Theoretically derived charts showing steady-state and first- and second-harmonic flapping coefficients are presented for helicopter rotors having hinged rectangular blades with a linear twist of 0, -8, and -16 degrees. The charts, showing the rotor flapping coefficients for combinations of inflow ratio and blade pitch angle, are presented for tip-speed ratios ranging from 0.05 to 0.50.

A rotorcraft is a class of aircraft that uses large-diameter rotating wings to accomplish efficient vertical take-off and landing. The class encompasses helicopters of numerous configurations (single main rotor and tail rotor, tandem rotors, coaxial rotors), tilting proprotor aircraft, compound helicopters, and many other innovative configuration concepts. Aeromechanics covers much of what the rotorcraft engineer needs: performance, loads, vibration, stability, flight dynamics, and noise. These topics include many of the key performance attributes and the often-encountered problems in rotorcraft designs. This comprehensive book presents, in depth, what engineers need to know about modelling rotorcraft aeromechanics. The focus is on analysis, and calculated results are presented to illustrate analysis characteristics and rotor behaviour. The first third of the book is an introduction to rotorcraft aerodynamics, blade motion, and performance. The remainder of the book covers advanced topics in rotary wing aerodynamics and dynamics.

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.

The frequency characteristics and statistical properties of the buffet loads measured on the unswept wing and tail of a fighter airplane have been studied in the stall and in the shock regime. The results indicate that the wing loads in buffeting can be treated as the Gaussian response of a simple elastic system. The tail loads appear to represent a more complicated pattern.