SEA03FA124 · Beech A36TC

The modified single-engine, turboprop airplane had a commercial-rated pilot/owner in the right front seat who was the pilot in command (PIC), a private pilot in the left front seat, and a student pilot in the rear seat. The purpose of the flight was to proceed to a nearby airport in order to refuel the aircraft prior to a longer flight back to its home base. According to the private pilot in the left seat, after the engine was started, the after-market, panel-mounted, fuel management system/fuel flow meter indicated a "Fuel Remaining" of 235 pounds, and at that same point in time, the left main fuel tank gauge was at the top of the yellow arc (approximately 15 gallons), and the right main fuel tank gauge needle was at the bottom of the yellow arc (approximately empty). There was no operating restriction indicating the aircraft could not be operated in that fuel configuration. Believing that there was adequate fuel for the flight, the PIC departed for what should have been a flight of ten minutes or less. After departure, a climbing right turn was made followed by the aircraft leveling off approximately 2,000 feet above the terrain, and soon thereafter the right fuel tank "Fuel Low" light came on. About one minute later the engine lost power. The PIC was not able to restart the engine, and therefore found it necessary to execute a forced landing in a wheat field located among hilly terrain. Because there were power lines at the approach end of the field, the PIC was not able to touch down until the aircraft was just past half-way down the field. Although the touchdown was successful, the PIC was unable to stop the aircraft before it exited the far end of the field and rolled/slid into a deep ravine. Subsequent inspections of the airframe, and an inspection/test run of the engine, revealed no system malfunctions. A post-accident review revealed that the aircraft's fuel system had been significantly modified during a major alteration that was never approved by the FAA. As part of the alteration, the route by which the excess fuel in the header tank was rerouted through the fuel system was significantly lengthened, and no approved flight tests had been performed to ensure that, after the alteration, adequate fuel would be supplied to the engine at all attitudes, power settings, fuel load totals, and fuel load distributions. It was also determined that, during the installation of the after-market fuel management system/fuel flow meter by an avionics shop, an incorrect calibration factor was entered in the unit, which would result in displaying an erroneous indication of the amount of fuel used by about 9 percent less than the actual amount. With an unaltered fuel system, the aircraft should have arrived at its destination with about 11 minutes of fuel remaining, and because there were no major alteration-related amendments made to the Pilot’s Operating Manual, the pilot had no way of knowing that the engine would lose power en route.

Verbatim NTSB analysis and probable cause from the NTSB dataset