The full throttle height at rated manifold air pressure and normal RPM for that manifold air pressure. This is the height at which a piston engine gives its maximum power. With more than one stage of supercharging, there will be, correspondingly, more than one rated altitude. The graph shown here gives a series of altitude power curves obtained at different RPM. The dotted lines show the maximum power available at each of the speeds for takeoff and climb purposes. The graph shows 710 BHP (brake horsepower) at 2750 RPM at 10,000 ft. The maintenance of full power at any given rated altitude necessitates some method of restricting the engine output at lower altitudes and at ground level to ensure that the engine is not damaged by excessive temperature and pressure.