CESSNA T310R — Cody, WY

What happened

After flying over Yellowstone National Park at 13,500 ft, the pilot requested an instrument flight rules (IFR) clearance direct to Billings Logan International Airport (BIL), Billings, Montana. At that time, the airplane was at 13,300 ft and was below the minimum en route altitude of 14,400 ft. After confirming that the pilot could maintain terrain and obstacle clearance, the controller issued an IFR clearance direct to BIL (to the north-northeast) and instructed the pilot to climb to and maintain 15,000 ft. An AIRMET was in effect for icing between 14,000 ft and FL (flight level) 220 in the area; the controller did not provide this information to the pilot, and it could not be determined if the pilot was aware of the AIRMET. After the airplane reached 15,000 ft, the controller made a radar handoff and attempted to transfer radio communications, but the pilot did not respond. The controller stated that the airplane turned east and began a rapid descent. The airplane impacted a creek bed in heavily wooded mountainous terrain at an elevation of 7,762 ft. Tree heights were about 100 ft. There was a scrape mark on the side of one tree, and another tree had the top broken off. No other trees were damaged, consistent with the airplane having descended through the tree canopy in a near-vertical attitude. The airplane was severely fragmented and had been exposed to a postimpact fire.

The wreckage, engines, propellers and turbochargers were subsequently examined. The left propeller bore evidence of little or no rotation. Disassembly revealed it was in the "low pitch/high rpm" position. Disassembly of the left engine revealed no anomalies. The left engine turbocharger turbine bore no rotational marks and could not be rotated. No rub marks were noted on the turbine housing. It is likely that the left engine was not operating at the time of impact. The outboard end of the recovered right propeller blade bore chordwise scratches. Disassembly of the right engine revealed no anomalies. The right engine turbocharger turbine rotated freely when turned by hand. The pilot likely lost control of the airplane following the loss of left engine power. Although the airplane was operating in an area conducive to aircraft icing, the reason for the loss of engine power could not be determined during postaccident examinations.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.