IRUs - Question Bank

Question 1

How do you select the IRU mode selector from NAV?

Answer 1

The selector must be pulled out

Question 2

What is the function of the ALIGN position of the IRU mode selector?

Answer 2

• Initiates alignment

- Removes sensor errors when selected from NAV mode

Question 3

How long does it take for full alignment of the IRS?

Answer 3

10 mins

Question 4

When is full alignment of the IRS required?

Answer 4

When the time from the last full alignment to the next expected arrival time exceeds 18 hours

Question 5

How do you accomplish a fast alignment of the IRS?

Answer 5

-Airplane must be parked
-Position the selectors to ALIGN
-Enter present position
-Reposition the selectors to NAV
-Takes 30 secs
(Fast alignment can be accomplished without entering present position. However, greater navigational accuracy is attained by entering present position)

Question 6

What does the IRS ON Battery (BAT) light mean, when displayed on the OVRHD panel?

Answer 6

-IRS operating on backup electrical power (APU hot battery bus)

Question 7

Explain what happens when alignment of the IRS is lost in flight.

Answer 7

• The navigation mode is inoperative for the remainder of the flight
• Attitude information can be obtained by moving the selector to ATT.

Question 8

What happens if the center IRU is operating on DC power?

Answer 8

The center IRU operates on DC power for 5 mins, then shuts down.