Somehow we missed this a few weeks back, but the Air Force recently released photos of the B-2 Spirit stealth bomber that crashed shortly after takeoff from Andersen Air Force Base in Guam on February 23, 2008. The pilot and co-pilot ejected safely from the $1.4 billion aircraft, which was not carrying any munitions at the time of the incident.
The Air Force concluded its investigation in June, and Popular Mechanics summarizes what went wrong:
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.
An even better way to understand what happened is by watching this excellent video produced by the folks at AVWeb. It contains both footage of the actual crash, as well an a technical summary of how the accident unfolded:
IMAGES: US Air Force