What happened
On 13 March 2018, a Eurocopter AS355N, registration 9M-PHJ, was conducting a training sortie at Sibu Airport (WBGS) in Sarawak, Malaysia. The flight was part of a captaincy upgrade program for a pilot, with a qualified instructor present in the left seat. The session focused on helipad procedures, specifically practicing rejected take-offs.
After several successful maneuvers, the crew attempted a simulated one engine inoperative (OEI) rejected take-off at an altitude of 50 feet. During the recovery phase, the aircraft failed to respond as expected when the pilot applied collective to cushion the descent. This resulted in a very hard landing on the runway. While the impact caused significant damage to the aircraft's structure, including bent skids and a cracked canopy, both pilots escaped without injury.
The investigation
The AAIB investigation examined the flight parameters, weather conditions, and the mechanics of the impact. Investigators noted that the aircraft's skids left distinct marks on the tarmac, indicating the helicopter bounced once and moved forward upon impact. The investigation also reviewed the aircraft's maintenance history and the environmental conditions at the time of the accident.
Findings
- The primary cause of the hard landing was a lapse in judgment regarding wind direction.
- The training exercise was performed using Runway 13, which, given the wind of 280° at 4 knots, presented a tailwind component to the aircraft.
- This tailwind reduced the aerodynamic efficiency of the aircraft during the critical flaring and cushioning phase of the recovery technique.
- Because of the tailwind, the application of collective was less effective at arresting the rate of descent, leading to the high-velocity impact.
- The aircraft's crashworthy seats successfully protected the crew from injury during the high-energy event.