What aircraft was involved and where did it happen?

The accident on 2001-10-13 involved a EUROPA, registration G-BWGH, at Little Sark, Island of Sark, GB.

What was the probable cause of the accident?

The engine seizure was caused by the loss of oil through a loose rocker cover, resulting from stripped threads in the cylinder head.

Engine failure leads to forced landing on Island of Sark

A Europa microlight experienced total engine oil loss and subsequent seizure during a flight from Jersey, resulting in a forced landing in a small field on Little Sark.

What happened

On 13 October 2001, a Europa aircraft, registration G-BWGH, was performing the final leg of a nine-day tour of northern France, flying from Jersey to Exeter. While climbing through approximately 2,600 feet, the pilot detected a hot smell and observed that the engine oil pressure had dropped to zero. Shortly after, the engine began running roughly before failing completely.

Following advice from Air Traffic Control, the pilot initially considered heading towards Guernsey but decided to attempt a landing on the island of Sark to avoid ditching in the sea. Upon approaching Little Sark, the pilot found the available fields to be extremely small. After assessing that the main island of Sark was too low for a safe approach, the pilot opted to force land in a small field. The pilot executed a heavy landing into the wind, attempting to use a bank at the edge of the field to arrest momentum. The aircraft ground-looped, causing the tail to strike a bank, but the occupants escaped the wreckage without injury.

The investigation

AAIB investigators recovered the wreckage to Guernsey to examine the engine and its components. The investigation established that the engine had seized due to a complete lack of oil. Detailed inspection revealed that the forward right-hand cylinder rocker cover was loose, which had permitted oil to escape the engine during operation.

Technical examination showed that the single steel screw securing the rocker cover to the aluminium alloy cylinder head had stripped the internal threads. While it was initially suspected that over-torquing the screw caused the damage, testing conducted by the AAIB and a Rotax distributor demonstrated that over-torquing the screw to levels beyond the recommended 10 Nm would cause the screw to fail in tension rather than stripping the aluminium threads. Records indicated the rocker covers had been recently handled by an approved overhaul organisation in May 2001.

Findings

The engine experienced a total loss of oil, leading to engine seizure.
The failure was caused by stripped aluminium threads within the cylinder head, which allowed the rocker cover to become loose.
The loose cover permitted engine oil to drain overboard while the engine was running.
There was insufficient evidence to determine the specific cause of the thread stripping.