What happened
During a demonstration procedure for loss of engine power, a check airman reduced the power lever to idle, activated the ignition, and advanced the emergency power lever (EBL). Upon advancing the lever, the check airman experienced vibration and noise. After re-stowing the EBL and advancing the engine power lever, flames exited the exhaust. The check airman subsequently shut down the engine and performed an emergency landing on a nearby road.
Following the landing, the two pilots attempted to move the Beechcraft aircraft from the roadway. During this process, a passing truck struck the left wing of the aircraft. There were no injuries reported in the incident.
The investigation
An examination of the fuel flow control unit revealed that the EBL lever dead band was 7 degrees below the minimum requirement of 25 to 35 degrees. Specifically, the fuel flow control unit began delivering fuel at 18 degrees of lever travel. Upon disassembling the manual override, investigators found that the plunger, which compresses the bellows, was allowed to contact the bellows prior to the required degrees of travel.
Findings
- The fuel flow control unit dead band was below the minimum specification.
- The plunger in the manual override contacted the bellows prematurely.