From today's (6/6/08) Aviation Week website:

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Jun 6, 2008
David A. Fulghum/Aerospace Daily & Defense Report


Crews and maintainers never formally recorded information on a vulnerability involving the B-2’s air pressure sensors and the simple workaround crews came up with to mitigate it, a crucial omission that set the stage for a Feb. 23 B-2 crash in Guam.

Aircrews and maintenance teams learned about the sensors’ susceptibility to moisture during a Guam deployment in 2006. They also discovered that turning on the 500-degree pitot heat would quickly evaporate the water and the flight computer would receive normal readings.

But the information was not formally “captured” in maintenance or lessons-learned publications, said Maj. Gen. Floyd Carpenter, president of the accident investigation board and vice commander of 8th Air Force. The result was that by the 2008 deployment, the information was passed on by word of mouth so that “some people knew about it and some people did not,” he said during a Pentagon briefing June 5. Crews never encountered the problem at the bomber’s home base of Whiteman Air Force Base, Mo.

Earlier incident

Earlier in the 2008 deployment, another B-2 had reached 70 knots in its takeoff roll when abnormal indications caused the pilot to abort. The aircraft taxied back to maintenance, the moisture was evaporated with pitot heat and the mission continued without incident.

But on Feb. 23, calibration of the sensors was done without turning the sensor heaters on. The skewed information from three of the 24 air pressure sensors on the Spirit of Kansas fed distorted information into the flight control computer. When the aircraft reached 130 knots, the computer thought it was at the 140-knot takeoff speed and rotated for takeoff.

The sensors also indicated the bomber was in a nose-down attitude so it commanded a rapid pitch up that reached 30-31 degrees before the pilots could correct and stop the climb at an altitude of about 80 feet. The effects of the low takeoff speed and high angle of attack caused the B-2’s speed to deteriorate until the aircraft stalled and began a roll to the left, when its left wing tip struck the ground. At that point the pilots ejected (Aerospace DAILY, March 28).

The aircraft’s remains were boxed and will be sent to the U.S., where the cockpit, seats and hatches will be used for training.

Additional information, including the crash investigators report and video, is posted on Air Combat Command’s Web site at http://www.acc.af.mil/aibreports/.

Photo: Anonymous



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dupe - there are already two long threads on this (incl. video)