Event Details
On November 11, 2016, at approximately 1650 Alaska standard time, a Piper Saratoga PA-32R-301 (registration N9084J) experienced a total loss of engine power and executed a forced landing on tundra terrain southwest of Bethel Airport (BET) in Bethel, Alaska. The aircraft, operated by the Alaska Department of Public Safety (DPS) as a visual flight rules (VFR) public-use flight, sustained substantial damage. The commercial pilot received minor injuries.
The flight departed BET at about 1635 en route to Nunapitchuk Airport (16A), Nunapitchuk, Alaska. Visual meteorological conditions prevailed, and a VFR flight plan was filed.
Pilot Report
After departing runway 1L and climbing through 800 feet westbound, the pilot felt a momentary vibration and observed zero oil pressure. He initiated an immediate left turn back to the airport and declared an emergency with the BET control tower. While maneuvering to land, the engine began popping loudly, and oil emanated from the oil access panel, splattering onto the windscreen. Shortly afterward, the propeller stopped rotating, and all engine power was lost. The pilot directed the aircraft toward tundra-covered terrain away from residential areas. During landing, the aircraft encountered uneven ground, collapsing the left main and nose landing gears, and the left wing struck the terrain, causing substantial damage.
The pilot reported that earlier that day, he had performed a preflight inspection, checking the engine oil quantity at 10 quarts without removing the dipstick from its housing. He flew two passengers to 16A and returned to BET, where he shut down the engine, installed an engine cover, and waited about three hours. Upon returning, the engine cowling was still warm, and no fluid leaks were apparent. The engine started normally, and no ground run-up was conducted for the second flight. All engine instruments were within normal ranges before departure.
Post-Accident Observations
After the accident, DPS employees discovered a significant amount of engine oil on the airport parking ramp where the aircraft had been parked. During recovery, the engine oil access panel was found open, and the oil dipstick was missing; it was not located during subsequent searches of the ramp area.
Engine Examination
External inspection revealed a hole in the crankcase above cylinder No. 4, with fractures radiating from the hole. A small amount of oil residue was present around the oil dipstick neck, but none near the crankcase hole or the top of the engine. All accessible fuel and oil lines were intact. The quick oil drain yielded no oil when opened. The oil access panel exhibited impact marks on its underside, corresponding to the approximate size of the dipstick top.
The engine was disassembled for detailed examination. Cylinders No. 1 showed no mechanical malfunction. Connecting rods for cylinders No. 2 and 6 were in place; however, the No. 2 rod cap displayed dark discoloration and extrusion, and the No. 6 piston skirt exhibited extensive scoring and carbon deposits in the direction of travel. Connecting rods for cylinders No. 3, 4, and 5 were separated from the crankshaft via rod shank fractures, with extensive thermal discoloration and deformation. These signatures indicated engine operation without sufficient oil lubrication.
The oil sump pan contained large quantities of metal debris and fractured rods. The oil suction screen revealed non-ferrous metal particles. The thermostatic oil cooler bypass valve was intact, with no anomalies in the crimp nut, valve seat, or spring. The oil pump impeller showed no damage.
Oil coolers were pressure-tested; the left cooler had no leaks. The right oil cooler (Aero-Classics, Inc., P/N 8000074, S/N 1041902) exhibited an air leak through a 2-inch separation at a mated brazed plate that had been undetected visually. Examination at the NTSB materials laboratory indicated the fracture at the brazed seam showed overstress signatures, with no evidence of fatigue, corrosion, or material anomalies.
Maintenance History
The aircraft, manufactured in 1985, was equipped with a Lycoming IO-540-K1G5 engine. The most recent annual inspection was completed on August 31, 2016, at a total aircraft time of 6,989.1 hours and 213.4 hours since engine overhaul. The engine was serviced with Phillips X/C SAE 20W50 oil and 0.5 bottle of CamGuard aviation additive during that inspection, which occurred 21.6 flight hours before the accident. According to the Piper Pilot Operating Handbook, this oil type was appropriate for ambient temperatures between 0°F and 90°F.
Lycoming Service Instruction 1505 requires engine preheating when the engine temperature drops below 10°F. Automated weather observations at BET recorded outside air temperatures between 25°F and 21°F while the aircraft was parked on the ramp before engine start.
Weather Conditions
The closest weather reporting facility (BET), located about 1 mile northeast of the accident site, reported at 1653: wind 030° at 10 knots; scattered clouds at 10,000 feet, broken ceiling at 25,000 feet; visibility 10 statute miles; temperature 21°F; dewpoint 19°F; altimeter 29.98 inches of mercury.