What happened
On 1 February 2020, a Bell 20CO6L-3 helicopter, registration 9M-AZK, was engaged in a mission to assist JUPEM, Sarawak, with the placement of border markers along the Malaysia-Brunei border. During the second attempt to lift an underslung load from landing point LP43, the aircraft experienced a sudden roll and yaw to the left immediately after liftoff.
The pilot-in-command attempted to stabilize the aircraft, applying maximum right cyclic input, but the main rotor blades struck nearby trees. The aircraft subsequently pitched downward and came to rest in an inverted position. Despite the impact, both pilots escaped the wreckage with only minor injuries.
The investigation
AAIB Malaysia investigators determined that the landing point at LP43 had been inadequately prepared by the ground team. Because building materials were scattered haphazardly around the site, the available space for landing was severely restricted. This forced the cargo net, containing two concrete markers, to be positioned only about two feet from the aircraft's left skid.
As the helicopter lifted off, the downwash from the rotor blades caused the cargo net to lift and become entangled with the front of the left-hand skid. While the aircraft's marshaller attempted to provide a warning, the movement happened too rapidly for the crew to react. The safety pilot also failed to notice the entanglement before the aircraft lost control.
Findings
- The primary cause of the accident was the entanglement of the cargo net with the aircraft skid.
- The landing site was poorly managed, with materials placed so close to the landing area that the underslung load was positioned out of the pilot's direct line of sight.
- The rotor downwash during takeoff was the catalyst that moved the cargo into the path of the skid.
Safety action
To prevent similar occurrences, the operator is required to implement comprehensive joint briefings involving all stakeholders, including JUPEM and ground contractors. These briefings must focus on the safety requirements of underslung operations, ensure landing points meet minimum safety specifications, and establish a protocol where tasks are aborted if site safety standards are not met.