Relationships between flying qualities and flight tests parameters for the F/A-18 aircraft

The relationships between flying qualities levels and flight test parameters such as Mach numbers, altitudes, angle-of-attack of the F/A-18 System Research Aircraft (SRA) can help in determining the stability and control derivatives dependent on flight test conditions. The stability and control derivatives were calculated at NASA Dryden Flight Research Center DFRC laboratories. The approximate method and the exact method were used to calculate the characteristic system eigenvalues. The natural frequencies and damping were determined from these eigenvalues, using the classic vibration equation for the longitudinal and for the lateral aircraft motion. Relative errors were calculated for frequencies and damping with the approximate method versus the frequencies and damping calculated with the exact method for the aircraft. The relative errors for the roll constant time increases with the increase of the altitude and with the reduction of the Mach number.