Mechanical malfunction brings down Debonair

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.

Comments

  1. Everything is a chain of events,I would not be responding to this without an attack against an unknown mechanic,(that is the “chain” in this case).
    1. 1165 SMOH, possibly the last time the fuel control was disconnected, the report does not say.
    2. Five months since the annual, things do go wrong on machines, the mechanic can only insure airworthiness at the time of the inspection.
    3. The engine was running hot with low fuel flow, could be trouble? Engine then stops operating.
    4. The aircraft is at 4500 AGL and the commercial pilot did not put the gear down before landing on a road.
    The engine failed either because (it ran a very long time if this were the case) of improper control installation, or more likely the attachment simply failed. The aircraft was damaged because the pilot did not get the gear down before landing despite starting 4500 feet in the air. Engine failure alone does not bend airplanes, fly what you have left and fly it to the ground, following the parts of the check-list that still apply.

  2. Why did he land gear up on a road? Somethings not right here.

  3. …uh oh – forgot to check on preflight for loose nut on mixture control…..or was the loose “nut” the mechanic that installed the thing improperly…………………go figure!

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