Pitts Special Engine Failure- Fuel Starvation
Chad had just completed a negative G maneuver followed by a four-point roll then a pitch up to vertical. At this point 22 seconds into the video, the engine hiccups and quits.
Trading altitude (2,500′) for airspeed, Chad dives in an attempt to aerodynamically re-start the engine. The blades turn a few times, but doesn’t restart the engine.
Twenty-one seconds after the engine quit, Chad is at 1,000’ and turning toward a gravel road. While setting himself up to land, he then uses the electric starter, which finally starts the engine.Why It Happened
Like many aerobatic planes, the Pitts has an inverted fuel system. Chad’s Pitts has a 19 gallon fuel tank that feeds fuel into a flexible hose with a weight on the end called a flop tube. Gravity being a constant, both the fuel in the tank and the flop tube will always seek the “bottom” of the tank.
Chad makes a habit of never flying aerobatics with less than 6 gallons of fuel, including this flight. In this situation, an extended negative G maneuver caused the flop tube to lose contact with the fuel, which starved the engine of fuel.Lessons Learned
Over time, the flop tube in Chad’s Pitts lost some flexibility, which made it harder to reach the available fuel as the fuel level decreased. The flop tube has since been replaced.
Old v. new shows decreased flop tube flexibility courtesy Biplane Forums.
Chad has also increased his personal fuel minimum for negative G maneuvers to no less than 10 gallons in the tank.
Chad Barber has been an active pilot for six years and resides in Palm Beach, Fla. As owner of Barber Aviation, Chad provides aircraft delivery, aerobatic training, aerial photography, and aviation management services.