PRIMARY DATA / BACKUP DATA INDICATIONS
The ITT thermocouples of each engine are directly connected to the on-side
EEC and to the on-side MAU.
The NG and TQ/NF sensors of each engine have two independent coil pickups
each and provide two independent analog output signals, one
connected to the on-side EEC, the other to the on-side MAU. The second
TQ/NF sensor (secondary) installed on each engine is connected to the
cross-side EEC. The NR sensor has three independent coil pick-ups and
similar interface (see chapter 62-00).
Each EEC outputs the primary engine data (NG, ITT, TQ, NF) and NR on a
digital bus to both MAUs.
The digital data available from EEC are selected by default for display on the
MFD (primary data source); in case any of the digital primary engine data is
not available from the EEC, the corresponding analog input from the sensor
to the MAU is automatically selected for display (backup data source). If the
primary engine data digital bus communication is lost, the 1(2) EEC DATA
caution message is displayed in the CAS.
The backup data can also be manually selected for display by checking the
Analog check box in the Pwr Plant page menu.
When backup data source is selected for display, PI indication is not
computed: PI pointer is removed and digital readout shows amber dashes.
In case of failure of an analog parameter, the caution message ENG
ANALOG FAILURE will be generated in the CAS window.
ENGINE PRIMARY DATA COMPARISON FUNCTION
A function of the MAUs permits the digital data received from the EECs and
the analog signals received directly from the engine sensors to be
continuously compared.
In case of miscompare between analog data and digital data, a caution
message is generated in the CAS identifying the parameter(s) involved:
- 1(2) NG MISCOMPARE
- 1(2) ITT MISCOMPARE
- 1(2) TQ MISCOMPARE
- 1(2) NF MISCOMPARE
- NR MISCOMPARE