Chip detectors used in the transmission oil system are similar to those used on engines. The rotor tachometer RPM indications are provided by the rotor tachometer-generator. The tachometer-generator drive is driven by the main transmission accessory gear train. The hydraulic pump drive is driven by the main transmission accessory gear train. The hydraulic pump provides hydraulic pressure for the flight control servo system.
Some helicopters use two separate flight control servo systems completely independent of each other.
A secondary servo system gets hydraulic operating pressure from a hydraulic pump driven by the engine. The upper bearing retainer plate has an oil jet fed by an external oil hose. Splints on the upper portion of the mast provide mounting for main rotor arid control assemblies. The shaft is made up of a series of hollow tubes with provisions for statically balancing and coupling attachments on each end. Flexibility in the shaft is provided by splined or rubber couplings.