MAIN ROTOR - INDICATIONS
The PFD default page and the MFD MAIN page display the values of NF
(engine free turbine speed) and NR grouped in the TRIPLE TACHOMETER
scale.
1 NF/NR Triple Tachometer
NR values are indicated by the central pointer and the central digital
readout.
The values of NF in engine no.1 and no.2 are represented by digital
readouts under the two NF labels on the left and on the right
respectively. Graphically these values are represented on a vertical
scale by means of two pointers (triangles) that match the color of the
area on the scale.
The digital readouts and the pointers are displayed red when the
pointer is in the red zone (warning), amber when the pointer is in the
amber zone (caution) and green in normal conditions.
A red horizontal line is displayed corresponding to the MIN
TRANSIENT NR 95% and the MAX TRANSIENT NR/NF 106%.
When the EECs and the Modular Avionic Units (MAUs) detect an invalid
NR/NF input signal, the associated pointer is removed from the display and
amber dashes replace the numerical readouts.
If the NF sensor fails, the relative pointer is removed and replaced by the
amber legend FAIL in reverse video.
The baseline of the triple tachometer is green at all times, even when the
pointers are amber or red.
When a parameter being monitored exceeds the normal range of operation
(green band), the colour of associated pointer matches the colour of
applicable range marking in order to highlight the particular critical condition.
The triple tachometer scale ranges automatically change according to the
power plant status, i.e. AEO, OEI or POWER OFF (Autorotation) conditions.
PRIMARY DATA / BACKUP DATA INDICATIONS
Each MAU receives NR data from the two EECs via digital busses and
directly from the NR sensor via an analog signal interface.
The digital value received from the EEC is selected to drive the NR
indication on DUs by default. In case the digital input is lost or becomes
invalid, the analog input is automatically selected for display (backup data
source).
The backup data can also be manually selected for display by checking the
Analog check box in the Pwr Plant page menu. See also chapter 71-00