MEASUREMENTS OF THE PRESSURE DISTRIBUTION ON THEnHORIZONTAL-TAIL SURFACE OF A TYPICALnPROPELLER-DRIVEN PURSUIT AIRPLANE IN FLIGHTnI - EFFECTS OF COMPRESSIBILITY IN STEADY STRAIGHTnAND ACCELERATED FLIGHT

摘要

Pressure-distribution measurements were made In steady straight and accelerated flight over both sides of the horizontal-tail surface of a typical pursuit airplane up to a Mach number of 0.79.The results showed that a sharply increasing down—load was required to balance the increased diving moment of the wing—fuselage—propeller group at Mach numbers above about 0.70, There was little change, up to a Mach number of O.65, of the tail—load gradient (rate of increase of tail load for a unit change in acceleration factor);beyond that Mach number, however, a rapid decrease of tail—load gradient to a Mach number of about 0.73 and then a very sharp increase up to a Mach number of O.785 was noted. The root bending moments increased considerably on the right tail and decreased, to a lesser extent, on the left tail at the higher Mach numbers, resulting in increased fuselage torsional moments at high speeds. At the higher values of lift coefficient (0.5 to 0.8), there was little change of the lateral distance to the center of pressure up to a Mach number of about 0.73> at the highest speed and at low lift coefficients (0 to 0.1) the center of pressure was inboard approximately 3 feet on the left tail and 1.5 feet on the right tail as compared with the values at lower speeds. It appears that satisfactory quantitative data on total tail loads may be obtained from measurements at four stations equally spaced along the entire tail span.