Aircraft and Flight Details
The accident involved an Enstrom F-28C helicopter, registered G-BURI, with a single Lycoming HIO-360-E1AD piston engine. The aircraft was manufactured in 1978. The flight was a training sortie with two pilots on board; the commander held a Private Pilot's Licence (Helicopters) with an Assistant Flying Instructor (AFI) rating and had accumulated 1,098 flying hours, including 802 hours on type.
Accident Sequence
On 3 October 2002 at 1508 UTC, the helicopter was conducting an instructional flight near Redhill Aerodrome, Surrey. The pilots had been airborne for approximately 45 minutes, during which both had handled the aircraft, including practice engine failures in the hover. No control issues were noted. For the final landing, the instructor, seated in the right seat, took control to demonstrate a simulated engine-off landing. Weather conditions were good, with surface wind from 330° at 10 knots, visibility 10 km, and broken cloud at 3,000 feet amsl.
The instructor established the helicopter for a run-on landing in a north-westerly direction near the 08/26 Helicopter Strip. After a normal flare, the instructor experienced difficulty raising the collective lever. As a result, G-BURI landed in a nose-high attitude with a higher-than-normal rate of descent, causing the tail rotor to strike the ground. Damage was sustained to the tail rotor blades, drive shaft, and guard. Neither pilot was injured.
Examination Findings
Post-flight examination revealed interference between the right collective lever retaining pin and surrounding trim. The Enstrom's right collective lever is designed for easy installation and removal via a quick-release retaining pin with a locking lever. On G-BURI, the retaining pin was found to be bent, and the locating holes in the collective lever were deformed, allowing the pin and locking lever to rotate freely. With the locking lever rotated 180°, it would rest on a thin plate surrounding the cutout for the collective lever in the seat floor. This plate was found distorted at its aft right-hand edge, consistent with the locking lever having been trapped between the seat floor and the plate. In this position, a soft restriction occurred as the collective lever was raised; applying more force caused the plate to distort and pull its aft bolt from the underside lock nut, allowing full lever travel. The helicopter manufacturer confirmed that even with the locking lever under the seat floor plate, the collective movement would not result in a hard restriction.
No similar occurrences were found in discussions with the manufacturer or in the CAA MOR database for piston-engine Enstrom helicopters with this collective lever retention design.