IRS MODE SELECTOR PANEL (LOWER) Flashcards
1
Q
ALIGN LIGHT
A
-
Illuminated (White): steady or flashing
- Steady: related IRS operating in ALIGN mode, initial ATT mode, OR shutdown cycle
-
Flashing: unable to complete alignment due to IRS detection of (NO BAD MOVE)
- NO PRESENT POSITION ENTRY
- BAD POSITION (i.e. significant difference between previous and current entered positions - assumed error or unreasonable present position (actual error))
- MOVE: aircraft movement stops the alignment
-
Extinguished:
- IRS not in align mode
- IRS is in NAV mode and alignment is complete
- IRS is in ATT mode and attitude info is available (hdg will be available after intial hdg entry)
2
Q
FAULT LIGHT
A
- Illuminated (AMBER) - there is a system fault affecting the related IRS ATT and/or NAV modes
[1sp - internal fault with the respective IRU]
3
Q
ON DC Light
A
- Illuminated (amber): related IRS is operating on DC power from the SWITCHED HOT BATT BUS (AC power is not normal and has been removed)
- Battery Switch MUST be on
- if this light comes on when on the ground, it sets off the nose wheel well call horn letting ground maint know there is a battery drain condition
- during alignment self-test it is normal to briefly go on (approx 10 seconds - backup DC power self test)
[1sp - the respective IRS is working on battery power]
Details:
- Left ADIRU: operates on DC power from the 28v SW Hot Batt Bus until power is less than 18v dc
- Right ADIRU: when AC power is lost, it gets powered for 5 min. After 5 min of continuous DC power, the circuit is de-energized and power to the right ADIRU is removed allowing the battery to drain at a slower rate.
4
Q
DC FAIL Light
A
- Illuminated (Amber): DC power for the related IRS is NOT NORMAL. (i.e. the related IRS has lost its backup DC power source < 18v DC). If this light is ON and all the others are OFF, the IRS is operating NORMALLY.
[1sp - the respective IRS doesnt have the backup power that is coming from the battery i.e. the dc power to the respective IRS has failed]
- could also come on if the Battery switch is in the OFF position.
Details.
- if BOTH DC FAIL LIGHTS ILLUMINATE: this means the battery is almost dead! When this happens - refer to the QRH because you lose a LOT of items such as alternate power to the AC/DC standby bus and the Hot Batt Bus.
5
Q
IRS MODE SELECTOR KNOB
- 4 positions -
OFF
ALIGN
NAV
ATT
A
-
OFF:
- in this mode, alignment is lost, when positioned to OFF (knob must be pulled out) all electrical power is removed from the system AFTER a 30 SECOND shutdown cycle.
- NOTE: after going to OFF, wait at least 30 SECONDS before powering down the aircraft
-
ALIGN:
- initiates the alignment cycle (from OFF to ALIGN (or OFF to NAV))
- Automatically updates alignment and zeroes ground speed error (from NAV to ALIGN - fast align)
- the plane must be parked
- * if you go to ALIGN IN FLIGHT = you will lose the alignment
-
NAV:
- system enters NAV MODE after: 1: entry of PPOS and 2: completion of the alignment cycle
- provides full IRS data to airplane systems for normal ops
- it may illuminate the ON DC light for about 10 seconds (test)
- * DO NOT MOVE OUT OF THIS POSITION IN FLIGHT - YOU WILL LOSE ALL NAV REFERENCE
- ** MOVING FROM NAV TO OFF - KICKS OFF THE YAW DAMPER
-
ATT:
- provides only attitude and heading (backup mode using gyro data if nav function of ADIRU fails)
- ATT info invalid (ATT flag in view) - until ALIGN light is out
- HDG invalid (hdg flags in view) - until actual MAG HDG is MANUALLY ENTERED AFTER the ALIGN light is extinguished
- POSITION & GND SPEED: not available until IRS is aligned ON THE GND
- Selector must be cycled to OFF: before reselecting ALIGN or NAV
- Info: when selector is in NAV you must pull OUT the knob to go to ATT to prevent accidentally moving it. It also has a 2 second delay
- usually the FMCs receive inertial data from onside ADIRU (left ADIRU to FMC 1 and rt to FMC 2) - if the on-side ADIRM fails OR its in the ATT or ALIGN mode, the FMC uses the data from the other ADIRU
