AIR DATA INERTIAL REFERENCE SYSTEM
PROVIDES FLIGHT DATA SUCH AS POSITION,
SPEED, ALTITUDE & ATTITUDE
THE DATA ARE USED FOR :
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FLIGHT DISPLAYS
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FLIGHT MANAGEMENT COMPUTER
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AUTOFLIGHT SYSTEMS
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OTHER SYSTEMS
MAJOR COMPONENTS OF THE AIR DATA
INERTIAL SYSTEMS
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2 AIR DATA INERTIAL REFERENCE UNITS ( ADIRU)
4 AIR DATA MODULES (ADMS)
INERTIAL SYSTEM DISPLAY UNIT (ISDU)
MODE SELECTOR UNIT (MSU) ON THE AFT OVHD PANEL.
THE AIR DATA INERTIAL REFERENCE SYSTEM COMBINES AIR DATA AND INERTIAL
REFERENCE FUNCTIONS OF OLDER, SEPARATE SYSTEMS.
THE PITOT STATIC SYSTEM SUPPLIES DATA FOR THE ADIRUS AND STANDBY FLIGHT
INSTRUMENTS.
THE ADMs RECEIVE RAM AIR
PRESSURE FROM THE PRIMARY
PITOT PROBES & STATIC PRESSURE
FROM THE PRIMARY STATIC PORTS.
THE ADMs SEND THIS DATA TO THE
ADIRUs.
3 PITOT PROBES (1 PRIMARY PER SIDE) 6
STATIC PORTS (2 PRIMARY PER SIDE)
THE AUXILIARY PITOT PROBES (FO
SIDE) AND ALTERNATE STATIC PORTS
(1 PER SIDE) SUPPLY PITOT AND
STATIC PRESSURE DATA TO THE
STANDBY ALTIMETER/AIRSPEED
INDICATOR
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1 TOTAL AIR TEMPERATURE ( TAT PROBE) PROVIDES
TEMPERATURE DATA TO THE 2 ADIRUs.
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THE ADIRUs THEN SUPPLY INFORMATION TO THE TAT
INDICATIONS WHICH IS SHOWN ABOVE ENGINE DISPLAY.
TWO ALPHA VANES SUPPLY ANGLE OF ATTACK DATA TO THE
ADIRUs.THE STALL MANAGEMENT SYSTEM, AUTO-THROTTLE,
AUTOPILOT AND AUTOSLATS ALL USE THIS DATA.
PART OF THE ADIRS (AIR DATA INERTIAL REFERENCE SYSTEM) OR IRSs, ARE THE
PRIMARY SOURCE FOR POSITION AND ATTITUDE DATA.
THERE ARE 2 ADIRUS. EACH
ADIRU CONTAINS AIR DATA AND
INERTIAL REFERENCE PARTS.
IRS ( INERTIAL REFERENCE SYSTEM) REPLACES OLDER
TECHNOLOGY SUCH AS MECHANICAL GYROS, INERTIAL
NAVIGATION
THE IRS CONTAINS ELECTRONIC SENSORS AND
NON-MECHANICAL LASER GYROSCOPES, WHICH MEASURE THE
AIRPLANE MOVEMENT IN ALL 3 AXES.
SIGNALS FROM THIS SENSORS ARE USED TO CALCULATE:
● ATTITUDE
● TRUE AND MAGNETIC HEADING
● ACCELERATION
● VERTICAL SPEED
● GROUND SPEED
● TRACK
● WIND
● AIRPLANES LATITUDE AND
LONGITUDE POSITION
THE IRS SUPPLY ATTITUDE, HDG,V/S AND
OTHER DATA FOR THE FLIGHT
INSTRUMENTS.
THEY SUPPLY THE FMC WITH POSITION,
WIND AND OTHER DATA.
THE IRS ALSO SUPPLIES DATA FOR THE
AUTO-THROTTLE ,FLIGHT CONTROL
COMPUTERS AND OTHER SYSTEMS.
