Cruise Performance of Fixed-wing Aircraft

Methods are presented for the determination of the range and endurance of fixed-wing airplanes with thrust-rated powerplants (e.g. turbo-jets and turbofans) and power-rated powerplants (e.g. piston-propeller and turbo-propeller). Range and endurance integral expressions are derived, and numerical techniques for their evaluation outlined. Analytical solutions for the integral expressions are presented based on the following sets of assumptions: (i) cruise at constant height and constant lift coefficient, (ii) cruise at constant airspeed and constant lift coefficient (i.e. the Breguet solution), and (iii) cruise at constant height and constant airspeed. There are two conventions for the definition of the specific fuel consumption (SFC): it can be defined either in terms of the mass flow rate or the weight flow rate of the fuel. This leads to two sets of expressions for range and endurance; both conventions are covered in this chapter. The determination of the fuel required for an airplane to fly a complete mission – which includes the takeoff, climb, cruise, descent, approach and land – is a relatively complex calculation; however, considerable insight into an airplane's range is achieved by studying the cruise segment in isolation – this approach is outlined.