Casualties unknown

1986-09-02: Boeing E75 (N4563N) — Sweetwater, TX

Sweetwater, TX, US

On September 2, 1986, a Boeing E75 (registration N4563N) was involved in an aviation accident near Sweetwater, TX. Investigators recorded the probable cause as: The pilot's inability to reach the intended landing area due to a sudden loss of engine power, which was caused by a disconnected throttle linkage resulting from a missing cotter pin. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 1781061362Data APIEditorial standards

During cruise flight, an aircraft experienced a sudden loss of engine power due to a disconnected throttle linkage. The pilot attempted a forced landing in a clearing but struck mesquite trees, resulting in damage to the landing gear and wings.

What happened

The aircraft was operating in cruise flight when the engine unexpectedly reduced to idle power without pilot input. Recognizing the loss of thrust, the pilot initiated an emergency procedure to land in a nearby clearing. However, the available altitude and glide ratio were insufficient to reach the intended safe area. During the descent toward the ground, the aircraft collided with low mesquite trees situated in the landing zone.

The investigation

Post-accident examination of the engine compartment revealed the mechanical cause of the power loss. Inspectors found that the throttle linkage had become disconnected. Specifically, a cotter pin that secures the linkage components was missing. This absence allowed the throttle control to move freely and unintendedly, causing the engine to drop to idle power during flight.

Findings

The primary factor in this incident was the failure of the throttle control system due to a missing retaining pin. The pilot's inability to reach the intended landing site was a direct result of the sudden power loss at cruise altitude. The collision with vegetation caused damage to the landing gear and wings. No further mechanical anomalies were reported that would have contributed to the event.

Safety message

Routine pre-flight inspections must include verification that all cotter pins and retaining hardware are present and secure on engine controls. Missing fasteners can lead to catastrophic control disconnection during flight.

Probable cause

The pilot's inability to reach the intended landing area due to a sudden loss of engine power, which was caused by a disconnected throttle linkage resulting from a missing cotter pin.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001213X34785. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.