INVESTIGATION OF THE RELATIONSHIP BETWEEN HELICOPTER GEOMETRICAL AND INERTIAL PARAMETERS AND SHIPBOARD SECURING REQUIREMENTS

Extensive experience analyzing the securing requirements and on-deck stability of maritime helicopters on ships has revealed a strong dependence of securing requirements on aircraft configuration. While studies have been conducted comparing various in-service aircraft, interpretation of results has been complicated by significant differences in aircraft configurations. To overcome this difficulty, a parametric study was undertaken where controlled variations of key aircraft parameters were considered for three typical tricycle-configuration aircraft having nominal weights of 5 tonnes, 10 tonnes, and 15 tonnes. Parameters considered in the study were the aircraft mass, track width, wheelbase, longitudinal and vertical positions of the centre of gravity, magnitude of induced rotor loads, lateral projected area, and vertical location of the centre of pressure. These eight parameters were varied using a 28 full-factorial experimental design and helicopter responses to two potentially severe ship motion conditions were predicted for each aircraft using the Indal Technologies Inc. Dynaface simulation software. The effect of the above parameters on landing gear reactions, vertical securing force, horizontal securing force, and relative angular motion were determined. Results were analyzed to determine the sensitivity of each outcome to each parameter individually and in all combinations for each aircraft and results were also analyzed to investigate trends in the sensitivities with aircraft size. Results demonstrate that securing requirements depend on aircraft configuration parameters and that in some cases the sensitivities increase significantly with aircraft weight. Detailed results are presented and discussed in this paper.