Tandemrotor is right - the cause was never positively determined. I was on the Sqn at the time (in fact I was supposed to be in the aircraft but we had a shift change and I went back to the accomodation complex). If I recall correctly the BoI initially went after DASH actuator runaway as a possible cause, but this was later discounted.
As a very young JNCO at the time, standing in front of the BoI president and giving testimony was one of the most haunting things I have ever done.
Great guys, fondly remembered, sadly missed.
FlightTester aka Roger Ramjet