Pilot May Have Inadvertently Caused Fullerton Crash

The pilot whose Beech Bonanza aircraft crashed into a Fullerton house last week might have inadvertently flipped a toggle switch that controls the mixture of fuel and air in the engine, possibly leading to a loss of power, a federal investigator said Tuesday.

“The fuel-air mixture is critical to the function of the engine,” said Bob Crispin, an air safety investigator for the National Transportation Safety Board in Los Angeles.

“Right now it is just a theory,” he said, adding that investigators are still gathering evidence. But he said the switch theory “looks promising.”

William Lofton, 50, of Sherman Oaks, an obstetrician at Kaiser Permanente Medical Center in Panorama City, died in the April 11 crash.

Witnesses reported seeing black smoke trailing the plane after it took off from Fullerton Airport about noon. The smoke was a sign that the toggle switch, which controls the fuel boost pump, was too high, allowing too rich a mixture of fuel, said the preliminary NTSB report.

“The engine manufacturer reported that if the fuel boost pump is turned to the ‘high’ position while the engine is at full throttle, there will be no appreciable loss of power,” the report said. “This will cause, however, dark smoke to become visible from the exhaust because this creates a rich air/fuel mixture.” But as the throttle is reduced, the aircraft will lose power and exhaust smoke will appear lighter, the report stated.

Witnesses near the crash site reported seeing grayish or light smoke. One witness said he heard the sound of the engine stopping just before the crash.

After the accident, investigators inspected the plane’s spark plugs, which “appeared sooted and black . . . consistent with a rich air/fuel mixture,” the report said.

Just after takeoff, Lofton reported that he had an open door and requested clearance to return for a landing, but NTSB investigators have found no connection between the door and the crash.

When a controller asked whether Lofton had an emergency, the pilot replied, “No emergency.” The controller said he then heard the same voice say, “Emergency, I got . . . “ before communications ceased.

The boost pump switch is immediately left of the gear selector handle, Crispin said. “It is possible that it could be bumped inadvertently. It is not a frequent cause [of crashes] but it is a recurring cause,” he said, adding that the final accident report won’t be finished for six to nine months.