Cirrus Design Corp SR22 N418CP accident near Blythe, California

Probable cause

Maintenance personnel's failure to properly torque an oil supply line fitting, which resulted in oil starvation, a subsequent engine failure, and an off-airport landing.

NTSB analysis

The flight instructor reported that he and the pilot receiving instruction were conducting an instructional, cross-country flight. About 1.3 hours into the flight, the oil pressure started to decrease, and the pilots decided to divert to a nearby airport. The oil pressure continued to decrease, and the engine subsequently lost all power. The airplane was unable to reach the runway, so the pilots chose to activate the parachute system. Upon ground impact, the parachute dragged the airplane for about 20 ft. The pilots then egressed the airplane, and the parachute then dragged it another 200 ft. The nose landing gear and left main landing gear collapsed, and the fuselage and engine firewall sustained substantial damage.

During postaccident examination of the airframe, an oil streak was observed covering the airplane’s belly. During engine examination, a b-nut fitting that attached the oil supply line to the turbocharger inlet check valve was found loose. A significant amount of fresh oil was observed in the area around the b-nut fitting and on the engine’s right side near the turbocharger next to the b-nut. The cowling bottom’s right side exhibited significantly more oil staining than the bottom’s left side. The b-nut and its threads were not damaged. A small hole was found on the top of the engine crankcase, consistent with an internal engine failure.

A review of the airplane’s maintenance records revealed that an annual inspection was completed earlier on the day of the accident flight and that actions were taken to comply with a turbocharger manufacturer's safety bulletin that recommended that the turbocharger oil supply inlet screen be inspected and cleaned on a regular basis. To inspect and clean the inlet screen, the oil line to the turbocharger bearing housing inlet and cap has to be removed, followed by the removal of the valve assembly from the turbocharger oil inlet fitting. The valve assembly must then be reassembled, during which the check valve should be torqued to 85-inch lbs. The valve assembly should then be reinstalled on the turbo oil adapter and torqued to 85-inch lbs. It is likely that, during the maintenance, maintenance personnel failed to properly torque the b-nut fitting that attached to the turbocharger inlet check valve oil line supply line to the turbocharger inlet check valve, which resulted in oil starvation and a subsequent engine failure.

Text from the NTSB. Open the NTSB docket for WPR18LA018 for the full record.