A survey of the latest available literature was made in order to qualitatively discuss stability and control problems of vertical takeoff and landing. (VTOL) aircraft during hover (out of ground effect) and the transition to level flight, Modes of propulsion and methods of performing the transition maneuver are discussed. Comparisons are made of the various methods utilized for providing control forces at zero and very low speeds. The need for quantitative control power requirements "and handling qualities criteria is presented. The instability of VTOL aircraft while hovering is discussed, as are the basic reasons for the poor damping characteristics at low speeds. Problems which have been encountered to date with research aircraft and which are peculiar to a given VTOL mode are discussed by mode. The need for automatic stabilization and precision instrumentation requirements are presented.
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