NTSB Identification: LAX01FA186.
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Accident occurred Saturday, May 19, 2001 in NORTH LAS VEGAS, NV
Probable Cause Approval Date: 12/30/2003
Aircraft: Beech M35, registration: N9820R
Injuries: 1 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The airplane collided with obstructions during a forced landing precipitated by a loss of engine power. In a radio exchange with the control tower, the pilot reported a total loss of oil pressure. The airplane had accrued about 1 hour of flight time since a owner-assisted annual inspection was accomplished during which the owner changed the oil and filter element. Post accident examination of the underside of the forward fuselage/engine compartment area revealed an oil filter element hanging free from the oil filter base by the installation safety wire and fresh oil on the underside of the fuselage. The airplane had a STC'd 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 is 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 the 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 about 5 threads with red Locktite and torqued into the base. No evidence of Locktite was noted on the shaft or in the base bore. According to the Aircraft Maintenance Technician and IA 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.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pilot/owner's failure to correctly install the oil filter, which resulted in oil exhaustion and a loss of engine power. Also causal was his attempt to modify the design of the oil filter element adapter by breaking the bond between the base and the threaded shaft, which resulted in a loss of torque during filter element installation.

Full narrative available

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