Cessna T337 N337J accident near Greenwood, South Carolina

Probable cause

The pilots' inadequate preflight inspection, during which they failed to adequately verify the quantity of fuel, which resulted in fuel exhaustion, a subsequent total loss of power to both engines, and a forced landing into trees. Contributing to the accident were the erroneous fuel quantity displayed by the fuel quantity indicating system fuel sender units and the operator's failure to comply with a mandatory service bulletin addressing inaccuracies in the fuel quantity indicating system.

NTSB analysis

The flight instructor and private pilot, who did not have a multiengine rating, were conducting a familiarization flight in the centerline thrust, multiengine airplane. Following the preflight inspection, the instructor and the pilot believed that both fuel tanks were about 1/2 to 3/4 full. After practicing maneuvers uneventfully for about 30 minutes, the front engine lost all power. The instructor told the pilot to return to the departure airport; the rear engine was operating at this time. However, before reaching the airport, the rear engine lost all power. With insufficient altitude remaining to reach a runway, the pilot transferred control to the instructor, who then conducted a forced landing into trees.

Postaccident examination of the accident site revealed no smell of fuel, and only about 6 gallons of fuel (of a possible 131 gallons with all fuel tanks filled to capacity, 3 gallons of which were unusable) were recovered from both wing fuel tanks. Examination of both engines revealed no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation. The four fuel quantity sender units (two for each main fuel tank) were removed and tested with an ohm meter. In the empty position, the left outboard fuel sender unit displayed a resistance value equal to an approximate 1/2-tank reading. The left and right inboard fuel sender units displayed a resistance value equal to an approximate full-tank reading. The right outboard fuel sender unit displayed inconsistent resistance readings throughout its range of travel.

The airplane manufacturer published a mandatory service bulletin (SB) about 18 years before the accident, which required inspection of the fuel quantity indicating system to verify that each fuel gauge indicated the accurate fuel amount. The SB also required that an initial inspection of the system be completed within 100 hours of operation and subsequent recurring inspections every 12 months. Examination of the airplane's maintenance logbooks revealed no evidence of compliance with the SB.

Given the lack of fuel found at the accident site and that postaccident examination of the engines revealed no mechanical issues, it is likely that the pilots did not adequately verify the quantity of fuel during the preflight inspection, in part due to erroneous fuel quantity indications provided by the fuel quantity indicating system, which resulted in fuel exhaustion and a subsequent loss of all engine power to both engines. The airplane operator's failure to comply with the SB precluded the pilots from being able to identify the fuel quantity in flight.

Text from the NTSB. Open the NTSB docket for ERA17LA235 for the full record.