Incident Overview
On 18 July 2004 at 1240 hours, an Enstrom 280C helicopter, registration G-BRPO, was involved in a crash-landing near Oulton Park Racing Circuit in Cheshire. The aircraft was on a private VFR flight from Hawarden to Knutsford. The sole occupant, the pilot, was uninjured. The helicopter sustained substantial damage.
Flight History and Initial Symptoms
The helicopter had been out of service for six months undergoing maintenance and awaiting parts. After its return to service, it had flown approximately 3½ hours over five flights spread across several days. The pilot performed a daily inspection, including an engine oil level check, at the start of each day's flying. On the day of the accident, the pilot completed the daily check as usual.
During the flight, near Oulton Park, the pilot contacted Manchester ATC to request en-route clearance. Two minutes later, ATC lost contact with the helicopter and subsequently received a phone call reporting the crash-landing. No distress call had been received.
Pilot's Account and Actions
The pilot reported that the first indication of a problem was light smoke in the cockpit, quickly followed by a feeling of heat at his back. He initiated an emergency descent with power, as there was no indication of engine malfunction at that time. At approximately 600 feet above ground level, while downwind of his intended landing area, he believed the engine stopped. He was poorly positioned for landing, and during the subsequent touchdown the helicopter rolled over.
In a later discussion with an AAIB inspector, the pilot stated he could not be certain the engine had stopped, noted no indications of engine failure, and candidly suggested that in his concern about the fire and the need to land immediately, he may have mishandled the landing, possibly by flaring late from a high rate of descent.
Post-Accident Inspection Findings
The helicopter remained on its left side for six to seven hours until recovery. AAIB inspection found no evidence of fire except for local overheating of the skin adjacent to the exhaust outlet. The engine turned normally, and the drive train appeared intact prior to landing. The engine contained very little oil, and when spark plugs were removed, large quantities of fairly clean oil were found in the cylinders. Overall, there was no indication of an engine malfunction.
The engine was turbocharged, with the turbocharger outlet passing via a short exhaust pipe through an aperture in the skin to dump overboard. This pipe was found detached from the turbocharger. The pilot assumed it had been dislodged during the landing, but the clamp securing it had fractured in fatigue, allowing it to become dislodged in flight. The pipe also connected to a bypass pipe from the engine exhaust system. Once dislodged, it allowed exhaust from near the cylinders to be directed at the bulkhead immediately behind the pilot, causing the entire engine compartment to fill with exhaust fumes, which accounted for the smoke in the cockpit.
Clamp Condition and Manufacturer's Advice
The manufacturer's agent advised that fractures of this type of clamp are rare, and in this particular case the clamp appeared quite old. However, there is no requirement to replace it if it appears serviceable.
Conclusion
It seems probable that the pilot took the only action available given the symptoms of smoke and heat, and that the subsequent roll-over was simply an unfortunate consequence.