Accident Overview
On May 1, 2019, at about 1100 Pacific daylight time, a Cessna T182P airplane, registration N7302S, was substantially damaged during an accident near Mill Creek, California. The pilot and one passenger sustained serious injuries, and one passenger was fatally injured. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
Flight and Power Loss
The pilot reported that the purpose of the flight was to circle Mount Lassen. After takeoff, the airplane climbed to between 11,000 and 11,500 ft mean sea level. While transitioning to the east side of the mountain, the pilot heard a muffled boom from the engine compartment, saw a puff of white vapor, and experienced a partial loss of engine power. Black smoke and the smell of burnt oil entered the cockpit. The pilot trimmed for best glide and began a descent at an estimated 1,000 ft per minute. He attempted to troubleshoot, noting a slight power reduction when retarding the throttle, indicating at least one piston still operated. He then advanced the throttle fully forward to minimize descent.
Emergency Landing and Impact
The pilot rejected his first selected field and turned toward a grassy meadow beyond trees. He planned to flare after clearing a 4-ft fence stretching northwest-southeast across the field. After passing over treetops, he extended flaps and continued toward the fence. Suddenly seeing powerlines ahead, he attempted to maneuver underneath. The airplane contacted the wires, spun from the impact, and came to rest inverted.
Evidence from Passenger's Cellphone
A rear-seated passenger's cellphone contained photographs and a video of the flight. A 24-second video, beginning at 1032:43, showed the cockpit. Images revealed the engine oil pressure gauge near 0 psi and the tachometer reading 4,249.7 hours, 24 minutes before the accident.
Pilot Information
The pilot held a mechanic certificate with airframe and powerplant ratings.
Airplane and Engine Information
Logbook entries and an interview with maintenance personnel indicated that during the last maintenance, the airplane's owner changed the oil, and another maintenance facility replaced the vacuum pump accessory driveshaft seal. The engine was equipped with an F&M Enterprises Inc. oil filter adapter, model C6LC-S, installed under FAA Supplemental Type Certificate (STC) No. SE09356SC. The adapter was originally designed to use two AN900-200 copper crush gaskets. At an unknown time, the inboard gasket was changed to a fiber gasket (part number FM07). The adapter was installed on the accident engine by the owner in February 2017.
Oil Filter Adapter Examination
Following the accident, the oil filter adapter was found loose, with the housing rotatable about the shaft by hand. The breakaway torque was less than 20 ft/lbs, below the required 65 ft/lbs. The fiber gasket was protruding and completely split. The copper crush gasket was intact. Testing with an exemplar adapter showed that insufficient torque allowed housing movement and oil leakage, but investigators could not duplicate the gasket blowout seen in the accident.
Maintenance and Instructions
The STC holder, Stratus Tool Technologies, had issued instructions for continued airworthiness. At the time of installation in February 2017, the applicable ICAW had been published in October 2013. It stated to replace gaskets if the adapter was removed and reinstalled, and to replace gaskets at 300 hours or 3 years. The fiber gasket on the accident airplane had 41.9 hours beyond the 300-hour recommendation. Revised instructions in April 2017 specified retightening the adapter to 65 ft/lbs after 8-12 hours of operation, using new gaskets upon reinstallation, and safety-wiring.
Wreckage and Impact Details
The debris field extended 565 ft along a magnetic bearing of 230° from the power lines, which were about 20 ft tall and oriented east-west. Initial ground contact marks were consistent with the airplane impacting terrain inverted. The fuselage came to rest inverted. An oil sheen covered the belly, horizontal stabilizer, and elevator. The left-wing strut had rub marks and holes consistent with electrical arcing. The left-wing fuel tank bladder was damaged. The right-wing flap actuator extension indicated flaps extended about 20° at impact.
Engine Examination
An external visual examination revealed oil staining on the firewall, a hole in the bottom of the crankcase near cylinder No. 3, and a hole in the upper crankcase near cylinder No. 4. The oil sump contained visible oil and metal debris, including pieces of pistons and connecting rods. Borescope examination showed no foreign object damage, detonation, or excessive oil consumption. The carburetor had intact floats and liquid resembling aviation fuel.
Additional Information
Stratus Tool Technologies issued a Service Bulletin (SB-001) dated October 25, 2019, with inspection and proper installation instructions. A review of NTSB data revealed at least six previous accidents involving oil starvation from the same oil filter adapter due to gasket failure or improper gaskets. The FAA's Aircraft Certification Office performed a risk assessment and determined mandatory regulatory action was not warranted but initiated a Safety Alert for Operators (SAFO), which had not been published as of the report.