Accident Overview
A public-use firefighting training flight supervised by the Department of Interior, Bureau of Land Management (BLM) ended when the airplane's engine lost power as the pilot turned onto the base leg of a simulated fire retardant drop pattern. The airplane subsequently stalled and collided with the ground during an uncontrolled descent.
Witness Account
A witness reported hearing the engine surge several times. After the surges, the airplane's bank angle increased, and the aircraft descended. The airplane impacted the ground in a near-vertical, nose-down pitch attitude.
Investigation Findings
Examination of the airframe and engine revealed no evidence of any preimpact mechanical malfunction. The airplane was dispatched with adequate fuel for the planned flight. However, during the investigation, no fuel was found in either the left wing fuel tank or the header tank; both had retained their integrity. The right wing fuel tank was found ruptured.
The pilot-operated valve that allows fuel to flow between the main fuel tanks to equalize the amount of fuel in each tank was found in the closed position. The flight manual provided guidance regarding equalizing unbalanced wing tank fuel quantity levels to avoid fuel starvation from unequal consumption of fuel in the tanks. The airplane was not equipped with optional low-fuel warning lights in the cockpit.
Propeller Replacement
Examination also determined that the AW-2-30 propeller certificated for the airplane had been replaced with a larger, unapproved AW-2 propeller. The airplane’s propeller logbook did not reflect this change.