Flight Details
The aircraft, a Piper PA-18-150 registered as G-WLAC, was engaged in circuit training at White Waltham Airfield, Berkshire, on 31 December 2000. The flight was a private training sortie focusing on crosswind approaches and landings to grass Runway 11. The handling pilot, under instruction, employed a left-hand oval circuit pattern and used the wing-down (side-slip) technique to counteract the crosswind. The surface wind was reported as 160° at 11 knots.
Incident Sequence
After three successful approaches, the fourth approach was initiated with a right-wing-low configuration using right aileron and left rudder from approximately 300 feet above ground level (agl). The touchdown was uneventful. The pilot then retracted the flaps, set carburettor heat to cold, and smoothly applied full power for a touch-and-go landing. At rotation speed, the pilot adopted the climb attitude, and the aircraft began climbing at 75 mph. At about 30 feet agl, the engine suddenly failed without warning.
The instructor assumed control and attempted a straight-ahead landing. However, insufficient runway remained to stop before the perimeter hedge. The instructor deliberately induced a ground loop to the right, bringing the aircraft to a halt south of the runway. During the ground loop, the engine restarted without crew input. The aircraft sustained a twisted fuselage and the tailwheel was damaged beyond repair. Both occupants were uninjured.
Investigation Findings
In his report, the pilot suggested carburettor icing as a possible cause. However, investigators deemed this unlikely due to the sudden nature of the power loss, the prior use of carburettor heat, and the absence of typical icing symptoms. An examination by the flying club engineers found no engine faults. There was no evidence of water in the fuel system; the right main tank was approximately three-quarters full. The fuel selector was correctly positioned to the right tank, and fuel flow checks were normal. The spark plugs showed no oiling or sooting, and the electrical system was serviceable.
Fuel System Considerations
The PA-18-150 features a main fuel tank in each wing, with a small header tank (approximately 2 US quarts) located between the main tank and the engine. The header tank for the right wing is mounted aft of the rear seat, oriented along the aircraft's horizontal axis. The engineers opined that the engine might have been starved of fuel after prolonged sideslipping. In a right-wing-down attitude, normal fuel feed from the right main tank could have been interrupted, making the engine dependent solely on the header tank. Repeated extended sideslip approaches may have depleted the header tank fuel, leading to exhaustion during the climb-out before flow from the right main tank could re-establish. The rightward ground loop likely restored fuel flow through normal gravitational forces.
A check of the manufacturer's database revealed no similar incidents of fuel starvation for this model. An airtest conducted after repairs, attempting to replicate the power loss after prolonged sideslips, was unsuccessful.