Heli crash down to ship?
 

BBC Scotland News 14 December

BBC Scotland has learned that an investigation into a helicopter accident is focusing on the ship it was attempting to land on.

The helicopter toppled over after it landed on a drilling ship to the west of Shetland, and a result one of the crew suffered a broken leg.

Now BBC Scotland has learned that the Air Accident Investigations Branch (AAIB) is focusing on the failure of a navigational system on the West Navion ship last month.

The incident, involving a Super Puma helicopter, happened on a routine flight to transport oil workers.

The inquiry is focusing on the ship

An AAIB bulletin reveals that five minutes after the aircraft touched down on the helideck the ship's Dynamic Position System (DPS) lost control of its heading.

DPS is a computerised system which uses signals from satellites to keep a ship on a steady course or in a precise location.

The West Navion began to drift slowly to the right and developed a list of one degree to starboard.

The helicopter then toppled over to the right. Its rotors struck the helideck and debris were sent flying.

The co-pilot was struck and suffered a broken leg. The drilling ship is owned by Norwegian company Smedveg and is operated by BP.

The investigation is continuing.

1 deg list ? , surely that would not be enough to cause it to topple over. I would imagine the problem would have been if the vessel moved broadside to the waves and the rolling then exceeded the normal specs.
On one of these vessels does the helicopter normally land nose in to the wave direction ( large pitch and small roll ) ?.

'spose it depends on the Puma AFCS. Was there a large heading change, was the list rapid (although 1 degree is pretty damn small). Does Puma have a weight-on-wheels switch to cancel AFCS functions such as heading hold, turn co-ord etc when on ground? Have seen a video of a US navy seahawk on deck when ship makes a rapid turn. Deck lists to about 10 degrees (I guess) which is within limits for type, but seahawk just keeps rolling in direction of turn and beats itself to death.

See variable load's post on page 3 of North Sea Crash thread for an explanation of how the ship contributed to the roll over. It's Good reading.

There's an AAIB special bulletin available about this accident <a href="http://www.aaib.detr.gov.uk/special/gbkze/gbkze.htm" target="_blank">here</a>.