PERFORMANCE CONSIDERATIONS OF GROUND EFFECT TAKE‐OFF AND LANDING (GETOL) TRANSPORT AIRCRAFT

The GETOL (ground effect take-off and landing) can be defined as a fixed wing aircraft which, during take-offs and landings, is either completely or partially supported by an air cushion. In this way, the take-off maneuver starts with a hovering phase at some height from the take-off surface (it could be solid ground, water, snow, etc . ) . This is followed by a run parallel to the take-off surface (without touching it) until a speed sufficient to develop lift required to support the aircraft out of ground effect is reached, and then a climb can be initiated. In landing, the procedure is reversed: after executing a conventional approach, the aircraft flares close to the ground, and starts to experience the influence of the ground cushion which gradually assumes complete support of the aircraft and permits it, eventually, to reach the hovering stage. Since, during the landing run, there is no direct contact between the airframe and the landing surface, all the braking must be performed by aerodynamic means (drag and reversed thrust), This lack of any direct contact between the aircraft and the ground represents a definite operational advantage, as it largely increases the freedom of selecting take-off and landing sites. As a matter of fact, for the GETOL, any relatively flat surface of sufficient dimensions for take-off and landing runs can serve as an airfield. Furthermore, the surface may consist of solid ground, water, snow, ice, etc. Thus, the omniphibious aspects should still further improve operational freedom of the GETOL. It becomes evident that operational freedom of the GETOL should be greater than that of conventional NTOL (normal take-off and landing) and even conventional STOL (short take-off and landing) aircraft. But, by the same token, the operational freedom of the GETOL will be less than that of the VTOL, and especially less than that of the helicopter. Whether the ground effect principle would represent sufficient operational advantages to establish a separate family of aircraft will depend on several factors: The most important of these will be performance, structural weight, and complexity penalties which may be associated with this type of machine. These will be weighted against operational advantages resulting from greater freedom of take-off and landing operations. Even if pure GETOL aircraft will not develop into a class of their own, it is still possible that some aspects of the ground effect principle may be incorporated into other aircraft systems, to improve STOL performance of overloaded (beyond their hovering capabilities) VTOL’s, or simply to