ESDU 94040 discusses how the maximum cabin pressure differential and the rate of change of cabin pressure affect rates of climb and descent@ particularly of civil aircraft. The cabin pressure differential is governed by the capability of the air-conditioning system@ the strength of the fuselage and the maximum operating altitude of the aircraft. A sketch illustrates how cabin pressure and pressure differential affect operating altitude and indicates where aircraft of various classes operate. Excessive rate of change of pressure can build up a differential pressure across the eardrums and at 0.5 lbf/sq in (3.45 kN/sq m) would cause pain. For civil aircraft restricting the rate of change of cabin pressure is a major factor in determining descent profile and has also to be considered in climb although to a lesser extent. A further sketch illustrates possible climb and descent profiles chosen to maintain cabin pressure and its rate of change within the necessary restrictions while not exceeding cabin differential pressure limits.