PITOT-STATIC/AIR DATA STANDBY INSTRUMENTS -STANDBY AIRSPEED INDICATOR/ALTIMETER
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PITOT-STATIC/AIR DATA STANDBY INSTRUMENTS -FUNCTIONAL DESCRIPTION
Power
The air data standby instruments get power from the standby instrument circuit breakers. The air data standby instruments send 13.5v dc to the SADMs.
SADM Signal Processing
The SADMs receive pressure inputs from a static port or pitot probe. The microprocessor converts this pressure to an ARINC 429 word and sends this data to the standby instruments.
SADM Bite
The SADM built-in-test equipment (BITE) detects internal faults which are in nonvolatile memory that are shop accessible only.
Air Data Standby Instruments Pressure Inputs
SADM data goes to the air data standby instrument ARINC 429 receiver. The receiver sends this data to the microprocessor. The microprocessor supplies display data to the LCD display.
Standby Instruments Brightness Inputs
Brightness data comes from:
*
The standby instruments
*
Integral light sensor
*
Remote light sensor
The microprocessor uses the brightness inputs to adjust the brightness of the LCD display.
Program Pin
Standby altimeter, standby airspeed indicator, and standby attitude indicator program pins select the appropriate standby instrument display format.
Push-button and Selector
The push-button and selector give the altitude correction value in the standby altimeter, and move the airspeed bug on the standby airspeed indicator.
The push-button and selector does not operate when the standby instrument is in the standby attitude indicator location.
Outputs
Brightness data goes from each standby instrument to the other two standby instruments. Fault data goes to the CMCF in the AIMS cabinets.
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PITOT-STATIC/AIR DATA STANDBY INSTRUMENTS -PITOT PROBE -HEAT
General
The pitot air data modules (ADMs) control the heat control relays in the power management panels. The heat control comes from data the ADMs receive from the primary flight computers (PFCs) through the flight controls ARINC 629 bus. If the PFCs are not valid, the ADMs use data from the autopilot/ flight director computers (AFDCs). The AFDC data also comes through the flight controls ARINC 629 bus.
The pitot ADMs control the pitot heaters for the onside pitot probes.
Ground Mode
The ground and the air heat control relays supply 115v ac when the airplane is on the ground and either engine is on.
Air Mode
The air heat control relay supplies 115v ac when any of these conditions are true:
*
The computed airspeed (CAS) is more than 50 knots
*
The airplane is in the air.
Pitot Heater Current Monitor
The probe heat sensor relay detects current when the pitot probe heat is on, and sends a ground signal to the pitot ADMs. The pitot ADMs send the status of the pitot heat to these units:
*
ADIRU
*
SAARU
*
AIMS cabinets.
Training Information Point
See the ice and rain protection chapter for information on how to do a test of the pitot probe heat (CHAPTER 30).
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777 AIRCRAFT MAINTENANCE MANUAL
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
AIR DATA INERTIAL REFERENCE SYSTEM -INTRODUCTION
General
These are the two functions of the air data inertial reference system (ADIRS):
*
Air data
