16.885J/ESD. 35J-Sept 2003 Force Coefficients It is convenient to use non -dimensional forms of the forces. called coefficients D Where g==p Allows scaling between different size aircraft (wind tunnel models vs full scale), different velocities, altitudes, etc Can use different ways, e. g IfCL,s,q are known, then L= Cisq Ifl=W and c, s are known, then flight speed which ives level flight is 2W16.885J/ESD.35J - Sept 2003 Force Coefficients • It is convenient to use non-dimensional forms of the forces, called coefficients • Allows scaling between different size aircraft (wind tunnel models vs full scale), different velocities, altitudes, etc. • Can use different ways, e.g. – If CL, S, q are known, then L = CLSq – If L=W and CL, S are known, then flight speed which gives level flight is CL LqS , CD DqS where q 12 U fVf2 Vf 2W UfCLS