What aircraft was involved and where did it happen?

The accident on 2000-12-31 involved a PIPER PA-18-150, registration G-WLAC, at White Waltham Airfield, Berkshire, GB.

What was the probable cause of the accident?

The engine likely suffered from fuel starvation because the fuel in the header tank was exhausted during repeated, prolonged side-slip maneuvers, leaving the engine without sufficient fuel until the ground loop re-established normal flow.

Engine failure during training flight at White Waltham

A Piper PA-18-150 experienced a sudden engine failure during a touch-and-go maneuver, leading to a deliberate ground loop to avoid an obstacle.

What happened

On 31 December 2000, a Piper PA-18-150, registration G-WLAC, was conducting a private training flight at White Waltham Airfield, Berkshire. The flight involved a circuit training session focused on practicing crosswind approaches and landings on the grass runway. During the session, the pilot under instruction utilized side-slip techniques to manage a 11-knot crosswind.

Following three successful approaches, the pilot attempted a fourth approach using a right-wing-low technique. The touchdown was successful, and the pilot proceeded with a touch-and-go maneuver by retracting flaps, adjusting carburetor heat, and applying full power. As the aircraft reached rotation speed and began its climb at approximately 75 mph, the engine suffered a sudden loss of power at an altitude of roughly 30 feet.

The instructor took control of the aircraft and attempted to land straight ahead. However, realizing there was insufficient runway to stop before hitting a perimeter hedge, the instructor executed a deliberate ground loop to the right. The aircraft eventually came to rest south of the runway, resulting in a twisted fuselage and damaged tailwheel. Notably, the engine restarted on its own during the ground loop.

The investigation

Investigators examined the engine and fuel systems to determine the cause of the power loss. While the pilot suggested carburetor icing as a potential factor, investigators found no evidence of icing symptoms or related mechanical issues. Maintenance checks by the flying club engineers revealed that the engine was in good working order, with no evidence of water in the fuel, no issues with the electrical system, and no signs of oiling or sooting on the spark plugs.

The investigation focused on the fuel delivery system, specifically the relationship between the right main tank and the small header tank. The aircraft's design includes a header tank intended to ensure constant fuel flow. Engineers considered whether the repeated side-slipping maneuvers during the training session had depleted the fuel in the header tank, leaving the engine dependent on a limited supply.

Findings

The engine failure occurred during the climb phase of a touch-and-go maneuver.
The engine restarted spontaneously during the ground loop maneuver.
Fuel starvation caused by the depletion of the header tank during prolonged side-slip maneuvers is the most likely cause of the power loss.
It is believed that the fuel flow from the right main tank was interrupted by the aircraft's attitude during side-slips, causing the engine to rely on the small header tank until it was exhausted.