737 Systems: Flight Management/Navigation

Question 1

Is IRS output info independent of, or reliant upon external navigation aids?

Answer 1

Independent of

Question 2

How long does IRS alignment take?

Answer 2

5-17 minutes, depending on aircraft latitude

Question 3

When does the steady white ALIGN on the IRS panel illuminate?

Answer 3

IRS is operating in either:

-ALIGN mode
-Initial ATT mode
-Shutdown cycle

Question 4

What does a white flashing ALIGN on the IRS panel during preflight indicate?

Answer 4

Alignment cannot be completed due to:
-Significant difference between previous and entered positions/unreasonable present position entry
-No present position entry

Question 5

Without AC power, how long can the IRSs operate? What lights will you see?

Answer 5

The left IRS will remain powered by the AC Standby Bus (Battery to Inverter) and the right IRS will be powered from the Switched Hot Battery Bus for 5 minutes.

You will see the ON DC amber light

Question 6

What does VERIFY POSITION FMC scratchpad message indicate?

Answer 6

If the lat/long position is not within 4nm of the origin airport

Question 7

How many GPS receivers are installed?

Answer 7

Two

Question 8

Are the FMCS independent of one another or do they compare information?

Answer 8

They compare information

Question 9

Where do the FMCS receive their inertial data from?

Answer 9

Their on-side ADIRU

Question 10

What’s the criteria for airports to be included in the NAV database?

Answer 10

-Must have on paved runways
-Must have one runway equal to or greater than 5000ft long
-Must have one runway equal to or greater than 100ft wide
-Must have at least one IAP(Exceptions may be made for operational needs)

Question 11

How can takeoff thrust be derated?

Answer 11

With the N1 Limit page which uses performance data from the AFM

With Assumed temperature, which makes the engine think its a higher OAT

Question 12

What sources do the FMCS use to determine position? In what order?

Answer 12

1) GPS (If not avail, IRS)
2) 2 or more DME stations
3) 1 VOR with co-located DME
4) 1 LOC and co-located DME
5) 1 LOC

Question 13

What criteria must be met for LNAV engagement?

Answer 13

-Laterally within 3nm of the active route leg

-If outside 3nm, on an intercept heading of 90 degrees or less and the intercept will occur before an active waypoint

Question 14

How does the FMC calculate a descent path during a VNAV PTH descent?

Answer 14

At thrust idle and prior to Top of Descent