Chapter 11: Flight Management, Navigation

Question 1

Explain the function of the FMC Source Select Switch.

Answer 1

BOTH ON L – selects left FMC for all FMC operations.

NORMAL –

• Left FMC controls CDUs and provides input to the autothrottle system.
• Right FMC operates in synchronization with left FMC.
• Maps display composite information from both FMCs.

BOTH ON R – selects right FMC for all FMC operations.

Question 2

Explain the function of the VHF NAV Transfer Switch.

Answer 2

NORMAL –-
-VHF navigation from default receiver. In the event of a receiver failure, this switch must be manually positioned to one of the below positions. (No Auto function)

BOTH ON 1 or BOTH ON 2 –
- Transfers VHF navigation source to selected receiver.

Question 3

Explain the function of the IRS Transfer Switch.

Answer 3

NORMAL –
-Attitude and heading information from default IRS. In the event of an IRS failure, this switch must be manually positioned to one of the below positions. (No Auto function)

BOTH ON L or BOTH ON R –
- Switches all attitude and heading to selected IRS.

Question 4

Explain the meaning of the amber FMC P/RST alert light on the forward panel.

Answer 4

An alerting message exists for both CDUs.

Note- P/RST (Push to Reset)

Question 5

Describe the alert associated with failure of a single FMC.

Answer 5

• If the right FMC fails, the FMC alert light and the FMC message light will illuminate. The message SINGLE FMC OPERATION will be displayed in both scratchpads.
• If the left FMC fails, the FMC alert light will illuminate. The MENU page will appear on both CDUs.

Question 6

Explain the alert associated when ANP exceeds RNP.

Answer 6

(1) If ANP exceeds the displayed RNP value, the UNABLE REQD NAV PERF–RNP message will be displayed on the CDU scratchpad.
(2) ANP and RNP annunciations on the MAP display turn amber.
(3) When in the approach environment an additional amber UNABLE REQD NAV PERF–RNP will be displayed on the MAP.

Question 7

Describe how to enter VNAV Speed/Altitude Restrictions into the FMS.

Answer 7

• All speed restrictions are considered by the FMC as “at” restrictions, unless modified by the pilot.
  When modified by the pilot:
• “At or above” airspeed restrictions are entered with a suffix letter A (example: 250A/).
• “At or below” airspeed restrictions are entered with a suffix letter B (example: 200B/).
• Mandatory airspeed restrictions are entered without any suffix letter (example: 220/).
• At or above altitude restrictions are entered with a suffix letter A (example: 220A).
• At or below altitude restrictions are entered with a suffix letter B (example: 240B).
• Mandatory altitude restrictions are entered without any suffix letter (example: 270).
• Altitude restrictions that are between two altitudes are displayed with the lower limit first, followed by a suffix letter A, then the upper limit, followed by a suffix letter B (example: 220A240B).

Question 8

Explain the meaning of the CDU messages DRAG REQUIRED and DES PATH UNACHIEVABLE displayed during a VNAV PATH descent.

Answer 8

The CDU message DRAG REQUIRED is displayed when airspeed is 10kts or more above FMC target speed.

The CDU message DES PATH UNACHIEVEABLE is displayed if the FMC determines that the planned descent profile cannot be accomplished.

Question 9

Describe the commanded acceleration after takeoff when VNAV is engaged.

Answer 9

• last MCP speed (V2) + 20 kts until acceleration height.
• if an engine failure is detected, target speed will be last MCP speed (V2) + 20 kts if the airplane is at that speed or greater, or the existing speed if the airplane is between V2 and V2 + 20 kts.
• the flap placard speed minus 5 kts.
• 230 kts or less when leading edge flaps are not fully retracted.
• 250 knots with flaps retracted.
• the active target speed.
• waypoint speed constraints, or the speed restriction associated with the origin airport, whichever is more restrictive.

Question 10

Explain the meaning of an illuminated GPS light on the IRS Mode Selector Unit. (ISDU).

Answer 10

• Indicates failure of both GPS units.
• Indicates failure of a single GPS unit when Master Caution recall is initiated.

Question 11

Explain the meaning of a flashing ALIGN light on the IRS Mode Selector Unit. (ISDU).

Answer 11

• No present position entry.
• Unreasonable present position.