Superimposed perspective visual cues for helicopter hovering above amoving ship deck

The subject of the investigation is a manual low-altitude hovering task above a small moving ship deck using visual field cues supplemented by superimposed display symbology. In this task, rather than tracking the ship-deck motion, the pilot should keep the helicopter inertiaUy stable at a desired inertial position with respect to the ship deck. This hovering stage lasts until the touchdown can be performed during some period of quiescent ship motion. The main difficulties during this task arise from the lack of appropriate visual references necessary to keep the helicopter inertially stable above the ship deck. This research investigates, both analytically and experimentally, the effects of the information superimposed on the visual field on hovering performance. This additional visual information can be implemented by inertial references generated on the ship deck, and/or by a helicopter-based head-up display. For the ship-deck references, inertially stable, three-dimensional visual structures such as line-drawn cubes are investigated. For the head-up display information, only an artificial horizon is investigated. The results of the investigation clearly show that hovering performance is improved by the inclusion of inertially stable visual cues. Moreover, it is shown that the performance is almost independent of the size of the three-dimensional structure. Thus, it is possible to implement the ship-based visual references within practical physical dimensions.