Stabilization of External Loads in High-Speed Flight Using an Active Cargo Hook

Abstract

The use of an active cargo hook for stabilizing external loads during high-speed flight is demonstrated in simulation. A CONEX cargo container with two rear-mounted stabilization fins is used as the subject load. Significant nonlinearities in the dynamics of the external load result in multiple equilibria and limit cycle oscillations. A full-state feedback linear quadratic controller is developed assuming an isolated load in a wind tunnel model and shown to be successful in stabilizing the originally unstable load at a target airspeed of 100 kt. The design is then completed to cover the target carriage envelope from hover to high-speed flight. Simulations of a coupled system incorporating a UH-60 Black Hawk helicopter with an actuated cargo hook and the external load show that the controller is successful in providing system stability throughout the target flight speed envelope.