The Alouette III SA 316B helicopter registered 5N-ALD was positioning on the off-shore helipad which was designated as Meren 24 jacket after a 60 second flight from the main oil platform designated as Meren I.
The helicopter was scheduled to lift four Flopetrol loads on a sling work. On entering a hover for the touchdown, the collective pitch control was lowered as usual and just at the instant of the right rear wheel making the first contact with the platform, the commander felt that the said wheel was sinking into the platform.
The collective pitch control was immediately raised for a lift off. The helicopter lifted off from its sunk position, but with the right rear wheel now caught in the edges of the displaced platform surface plating, a right turning moment was induced on the helicopter. The helicopter flipped on its right side sustaining an extensive damage.
It is concluded that the accident was caused by the displacement of the loose platform surface plate induced by the side forces transmitted on it as the right rear wheel oleo strut was compressed at an obtuse angle at the point of touchdown.