CESSNA 337G — Alamosa, CO

What happened

One witness reported that the pilot started both engines before takeoff and that both the front and rear engines were running for about 5 minutes before he started to taxi the airplane. Another witness reported seeing the airplane flying just after takeoff at a low altitude and then hearing the engine shut off before the airplane went out of sight behind a stand of trees. Another witness reported seeing the airplane flying at a low altitude when it suddenly lost altitude and nose dived toward the ground.

The twin-engine airplane's fuselage had two engines in tandem, one engine in front of the cabin and one engine behind the cabin. The airplane had retractable landing gear and a belly-attached cargo pod. Examinations of the rear engine's propeller blade assembly showed evidence that it was not producing power at impact. The front engine's propeller blade assembly showed evidence that it was producing power at impact. Examinations of the fuel distribution system revealed that the front engine fuel selector handle was set to the left tank. The front engine fuel selector valve was found between the "left tank" and "off" positions. The rear engine fuel selector handle and valve were found in the "off" position; therefore, the rear engine was most likely starved of available fuel, which is consistent with the physical and witness evidence of a loss of power to the rear engine. Further, given the witness statement that both engines were running before departure, it is likely that the fuel selector was inadvertently moved to the "off" position during, or shortly after, takeoff.

Detailed examinations of the airframe components and teardowns of both engines did not reveal any preexisting mechanical anomalies that would have contributed to the accident. The Pilot's Operating Handbook (POH) noted that the airplane's single-engine climb rate is reduced 15 feet per minute (fpm) with the belly cargo pod attached and 240 fpm when the gear is in transit. The actual weight of the airplane at the time of the accident could not be determined due to a lack of fuel and airplane empty weight information. A weight of 4,000 pounds, the lightest weight shown in the POH, was used for airplane performance calculations, which showed that, at the time of the accident, the airplane's single-engine climb rate with the belly cargo pod attached was about 99 fpm. Given that the main landing gear were likely in transit, the climb rate could have been reduced by as much as 240 fpm. In this condition, the airplane would not have been able to climb and the pilot would not have been able to maintain level flight.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.