Apparatus for indicating pitch angle of a propeller blade

Abstract

An apparatus for detecting the pitch angle of a propeller blade comprises a sensor and two transmitters. The transmitters are strategically located so as to identify a first fixed reference point on the propeller hub and a second movable point on the propeller blade. The sensor is mounted on a non-moving reference such as the engine housing. The sensor detects the time difference in signal arrival from each magnetic transmitter as they rotate on the propeller assembly and pass by the sensor. The fixed transmitter, although spinning with the propeller hub, does not move relative to the hub itself, and is mounted in a fixed position relative to the hub such as on the bulkhead plate. Each time the fixed transmitter passes by the sensor it generates a reference signal. The movable transmitter moves with the propeller blade as it rotates about the pitch axis thus changing the distance between the two transmitters. After the fixed sensor passes by the sensor, the movable transmitter passes by the sensor generating a second signal such that there is a measurable difference in the time of arrival between the two signals. The measurable difference is indicative of the blade pitch angle.

Dependencies are inferred from the claim text.