Safely moving helicopters aboard frigates

An NLR test program SAMAHE (Système d’Áide à la MAnutention d’Helicoptères Embarqués) helps to improve the design of a helicopter transport system aboard Dutch navy frigates.

Introduction of the new NH-90 helicopter means acceptance and qualification tests are needed for various aspects of operations to determine whether the helicopter complies with specifications on delivery. One mandatory test involves the transport system for moving helicopters from the landing platform on deck to the ship’s hangar.

In 2009, NLR began qualification tests on the helicopter transport system used on board Dutch Air Defense and Command Frigates. The objective of these tests, commissioned by the Defense Materials Organization, was to investigate under which weather conditions the crew could safely use the transport system without risking harm to themselves and damage to the helicopter.

The transport system consists of a component attached by means of a probe to the belly of the helicopter fuselage and another component which secures the nose wheel. Once the helicopter is coupled to the transport system, the whole rig is dragged by cable over two rails into the frigate’s hangar. Trials were conducted to establish whether the forces exerted on the helicopter remained within previously defined margins safeguarding the helicopter’s airworthiness.

To analyze static and dynamic forces, NLR technicians attached monitoring instruments to the probe. This was essential given that a vessel at sea moves in all directions with fluctuating force. The probe was first calibrated on shore at the NLR testing facilities. Monitoring at sea could be carried out safely by adjusting the frigate’s roll stabilization system to ensure that in calm conditions the vessel made a more or less controlled movement (rolling movement) around its own longitudinal axis.

The study revealed that the helicopter transport system needed improvement, a conclusion that the supplier of the transport system has taken to heart.

The measurements were completed in limited time (the frigate was actively deployed at sea) and could be carried out successfully thanks to the combined effort of NLR specialists in the fields of helicopters, aircraft loads, flight tests, structures testing and evaluation, structural integrity, and materials technology.