VERTICLE/SHORT TAKEOFF AND LANDING (V/STOL) STABILITY AND CONTROL IN GROUND EFFECTS

IN HOVER THE JET STEAMS FROM A V/STOL AIRCRAFT IMPINGE ON THE GROUND AND SPREAD OUT FROM THE IMPINGEMENT POINT IN RADICALLY FLOWING WALL JETS WITH FOUNTAIN FLOWS BETWEEN THE JETS WHERE THE WALL JETS MEET. THE FOUNTAIN FLOWS TEND TO PRODUCE A LIFTING FORCE BUT THE WALL JET ENTRAINMENT CAUSES AN OPPOSING LIFT LOSS OF SUCKDOWN. AT FORWARD SPEED, AS IN STOL OPERATION, THE FORWARD FLOWING WALL JET IS OPPOSED BY THE FREE STREAM AND ROLLED BACK ONTO ITSELF TO FORM A GROUND VORTEX WHICH ALSO INDUCES FORCES AND MOMENTS ON THE AIRCRAFT. OUR UNDERSTANDING OF THESE FLOW FIELDS IS INCOMPLETE AND OUR ABILITY TO ESTIMATE THE FORCES AND MOMENTS INDUCED IS INADEQUATE. THIS PROPOSAL IS SUBMITTED TO DEFINE THE FLOW FIELDS INVOLVED TO THE EXTENT POSSIBLE FROM THE EXISTING DATA BASE AND TO RECOMMEND AN EXPERIMENTAL PROGRAM TO EXPAND THE DATA BASE AND DEVELOP METHODS FOR ESTIMATING THESE INDUCED STABILITY AND CONTROL PARAMETERS.