Accident Overview
The airplane collided with obstructions during a forced landing that was precipitated by a loss of engine power.
Pilot Communication
In a radio exchange with the control tower, the pilot reported a total loss of oil pressure.
Maintenance History
The airplane had accrued about 1 hour of flight time since an owner-assisted annual inspection was accomplished. During that inspection, the owner changed the oil and filter element.
Post-Accident Examination
Post-accident examination of the underside of the forward fuselage and engine compartment area revealed an oil filter element hanging free from the oil filter base by the installation safety wire. Fresh oil was present on the underside of the fuselage. The airplane had a Supplemental Type Certificate (STC) for a remote-mounted oil filter base that used a screw-on filter element. The installation location was in the aft engine compartment on the forward side of the firewall, requiring a blind insertion of the element by feel only onto the threaded shaft. The only way to see the element pad and threaded shaft was by mirror or by looking up through the right cowl flap with a light.
Examination of the filter base revealed evidence of thread damage to the first complete thread in the bore. The first 5 or 6 threads of the shaft were damaged, also with a cross-thread appearance to the first 2 or 3 threads. Other threads were damaged and had the appearance of attempted file repair. Both ends of the shaft revealed internal damage to the bore of the shaft. During manufacture, the shaft is permanently factory-installed to a depth of about 5 threads with red Loctite and torqued into the base. No evidence of Loctite was noted on the shaft or in the base bore.
According to the Aircraft Maintenance Technician and the Inspection Authorization (IA) holder who approved the annual inspection, the pilot/owner had recently commented to him that other filter elements could be used besides the one specified for the system. The pilot reportedly told the mechanic that you could either unscrew the 3/4-16 shaft from the other elements or the ones without a shaft could be screwed onto the shaft in the base unit.