History of Flight
On July 29, 2016, at about 0105 Pacific daylight time, a Piper PA-31T Cheyenne II, registration N661TC, experienced an in-flight breakup and impacted the ground near Arcata/Eureka Airport (KACV), McKinleyville, California. The aircraft was operated by Cal-Ore Life Flight as an instrument flight rules (IFR) air ambulance flight under Part 135. It departed Jack Mc Namara Field (KCEC), Crescent City, California, at 0045, destined for Oakland International Airport (KAOK).
According to FAA radar data and voice communications, the flight (call sign Lifeguard November 661TC) was radar identified and cleared to climb to 15,000 ft mean sea level. At 0058:13, the pilot contacted Seattle Air Route Traffic Control Center reporting smoke in the cockpit and intention to return to Crescent City. The controller cleared the pilot direct to Crescent City and authorized descent to 9,000 ft. The pilot stated he was losing power, declared an emergency, and was depressurizing. At 0059:28, he reported three souls on board. No further communications were received. Radar data showed the aircraft turning and then lost Mode C altitude information at 0059:26. Primary radar returns continued until 01:02:50 when the aircraft was lost near 53.5 miles south of KCEC. An alert notice was issued, and wreckage was located the next morning.
Aircraft Information
The 1981 Piper PA-31T was equipped with two Pratt and Whitney PT6A-135A engines and controllable pitch propellers. It had a LifePort stretcher system installed. The aircraft was maintained under Piper Progressive Inspections on a 100-hour cycle. The last inspection was on July 14, 2016, at 7,286.6 hours total time. At the accident, airframe time was 7,309 hours. Both engines had 3,712 hours since new; both propellers had 1,662 hours since overhaul.
The electrical system was a 28-volt DC split-bus design with two starter generators. The main bus tie circuit breaker panel was located in the floor between the pilot and copilot seats. The LifePort modification added two circuit breakers (EMS INV 50 A and EMS PWR 30 A). The hydraulic system included lines for landing gear and brakes; a hand pump was stowed near the circuit breaker panel. The fuel system had independent left and right tanks with crossfeed capability; fuel lines did not pass through the structural bay containing the circuit breaker panel.
Wreckage and Impact Information
The wreckage was scattered along a debris path about 2,400 ft long on a magnetic heading of 354°. Initial pieces included the horizontal stabilizer tip, nose baggage door, and vertical stabilizer. The right engine and both wings were near the middle of the debris field; the fuselage and left engine were at the end. The fuselage came to rest on its left side. The cockpit was heavily damaged; the cabin was largely intact. Light soot covered the fuselage exterior, with heavier deposits in some areas. Thermal damage was present in the forward fuselage floor near the circuit breaker panel.
The right wing separated in two sections; the inboard section was thermally damaged. The left wing also separated; the inboard section was severely burned. Control continuity could not be established due to fractures. Both engines showed no pre-impact mechanical anomalies. The combustion heater had no thermal damage. Examination of wreckage revealed evidence of an in-flight fire limited to the forward floor area.
No probable cause was stated in the provided source.