IHS ESDU Contribution of ventral fins to sideforce and yawing moment derivatives due to sideslip at low angle of attack. 92029

ESDU 92029 applies at subsonic and supersonic speeds to configurations with a body- or fin-mounted tailplane and a main fin in the plane of symmetry for angles of attack and sideslip up to 5 and 4 degrees respectively. The method is an empirical modification of long-standing theoretical calculations that allow for the interference of body, wing, tailplane and main fin. The sideforce is obtained from the lift-curve slope (from ESDU 70011 at subsonic speeds or ESDU 70012 at supersonic speeds, or from slender body theory for low aspect ratios, empirically modified) factored by the appropriate interference factor. The yawing moment derivative is calculated by taking the point of action of the sideforce at quarter- or mid-point of a chord 0.4 of the height of the fin from the root; more precise methods resulted in little improvement in accuracy and so did not warrant the greater complexity. Sketches comparing predictions with experimental data extracted from the literature show the accuracy of both derivatives to be within 0.15 plus 15 per cent. The ranges of geometry and Mach number for the experimental results are tabulated.