Main Rotor Indicating
Last updated
Last updated
The main rotor indicating provides an electrical signal which indicates the angular speed of the main rotor shaft. This signal is used by other systems to determine NR and RPM warnings which are presented to the pilot. It includes the sensor No.1.
The Nr sensor No.1 is a transducer that is mounted under the transmission pump adapter and provides an indication of the RPM of the main rotor shaft via a digital bus. Based on this signal, values of Percentage Main Rotor RPM (NR) and RPM warning are determined by other systems on the helicopter. The sensor is an electromechanical component. The gap between the sensor and the moving mechanical part must be adjusted.
The Nr sensor No.1 senses the magnetic fluctuations caused by the machined slots in the hydraulic pump shaft assembly as they rotate around the Nr sensor No.1. The Nr sensor No.1 conditions and amplifies these raw analog sensor signals and converts them to digital and puts them on the digital bus. The engine and airframe interface unit (GEA) supplies 5 VDC to the Nr sensor No.1 and the Nr sensor No.1 sends digitized RPM data on the digital bus to the GEA. The GEA converts the RPM values received from the Nr sensor No.1 to a percentage value and routes them to the integrated avionics unit (GIA). The GIA receives the percentage RPM values and routes them to the displays. The displays display unit uses the percentage RPM signal for several uses:
It produces a symbiology display for the NR.
It produces and displays Crew Alerting System (CAS) messages, as needed.
It uses the NR signal in the Weight On Gear (WOG) calculations.
It creates the trigger for the RPM annunciator light and the audio warnings.
Any warnings that the displays put out are routed back to the integrated avionics unit (GIA). Both the high and low RPM warnings are routed to the RPM annunciator light for a visual indication for the pilot and copilot. For the low RPM warning, the GIA also generates an audio signal and routes it to the audio panel (GMA) that broadcasts it to the pilot and copilot through their headsets.
