Evaluation of a slung load control system for piloted cargo operations

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Nonnenmacher, D.
Kim, H.M.
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Helicopter operations with externally slung loads are highly demanding for the flight crew. Without having a direct view on the load, the pilot requires assistance from an additional crew member for load handling to achieve operational requirements (e.g. precise load positioning). An automatic load stabilization and positioning system for cargo operations has been designed with the aim to reduce pilot workload, damp load pendulum motion and to improve the load positioning performance. This system uses the concept of load- motion feedback to the rotor control. To avoid degradation of Handling Qualities (HQs), as found in previous investigations, a function has been developed that monitors pilot control inputs. Dependent on the amplitude and duration of pilot control stick deflection, the feedback signal for slung load damping is blended between two different gain sets. One set provides improved HQs during piloted control and one set provides good load damping when the pilot is passive. A further novel aspect is the evaluation of an automatic load control system using a Translational Rate Command as method of helicopter control. A piloted simulation study has been conducted using this advanced load control system with automatic load stabilization and positioning. Three test pilots evaluated the system in different control law configurations using a Mission Task Element simulating an external load cargo operation. HQs and pilot workload were evaluated using the Cooper- Harper Rating Scale and NASA Task Load Index respectively. The results of the study show that improved HQs in combination with improved task performance can be achieved with the advanced slung load control system.