Charts For Estimating Rotor Blade Flapping Motion Of High Performance Helicopters PDF Download

An investigation has been conducted at speeds up to a Mach number of 0.90 to determine the effects of operating propellers on the longitudinal characteristics of a four-engine tractor airplane configuration having a 40 degrees swept wing with an aspect ratio of 10. Results of wind-tunnel tests of a model representing such an airplane configuration (see NACA TN 3789) show that these effects are of most concern in the low-speed high-thrust flight regime. In the present report the low-speed data are analyzed to determine the source of the various effects and to indicate how the adverse effects can be reduced, and the high-speed data are discussed primarily from the standpoint of Mach number effects. The analysis of the low-speed data indicates that the large variations of longitudinal stabil.itywith angle of attack resulted primarily from passage of the tail into and out of the slipstream. The slipstream also created large lift increments on the wing, particularly with flaps deflected, which resulted in increases in stability (with increasing thrust coefficient) from the outboard propeller and decreases in stability from the inboard propeller. It was concluded that the longitudinal stabiltty characteristics of the model couldbe improved by moving the nacelles outward, increasing the tail height, and reducing the tail span.