mission lasted 44 hours, the longest combat sortie in the history of air warfare, with B-2s flying out of Whiteman to Afghanistan, dropping their loads, and then landing on Diego Garcia island in the Indian ocean to refuel, rearm, and take on new crews while the engines remained on idle. This done, the B-2s went back to Afghanistan to drop their loads, and finally returned to Whiteman. Four B-2s were also committed to Operation Iraqi Freedom, the American invasion of Iraq in the spring of 2003.

B-2 Crash on Guam

On the 24th of February, 2008, a B-2 bomber crashed shortly after take-off on Andersen AFB, Guam at approximately 10:30 a.m. local Guam time. Two pilots from the 509th Bomb Wing were on board and they ejected prior to the crash. After a 53-day safety pause the B-2 returned to flight on April 15, while an accident investigation board was still ongoing.

Distorted data introduced by a B-2 Spirit's air data system skewed information entering the bomber's flight control computers ultimately causing the crash of the aircraft. Moisture in the aircraft's Port Transducer Units during air data calibration distorted the information in the bomber's air data system, causing the flight control computers to calculate an inaccurate airspeed and a negative angle of attack upon takeoff. According to the accident report, this caused an, "uncommanded 30 degree nose-high pitch-up on takeoff, causing the aircraft to stall and its subsequent crash."

Moisture in the PTUs, inaccurate airspeed, a negative AOA calculation and low altitude/low airspeed are substantially contributing factors in this mishap. Another substantially contributing factor was the ineffective communication of critical information regarding a suggested technique of turning on pitot heat in order to remove moisture from the PTUs prior to performing an air data calibration.

The pilot received minor injuries, and the co-pilot received a spinal compression fracture during ejection. He was treated at Tripler Army Medical Center, Hawaii, and released. The aircraft was assigned to the 509th Bomb Wing at Whiteman Air Force Base, Mo.





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Sources and relevant links

Information from VectorSite.net and various Northrop Grumman press releases.
This article is part of the public domain, and thus holds no copyrights.


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