PILOTED SIMULATOR INVESTIGATIONS OF A CIVIL TILT-ROTOR AIRCRAFT ON STEEP INSTRUMENT APPROACHES

Two piloted simulation experiments were conducted in the NASA Ames Research Center Vertical Motion Simulator to investigate instrument approaches on steep glide slopes for a civil transport tilt-rotor aircraft. In the first experiment, pilots used raw glide slope and localizer error data for approaches on glide slopes ranging from 6 to 25 degrees, terminating in slow, roll-on landings. The second experiment featured the use of a flight director which commanded manual conversion from airplane mode to helicopter mode and a deceleration on the glide slope to a vertical landing on a small urban vertipad. Evaluations were conducted with low visibility and ceilings and with crosswinds and turbulence, with all aircraft systems functioning normally and were carried through to a landing. During the first experiment with raw data, only the shallowest glide slope tested, 6 degrees, yielded at least desired tracking performance and marginally satisfactory pilot ratings. For steeper glide slope angles, control problems occurred which were directly related to the slow approach speeds required on the glide slope. In the second experiment, cockpit augmentation in the form of a four-cue flight director provided generally satisfactory pilot ratings up to a 15 degree glide slope. Cockpit field of view became an issue in both experiments for approach angles of 15 degrees and above as some pilots became concerned by the obscuration after breakout of the intended landing spot by the simulated aircraft nose and cockpit glare shield. Cockpit automation such as alternate automated flap schedules and a semi-automated nacelle movement system were developed to decrease pilot workload for level flight conversions during instrument meteorological conditions.