On the representation of the drag polar of a fighter aircraft

The values of lift coefficient encountered during manoeuvres13; of a fighter aircraft are known to be wel1 beyond the range where the classical representation CD = CDo + k ci is a good approximation. Examination of available test data on several configurations showed that the drag polars can be approximately represented as CD = CDo + k ci + a C with a suitable choice of a and n.13; A simpler representation with the value of n equal to 413; was carefully tested against detailed test data on two configurations for Mach numbers ranging from 0.5 to 1.5 and angles of attack from -4xB0; to 20xB0;. Agreement was generally better than 5% in transonic and supersonic range. The agreement was satisfactory in the subsonic range, although the departures were occasionally larger in magnitude. It is suggested that the representation with n = 4 can be advantageously used in the turn calculations of fighter aircrafts