Analyses of available handling qualities data were performed to determine lateral/directional dynamic requirements for VTOL aircraft in hover and low speed flight. The basis for this treatment is an examination of the pilot/vehicle as a closed-loop servo system. The quasi-linear pilot describing function is applied. The results of the studies suggest that the primary factors identifying satisfactory and unacceptable hover mode dynamic features are related to the closed-loop deficiencies. Detailed consideration is made of the control task and piloting functions in transition flight. The results of this generic appraisal are evoked to confirm and justify preliminary lateral/directional requirement for control in transition. (Author).

Analyses of results from available handling qualities experiments were performed to determine dynamic and control requirements for VTOL aircraft. The basis for this treatment was an examination of the pilot/vehicle as a closed-loop servo system. The quasi-linear pilot describing function has been applied. The results of the studies suggest that the primary factors identifying satisfactory and unacceptable hover mode dynamic features are primarily related to the closed-loop pilot/vehicle system. Preliminary consideration is given to the longitudinal techniques and multiloop control structures suitable for manual control in transition. (Author).

The hover analysis considers pilot attitude and position control tasks in the presence of horizontal gusts. The effects of each of the stability derivatives on the difficulty of the control tasks and on the closed-loop gust responses are determined. It is clearly shown that the handling qualities studies of control sensitivity and angular damping must consider the influences of M sub u (or L sub v) and should include gust inputs. These conclusions are substantiated by previous variable-stability-helicopter experiments. The effects of vehicle size and geometry are investigated by several approaches. The key result of increasing size is found to be a reduction in M sub u and L sub v which can, in turn, lower the requirements for control power and damping. The handling qualities during transition of two vehicles, a tilt duct and a tilt wing, which were previously tested on a simulator are analyzed. It is shown that both trim control and perturbations about the trim conditions must be considered. In fact, part of the increased difficulty in landing transitions, in comparison with takeoff transitions, is due to more difficult trim control; the much more stringent position control requirements in landing are also a contributing factor.

"This report presents a series of discussions on selected topics related to the development of VTOL flying qualities criteria. The topics were chosen on the basis of their importance to flying qualities and the potential significance to the Air Force VTOL Integrated Flight Control System (VIFCS) program. The treatment given to the selected topics was aimed at identifying those areas that require further study and research within the scope of the VIFCS program. -- page iii.