ESDU 87008:2014

ESDU 87008 predicts semi-empirically the sideforce due to rudder
deflection and its point of action on the fin, from which the
rolling and yawing derivatives due to rudder deflection are easily
calculated. To obtain the sideforce, ESDU data for wing lift-curve
slope and for plain control effectiveness are applied to the fin
with appropriate corrections. The corrections allow for body
interference (which depends on the body cross-section in the region
of the fin) and for tailplane position on the fin between a T-tail
and a tailplane at the fin/fuselage intersection. In addition,
another correction is applied for a rudder that does not occupy the
whole trailing-edge of the fin. Graphs show the accuracy of the
predictions by comparing them with wind-tunnel data extracted from
the literature. The ranges of geometry and Reynolds number covered
by the tests are quoted. The data used were in the incidence range
from 0 to 10 degrees, and the effect of any control gap was
neglected. The sideforce derivative is thought to be predicted to
within 0.04, the yawing moment derivative to within 0.02 and the
rolling moment derivative to within 0.01. A worked example
illustrates the use of the prediction method. A computer program of
the method is provided as ESDUpac A8708.