Using Wind Tunnel Tests for Slung Loads Clearance

Previously the authors showed that dynamic wind tunnel tests of a suspended CONEX cargo container model exhibited encouraging levels of success in predicting the stability characteristics and speed envelope of the full scale load. Following that, a new integrated procedure for developing methods to stabilize problematic slung loads and extend their flight envelope was presented and applied successfully to extend the flight envelope of the CONEX. The present paper describes an extension of the investigation in two main directions. The first direction includes further use of the UH-60/CONEX system to study effects that were observed previously, but not fully addressed. These effects include: the influence of pilot inputs and helicopter motions on the coupled pilot/helicopter/slung load dynamics, the influence of cg offset of the slung load, and the influence of not using a swivel compared to previous studies that included free yaw due to a swivel. It is shown that all three effects are important and affect the slung load dynamics. The second direction extends the investigation to include other load geometries. The first new load is the TRIO container that can be flown in three configurations with different heights. The second new load is a ribbon bridge interior bay section. Wind tunnel results with models of the new loads exhibit in general good agreement with flight test results. All the new results strengthen further the approach of using wind tunnel tests to accelerate, as well as reduce risk and cost, of slung load clearance.