IRS CBT's

Question 1

How many IRU’s? How many IRS’s?

Answer 1

3 IRU’s

1 IRS

NOTE: The 3 IRU’s all feed into the IRS (Inside the plane it is referred to IRS L, C, R)

Question 2

How long does IRS alignment take?

Answer 2

About 10 minutes.

Do not move the aircraft during alignment

Question 3

There are 3 possible sources of coordinates to align the IRS. What is the order of those from most preferred to least preferred?

Answer 3

1.) GPS position
2.) Gate coordinates from Jepp chart
3.) Plotted coordinates from Jepp chart

Question 4

If you switch into ATT mode on the IRS, can you reverse that action?

Answer 4

No, it will require a full alignment on the ground. It is a non-normal procedure to select ATT

Question 5

Why must you shut down the IRS’s before powering down the airplane?

Answer 5

Because DC power (via the APU hot battery bus), is the IRS backup power if AC power is lost. If you remove AC power before shutting down the IRS’s, it will drain the battery.