Event
On 25 July 1998 at 1834 hours UTC, an Enstrom F-28C-2-UK helicopter (registration G-BHAX) was en route from Hereford to a private landing site at Neston on the Wirral. The pilot, who held a Private Pilot's Licence (Helicopters) and had 197 hours total flying experience (all on type), had obtained permission from Liverpool Approach to enter the Control Zone. During the flight, the pilot became aware of a burning smell in the cockpit, accompanied by some smoke. A Mayday call was transmitted immediately, and the pilot performed an emergency landing into a nearby field. After landing, the helicopter was shut down and evacuated. Police attended the scene but their assistance was not required. The pilot subsequently made a further radio call to Liverpool ATC to cancel the Mayday. No injuries were reported among the crew (1) or passengers (2). The helicopter sustained damage limited to a charred cable shroud.
Investigation
Post-flight inspection revealed a small hole in the exhaust pipe assembly, located immediately upstream of the turbocharger unit. Closer examination determined that the hole was in the bead of a weld that had been part of an earlier repair. This hole allowed a jet of exhaust gas to be directed onto a shroud-covered electrical wire that supplied the landing light, resulting in partial melting of the shroud. Approximately three months had elapsed since the last inspection, an Annual Inspection performed on the engine. A search of the CAA database found no similar occurrences.
Cause
A hole in the exhaust pipe assembly weld, originating from an earlier repair, caused a jet of exhaust gas to be directed onto a shroud-covered electrical wire, leading to partial melting of the shroud and the subsequent burning smell and smoke in the cockpit.