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Piloted, moving-base simulations have been performed in the evaluation of several VTOL control system concepts during landings on a destroyer in adverse weather conditions. All the systems incorporated attitude control augmentation; most systems incorporated various types of translational control augmentation implemented either through aircraft attitude or, more directly, through the propulsion system (thrust magnitude and deflection). Only one of the control systems failed to provide satisfactory handling qualities in calm seas. Acceptable handling qualities in sea state 6 seem to require a system with control augmentation in all translational degrees of freedom.

Takeoff predictions for powered lift short takeoff (STO) aircraft have been added to NASA AMES Research Center's aircraft synthesis (ACSYNT) code. The new computer code predicts the aircraft engine and nozzle settings required to achieve the minimum takeoff roll. As a test case, it predicted takeoff ground rolls and nozzle settings for the YAV-8B Harrier that were close to the actual values. Analysis of takeoff performance for an ejector-augmentor design and a vectoring-nozzle design indicated that ground roll can be decreased, for either configuration, by horizontally moving the rear thrust vector closer to the center of gravity, by increasing the vertical position of the ram drag-vector, or by moving the rear thrust vector farther below the center of gravity.

Using a generalized simulation model developed for piloted evaluations of short take-off/vertical landing aircraft, an initial fixed-base simulation of a mixed-flow, remote-lift configuration has been completed. Objectives of the simulation were to evaluate the integration of the aircraft's flight and propulsion controls to achieve good flying qualities throughout the low-speed flight envelope; to determine control power used during transition, hover, and vertical landing; and to evaluate the transition flight envelope considering the influence of thrust deflection of the remote-lift component. Pilots’ evaluations indicated that Level 1 flying qualities could be achieved for deceleration to hover in instrument conditions, for airfield landings, and for recovery to a small ship when attitude and velocity stabilization and command augmentation control modes were provided.

Propulsion induced effects encountered by moderate- to high-disk loading STOVL or VSTOL aircraft out-of-ground effect during hover and transition between hover and wing-borne flight are discussed. Descriptions of the fluid flow phenomena are presented along with an indication of the trends obtained from experimental investigations. In particular, three problem areas are reviewed: 1) the performance losses sustained by a VSTOL aircraft hovering out-of-ground effect, 2) the induced aerodynamic effects encountered as a VSTOL aircraft flies on the combination of powered and aerodynamic lifts between hover and cruise out-of-ground effect, and 3) the aerodynamic characteristics caused by deflected thrust during maneuvering flight over a wide ranges of both angle of attack and Mach number.

Over the years, a wide variety of aircraft configurations have been flown with varying degrees of success. A brief survey of the handling qualities of canard, tandem wing, and flying wing designs indicates that longitudinal stability and control, lateral/directional stability and control, and stall behavior of these concepts were important factors in achieving pilot acceptance.