The design and flight-testing of a multivariahle helicopter flight-control system is reported on. The design was based on H , optimization and a low-order rigid-hody model of the aircrafl dynamics. The test-aircraft was a modified Rell 205.Evaluations were carried out at hover and lowlmoderate speed. The controller successfully engaged first time and provided adequate-to-desired (level 2) performance on a number of tasks. This is believed to he the first successfnl Right-test of an H-infinity optimal multivariahle controller on a mtorcraft.

The concept and rationale involved in developing a Limited Authority Response v p e (LART) to improve handling qualities of a helicopter for operations in degraded viFual envimoments (DVE) is explained. A LART may be achieved by reprogramming existing, limited authority stability augmentation system actuators to produce a moderate bandwidth, low authority attitude response. A summary of the results from a piloted handling qualities experiment, conducted on the NRC Bell 205 Airborne Simulator, a d d m i n g this concept are presented. This experiment examined the handling qualities of a "UH-60like" helicopter with various LART systems while conductmg operations in degraded night vision goggle conditions. The m$ults indicate an improvement in handling qualities for systems with attitude authority as low as 25 d e g w and a general dislike of systems using parallel servos to increase the overall attitude authority. Pmvision of a pilot selectable height hold system during flight in DVE provided the greatest handling qualities improvement. Some inconsistancy in pilot ratings and comments suggest more detailed research is required to confirm the mults prior to practical applications of the concept.

The National Research Council's (NRC) Cockpit Technologies Program flight tested a stereoscopic three-dimensional display format to determine the feasibility of using pictorial and stereoscopic cues during helicopter instrument approach procedures (TAP). Three qualified test pilots flew a series of approach procedures using a modified conventional electronic flight instrumentation format , a pictorial display format, and a pictorial stereoscopic display format. The preliminary evaluation focused on the effect of display format on pilot performance during the approach task, from an approach intercept to the decision height.Performance criteria such as aircraft speed error, localiser error, and glide slope error were measured. Additionally, pilots answered a questionnaire on each display format, and rated the workload required to fly the approaches using the Cooper-Harper scale.Pilots were able to complete approaches to safe landings using any of the display formats. Pilots reported that the pictorial format improved their situation awareness during the approach. Pilots also reported that the stereo cues incorporated in the display design did not significantly enhance their ability to perform TAP. The pictorial display contained several strong monocular depth cues such as occlusion, linear perspective, and motion flow; therefore the stereo cues were of limited value. Pilots most preferred the conventional display, which provided the most accurate tracking capabilities and lowest workload. Pilots encountered a few acceptance problems with the stereo display, most notably, losing the stereo effect when viewing the prototype stereo display off the ceniral viewing axis.

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