PREFLIGHT ALIGNMENT
BEFORE THE IRSs CALCULATE ATTITUDE AND POSITION INFORMATION, YOU MUST DO
PREFLIGHT ALIGNMENT. PREFLIGHT ALIGNMENT SENSES A TTITUDE, TRUE NORTH,
AND POSITION. THE IRSs DO NOT USE NAVIGATION AIDS TO DO
THE ALIGNMENT.
THE IRS USES
● GRAVITY TO CALCULATE INITIAL ATTITUDE.
● EARTH ROTATION TO CALCULATE TRUE NORTH AND
POSITION. (AIRPLANE MUST NOT MOVE DURING
ALIGNMENT TO MAKE SURE THAT EARTH'S ROTATION IS
THE ONLY MOVEMENT SENSED BY THE IRSs)
ALIGNMENT TIME IS BETWEEN
5-10 MIN.
●5 MIN AT THE EQUATOR
●10 MIN AT 70º LATITUDE.
●17 MIN AT HIGH LATITUDE (70º
TO 78º)
THE IRS MODE SELECTOR UNIT (MSU) IS ON THE AFT OVRH PANEL
TO START ALIGNMENT YOU USUALLY MOVE THE MSU TO NAV. THIS
MAKES THE IRSs GO INTO NAV MODE WHEN ALIGNMENT IS
COMPLETE.
1-MSU NAV
ON DC LIGHTS ILLUMINATE WHILE THE IRSs DO A DC
POWER TEST.
2-WHEN ALIGNMENT STARTS-ALIGN LIGHTS
ILLUMINATE. (WHITE)
3-PUT IN THE AIRPLANES POSITION.
(USUALLY USE DE CDU TO PUT THE AIRPLANES)
4-WHEN ALIGNMENT ENDS, ALIGN LIGHTS EXTINGUISHED.
DURING ALIGNMENT, THE IRSs SENSE THEIR POSITION.
THEY COMPARED SENSED POSITION WITH THE POSITION
YOU PUT IN, AND WITH THE POSITION AT THE TIME THE IRSs
WERE SHUT DOWN.
THE ALIGN LIGHTS FLASHES IF
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THE SYSTEM SENSES THAT THE POSITION IS TO FAR FROM THE POSITION YOU PUT
IN OR FROM THE POSITION AT SHUT
DOWN.
THE CDU SCRATCHPAD WILL SHOWS THE IRS
POSITION MESSAGE-YOU MUST PUT THE POSITION
AGAIN
DURING FLIGHT, EACH IRSs CALCULATES ITS
POSITION
ALTHOUGH VERY ACCURATE, ERRORS
ACCUMULATE
THE FMC ALSO USES NAVIGATION RADIO DATA TO
CALCULATE AND SHOW ITS POSITION.
SPECIAL PROCEDURES ARE NECESSARY FOR FLIGHT
AT HIGH LATITUDES, AND IN SOME AREAS NEAR THE
MAGNETIC POLES.THE IRSs CANNOT PROVIDE
MAGNETIC HEADING IN THESE AREAS. THE IRSs
CONTINUE TO SUPPLY TRUE HEADING.
AFTER A FLIGHT, TURN THE MSU OFF - THE IRS
WILL START A 30 SEC SHUT DOWN
THE ALIGN LIGHT WILL ILLUMINATE, THEN
EXTINGUISHES WHEN SHUT DOWN CYCLE IS
COMPLETED.
DURING A THROUGH FLIGHT, A COMPLETE IRS
SHUTDOWN IS RECOMMENDED, THEN, DO A FULL
ALIGNMENT.
WITH NO SUFFICIENT TIME- FAST
REALIGNMENT-AIRPLANE MUST NOT MOVE
1-TO START MSU TO ALIGN
2-YOU CAN PUT IN A NEW POSITION IF
NECESSARY (NOT MANDATORY)
3-TURN MSU TO NAV
4-ALIGNMENT COMPLETES IN 30 SEC OR LESS
AND ALIGN LIGHTS EXTINGUISH
THE INERTIAL SYSTEM DISPLAY UNIT (ISDU), IS ON THE
AFT OVERHEAD PANEL. YOU USE THE ISDU TO PUT IN
AND SHOW IRS DATA.
