Abstract:

ESDU Aero C.04.01.04 gives graphs based on a correlation of experimental data that allow, for trailing-edge controls fitted with Irving internal balances, the increments to the slopes of the hinge moment curves against incidence and control deflection to be determined. The curves are plotted for various values of balance ratio. For the rate of change of hinge moment coefficient with incidence a value of the lift-curve slope is required and may be obtained from ESDU Aero W.01.01.05. For the rate of change of hinge moment with control deflection three factors are required for which additional curves are provided. They depend on aerofoil section trailing-edge angle, on vent position defined as the distance between the shroud and the position of the pressure peak on the control, and on the leakage through the nose seal defined by the ratio of leak area to vent area. The influence of a flexible nose seal on the increments is discussed. The increments must be added to values of the slopes determined for the control without balance and they may be found from ESDU Aero C.04.01.01 or ESDU Aero C.04.01.02 as appropriate. ESDU 89009 may be used to correct to finite aspect ratio or, if there is a spanwise variation of geometrical properties, the method of ESDU Aero C.04.01.06 may be required.