Accident Overview
During a low-level mapping flight, a twin-engine airplane suffered a loss of power in both engines, leading to an emergency landing in a field. The aircraft stalled just above the ground, and the right wing struck first. Seconds later, the right outboard fuel tank exploded. Both pilots exited the aircraft through the rear door.
Flight and Fuel Management
The pilot and copilot were conducting mapping flights at an altitude of about 300 feet above ground level. Although the copilot was not multi-engine rated, they regularly switched control of the airplane. On the accident flight, the pilot was in the right seat and the copilot in the left. After approximately 2 hours of flight, the pilot, who was flying at the time, switched fuel tanks from the inboard tanks to the outboard tanks. He did not inform the copilot of the switch. About 1.5 hours later, while the copilot was flying, the left engine began to surge and lose power. The pilot initiated the emergency procedure for an engine failure, starting with moving the fuel selectors back to the inboard tanks. However, power was not restored, and the airplane began losing altitude. The pilot took over control. The copilot stated that at that moment, both fuel quantity gauges read zero.
Emergency Landing and Egress
The pilot reported that the airplane stalled just above the ground during the emergency landing in a field. The right wing struck first, and the right outboard fuel tank exploded within a couple of seconds. The pilot and copilot egressed out the rear door without reported injuries.
Wreckage Examination
Examination of the wreckage revealed that neither engine showed evidence of power at impact. The left outboard fuel tank was completely full of fuel, while the left inboard tank was empty. Both right wing tanks were fire-damaged, and their fuel quantity at impact could not be determined. The fuel crossfeed valve was found in the crossfeed/open position, with no fuel observed in the valve or attached fuel lines during disassembly. The left fuel selector valve was in the OFF position, and no fuel was present in the fuel line between the valve and gascolator. The right fuel selector valve was damaged by fire, and its position at impact could not be determined. No other anomalies were noted in the engines or airframe.
Fuel Consumption Analysis
According to the pilot, all fuel tanks were full before the flight. The pilot's operating manual indicated that the airplane likely consumed about 33.1 gallons per hour, or about 115 gallons during the 3.5-hour flight. Since the inboard fuel cells held 56 gallons each (112 gallons total), and the left inboard tank was found empty, it is likely that each engine was drawing fuel from its respective inboard tank throughout the flight until those tanks were empty. The left engine lost power first, and the right engine likely lost power just before impact. The post-accident positions of the crossfeed valve (on) and left fuel selector (off) did not correspond to the pilot's statements about his positioning of the fuel selector valves during the flight.
Investigation Findings
The fuel panel was located between and behind the pilots' seats, requiring them to look down and back to see it when making changes. The investigation concluded that it is likely the pilot misconfigured the valves when he switched tanks 2 hours into the flight, when he switched tanks after the left engine lost power, or on both occasions. The copilot was unlikely to have noticed an incorrect switch selection due to the panel's location and because the pilot did not verbalize the change.