PITOT AND STATIC (AIR DATA SENSORS) -PITOT PROBE HEAT -GENERAL DESCRIPTION
EFFECTIVITY BEJ ALL 30-31-00
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D633W101-BEJ Jan 05/2002
PITOT AND STATIC (AIR DATA SENSORS) -PITOT PROBE HEAT -FUNCTIONAL DESCRIPTION
General
The left, center, and right pitot probe heat systems operate the same. The left, right, and center pitot air data modules (ADMs) supply control and indications for the pitot probe heat systems.
Ground Mode
The primary flight computer (PFC) supplies air/ground signals for the ADM to energize the ground and air heat control relays. When the airplane is on the ground and either engine is on, the pitot probe gets 115v ac through the ground and the air heat control relays.
Air Mode
When the airplane gets to 50 knots or is in the air, the air heat control relay supplies 115v ac.
Indications
The probe heat sensor relay supplies a ground signal to the ADM when the pitot heat is on. The ADM supplies the pitot heat fault information directly through the data buses to the AIMS. It also supplies the information through the air data inertial reference unit (ADIRU) and the secondary attitude air data reference unit (SAARU) for advisory and status messages.
EFFECTIVITY BEJ ALL 30-31-00
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PITOT AND STATIC (AIR DATA SENSORS) -PITOT PROBE HEAT -FUNCTIONAL DESCRIPTION
EFFECTIVITY BEJ ALL 30-31-00
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D633W101-BEJ Jan 05/2002
777 AIRCRAFT MAINTENANCE MANUAL
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30-32-00
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PITOT AND STATIC (AIR DATA SENSORS) -ANGLE-OF-ATTACK PROBE HEAT -GENERAL DESCRIPTION
Purpose
The heaters in the AOA sensors keep ice off of the sensors so the data is reliable.
General Description
There is an AOA sensor on each side of the airplane nose. The sensors are interchangeable.
The sensor has heaters for the case and for the vane. There are two electrical connectors. Each sensor is an LRU. The components on the sensors are not LRUs.
EFFECTIVITY BEJ ALL 30-32-00
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D633W101-BEJ Sep 05/2002
PITOT AND STATIC (AIR DATA SENSORS) -ANGLE-OF-ATTACK PROBE HEAT -GENERAL DESCRIPTION
EFFECTIVITY BEJ ALL 30-32-00
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D633W101-BEJ Jan 05/2002
PITOT AND STATIC (AIR DATA SENSORS) -ANGLE-OF-ATTACK PROBE HEAT -FUNCTIONAL DESCRIPTION
General
The left and right angle-of-attack (AOA) sensor heat systems operate the same. The left and right pitot air data modules (ADMs) supply control and indications for the related AOA sensor heat system. Each system has a heater for the case and a heater for the vane.
The ADMs use information about these airplane conditions to calculate when to make AOA probe heat come on:
*
Engine on/off from the primary flight computer (PFC) and autopilot flight director computer (AFDC)
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Air/ground from the PFC and AFDC
*
Computed airspeed from the air data inertial reference unit (ADIRU)
*
Ground test and data load from the AIMS.
The ADMs use probe heat sensor relays in the power management panel to monitor the operation of the probe heaters. There is one sensor relay for the vane heater and one for the case heater.
Ground Mode
The left pitot ADM sets the left AOA probe heat to on if the airplane is on the ground and one or both engines are on. The ground heat control relay energizes and supplies 115v ac to the case and vane heaters.
Air Mode
The left pitot ADM sets the left AOA probe heat to on if the airplane is in the air or if the computed airspeed (CAS) is more than 50 knots. The air heat control relay energizes and supplies 115v ac to the case and vane heaters.
AOA Heater Current Monitor/Indication
The case and vane probe heat sensor relays monitor the heater current and give the status of the heaters to the left pitot ADM. The ADM gets an open (high) signal when the related heater is off and a ground signal (low) when the related heater is on. The pitot ADM sends the status of the AOA probe heaters to these components/system:
*
ADIRU
*
SAARU (secondary attitude and air data reference unit)
*
AIMS.
The ADIRU and SAARU use heater status to calculate if AOA data is valid.
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