Flight Management, Navigation

Question 1

FMGT_001

Explain the function of each position of the IRS MSU (Mode Selector Unit):

Answer 1

• OFF – Removes electrical power after a 3 second time delay.
• ALN – Selecting OFF to ALN powers up the IRU and performs and internal BITE check. ON BAT annunciates on MSU for 15 seconds. After BITE check, IRU enters align submode until switched to NAV. Full alignment requires from 2.5 to 10 minutes.
• NAV – Normal position. If selected from the OFF mode or ALN mode prior to completion of the alignment sequence, the IRU will begin the alignment phase automatically terminating at the end of the alignment sequence. Upon completion of the align sequence, the ALIGN lights will extinguish, and EFIS attitude and heading data will be displayed.
• ATT – Selects back-up attitude mode. This mode may be selected directly in flight following a partial failure of an IRU (indicated by a FAULT annunciation on the MSU). When either IRS is in the attitude mode, autoland is inhibited. Heading updates are required for the failed system.

Question 2

FMGT_002

Explain the meaning of each advisory light on the IRS control panel:

Answer 2

• ALIGN (white) – Indicates IRU is in alignment mode. Light flashes if the position data has not been entered after alignment completed or incorrect data entry.
• ON BAT (amber) – Indicates IRU is operating from its back-up battery.
• BAT FAIL (amber) – Indicates battery voltage is less than required.
• FAULT – Indicates IRU has detected a problem in its alignment and navigation modes.

Question 3

FMGT_003

Explain what the altitude range arc (Green arc) indicates during a climb or descent:

Answer 3

The ALTITUDE RANGE ARC, when intersected with the track line, predicts the point where the reference altitude will be reached at current vertical rate.

Question 4

FMGT_004

Recall how the active waypoint is displayed on the ND in the MAP/PLAN mode and on the MCDU:

Answer 4

The active waypoint is the first waypoint displayed on the legs page. The active waypoint is magenta on the map display.

Question 5

FMGT_005

Recall how to accomplish a downmode alignment (quick align):

Answer 5

Selecting ALN from NAV provides a 30 second downmode alignment (quick align) which zeros all computed velocity errors and updates heading accuracy.