Tail Rotor Drive Indicating

The system of the tail rotor drive indicating monitors the quantity of ferrous metal particles in the lubrication oil of the tail rotor gearbox and gives indications to the pilot and copilot. The system of the tail rotor drive indicating includes the tail rotor gearbox chip detector.

Tail rotor gearbox chip detector

The tail rotor gearbox chip detector is referred to as the chip detector in this paragraph.

The chip detector is installed on the housing of the tail rotor gearbox. It is a two-pole, single-wire type of chip detector that includes a self-closing valve. The chip detector controls the Crew Alerting System (CAS) indications through the detection of ferrous metal (steel) particles in the lubrication oil.

The chip detector uses a bayonet-type mount for attachment to its self-closing valve. The valve is spring loaded and closes to prevent an oil leakage when the chip detector is removed. It is also used as a drain port for the tail rotor gearbox.

The chip detector has a metallic outer electrode, a permanent ceramic magnet, and a metallic inner electrode. The magnetic field from the magnet causes steel particles to collect between the outer and inner electrodes. When there is a sufficient quantity of particles to bridge the gap between the electrodes, the circuit closes.

Operation

The tail-rotor-gearbox chip detector is referred to as the chip detector in this paragraph.

When a sufficient quantity of particles collect to close the circuit, the chip detector applies a ground to the integrated avionics unit (GIA). This causes the T/R CHIP caution message to come on. The GIA applies a ground through a diode to do a check of the wiring. If the wiring is defective, the fault will cause the DRIVE CD INOP caution message and the T/R CD INOP advisory message to come on.