NTSB Factual Report

HISTORY OF FLIGHT

On April 2, 2014, about 1940 eastern daylight time, a kit-built, experimental-amateur built Zenith CH-750, N938VP, was substantial damaged during a forced landing near Venus, Florida. The certificated private pilot and passenger were not injured. The airplane was registered to and operated by a private individual under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91, as a personal flight. Visual meteorological conditions prevailed and no flight plan was filed for the flight, which departed from Lakeland Linder Regional Airport (LAL), Lakeland, Florida, about 1850, and was destined for LaBelle Municipal Airport (X14), LaBelle, Florida.

The pilot reported that prior to departure the fuel gauges indicated approximately three-fourths full for both the left and right fuel tanks; however, he did not visually inspect the fuel quantity. About 18 miles from the destination, the engine lost total power and he attempted to restart the engine. The pilot subsequently made an off airport landing to a pasture. During the off airport landing, the airplane encountered some brush, which separated the nose wheel from the airplane; the airplane nosed over, and subsequently came to rest inverted. He further reported that after the airplane came to rest the fuel selector valve was selected from the "ON" to the "OFF" position and noted that no fuel was leaking from either of the fuel tanks.

A postaccident examination by a Federal Aviation Administration inspector revealed that the left fuel tank was devoid of fuel and the right fuel tank had approximately 6 gallons of fuel remaining. The forward portion of the airplane's fuselage, both wings, and the rudder were substantially damaged. The fuel line to the carburetor was disconnected, the fuel selector valve was placed 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 noted around the hole or vents.

PERSONNEL INFORMATION

The pilot, age 75, held a private pilot certificate with a rating for airplane single-engine land, and a third class medical certificate. The pilot reported 1,434 total hours of flight experience, 76 hours of which were in the accident airplane make and model.

AIRCRAFT 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-hp engine, driving an Ed Sterba fixed-pitch propeller. The airplane's most recent condition inspection was completed on March 5, 2014 with an airframe total time of 76.3 hours.

METEOROLOGICAL INFORMATION

The 1953 recorded weather observation at Punta Gorda Airport (PGD), Punta Gorda, Florida, located about 26 miles to the west of the accident location, indicated wind from 280 degrees at 6 knots, 10 miles visibility, clear skies, temperature 23 degrees C, dew point 16 degrees C; altimeter setting 30.14 inches of mercury.

ADDITIONAL INFORMATION

The airplane was equipped with two rigid 12-gallon fuel tanks, in which one tank was located in each wing. The fuel system routed fuel, via gravity feed, from the aft side of the fuel tank, through a fingerscreen which was attached to a 3/8 inch inside diameter hose. The fuel hose from the right fuel tank was routed along the top of the airplane cabin to a 3/8 inch Tee where it was connected to the left fuel tank. From the Tee, the fuel line routed down the side of the airplane, inside the side channel on the pilot side, to the gascolator, the fuel "ON/OFF" valve, and then through the firewall to the carburetor. The fuel indication system was an electric float type system. The airplane had no interconnecting fuel venting system and each fuel tank was independently vented through the fuel caps. The fuel system does not, nor was it required to utilize, a fuel boost pump. A note located on the manufacturer provided "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."

Zenith Aircraft Builders and Flyers Internet Forum

According to several postings on the forum dated between May 18, 2011, and August 24, 2011, revealed similar in flight fuel starvation issues. The general consensus of the forum discussion supported that a partial or complete vacuum developed during fuel consumption, which resulted in the fuel in the left fuel tank being consumed prior to the total power loss and the right fuel tank being at or near maximum capacity. One comment reported that the fuel caps provided with the kit were replaced with fuel caps that had a tube protruding forward in the airstream to provide a "positive pressure" within the fuel tanks. Several of the comments revealed that after landing the fuel quantity would equalize in each fuel tank.

CFR 23.975(a)(3) "Fuel tank vents and carburetor vapor vents" stated "The venting capacity must allow the rapid relief of excessive differences of pressure between the interior and exterior of the tank."

Advisory Circular 90-89A "Amateur-Built Aircraft and Ultralight Flight Testing Handbook" Chapter 1, Section 11 "Additional Engine Tests" 4e(2) stated in part "…with minimum fuel in the tanks, disconnect the fuel line to carburetor. The fuel flow with a gravity flow system should be 150 percent of the fuel consumption of the engine at full throttle…"

NTSB Probable Cause

The fuel system’s inadequate design, which resulted in negative pressure in the right fuel tank and a total loss of engine power during cruise flight due to fuel starvation.