11 - Flight Management, Navigation

Question 1

1. How many GPS receivers are installed?

Answer 1

2

Question 2

2. Are IRS outputs independent of external navigation aids?

Answer 2

Yes

Question 3

3. What is indicated by a white ALIGN light on the IRS panel?

Answer 3

The respective IRS is operating in either the:
- ALIGN mode
- initial ATT mode
- shutdown cycle

Question 4

4. What is indicated by a white flashing ALIGN light on the IRS panel?

Answer 4

Alignment cannot be completed due to:
-Significant difference between previous and entered positions, or
- no present position entry

Question 5

5. What does an illuminated FAULT light on the IRS panel indicate?

Answer 5

A system fault affecting the related IRS ATT and/or NAV modes.

IRS System Annunciator and MASTER CAUTION also illuminate

Question 6

6. What does the illumination of an ON DC light on the IRS panel indicate?

Answer 6

The related IRS is operating on DC power from the switched hot battery bus

Question 7

7. How long can the right IRS operate without AC electrical power?

Answer 7

5 minutes

Question 8

8. How long does a full IRS alignment take?

Answer 8

5-17 minutes, depending on aircraft latitude

Question 9

9. What is Automatic Navigation Realignment (ANR) and when does it activate?

Answer 9

When a fast realignment is initiated or the aircraft parks after a flight and remains motionless for at least 7.5 to 15 minutes with the ADIRUs still in the NAV mode and valid GPS data available, the Automatic Navigation Realignment (ANR) mode will perform a complete realignment automatically.

EXTRA CREDIT:
Automatic Nav Realignment is not available on NG aircraft

Question 10

10. What does the illumination of the ILS light on the IRS panel indicate?

Answer 10

A failure of both ILS sensor units.

Illumination of the ILS light during a MASTER CAUTION recall indicates a single ILS sensor unit has failed.

Question 11

11. Do the FMCs operate independently?

Answer 11

No.

With the FMC source select switch in the NORMAL position, the primary FMC (left FMC by default) is responsible for synchronizing with the secondary.

Data from both FMCs is combined to determine a composite position and velocity.

Question 12

12. Where do the FMCs receive their inertial data from?

Answer 12

Usually, the FMCs receive inertial data from their on-side ADIRU.

If the on-side ADIRU malfunctions or it is in ATT or ALIGN mode, the FMC uses data from the other side ADIRU.

Question 13

13. How is FMC position data calculated with the loss of GPS inputs?

Answer 13

First, the FMC uses radio navigation. If radio navigation is not available, the FMC uses IRS position.

EXTRA CREDIT:
When the IRS is the only position reference, the FMC applies an automatic correction to the IRS position to determine the most probable FMC position.

This correction factor is developed by the FMC’s monitoring IRS performance during periods of normal position updating to determine the typical IRS error value.

Question 14

14. How is takeoff thrust reduced from maximum takeoff thrust?

Answer 14

First by a derate of 10% or 20%. Then derated trust can be further reduced by using assumed temperature

Question 15

15. Where does the FMC receive fuel quantity information from?

Answer 15

• From the Fuel Quantity Indicating System (FQIS) and from the engines

or

• Manual entries on the MCDU

EXTRA CREDIT:
The FQIS calculates the usable fuel quantity in each tank. Excitation signals in each tank detect the amount of fuel in weight using a processor unit.

Question 16

16. What are the sources of position data to the FMC?

Answer 16

-GPS
-Navigation radios
-IRS

(in that order)

Question 17

17. Which input has the highest-weighted priority for FMC position?

Answer 17

Hybrid GPS

Question 18

18. What criteria must be met for LNAV to engage?

Answer 18

• LNAV engages when laterally within 3 nm of the active route leg

• outside of 3 nm of the active route leg, LNAV engages if on an intercept heading of 90° or less and the intercept will occur before the active waypoint

Question 19

19. How is a VNAV descent path calculated by the FMC?

Answer 19

The descent path starts at the calculated T/D point and includes waypoint altitude restrictions. The path is based on:
• E/D point
• idle thrust
• speedbrakes retracted
• descent wind speed decreasing with decreasing altitude (or loadable winds)
• applicable target speed