11 Navigation Systems

Question 1

a. Which systems supplies position information to the FMCs?

b. What happens in the event of an IRS failure?

Answer 1

a. Left and right GPS receivers are independent and supply very accurate position data to the IRS. The IRS in turn supplies a very accurate hybrid GPS-inertial position to the FMC.
b. The GPS supplies position and track data directly to the FMC

Question 2

How many pitot/static systems supply air data to the Air Data Reference System (ADRS)?

Answer 2

Three, left, center and right.

Question 3

If voted ADRS air data is invalid and the AIR DATA/ATT switch is in AUTO, which systems supply backup airspeed and /or altitude?

Answer 3

Backup airspeed (AOA SPD) and/or backup altitude (GPS ALT) are automatically provided by the IRS and GPS systems.

Question 4

What is the source of altitude and airspeed if both voted and backup air data is unavailable?

Answer 4

Integrated Standby Flight Display (ISFD) altitude and airspeed are displayed on the PFDs

Question 5

What are the major components of the Inertial Reference System (IRS)?

Answer 5

The inertial reference units (IRUs), and attitude and heading reference units (AHRUs)

Question 6

How do the IRUs compute position information?

Answer 6

The IRUs combine inertial reference functions with GPS position information to provide hybrid GPS-inertial position output

Question 7

a. What power is required for initial IRS alignment?

b. Are attitude and heading/track shown on the PFD during alignment?

Answer 7

a. Battery bus power. b. No.

Question 8

On the ground, if electrical power is removed, and the battery switched off, leaving the IRS switches ON; what happens?

Answer 8

The hot battery bus continues to supply power to the IRS, the ON BAT light illuminates and the ground crew call horn sounds.

Question 9

When must the crew enter the aircraft position on the CDU POS INIT page?

Answer 9

If the GPS position is not available during the alignment.

Question 10

What do the following CDU help window messages indicate?

a. INERTIAL/ORIGIN DISAGREE
b. ENTER INERTIAL POSITION
c. ALIGNMENT REINITIATED

Answer 10

a. The latitude/longitude position is not close to the position of the origin airport.
b. The crew–entered latitude/longitude position does not pass internal IRU comparison tests.
c. The new airplane present position entry fails the internal check twice. The system automatically starts a new alignment cycle

Question 11

a. What, if anything, can be done after a power interrupt causes an in-flight loss of alignment of an IRU?
b. When is this capability not available?

Answer 11

a. The IRU can complete an alignment whilst in flight.

b. When the GPS receivers are not functioning

Question 12

How long can the IRU remain in NAV mode before a position update?

Answer 12

A position update is recommended if the total time in the navigation mode is expected to exceed 18 hours

Question 13

In the event of both IRUs failing, which systems supply position information to the FMC?

Answer 13

A hybrid GPS-inertial position solution using the AHRUs inertial sensors combined with GPS position.

Question 14

a. What has happened if the EICAS caution message NAV INERTIAL SYS
displays?
b. Are the LNAV/VNAV AFDS modes still available?
c. Are the ND map modes still available?

Answer 14

a. Both AHRUs and both IRUs have failed.
b. No.
c. Yes.

Question 15

If the NAV INERTIAL SYS message is displayed, which systems provide the following data: -
(Refer to the FCOM IRS Schematic ‘With NAV INERTIAL SYS Message’)
a. Altitude/airspeed?
b. Attitude?
c. Heading?
d. Positionandtrackdata?

Answer 15

a. ADRS.
b. ISFD.
c. Heading must be manually set on the CDU POS INIT page.
d. GPS

Question 16

How many ADF systems are fitted?

Answer 16

Two.

Question 17

Are the ADF systems tuned manually or automatically?

Answer 17

Manually tuned from the left or right CDU on the NAV RADIO page.

Question 18

Where are the left and right ADF bearings automatically displayed?

Answer 18

PFD mini-maps.

Question 19

What manual entry must be made to tune an ADF for BFO reception?

Answer 19

The frequency and suffix letter “B”.

Question 20

How many ILS receivers are installed?

Answer 20

Two.

Question 21

How is the ILS frequency and front course selected?

Answer 21

They are usually tuned by the FMC, but can be tuned manually on the NAV RADIO page.

Question 22

What two conditions must be met for FMC ILS autotuning to occur?

Answer 22

1. An ILS, LOC, back course, LDA or SDF approach selected to the active route.
2. The airplane is within 50 NM from the top of descent, 150 NM of the landing runway threshold, or the FMC is in descent mode.

Question 23

ILS autotuning is inhibited for 10 minutes after initial takeoff. What must be done if an immediate return to the origin airport is required?

Answer 23

Selection and execution of a new approach in the active flight plan causes the ILS to autotune to the new approach frequency, even if this is accomplished during the 10 minute takeoff inhibit period.

Question 24

How can the ILS be tuned if all three FMC’s have failed?

Answer 24

The left ILS can be tuned from ALTN NAV RADIO page 2/2 on the TCP

Question 25

What does the word PARK adjacent to the ILS - GLS line on the NAV RADIO page mean?

Answer 25

The ILS or GLS is not being used and is not tuned.

Question 26

How many VOR/DME systems are installed?

Answer 26

Two.

Question 27

Can the VOR/DME systems be automatically tuned by the FMC?

Answer 27

Yes.

Question 28

What tuning methods are indicated by the white letters P; R; A and M on the NAV RAD page adjacent to the tuned VORs?

Answer 28

• P (procedure autotuning)–FMC selects nav aids for approach or departure procedure guidance.
• R (route autotuning)–FMC selects nav aids on the active route.
• A (autotuning)–FMC selects a nav aid for best position orientation.
• M (manual)–VOR is manually tuned

Question 29

Is the current radial for a tuned VOR/DME displayed on the NAV RAD page?

Answer 29

Yes.

Question 30

How are the two transponders controlled?

Answer 30

Through the TCP and ATP.

Question 31

a. What specified transponder/TCAS control is available with the ATP?
b. What happens if the ATP fails?

Answer 31

a. The ATP controls the Transponder/TCAS modes.

b. The Transponder/TCAS modes can be set through the backup function of the TCP.

Question 32

a. Selecting the XPDR mode select key accesses the transponder control pages on the TCP. What transponder controls are available?
b. What do the Captain’s and First Officer’s TCP’s share control of?

Answer 32

a.
• Altitude Mode (Absolute or Relative).
• ATC IDENT function.
• Mode A numeric code.
• TCAS envelope (Above, Normal ,or Below).
• Transponder select (Left or Right).
b. 
• IDENT function
• left or right side selection
• XPDR code

Question 33

What happens if the on-side transponder fails?

Answer 33

The TCP automatically switches to the cross-side transponder.

Question 34

How is the weather radar controlled?

Answer 34

Through the TCP.

Question 35

a. Which controls are used to activate the radar and display returns on an ND and/or mini-map?
b. What must be selected on first to allow these controls to work?

Answer 35

a. The WXR switch on the EFIS control panel and the WXR check box on the ND drop-down menu.
b. At least one weather radar system must be selected ON from the TCP SYS POWER screen.

Question 36

What is the maximum range that weather returns can be seen on the ND?

Answer 36

320 NM.

Question 37

What is the maximum range at which turbulence returns are processed?

Answer 37

40 NM.

Question 38

What colour is used to display turbulence?

Answer 38

Magenta