The pilot of a Bell 206 helicopter, registered VH-NKW, was tasked to drop equipment bags for seismic operations by using a magnetic bag runner connected to the helicopter by a 100 ft long-line.
The helicopter lifted off with seven bags loaded on the runner. During the flight of about 2 NM, the pilot observed that the bag lanyards became tangled. The pilot manoeuvred the bags onto the ground and using dual switches on the cyclic control, released the two solenoids to drop the first bag. The lanyard was tangled around the others and the released bag remained hanging and entangled with the other bags. The pilot then released the second bag and attempted to make the bags drop. He then repeated this for six bags and eventually one bag remained connected to the runner with the other bags entangled and hanging from it.
The pilot elected to land the helicopter to untangle the bags. He manoeuvred the helicopter backwards down the slope to land on a more suitable site. When about 10 ft above the ground, the pilot manoeuvred slightly further to the right however the long-line became fully extended. As the line pulled taut it came directly out the left side of the helicopter from under the centre of the left skid. This caused the helicopter to roll to the right.
The main rotor blade collided with the ground before the pilot reached the long-line release switch. The helicopter rolled over and came to rest inverted, resulting in substantial damage.
This incident demonstrates the importance of using equipment in accordance with established best practice. The operator advised that the bag runner is no longer to be used for bag layout operations; it is only to be used for bag retrieval/pick-up.