777 AIRCRAFT MAINTENANCE MANUAL
ADIRS -STANDBY ATTITUDE INDICATOR
EFFECTIVITY BEJ ALL 34-20-00
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D633W101-BEJ Jan 05/2002
ADIRS -STANDBY ATTITUDE INDICATOR FUNCTIONAL DESCRIPTION
Power Outputs
The standby attitude indicator gets 28v dc for power. Brightness data goes to the standby altimeter and the standby airspeed indicator. Fault data goes to the central maintenance
Attitude Inputs
computing function (CMCF) of the AIMS.
The secondary attitude air data reference unit (SAARU) supplies attitude data to the standby attitude indicator. The data goes to a microprocessor. The microprocessor supplies display data to the liquid crystal display (LCD).
Brightness Inputs
Brightness data comes from the:
*
Standby altimeter
*
Standby airspeed indicator
*
Integral light sensor
*
Remote light sensors.
The microprocessor uses the brightness inputs to adjust the brightness of the LCD.
Program Pin
A standby attitude indicator program pin selects the standby attitude indicator display format.
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ADIRS -STANDBY ATTITUDE INDICATOR FUNCTIONAL DESCRIPTION
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ADIRS -TOTAL AIR TEMPERATURE PROBE
Purpose
A total air temperature (TAT) probe measures temperature outside the airplane.
Sensing Elements
There are two sensing elements in a TAT probe. Each sensing element is a resistive element. The value of resistance changes when the temperature of the air flow across the element changes.
Air from the left air conditioning pack cross manifold makes a negative pressure inside the probe. The negative pressure pulls outside air across the sensing elements. This gives an accurate temperature measurement when the airplane is on the ground or moving at low speed.
Electrical Connector
The analog connection to AIMS and the heater power connection comes through the electrical connector. The heater in the TAT probe prevents ice buildup.
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777 AIRCRAFT MAINTENANCE MANUAL
ADIRS -TOTAL AIR TEMPERATURE PROBE
EFFECTIVITY BEJ ALL 34-20-00
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D633W101-BEJ Jan 05/2002
ADIRS -TAT PROBE FUNCTIONAL DESCRIPTION
Probe Heater
The TAT probe heater gets 115v ac from the P110 left power management panel. The TAT probe has heater power only when the airplane is in the air.
Total Air Temperature (TAT)
TAT element 1 connects to the TAT element 1 sense and return in the left AIMS cabinet. TAT element 2 connects to the TAT element 2 sense and return in the right AIMS cabinet.
The AIMS cabinets change the analog TAT probe data to ARINC 629 data. AIMS sends TAT temperature data from element 1 to the left flight controls ARINC 629 bus. AIMS sends TAT data from element 2 to the right flight controls ARINC 629 bus.
The ADIRU and SAARU receive TAT data to calculate air data.
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777 AIRCRAFT MAINTENANCE MANUAL
ADIRS -TAT PROBE FUNCTIONAL DESCRIPTION
EFFECTIVITY BEJ ALL 34-20-00
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