767 IRS Flashcards
3 conditions that cause the align lights to flash?
- Must enter the initial position in the CDU within 10 minutes.
- The airplane is moved during the alignment phase(wheel rotation).
- Give it bad info.Lat or Long is not within 1 degree of Last POS.
4 basic NAV references FMC needs from the IRS?
Velocity
Position
Heading
Attitude
What type of electrical power is needed to initialize the IRS
Both AC and DC. After initialization either will work but AC is preferred.
What does the OD DC light indicate?
The IRS is operating on DC power from the HBB. This light illuminates briefly during initial power-up and alignment.
What indications are given when the IRS is using DC power?
The ON DC light illuminated and a horn sounds in the wheel well to alert someone.
What does the DC FAIL light mean?
The IRS is being powered by AC and that you have lost the (HBB)DC backup power.
Is there a problem if the DC FAIL light is illuminated?
No as long as AC power is available.
What does the FAULT Light mean?
A fault affecting the related IRRS ATT and/or NAV mode has been detected. This is a maintenance item so just turn it off.
If the Left FAULT light illuminated what should you do?
Refer to the QRH. It tells you to select the Captain’s ALTN IRS switch to ALTN.
What happens when you select the Captain’s IRS switch to ALTN?
The center IRS becomes the source for the Left and Center DCU’s and Captain’s VSI.
What happens when you select the FO”s IRS switch to ALTN?
The center IRS becomes the source for the right DCU and the FO’s VSI.
What indications will you see when an IRU fails?
You will lose the attitude indicator, the compass rose and the opposite RDMI.
What do you get with the selector switch in ATT?
ADI attitude and Magnetic heading.
Normal power source for the IRU’s?
Left-L AC transfer Bus, Center-Center AC Bus, Right-Right AC Bus.
With a loss of electrical power, what is the backup power for the IRU’s?(non ETOPS)
Standby power to the left and center IRU’s is limited to 5 minutes to save battery power and the right IRU is powered by the HBB.
With a loss of electrical power, what is the back-up power for the IRU’s(ETOPS aircraft)?
Standby power to the right IRU is limited to 5 minutes to save battery power and the L and C IRU’s are powered by the HBB.
How long does a “full alignment” take and what does it do?
10 Minutes. Defines new reference for true north, establishes present position and zeros the groundspeed.
How long does a “Quick alignment” take and what happens?
30 seconds. Establishes a new starting position and zeros the groundspeed.
What is the difference between a Quick alignment and an Abbreviated Quick Alignment?
The Abbreviated Quick Alignment does not input a position and just zeros the groundspeed.
What is the max time limit between Full Alignments?
18 hours.
Is the IRS updated after it is initialized?
No, only the FMC is updated.
At what Latitude is IFR or Night flight limited to when NAV aids are referenced to MAG North?
73 degrees North and 60 degrees south.
When do the set IRS boxes appear on the FMC POS INIT page?
When any IRS is in the align mode and a present position has not been entered.
During the alignment process, with the display selector in heading, What will be displayed?
Time to NAV mode will be displayed. 7-0
