Unsteady Fuselage Loads on Rotorcraft in Ground Effect 2005-01-3153

In ground effect, helicopters experience severe loads that change rapidly with flight condition and ground clearance. Even under nominally steady conditions, wake vortex interactions and vortex recirculation into the rotors cause transient loads separated by apparently random intervals. In prior work, these loads have been isolated and classified into transient versus quasi-steady using flow imaging, hot-wire anemometry and integrated load measurements. This paper looks at wind tunnel experiments studying the fuselage loads on two typical helicopter fuselage shapes decoupled from rotor disk moments. The likely effect of this load variation is outlined in the paper, in an attempt to begin relating these back to the forces reported by pilots.