Helicopter Control Response Types for Hover and Low-Speed Near-Earth Tasks in Degraded Visual Conditions

A piloted ground-based simulation was conducted to assess several control response types during helicopter low-level flight in degraded visual conditions. The NASA Ames Vertical Motion Simulator and the Singer-Link Dig 1 Computer Image Generator (CIG) were used to simulate a helicopter cockpit in a degraded visual environment. The CIG visibility was reduced to a point where the horizon and other far-field cues were not discernible. The control response types included a rate command, an attitude command/attitude hold, and a translational rate command. Pilot control was implemented through conventional controls: a cyclic, collective, and pedals. A simple stability derivative mathematical model of a helicopter with known dynamics and no coupling was used to perform the evaluations. The piloting tasks were a hover, a “vertical landing,” a pirouette, an acceleration/deceleration, and a sidestep maneuver. These tasks were flown in sequence, and both desired and adequate performance levels were specified for each task. Visual cue ratings with a rate command response type were initially collected to set the usable cue environment (UCE) at UCE = 3. The results of the simulation indicate that the qualitative determination of the UCE was consistent among the five evaluation pilots. Cooper-Harper handling qualities ratings were collected for each task and control response type. The results indicate that a rate command response type provided poor Level 2 handling qualities in UCE = 3 for the five tasks evaluated. The attitude command response type provided good Level 2 handling qualities. For the hover and vertical-landing tasks the ratings of the translational rate command response type were all Level 1. For the pirouette, the acceleration/deceleration, and the sidestep tasks, the ratings of the translational rate command response type were a mixture of Level 1 and Level 2.