Chapter 7 - Section 4: Maintenance practices

Question 1

What are the two fault indications on the front of the MU?

Answer 1

• MU FAIL, management failure
• CU FAIL, control unit failure

Question 2

Why does the MU need to be connected to the HOT BATT BUS?

Answer 2

To allow the GMT clock to continue to run, even after unit enters OFF mode

Question 3

What is retained in a non-volatile memory?

Answer 3

Certain data from previous operations

Question 4

How does VOICE mode work?

Answer 4

Central ARINC control computer on the ground automatically dials the telephone number which has been downlinked by the crew

If the number is not busy and the call is connected, the system automatically tunes the VHF communication transceiver ACARS voice frequency for that locality, turns on the ACP C-VHF call light, and causes the chime to sound