The skin-flush sensors, which collect information about air pressure and density, much like a pitot tube on a conventional aircraft, provide angle-of-attack and yaw data to the B-2’s computerized flight control system. After heavy, lashing rains, water got into the sensors and caused them to give faulty readings to the flight control system, the official said. As a result, the aircraft’s computers determined—based on the bogus data—that the aircraft was in an improper attitude and corrected automatically. The B-2 made a sudden pitch-up and yaw that was not commanded by the pilot. The aircraft quickly stalled, became unrecoverable, and the crew of two ejected.
Moist air most likely caused the US Air Force to lose one of its prized Northrop Grumman B-2 bombers earlier this year, a loss calculated at $1.4 billion, the US Air Force reported on 5 June.
During a takeoff on a Guam runway on 23 February, moisture contamination on the fly-by-wire B-2’s air data sensors threw off the tailless bomber’s sensitive flight control system. (See video of the crash here.)
This is edited together from US Air Force video and reconstruction animation of the Northrop Grumman B-2 crash at Guam on February 23, 2008. The crash was caused by moisture in the air-data pressure sensors - a known problem, with a known fix that was never written down