Aircraft: Beechcraft Debonair. Injuries: None. Location: St. George, Utah. Aircraft damage: Substantial.
What reportedly happened: According to the pilot, during cruise flight, the engine’s exhaust gas temperature was hotter than normal and the fuel flow was lower than normal.
The engine lost power and multiple attempts to restart the engine were unsuccessful. The pilot made a gear-up forced landing on a road.
The post-accident examination of the engine revealed that the mixture control arm was loose on the control shaft, and the nut that secured the control arm to the shaft was loose. The mixture control arm machined chamfer had formed splines and exhibited deformation and movement of material. The nut and control arm mating surfaces showed corresponding rub marks.
Investigators determined that it was likely that the loose mixture control arm and the vibration of the engine allowed for the mixture control shaft to rotate to an idle cut-off position, resulting in the loss of engine power.
Probable cause: The total loss of engine power due to the loose mixture control arm.
NTSB Identification: WPR12LA147
This March 2012 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.