Abstract: An omnidirectional speed sensing system includes a rotatable member; a channel supported by the rotatable member and having an inlet and an outlet; a single pressure sensing port in the system disposed the channel between the inlet and the outlet for sensing the dynamic pressure of the fluid flow through the channel which pressure is a function of the rotational speed of the rotatable member and the velocity of the rotatable member through the fluid; transducer means responsive to the pressure at the sensing port for producing a pressure signal; means responsive to the pressure signal for extracting the first harmonic of the pressure signal; and means responsive to the magnitude and phase of the first harmonic of the pressure signal for indicating the velocity and direction of the sensed speed.

Abstract: Power required curves for ratios of helicopter weight to air density ratio form a background over which move perpendicular bars representing air speed and engine torque. The intersection of the relatively movable bars indicates which power required curve the helicopter is operating on. An area to the right and above that curve represents power margin available for maneuvering. A knob positions a mask over a portion of the background to indicate the actual maximum power limitation of the helicopter. A maximum power setting is varied according to ambient pressure and temperature. A minimum speed warning is produced by comparing air speed and engine torque. A rapid descent automatically raises the minimum speed warning.