additional configurations can be output: Body alone Wing alone Horizontal tail alone Vertical tail alone Wing-Body Configuration Body-Horizontal Tail Configuration Body-Vertical Tail Configuration Wing-Body-Horizontal Tail Configuration Wing-Body-Vertical Tail Configuration Wing-Body-Horizontal Tail-Vertical Tail Configuration For each configuration, stability coefficients and derivatives are output at each angle of attack specified. The details of this output are defined in Section 6 of the USAF Digital DATCOM Manual Volume I. The basic output includes: CL - Lift Coefficient CD - Drag Coefficient Cm - Pitching Moment Coefficient CN - Normal Force Coefficient CA - Axial Force Coefficient CLα - Lift Curve Slope (Derivative of Lift Coefficient with respect to angle of attack) Cmα - Pitching Moment Curve Slope (derivative of Pitching Moment Coefficient with respect to angle of attack) CYβ - Derivative of side-force coefficient with respect to sideslip angle Cnβ - Derivative of yawing-moment coefficient with respect to sideslip angle Clβ - Derivative of rolling-moment coefficient with respect to sideslip angle For complete aircraft configurations, downwash data is also included. When compared with modern methods of computational fluid dynamics, Digital DATCOM may seem antiquated. However, in its day, the program was an advanced estimation tool, and certainly much faster than plowing through pages and pages of engineering texts. Digital DATCOM is no longer supported by the USAF and is now public domain software. Limitations Inlets, external stores, and other protuberances cannot be input because Digital DATCOM analyzes the fuselage as a body of revolution. The simplification affects the coefficient of drag for the aircraft. Dynamic derivatives are not output for aircraft that have wings that are not straight-tapered or have leading edge extensions. This problem can be overcome by using experimental data for the wing-body (using non-straight tapered wing). There is no method to input twin vertical tails mounted on the fuselage, although there is a method for H-Tails. This problem can be addressed by approximating the twin vertical tails as a single equivalent vertical tail mounted to the fuselage. Digital DATCOM cannot provide outputs for the control derivatives with regard to the rudder control surface. According to the manual, there is no any input parameters which define the geometry of rudder. Digital DATCOM cannot analyze three lifting surfaces at once, such as a canard-wing-horizontal tail configuration. This problem can be addressed by superposition of lifting surfaces through the experimental input option. Current Development There are intentions among those that use this package