Aero Database

In general the aero database obtained from wind tunnels is supplied in tabular formats along with the application formulae [1,6] that are used for computation of force and moment coefficients; the latter form a part of the EOMs (Figure 4.1). The EOMs are then numerically integrated to obtain the dynamic responses of the aircraft, which are called the time histories. An application formula for the axial force coefficient of a typical aircraft is given as

Cx = Cxa0ds (m&ch,8 siat) + Cxads(mach, a ,8 sklt) + CI„c(a, mach, UC) + CxAis(mach, a,8AB)

^ Cxdlds(mach, a,dlob, dslat) * KCxdlob(mach, a,dlob) ^ Cxdlds(mach, a,dlib, dslat)

* KCxdlib(mach, a,dlib) ^ Cxdlds(mach, a,drib, dslat) * KCxdrib(mach, a,drib)

^ Cxdlds(mach, a,drob, dslat) * KCxdrob(mach, a,drob) (6-l)

In the parentheses the terms are independent variables, which signify the dependen­cies of the coefficients on these terms. The above application formula is translated into the following expression:

Coefficient for axial force = Cx for a = 0 + Cx due to a with slat deflection + effect of undercarriage (up or down) + effect of airbrake deflection + Cx due to left outboard elevon (combined elevator/aileron) deflection * factor on Cx due to left outboard elevon deflection + Cx due to left inboard elevon deflection * factor on Cx due to left inboard elevon deflection + Cx due to right inboard elevon deflection * factor on Cx due to right inboard elevon deflection + Cx due to right outboard elevon deflection * factor on Cx due to right outboard elevon deflection. Similar application formulae are available for other five coefficients. The intermedi­ate values of a given coefficient base for the specific independent parameters can be obtained by interpolation (Exercise 6.1).