N337JCessna T337D · 1968

On July 7, 2017, about 0735 eastern daylight time, a Cessna T337D, N337J, was substantially damaged during a forced landing near Greenwood County Airport (GRD), Greenwood, South Carolina. The flight instructor and a private pilot sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the local instructional flight. The airplane was operated under the provisions of 14 Code of Federal Regulations Part 91.The flight instructor stated that the purpose of the flight was for the single-engine rated private pilot (student) to become familiar with the accident airplane as he worked toward an instrument rating. The private pilot performed the preflight inspection with no anomalies noted. The flight instructor stated that their inspection of the fuel tanks revealed that they were ¾ full, which they verified on the airplane's fuel gauges. The student stated that during the preflight inspection they did not visually check the fuel tanks but noted that the fuel gages read between ½ and ¾ full. The engine run-up was normal and they departed from runway 27.

After departure, they practiced maneuvers uneventfully for about 30 minutes and then performed one aerodynamic stall. After practicing the stall, the front engine started to surge from high power to low power and then lost all power. The flight instructor told the pilot to turn back to the airport and fly to the runway while he looked in the emergency checklist for the engine-out procedure. The rear engine was still operating normally at the time. The flight instructor turned the fuel boost pump on, switched the fuel tank from main to auxiliary, and then back to main in an attempt to restore power to the front engine, to no avail. He recalled that sometime during the flight back to the airport, the rear engine also experienced a total loss of power. The airplane was too low to reach the runway, and the pilot transferred control to the flight instructor, who performed a forced landing into trees.

Examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed that the airplane came to rest on its right side. The right wing separated from the fuselage and was found inverted on the fuselage. The left wing and strut were still attached to the fuselage. A fuel sample was taken from the left wing auxiliary sump and found to be blue in color and absent of visible debris. The right-wing fuel tanks were not accessible. The salvage crew that removed the airplane from the accident site, stated to the FAA inspector that they removed 6 gallons of fuel in the left wing and no fuel was in the right wing. The FAA inspector further stated there was no smell of fuel at the accident site. Both wings had impact marks consistent with hitting trees. The front and rear engine propellers did not exhibit rotational scoring. The landing gear were extended.

Examination of both engines revealed evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation. The four-main fuel tank fuel quantity sender units were removed and tested with an ohm meter. In the empty position, the left outboard fuel sender had a resistance valve equal to an approximately half-full reading. The left and right inboard fuel senders had a resistance valve equal to an approximately full tank reading. The right outboard fuel sender unit displayed inconsistent resistance readings throughout its range of travel.

The airplane was equipped with a main fuel tank in each wing and an auxiliary fuel tank in each wing, which combined held a total of 131 gallons of fuel, with 128 gallons of useable fuel, and 3 gallons of unusable fuel. Each main fuel tank was comprised of two metal tanks, one outboard of the other, connected with hoses. Fuel automatically flowed from the outboard tank to the inboard tank through the hoses via gravity.

Each main fuel tank was equipped with two float-type fuel level sender units, one in the outboard tank and one in the inboard tank. The two sender units were connected electrically in parallel to a fuel quantity gage in the cockpit.

On November 29, 1999, the airframe manufacturer released mandatory Service Bulletin MEB99-21, which was applicable several models of airplane including the accident airplane . The purpose of the service bulletin was, "To inspect the Stewart Warner manufactured fuel quantity indicating system for verification that each fuel tank quantity gauge indicates empty when the fuel tank contains only unusable fuel and indicates full when the fuel tank is full." The service bulletin dictated that an initial inspection be completed within 100 hours of operation or 12 months, whichever occurred first, and should subsequent reoccur every 12 months.

The airplane's most recent annual inspection was completed on February 24, 2017 at 2,591 total airframe flight hours. Review of the airplane's maintenance logbooks revealed no evidence that MEB99-21 had been complied with.