IRS

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 minutes

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 seconds
• 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 Overhead Maintenance 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 minutes, then shuts
down.