Accident Overview
On June 20, 2024, about 1031 Pacific daylight time, a Lancair LC42-550FG (Columbia 350), registration N141PB, was substantially damaged during an emergency landing near Humboldt Bay, California. The pilot, the sole occupant, was not injured. The flight was operated under 14 CFR Part 91 as a personal flight, having just departed Murray Field Airport (EKA) in Eureka, California, on an instrument flight rules clearance to Napa County Airport (APC) in Napa, California.
During initial climb, the airplane passed through a cloud layer and broke into visual meteorological conditions at about 1,500 ft mean sea level. As it climbed through 2,300 ft, the pilot established communications with Seattle Air Route Traffic Control Center. About one minute later, he noticed a change in engine noise accompanied by vibration. The engine monitor indicated a rising cylinder head temperature for cylinder No. 6, and shortly afterward the engine lost all power and appeared to seize.
The pilot declared an emergency and received vectors back to EKA. While turning toward the airport, the airplane descended into the cloud layer and broke out into visual conditions about 700 ft msl over coastal marshland. The pilot maneuvered toward the flattest area; on touchdown, the airplane nosed over. The vertical stabilizer, rudder, and forward cabin roof sustained substantial damage.
Engine Examination
Postaccident examination revealed the engine had lost most of its oil in flight, with only 1 quart remaining in the sump (capacity 8 quarts). The airplane's belly was coated in oil, and within the engine compartment, the lower inner surface of the lower cowling and the left side of the engine were coated in an oil sheen.
Inspection of the rocker covers showed that the gasket for the exhaust rocker of cylinder No. 2 (left aft side of the engine) was misaligned in its lower right corner, creating a gap between the rocker cover and cylinder head. The cover was removed, revealing a dark stain on the face of the gasket mating surface that mirrored the misalignment. The oil cooler and all oil lines were intact with no evidence of leaks. Both the oil sump drain plug and the quick drain plug were intact and locked. The oil filter, mounted behind the aft engine baffle and forward of the firewall, was clean, dry, and firmly attached; its element was covered in fine metallic particles. The engine crankshaft could be rotated by hand at the propeller hub but felt stiff with more resistance than typical. No other preimpact mechanical malfunctions or failures that would have precluded normal operation were found.
Maintenance History
The most recent airplane maintenance was completed about 20 flight hours before the accident, on September 17, 2023. At that time, an annual inspection was performed along with replacement of all six engine cylinder and valve assemblies. The logbook entry stated that ground operation checks were performed following maintenance, and no leaks were noted.
Additional Information
Continental Aerospace Technologies issued Service Information Letter SIL21-04B in August 2021, applicable to the accident engine. It provided instructions for installing an updated 100% silicone rocker cover gasket (part number 668893) in place of previous fiber and combination fiber/silicone bead gaskets. The letter stated that the new gasket “provides a more flexible seal than the previous gasket, when properly installed.” It cautioned that failure to adequately clean the rocker and rocker cover flanges would cause an oil leak, and specified reduced torque values for attaching the cover fasteners compared to those for fiber-based gaskets, noting that failure to use the lower values would damage the gasket and cover. The newer silicone gasket had been installed and was undamaged. A review of the FAA’s service difficulty reporting system database found no reports of failures of this gasket.