ESDU 81046 gives algebraic, numerical and graphical forms of "acceleration factors" which provide a simple, direct method of taking into account the acceleration of an aircraft along the flight path in the calculation of instantaneous (or point) rates of climb and descent. The particular cases considered are climb or descent at constant equivalent airspeed (EAS), constant calibrated airspeed (CAS) and constant Mach number. The main text gives the general relationships for these acceleration factors while separate Tables give the numerical forms of the equations appropriate to the International Standard Atmosphere and associated off- standard atmospheres.