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
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Posted by: allan | 04 August 2008 at 08:10 AM
thats so LAME!!!!
Posted by: tnh | 04 August 2008 at 02:37 PM
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Posted by: CC | 06 August 2008 at 11:59 AM
A few drops of water. That's all we needed to know.
Posted by: RealBoy | 06 August 2008 at 01:09 PM
It is amazing how this bird looks impresive even when it's down.
Posted by: Budapest Boy | 06 August 2008 at 02:30 PM
If a few drops of water could caused such a crash, what about commercial aircraft using this device?
Posted by: Nick | 09 August 2008 at 07:00 AM
The important thing is that the crew got out safely. Machines can be replaced, people cannot. Good that they figured out what went wrong, hopefully that will prevent future accidents.
Posted by: David | 16 August 2008 at 09:36 AM
At 1.4 billion dollars a pop I hope their analysis is correct and the pre-flight is improved to allow for what brought this plane down.
Posted by: Richard | 16 August 2008 at 01:04 PM
Better periodic inspections of dehydration elements and moisture sensors would help avoid future incidents.
Posted by: Covepheonix | 18 August 2008 at 10:21 AM
What I want to know is how did water get into such a sensitive area that could cause such a disaster? Wouldn't it be prudent to seal that could cause catastrophic failure because of a couple drops of H2O? But you cannot blame the Air Force, blame the contractors who built the damn thing and made $1.4 billion doing it. I wonder how many low level engineers screamed to have this one area sealed but the big shots didn't think it would matter. The contractors should supply another one free of cost.
Posted by: wes | 17 October 2008 at 04:08 AM
Fit it so that the problem is history.
Posted by: Willard D. DeTour | 01 January 2009 at 09:06 PM
In reply to the comments above. The Pitot tube and static pressure ports cannot be sealed or they will not perform the function they are designed for. They must be open on one end to read the air pressure in flight. Airplanes have flown with this basic system for 70 years. Water did not cause the accident, improper maintenance of the pitot/static FCS system did. The Mx personel should have identified why the calibration was off before they re-calibrated it.
Posted by: Chris | 16 January 2009 at 05:59 PM
This is not a first. remember the 767 "lawn mower". Things like this will continue to happen until engineers figure out that the pilot should have the final "over ride" over the computer. Not the other way around.(Delta capt, ret).
Posted by: mike | 31 January 2009 at 07:10 AM
The man was a twit when he was on the job and is a twit still. Now he writes a book telling people what they already know and they run off to buy it.
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