On January 26, 2001, a Cessna 152 (registration N5295Q) operated by Airline Training Academy Inc. was involved in an aviation accident near Lancaster, TX. Investigators recorded the probable cause as: The lack of a cotter pin on the castellated lock nut securing the throttle lever to the throttle shaft, which resulted in loosening and loss of throttle actuation. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 8 related events involving the same aircraft type or operator are linked below.
An instructional flight ended with a forced landing after the engine lost power. Investigation revealed that a loose throttle lever lock nut, lacking a required cotter pin, prevented throttle actuation.
Accident Sequence
Approximately five minutes into a cross-country instructional flight, the engine RPM began to drop. The RPM continued to decrease steadily until the engine lost total power. Attempts to restart the engine were unsuccessful. During the subsequent forced landing to a field, the nose wheel contacted soft ground, causing the airplane to nose over and come to rest inverted.
Investigation Findings
At the time of the accident, the airplane had accumulated 2 hours of total time since its last annual inspection. During that annual inspection, the carburetor had been removed for additional maintenance. Examination of the carburetor revealed that when the throttle control was actuated from inside the cockpit, the throttle cable and lever did not actuate the throttle shaft and throttle valve. The castellated lock nut securing the throttle lever to the throttle shaft on the carburetor was found not to be safetied via a required cotter pin. The lock nut had loosened, allowing the throttle cable and lever to move without corresponding movement of the throttle shaft and throttle valve.
Probable cause
The lack of a cotter pin on the castellated lock nut securing the throttle lever to the throttle shaft, which resulted in loosening and loss of throttle actuation.