CEN17LA092

The private pilot had recently completed building the airplane and had flown it about 10 hours. He reported that, during that time, the airplane had experienced fuel flow issues; specifically, fuel was not flowing evenly from the wing tanks. Fuel was supplied to the engine from both tanks via gravity; the tanks were not individually selectable. To remedy the uneven fuel flows, the airplane kit manufacturer suggested that the pilot add snorkels to each vented fuel tank cap. The pilot did so; however, this did not correct the uneven fuel flow. The pilot tried several combinations before closing the vented caps completely and using only snorkels, which was the configuration of the fuel system on the day of the accident. The pilot departed on the accident flight with 7 gallons of fuel in one tank and 8 gallons in the other. He flew for about one hour, and, while returning to the airport, he noted that the left fuel tank gauge was reading low and that the right fuel tank gauge was reading high. The engine subsequently experienced a total loss of power and the pilot performed an emergency landing in a field short of the runway. Although the loss of engine power is consistent with fuel starvation, it could not be determined why the fuel in the right tank failed to supply the engine; nor could the underlying reason for the uneven fuel flow be determined based on the information available.

On January 30, 2017, about 1000 central standard time, the pilot of a Zenith CH750 STOL, N1971C, made a forced landing in a field 3 miles east of Jennings, Louisiana, after the engine lost power. The pilot, the sole occupant on board, received minor injuries. The airplane was substantially damaged. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations (CFR) Part 91 as a personal flight. Visual meteorological conditions (VMC) prevailed at the time of the accident, and no flight plan had been filed. The local flight originated from Jennings, Louisiana, Airport (3R7) about 0900. The pilot had recently completed building the airplane and had logged about 10 hours. He was having fuel flow issues; specifically, fuel was not flowing evenly from the wing tanks. The Zenith CH750 is a high wing airplane and the fuel tanks, each holding 15 gallons, are in each wing. Fuel is gravity-fed to the carburetor and engine. Early tests showed a fuel flow of 2.5 gallons per minute via gravity feed, and 1.5 gallons per minute with the auxiliary fuel pump on. The vented fuel caps were plumbed together with a T-fitting above and behind the pilot seats. Fuel flowed down to an ON/OFF selector valve before travelling to a gascolator, an in-line fuel filter, an auxiliary fuel pump, and the carburetor. Sitting on the ramp, the fuel level in each tank evened out to within ¼-gallon of each other within minutes. Because of the uneven fuel flows, Zenith – the airplane kit manufacturer -- suggested that the pilot add snorkels to each vented cap. The pilot did so and the next test flight revealed fuel was being pushed out of one tank and draining from the opposite tank. The pilot tried several combinations before closing the vented caps completely and using only snorkels. On the morning of the accident, the pilot departed 3R7 with 7 gallons of fuel in one tank and 8 gallons in the other. He flew for about one hour, performing several full power climbs as per the Phase 1 certification protocol. Returning to the airport, he noted the left fuel tank gauge was reading low and the right fuel tank gauge was reading high. Zenith had told him that once the fuel level in one tank reached 1 to 2 gallons, the other tank would continue to supply fuel. He was aligned with the runway and on a 3-mile final approach and 1,800 when the engine lost power. Realizing he could not glide to the airport and was approaching a fence line with trees and a power line, he elected to make a forced landing in a field. When the airplane touched down, the nose gear dug into the soft ground and the airplane nosed over. The pilot said, "The cause of the crash. . .was fuel starvation due to the left tank running empty and the right tank not flowing to the engine."