On April 27, 2004, at 0300 central daylight time, a Cessna 208B, N738FX, registered to and operated by Federal Express Corporation, made an emergency landing on a road during a training flight near Tunica, Mississippi. The non-scheduled flight was operated under the provisions of Title 14 CFR Part 135 with an instrument flight plan filed. Visual meteorological conditions prevailed at the time of the incident. The airline transport rated check airman, and airline transport rated pilot were uninjured, and the airplane was not damaged. The flight departed Memphis International Airport, Memphis, Tennessee, on April 27, 2004 at 0238. According to the check airman, during a demonstration procedure for loss of engine power, the check airman reduced the power lever to idle, turned on the ignition, and un-stowed and advanced the emergency power lever (EPL). The check airman felt a vibration and then heard a noise. He re-stowed the EPL and advanced the engine power lever. Flames exited the exhaust and the check airman shut down the engine, and made an emergency landing on a nearby road. After landing the airplane the two pilots attempted to remove the airplane from the roadway, and a passing truck struck the left wing of the airplane. Examination of the fuel flow control unit revealed that the EPL lever dead band was 7 degrees 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 dissembled and it was found that the plunger, which compresses the bellows, was allowed to contact the bellows prior to the required degrees of travel. In review of the Pratt & Whitney Canada service information letter it states: The Cessna Caravan 208/208B aircraft is equipped with a fuel control incorporating an emergency manual override system which is intended to be used in the event of a loss of Power Lever control due to loss of air pressure to the Fuel Control Unit during flight. The Emergency Power Lever does not duplicate the function of the Power Lever Assembly and should not be used as an optional means of controlling the engine. It must be left in the "Normal" position during all normal engine operation. 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.