This maneuver is a procedure for establishing the fastest practical rate of descent during emergency conditions which may arise as the result of an uncontrollable fire, a sudden loss of cabin pressurization, or any other situation demanding an immediate and rapid descent. The objective, then, is to descend the airplane as soon and as rapidly as possible, within the limitations of the airplane, to an altitude from which a safe landing can be made, or an altitude where pressurization or supplemental oxygen is not needed.
The simulated emergency descent must be started high enough to permit recovery at a safe altitude. Before entering the maneuver, the area below must be free of other air traffic, since the loss of altitude is quite rapid. In no case should the airplane's never exceed speed (Vne), maximum gear extended speed (Vle), or maximum flap extended speed (Vfe) be exceeded.
Generally, the maneuver should be performed with the airplane configured as recommended by the manufacturer. Except when prohibited by the manufacturer, the power should be reduced to idle, and the propeller control (if so equipped), should be placed in the low pitch (or high RPM ) position. This will allow the propeller to act as an aerodynamic brake to help prevent excessive airspeed during the descent. As quickly as practical, the landing gear and full flaps should be extended to provide maximum drag so that a descent as rapidly as possible can be made without excessive airspeed. This, of course, should be done only in accordance with the airplane manufacturer's recommendations.
To maintain positive load factors (G forces) and for the purpose of clearing the area below, a 30 to 45 degree bank should be established for at least a 90 degree heading change while initiating the descent.
Normally during student training, as soon as all prescribed
procedures are completed and the descent is established and stabilized,
the maneuver should be terminated. In airplanes with piston engines, a
prolonged practice emergency descent should be avoided to prevent excessive
cooling of the cylinders.