UAS due to icing in the Kiel probe causes X-31 flight computer anomaly.
In case someone haven't seen it yet.
The 43-minute mission was nearing its conclusion when ice began forming on the X-31's pitot tube. The ice caused incorrect airspeed information to be sent to the craft's flight control computers, which were responsible for reconfiguring the aircraft for lower speeds. The result was a series of sudden, uncontrollable oscillations in all axes. The aircraft then pitched to 90 degrees angle of attack, and Lang was forced to eject as the X-31 crashed near the northern boundary of Edwards Air Force Base.
From:
NASA - Dryden Flight Research Center - X-Press: January 2004