Background
Prior to the flight, the pilots of a MiG-21 and a Piper PA-42 Cheyenne III met to discuss a photo mission in which the Cheyenne would take aerial photographs of the MiG. They agreed on a minimum altitude of 2,500 to 3,000 feet above ground level and a minimum airspeed of 200 knots. A minimum separation distance was not established, as the flight was not intended to be a formation flight.
Flight Details
After takeoff, the MiG pilot experienced a problem with the landing gear retraction. The gear was recycled and a successful retraction was indicated. The MiG pilot notified the Cheyenne pilot, who indicated they would join up to inspect the landing gear and report their observations. The MiG flew at 9,000 feet mean sea level in a 30-degree right turn at 200 knots with approximately 90 percent power and approach flaps selected (about 25 degrees) until the Cheyenne caught up.
The Cheyenne met the MiG at the MiG's 5 o'clock position, approximately 300-400 feet behind and at the same altitude. This placed the Cheyenne directly in the path of the high-velocity jet core exhaust from the MiG. The MiG pilot looked forward, and when he looked back, he could not see the Cheyenne. The Cheyenne pilot then made an incomplete comment about the right landing gear or gear door before communication ceased. The MiG pilot observed smoke rising from the desert terrain and notified air traffic control.
The airport manager, who was monitoring the conversation between the two aircraft, reported hearing the Cheyenne pilot indicate that he would "drop down and go underneath and let you know how it looks."
Wreckage Examination
The main wreckage was found inverted on flat terrain. The T-tail, consisting of the upper half of the vertical stabilizer, horizontal stabilizer, and elevator, had separated in flight and was located about half a mile south of the main wreckage. Inspection of the upper portion of the aft vertical spar revealed a right bend and twist at the point of separation. No evidence of pre-existing cracks, corrosion, or wear was found. Examination of the MiG aircraft showed no evidence of contact between the two aircraft.
Probable Cause
The official probable cause is: "The failure of the pilot following a jet aircraft to maintain adequate separation from the high velocity jet core exhaust. The separation of the T-tail upper section vertical stabilizer of the following aircraft due to contact with the high velocity jet core exhaust was a factor."