Cirrus Design Corp SR22 N22WX accident near Langola Township, Minnesota

Probable cause

Maintenance personnel’s failure to apply sufficient torque on the throttle control lever nut, which resulted in a loss of throttle control and subsequent loss of engine power.

NTSB analysis

The commercial pilot was conducting a cross-country personal flight. He reported that, during cruise flight, the airspeed began to decrease, and the engine began to lose power. The pilot attempted to restore engine power but was not successful. He then conducted a forced landing to a road. During the landing roll, the pilot maneuvered the airplane to miss an oncoming car, and the airplane subsequently struck a guy wire, which resulted in substantial damage to the left wing.

A postaccident examination of the engine revealed that the throttle control lever nut was not torqued to factory specifications in accordance with an engine manufacturer service bulletin (SB). The knurl teeth of both the throttle control lever and shaft displayed signatures of machining with adhesive wear scars on the surfaces. In addition, the surface of the control lever that the nut was normally secured to displayed scoring wear scars. The surface signatures were consistent with the throttle control lever nut not having been properly torqued.

A review of the engine logbook entries revealed that a rebuilt engine was installed on the airplane about 73.1 flight hours before the accident. The mechanics at the repair station who installed the engine, which would have included installing the throttle body and torqueing the throttle control lever nut, reported that they were knowledgeable of the manufacturer SB, and no discrepancies in their procedures were found. Even though the mechanics reported that they were familiar with the SB, it is likely that they did not apply sufficient torque on the throttle control lever nut during the installation of the engine.

Text from the NTSB. Open the NTSB docket for CEN14LA486 for the full record.