AFTER THE IRSs ARE ALIGNED, YOU CAN USE THE ISDU
DISPLAY SELECTOR TO SHOW
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CURRENT TRUE HEADING
TRUE WINDS AT THE CURRENT ALTITUDE
PRESENT POSITION IN LATITUDE AND
LONGITUDE
TRUE TRACK AND GROUND SPEED
YOU CAN ALSO USE THE ISDU TO PUT IN THE PRESENT
POSITION DURING ALIGNMENT.
1-TURN THE IRS MSU TO NAV TO START ALIGNMENT
(DC LIGHT ON, THEN EXTINGUISH, THEN ALIGN WHITE)
2-ISDU IN PPOS
3-ENTER POSITION IN ISDU KEYBOARD (FIRST LAT, PRESS
ENTER THEN LONG + ENTER KEY). IF YOU MAKE AN ERROR,
USE THE CLR KEY AND START AGAIN.
FAULTS
IN THIS CASE, SHOWS THERE IS A FAULT IN
THE SELECTED MODE. LEFT IRS NAV MODE
FAILED.
BECAUSE OF THIS, ATTITUDE AND HEADING
INFORMATION ARE NOT AVAILABLE TO THE
CAPTAIN. TO MAKE THE ATTITUDE
INDICATOR AVAILABLE AGAIN, TURN THE
LEFT IRS MODE TO ATTITUDE (ATT)
THE ALIGN LIGHT WILL ILLUMINATE. YOU MUST
KEEP WINGS LEVEL, CONSTANT SPEED FLIGHT
FOR APROX
30
SECONDS
WHILE THE
IRS ALIGNS
IN THE
ATTITUDE
MODE.
IN ATTITUDE MODE, THE IRS DOES NOT CALCULATE
● ACCELERATION
● VERTICAL SPEED
● GROUND SPEED
● TRACK
● POSITION
● HEADING
● WIND
TO DISPLAY HEADING DATA, YOU MUST PUT THE
CURRENT MAGNETIC HEADING ON THE CDU POS INIT
PAGE.
REGULARLY EXAMINE THE IRS HEADING AND PUT IN
THE NEW HEADING IF NECESSARY
RESET THE MASTER CAUTION SYSTEM
THE ON DC LIGHT SHOWS THAT AC POWER
IS NOT NORMAL AND THE BATTERY
SUPPLIES DE ADIRU WITH POWER.
THE RIGHT ADIRU OPERATES WITH
BATTERY POWER FOR 5 MINUTES. IF AC
POWER IS NOT AVAILABLE AFTER 5
MINUTES, THE RIGHT ADIRU
AUTOMATICALLY SHUTS DOWN.
IF THE LEFT ON DC LIGHTS ILLUMINATES,THE LEFT ADIRU OPERATES
AS LONG AS BATTERY POWER IS AVAILABLE.
IF THE AIRPLANE IS ON THE GROUND AND THE ON DC LIGHT
ILLUMINATES, A GROUND CALL HORN OPERATES TO TELL OF
BATTERY DRAIN CONDITION.
DC FAIL LIGHT
RESET THE MASTER CAUTION SYSTEM- DC FAIL LIGHT SHOWS THAT DC
POWER FOR THE ADIRU IS NOT NORMAL. IF THE OTHER LIGHTS ARE OFF,
THE ADIRU CONTINUES TO OPERATE NORMALLY ON AC POWER.
THE IRS TRANSFER SWITCH IS ON THE OVRH PANEL. YOU
CAN USE THIS SWITCH TO SELECT THE IRS SOURCE FOR
THE DISPLAYS.
THE LEFT IRS DISPLAY HAS FAILED, MOVE THE
TRANSFER SWITCH TO BOTH ON RIGHT
THE RIGHT IRS NOW SUPPLIES DATA TO BOTH CAPTAINS
AND FO DISPLAYS.
THE INSTRUMENT SWITCH FLAGS COME
INTO VIEW TO TELL THAT 1 IRS SUPPLIES
DATA TO ALL OF THE DISPLAYS