What happened
On 27 June 1998, an Aerospatiale AS350B1, registration G-ROIN, was conducting a private training flight at Redhill Aerodrome in Surrey. During the flight, the instructor was demonstrating the consequences of small reductions in the collective lever while maintaining a hover at approximately 10 feet above ground level.
During the third iteration of this demonstration, the helicopter descended as expected to roughly 5 feet above the ground. However, the rate of descent then increased abruptly. Although the instructor reacted immediately by raising the collective lever, the aircraft was unable to arrest the descent in time, resulting in a firm landing.
Following the touchdown, the crew did not perceive the event to be a significant emergency, and the flight proceeded without further incident. However, upon landing, the instructor identified a crease in the lower surface skin of the tail boom, located just behind the transport joint. The instructor noted that while the landing was harder than intended, it did not meet the criteria for a heavy landing.
The investigation
The investigation focused on the circumstances surrounding the sudden increase in the descent rate and the resulting impact. The examination established that the aircraft sustained structural damage to the tail boom skin as a direct result of the landing impact.