Methods to realize the haul down and landing of a helicopter on the flight deck of a destroyer escort are investigated. The investigations proceed under the assumption that the helicopter is to be hauled to the ship's deck by means of a cable attached to the helicopter from a winch located on the ship.
During the haul down, disturbances to the helicopter have two main sources, namely, ship motion, which is transmitted to the aircraft through the haul down cable, and external forces such as wind buffeting, acting directly on the helicopter. These disturbances are to be minimized. At touch down the objective is to execute a smooth landing while the ship's deck is pitching and heaving under the influence of wave motion. The problem is further complicated by the nature of wave motion. Under severe sea conditions, wave motion is almost periodic in time but the wave peaks are randomly distributed in space. A haul down system must then make some provision for the random component of ship motion.
A peak landing system is developed which will haul down and land the helicopter causing small disturbance to the aircraft and pilot. This system is successful except under extreme sea conditions. The difficulty arises through the failure of the system to accurately predict the height of the ship above the datum when the helicopter is to be landed. A series of recommendations are then made, aimed at improving the system.
A controlled tension system is considered, but rejected on the grounds that the hauling and landing-processes are manually controlled and rely to a great extent on the judgement of the operator. An automatic system is also considered in which the helicopter is raade to reproduce ship motion as it approaches the ship's deck. This method is rejected since it leads to prohibitively high cable tensions.