Beech A23-24 N3412C accident near Burns Flat, Oklahoma

Probable cause

The mechanic’s improper maintenance when he reinstalled the fuel servo during the last annual inspection, which resulted in a loss of engine power during cruise flight when the throttle control rod-end disconnected from the fuel servo throttle linkage.

NTSB analysis

The pilot and his 3 passengers were on a personal night flight when the airplane had a gradual loss of engine power. The pilot was unable to restore engine power and a forced landing was completed to a grass field. The airplane’s main landing gear collapsed when the pilot intentionally swerved the airplane to avoid a tree after landing, which resulted in substantial damage to the horizontal stabilizer and both wings.

A postaccident examination revealed that the throttle control rod-end was not connected to the fuel servo throttle linkage. Additionally, the required retaining bolt, washer, and self-locking nut were not located during the investigation. The airplane had accumulated 8.72 flight hours since the last annual inspection, during which the fuel servo had been removed from the engine and overhauled. It is likely that the mechanic who reinstalled the fuel servo did not adequately torque the self-locking nut that secured the retaining bolt, which allowed the self-locking nut to back-off the retaining bolt. The airplane had a partial loss of engine power when the throttle control rod-end disconnected from the unsecured retaining bolt. The pilot did not have the ability to control engine power after the throttle control rod-end disconnected from the fuel servo throttle linkage.

Text from the NTSB. Open the NTSB docket for CEN20LA292 for the full record.