First pictures. Smoke billows from the runway at Andersen Air Force Base, Guam Saturday Feb. 23, 2008 after a B-2 stealth bomber crashed.
The two pilots aboard the bomber ejected before the crash and are safe the U.S. Air Force said. A board of Air Force officers will investigate what
happened. Each B-2 bomber costs about $1.2 billion to build.
All 21 stealth bombers are based at Whiteman Air Force Base in Missouri, but the Air Force has been rotating several of them through Guam since 2004,
along with B-1 and B-52 bombers.
posted on 24-2-2008
The B-2 that crashed Feb. 23 in Guam “basically stalled” and is “absolutely a total write-off,” Gen. John Corley, head of Air
Combat Command, told defense reporters at a meeting March 27 in Washington, D.C.
Corley said the pilots reported that the airplane “rotated early,” meaning the nose came up sooner and faster than the pilots commanded,
and they could not get it to come down again. The airplane stalled—meaning the pitch was too high for airflow over the wings to create
lift—and, when the left wing started dragging against the ground, the two-man crew ejected.
Corley made no mention of an onboard fire, which has been reported by some publications. He said there are two investigations underway: a safety and
an accident probe. The former is due mid-April, the latter in mid-May.
The 20 remaining B-2s are not technically grounded, Corley said, but are not flying while the 509th Bomb Wing at the B-2’s home
base of Whiteman AFB, Mo., reviews its training and inspection procedures. In the meantime, Corley said, crews are staying proficient by flying in the
simulator and in the T-38 companion trainer.
The spectacular crash of a B-2 stealth bomber in February could have been prevented by a simple, unofficial “bootleg” maintenance procedure that some
ground crews have used for years.
Small errors, it now turns out, caused a large accident. A B-2 has four computers, called the flight control system (FCS), that translate the pilot’s
cockpit inputs into movement of the plane’s control surfaces.
The $1.4 billion warplane was brought down by a few drops of water in three of the 24 air-pressure sensors that feed data to the FCS. The moisture
distorted the plane’s air-pressure readings and confused the FCS badly enough to cause the crash, the first one of the B-2’s career.
February’s crash was caused by maintenance crews trying to do the right thing: They saw the wrong data and recalibrated the sensors. However, once the
moisture evaporated, the sensors “fixed” by the crew were actually set incorrectly and were feeding the flight computer false data on airspeed and air
pressure, which is used to measure altitude. “The pressure differences were miniscule, but they were enough to confuse the FCS, ” Maj. Gen. Floyd
Carpenter, who headed the Air Force’s investigation, tells PM.
The FCS then took control; triggering a premature takeoff, automatically driving the airplane into a 30-degree, nose-up pitch and overruling the
pilot’s efforts to regain control. Fortunately, the pilot and commander were able to eject safely just before the B-2, the Spirit of Kansas, crashed
The accident might have been avoided if the crew that readied the B-2 for?takeoff knew of an unofficial fix that had been used by maintenance
personnel for at least two years. During the occasional, temporary B-2 deployments to rainy, humid Guam, where the planes were often stored outside,
some B-2 ground crewmen noticed that air data calibration was required much more often.? In 2006, a Air Force engineer based in the United States
suggested turning on the heat before the calibration to boil off any water in the system before adjusting the sensors.
The procedure worked, and some ground crewmen adopted it,? but it was never formalized into a technical order change or captured in any after-action
reports. Unfortunately, the Spirit of Kansas’ pilots and ground crew were out of the loop.
Even those ground crewman who used the bootleg procedure had no inkling of the potential dangers of a slight miscalibration. Before the crash, air
data calibrations were considered a benign way to double-check the altimeters.? Apparently no one made the connection that the air data sensors also
fed info to the FCS computers about airspeed, angle of attack, and sideslip—and that the FCS flew the plane based largely on those numbers.
The B-2’s computerized fly-by-wire wizardry is a supreme technical achievement, but the Guam crash—the only one in the stealth bomber’s 19-year flying
history—underlines the vulnerability of even sophisticated computer systems to mundane glitches. And it doesn’t matter how sophisticated a military
system is if the people taking care of it can’t communicate.