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 pil ot selection standards in respect to pilot strength. Some studies have prov ided evidence that a large number of pilots mak. not be able to match the c ontrol force levels specified in both military and civilian aircraft design standards. However, both sets of design standards have been based on the s ubjective comments of test pilots and may not, therefore, be applicable for the majority of pilots. The aim of this study was to quantify aircraft con trol forces during emergency maneuvers in an Iroquois helicopter and compar e these forces with design standards. The examination of muscle activation patterns of pilots during maneuvers, when normalized, can provide additiona l information on the relative activation levels that pilots are using to pr oduce the aircraft control forces. Methods: Six pilots were tested in a UH- 1H Iroquois helicopter. The maneuvers were three engine-out landings and a hydraulics-off landing. The variables recorded were pilot applied forces an d EMC activity. Multivariate analysis of variance was used to test for diff erences between maneuvers. Results:The greatest cyclic and upward collectiv e 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 con sistently observed during hydraulics-off landing than during the engine-out landings. Control forces consistently exceeded military design standards f or cyclic and collective controls, however muscle activity levels were sub- maximal for ail maneuvers. Conclusion: Comparisons between existing aircraf t control-force design standards and pilot strength may overestimate the nu mber 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 e ffort.