History of Flight
On April 2, 2014, at approximately 1940 eastern daylight time, an experimental amateur-built Zenith CH-750, registration N938VP, sustained substantial damage during a forced landing near Venus, Florida. The certificated private pilot and a passenger were not injured. The flight was operated as a personal flight under 14 CFR Part 91, having departed from Lakeland Linder Regional Airport (LAL), Lakeland, Florida, about 1850, with a destination of LaBelle Municipal Airport (X14), LaBelle, Florida. Visual meteorological conditions prevailed, and no flight plan was filed.
The pilot reported that before departure, the fuel gauges indicated approximately three-quarters full for both the left and right fuel tanks, but he did not visually inspect the fuel quantity. About 18 miles from the destination, the engine lost total power, and the pilot attempted to restart it. He subsequently executed an off-airport landing to a pasture. During the landing, the airplane encountered brush, which separated the nose wheel from the airframe; the airplane nosed over and came to rest inverted. After the airplane came to rest, the pilot moved the fuel selector valve from the ON to the OFF position and noted that no fuel was leaking from either fuel tank.
Aircraft and Pilot Information
The two-seat, high-wing, fixed-leading-edge slats, fixed-gear airplane was manufactured in 2013 and issued a special airworthiness certificate on March 9, 2013. It was powered by a Lycoming O-320-E2D 150-horsepower engine driving an Ed Sterba fixed-pitch propeller. The most recent condition inspection was completed on March 5, 2014, with an airframe total time of 76.3 hours. The pilot, age 75, held a private pilot certificate with a rating for airplane single-engine land and a third-class medical certificate. He reported 1,434 total hours of flight experience, of which 76 hours were in the accident airplane make and model.
Postaccident Examination
A Federal Aviation Administration inspector conducted a postaccident examination. The left fuel tank was devoid of fuel, and the right fuel tank had approximately 6 gallons of fuel remaining. The forward fuselage, both wings, and the rudder were substantially damaged. The fuel line to the carburetor was disconnected, the fuel selector valve was in the ON position, and fuel flowed freely with no debris or restriction noted. The vented fuel caps were examined, and no blockage or obstruction was found around the holes or vents.
Fuel System Details
The airplane was equipped with two rigid 12-gallon fuel tanks, one in each wing. Fuel was routed via gravity feed from the aft side of each tank through a fingerscreen attached to a 3/8-inch inside diameter hose. The fuel hose from the right tank ran along the top of the cabin to a 3/8-inch Tee, connecting to the left tank. From the Tee, the line ran down the side of the airplane, inside the pilot-side channel, to the gascolator, the fuel ON/OFF valve, and then through the firewall to the carburetor. The fuel indication system used electric float-type senders. There was no interconnecting fuel venting system; each tank was independently vented through the fuel caps. The fuel system did not include, nor was it required to have, a fuel boost pump. A note on the manufacturer's fuel line routing drawing stated, "check fuel flow prior to running the engine to ensure proper fuel flow and tank venting. Fuel flow should exceed twice required fuel flow at maximum engine RPM at high angle of attack."
Postings on the Zenith Aircraft Builders and Flyers Internet Forum, dated between May and August 2011, described similar in-flight fuel starvation issues. The forum discussion indicated that a partial or complete vacuum could develop during fuel consumption, resulting in fuel from the left tank being consumed before total power loss, while the right tank remained near maximum capacity. One comment noted that fuel caps provided with the kit were replaced with caps having a tube protruding forward in the airstream to provide positive pressure inside the tanks. Several comments indicated that after landing, fuel quantity would equalize between tanks.
Reference was made to 14 CFR 23.975(a)(3), which states that "the venting capacity must allow the rapid relief of excessive differences of pressure between the interior and exterior of the tank." Additionally, Advisory Circular 90-89A, "Amateur-Built Aircraft and Ultralight Flight Testing Handbook," recommends that for gravity feed systems, with minimum fuel in the tanks, fuel flow at the carburetor should be 150 percent of the engine's fuel consumption at full throttle.