Incident
On 12 August 1998, at approximately 1535 hours, a Schweizer 269C-1 helicopter, registration G-BXTL, was engaged in dual instruction at Oxford Airport. The aircraft, powered by a single Lycoming piston engine and manufactured in 1998, was being used for engine-off landing practice. The weather was fine with a westerly wind of 15 knots.
The student pilot performed four approaches, with the instructor either demonstrating or assisting during the flare and touchdown. Three landings were uneventful, but during one landing on grass, the aircraft yawed left and right during the ground slide. After a brief debrief on the ground, the student lifted off and executed a spot turn into a downwind hover at approximately 10 feet. At that point, a loud bang was heard. The instructor immediately assumed control and landed the helicopter on the grass, where it was observed that the tail boom had collapsed. The aircraft remained upright, and both crew members evacuated without difficulty.
Examination
An engineering inspection of the tail boom revealed that the attachment fittings had failed in overload. No evidence of pre-existing damage or cracks was found. The instructor, who held a Commercial Pilot's Licence with an Instructor Rating (Helicopters), aged 39, with 3,510 total flying hours (270 on type, 210 in the last 90 days, 71 in the last 28 days), considered that all landings during the flight had been normal. However, he concluded that damage to the tail boom likely occurred during one of the earlier landings.
The nature of damage was limited to the failure of the tail boom attachment fittings. No injuries were reported among the two crew members.