Incident Details
During a demonstration procedure for loss of engine power, a check airman reduced the power lever to idle, turned on the ignition, un-stowed the emergency power lever (EPL), and advanced it. The check airman subsequently felt a vibration and heard a noise. He re-stowed the EPL and advanced the engine power lever. Flames exited the exhaust, prompting the check airman to shut down the engine and make an emergency landing on a nearby road.
After landing, the two pilots attempted to remove the airplane from the roadway. A passing truck struck the left wing of the airplane.
Examination Findings
Examination of the fuel flow control unit revealed that the EPL lever dead band was 7 degrees, which is below the minimum requirement of 25 to 35 degrees. The fuel flow control unit began fuel flow at 18 degrees of lever travel. The manual override was disassembled, and it was found that the plunger, which compresses the bellows, was allowed to contact the bellows prior to the required degrees of travel.
Operating Handbook Notes
Review of the pilot's operating handbook emergency procedures states: When using the emergency power lever, monitor gas generator RPM when reducing power near idle, to keep it from decreasing below 65% in flight. The emergency power lever may have a dead band, such that no engine response is observed during the initial forward travel from idle position.