History of Flight
On December 15, 2012, about 1000 Pacific standard time, a Piper PA31T1 Cheyenne, registration N93CN, was destroyed during an in-flight breakup near Ely, Nevada. The flight was operating under Title 14 CFR Part 91 as a cross-country personal flight. It departed Falcon Field Airport in Mesa, Arizona, at 0818, with a planned destination of Portland-Troutdale Airport in Portland, Oregon. Visual meteorological conditions prevailed, and the flight was on an IFR flight plan.
Radar data from Cedar City, Utah, and Battle Mountain, Nevada, showed the airplane on a northerly track for about 30 minutes, then turning northwesterly. It maintained a cruise altitude of 24,000 feet at about 230 knots ground speed. At 0937, the heading turned to about 320 degrees. The last radar returns, covering about 30 seconds, showed a steep right spiral descent from cruise altitude to 14,500 feet. The final radar target was at 1000, located 0.35 nautical miles northeast of the accident site.
The pilot's last radio transmission was at 0959:40, requesting to leave the frequency for a few minutes. Air traffic control approved and asked him to report back.
Personnel Information
The pilot, age 84, held a private pilot certificate with ratings for single-engine and multi-engine land and instrument flight. His most recent third-class medical certificate was issued October 5, 2012, with a requirement for corrective lenses and glasses for near/intermediate vision. His personal flight records were not recovered. On his last medical application, he reported 6,336 total flight hours, 51 of which were in the prior 6 months. FAA records indicated he had been involved in two previous mishaps.
Aircraft Information
The Piper Cheyenne PA-31T1, serial number 31T-8004029, was manufactured in 1980 and equipped with two Pratt and Whitney PT6-11A engines. The most recent Piper Progressive Inspection (Program 1 and 2) was on March 23, 2012, at 5,725 airframe hours. The last maintenance was October 15, 2012, at 5,800 hours, which included repair of the left tip tank nosecone due to ground damage. The tachometer at the accident site showed 5,824.X hours. The pilot's flight log recorded parameters including altitude 24,000 feet, outside temperature -36°C, indicated airspeed 160 knots, and other engine data.
The airplane was equipped with a King/Bendix KFC250 autopilot, originally installed. The autopilot could be engaged by pressing the ON switch and selecting a mode; disengagement could be via mode switch, disengage switch on the control wheel, or turning off the autopilot switch. All servos had a clutch mechanism allowing manual override.
Meteorological Information
An NTSB meteorologist studied the conditions. The NWS Surface Analysis showed light or calm winds with variable directions, temperatures in the low 30s°F. NEXRAD radar showed no reflectivity near the accident site. The closest official observation station, Ely Airport (18 miles northwest), reported at 0953: wind 160° at 5 knots, temperature 23°F, dew point 19°F, clear skies below 12,000 feet, altimeter 29.85 inHg. A NAM model indicated winds below 10 knots from varying directions below about 26,000 feet. RAOB calculations identified no significant icing or turbulence above about 12,000 feet. A pilot report at 1153 from 40,000 feet noted wind 240° at 40 knots and no turbulence. Satellite imagery showed partly cloudy skies with cloud-top heights around 16,000 feet. An Area Forecast for northeastern and east-central Nevada forecast broken ceilings 7,000-9,000 feet, overcast bases at 12,000 feet, tops to 18,000 feet, and widely scattered light snow showers.
Wreckage and Impact Information
The accident site was in a canyon in the Schell Creek mountain range, about 17 nautical miles southeast of Ely, at approximately 39°05.233' N, 114°35.017' W, elevation about 6,850 feet. Debris was scattered over about 1,500 feet of hilly terrain. The main wreckage (cabin, right wing, inboard left wing, both engines, empennage, part of vertical stabilizer) came to rest inverted on a heading of 284 degrees. All fracture surfaces showed overstress failures with no evidence of fatigue.
The cockpit was crushed; landing gear and flap levers were retracted; static pressure selector was in normal source. The oxygen knob was near the off position. The pilot's oxygen mask was stowed; the passenger's mask and hoses were entangled around her. The oxygen tank valve was off. Cockpit gauge lights showed stretched filaments on several lights, but illumination at the time could not be determined for some. The heading bug was set at 310 degrees.
Both engines had severe impact damage. Examination revealed no pre-impact distress, no fatigue, and no debris on chip detectors. Both propellers were not feathered at impact and were in a low-operating blade angle position (near flight idle). Damage was consistent with impact.
Medical and Pathological Information
An autopsy by the Clark County Coroner determined the cause of death for both occupants as blunt force injuries. FAA toxicology on the pilot was negative for ethanol; warfarin, metoprolol, and pseudoephedrine were detected. Carbon monoxide testing was not conducted. No medical conditions that would cause impairment or incapacitation were identified. The investigation could not determine if hypoxia or other medical impairment contributed.
Tests and Research
A complete examination report is in the public docket. All examined fracture surfaces exhibited overstress failures without fatigue.