Accident Summary
On August 4, 2015, about 1305 central daylight time, a Beech A36 airplane, N17544, experienced a loss of engine power near Austin, Texas. The pilot and passenger sustained minor injuries, and the airplane was substantially damaged during the forced landing. The aircraft was registered to N17544 LLC and operated by a private individual under 14 CFR Part 91 as a personal flight. Visual meteorological conditions prevailed, and no flight plan was filed. The local flight originated from Austin-Bergstrom International Airport (KAUS) just prior to the accident.
Flight Details
The pilot reported that the engine's manifold pressure was decreasing at a lower altitude than normal and that the high-end fuel flow was not set properly. The purpose of the flight was to monitor manifold pressure and fuel flow, and to make adjustments to the turbonormalizer wastegate system and fuel pump. Before the flight, a mechanic had repaired a minor induction leak.
The pilot described the takeoff roll as normal with full engine power. Immediately after rotation, about 150 feet above ground level, the fuel flow was slightly below normal at 25 to 26 gallons per hour (GPH), compared to the usual 30 to 31 GPH. The pilot considered this not unusual since the fuel pump had been overhauled a few hours prior. The boost pump was set to HIGH, and fuel flow increased to 30 GPH and stabilized. A few seconds later, fuel flow dropped to about 3 GPH, and the engine stopped producing power. Switching the boost pump off and on did not change fuel flow. When the throttle was reduced, the engine momentarily surged, but power could not be restored. The pilot performed a forced landing to a field.
Engine Examination
The airplane was transported to a secure facility for examination. The J.P. Instruments Engine Data Monitor recorded data showing fuel flow decreasing from 24.9 GPH at 1301:10 to 3.9 GPH at 1302:10, with a corresponding drop in RPM from 2628 to 1503. Review of data from previous flights indicated intermittent fuel pressure readings on numerous flights, with fuel pressure varying with fuel flow at high RPM settings, though on some flights it remained constant at 6.4 psi.
An engine test run was conducted on October 29, 2015, with the engine still mounted on the airplane. Representatives from the NTSB, Continental Motors, Textron Aviation, and Tornado Alley attended. The engine started and reached maximum rated power but then lost power. The electric fuel boost pump temporarily restored power, but the engine lost power again. Maximum fuel flow recorded was 33.3 GPH with the boost pump off and 31.2 GPH with it on.
The fuel pump was examined and found to be part number 646210-2, which was not the engine manufacturer's recommended pump for this engine model. According to Tornado Alley, the correct part number should have been FT-B8.5/1-632818-2.
The fuel pump was sent to Great Planes Fuel Metering for flow testing under FAA auspices. Against Tornado Alley's specifications, at 2,700 RPM, the pump's flow pressure was 59.2 psi, far exceeding the maximum of 31 psi. When reduced to 31 psi, the pump provided 51.5 GPH, whereas the recommended maximum fuel flow is 32 GPH. When the aneroid was adjusted correctly, the pump produced 31.3 GPH. The engine data monitor did not record fuel flows comparable to those found during testing, and the reason for the discrepancy could not be determined.
Maintenance History
The Continental IO-520-BA12A engine had been modified in 2001 via supplemental type certificate for a Tornado Alley conversion. It was overhauled on December 28, 2014, with the last annual inspection completed on January 2, 2015. On June 23, 2015, the fuel pump, part number 646210-2, was overhauled at the owner's request. An Authorized Release Certificate Form 8130-3 noted: "Overhauled calibrated good as per TCM fuel injection OH manual." The pump was reinstalled on June 30, 2015, the fuel flow adjusted, and the airplane returned to service. It could not be determined when the incorrect fuel pump was originally installed.