Aircraft control forces and EMG activity in a UH-1H Iroquois helicopter during emergency maneuvers

BACKGROUND: Some air forces are concerned with the adequacy of existing pilot selection standards in respect to pilot strength. Some studies have provided evidence that a large number of pilots may not be able to match the control force levels specified in both military and civilian aircraft design standards. However, both sets of design standards have been based on the subjective comments of test pilots and may not, therefore, be applicable for the majority of pilots. The aim of this study was to quantify aircraft control forces during emergency maneuvers in an Iroquois helicopter and compare these forces with design standards. The examination of muscle activation patterns of pilots during maneuvers, when normalized, can provide additional information on the relative activation levels that pilots are using to produce the aircraft control forces. METHODS: Six pilots were tested in a UH-1 H Iroquois helicopter. The maneuvers were three engine-out landings and a hydraulics-off landing. The variables recorded were pilot applied forces and EMG activity. Multivariate analysis of variance was used to test for differences between maneuvers. RESULTS: The greatest cyclic and upward collective control forces were observed during constant attitude and variable flare engine-out landings. The greatest downward collective forces were observed during hydraulics-off landing. Greater levels of muscle activation were consistently observed during hydraulics-off landing than during the engine-out landings. Control forces consistently exceeded military design standards for cyclic and collective controls, however muscle activity levels were sub-maximal for all maneuvers. CONCLUSION: Comparisons between existing aircraft control-force design standards and pilot strength may overestimate the number of pilots who are able to produce sufficient force to fly the aircraft. Despite the high control forces observed, all pilots tested were able to successfully maneuver the helicopter without requiring a maximal muscular effort.