ERA18LA239

The pilot departed on a 35-nautical-mile flight with 9 gallons of fuel onboard. While en route, he noticed that the fuel quantity was decreasing faster than normal, and he elected to stop for fuel. During the descent toward the airport, the engine lost total power and the pilot subsequently performed a forced landing in a field. After touchdown, the airplane nosed over and came to rest inverted, resulting in substantial damage to the wings and fuselage. Examination of the airplane and engine revealed no evidence of preimpact mechanical anomalies that would have prevented normal engine operation. About 1/2 gallon of fuel was drained from the fuel tank after the accident; however, an unquantified amount spilled onto the ground during recovery, and the amount of fuel onboard at the time of the accident could not be determined. The right wing fuel tank was vented by a modified fuel cap. Holes were drilled in the top of the cap to allow air in the tank as fuel is consumed. The pilot recommended that a forward-facing tube vent be installed per a service letter issue by the kit manufacturer of a similar experimental, amateur-built airplane; however, the reason for loss of engine power and whether the modified fuel cap contributed to the accident could not be determined based on the available information.

On August 30, 2018, about 1530 eastern daylight time, an experimental, amateur-built Avid MK-4, N628X, was substantially damaged when it was involved in an accident near Harnett, North Carolina. The private pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The airplane was equipped with a 10-gallon fuel tank in each wing; however, the left wing tank had been previously capped due to a fuel contamination issue and was not in use during the accident flight. The pilot noted during his preflight inspection that there were about 9 gallons of automotive gas in the right tank, which he said, "should have been sufficient" for the 35-nautical-mile flight. The pilot stated that, less than 30 minutes into the flight, he noted that the fuel level had decreased below about half, which he described as abnormal, and he diverted to Harnett Regional Jetport Airport (HRJ), Harnett, North Carolina to refuel; however, during the descent, the engine lost total power. He turned on the auxiliary fuel pump but was unable to restart the engine, and subsequently performed a forced landing in a field. After touchdown, the airplane nosed over and came to rest inverted, resulting in substantial damage to the wings and fuselage. The pilot turned the fuel selector to the OFF position after the accident. According to the Federal Aviation Administration (FAA) inspector who performed an examination of the airplane, fuel was present on the ground under the right wing tank. When the airplane was recovered, fuel poured out of the wings, and about 1/2 gallon of fuel was captured from the right tank. The electric fuel pump was turned on and operated normally. All fuel lines were intact and a small amount of debris was noted. The engine's crankshaft was rotated by hand, and internal and valvetrain continuity was established. Examination of the airplane and engine revealed no evidence of preimpact mechanical anomalies that would have prevented normal engine operation. On the Pilot/Operator Aircraft Accident/Incident Report (NTSB form 6120.1/2), the pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation. Furthermore, in the "Operator/Owner Safety Recommendation" section of the report, he stated, "ensure that Avid and Kitfox aircraft wing tank fuel caps are vented with a forward facing 1 1/2 tube as per Kitfox Service Letter #7,” which was issued on May 6, 1997. The accident airplane's right wing fuel tank was vented by a modified fuel cap; holes were drilled in the top of the cap to allow air in the tank as fuel was consumed.