Significant lashing loads can be imparted to a helicopter in high sea states.
Helicopter manufactures generally recommend a scheme, however in practice it can be very difficult to achieve the desired layout of the lashings given limited deck tie down points or hangar space.
A poorly laid out chain lashing scheme can cause particular problems because of in-effective load sharing. Further difficulties can arise due to the requirement to maintain adequate clearance between lashings and airframe fittings.
The Ondeck code can be coupled with various constrained optimization codes or monte-carlo batch processes to assess the performance of a lashing scheme or optimize the layout over a range ship motion input.
Sinusoidal ship motion, simulated time domain irregular wave ship motion data, or frequency domain regular wave simulation data covering a range of ship speeds, relative wave headings and significant wave heights can be utilised.
Top: Simulated image from the Seaking Lashing Scheme Optimisation & Sensitivity Analysis
Centre: Constrained Tie Down Optimisation Envelope for Each Lashing
Bottom: Sensitivity plot of a Particular Lashings
Left: RAN Sea King helicopter lashed to the deck.