Flight Management and Navigation

Question 1

During climb out on the RAMBL6 from DAL departing runway 31L, ATC issues a climb and maintain 17000ft. How should you delete the hold down over NNOLN without using the FMC?

Answer 1

Each selection of ALT INTV deletes the next altitude restriction if the MCP altitude is beyond the next altitude restriction.

Note: The use of ALT INTV Switch does not affect speed restrictions on the FMC LEGS page.

Question 2

You are VNAV cruise at FL380 100 miles from TOD from TOD and ATC issues a descent clearance to FL240. How would you initiate an early descent.

Answer 2

The use of early descent is recommended for VNAV PATH descents prior to the TOD. To initiate an early descent, use the following procedure:
FMC:
1. Set the clearance altitude in the MCP.
2. Select the DES page.
3. Select DES NOW>prompt(LSK 6R)
4. Press the EXEC function key. The MOD DES page changes to ACT and the descent is initiated.

Question 3

How would you initiate a cruise descent when greater than 50 miles from TOD?

Answer 3

ALT INTV(When greater than 50 NM from T/D point and MCP altitude is at or above an FMC altitude constraint):
1. Set the clearance altitude limit in the MCP.
2. Push ALT INTV. The ACT ECON CRZ page changes to ACT CRZ DES and the descent is initiated.

When initiating a cruise descent, the FMC calculates ECON speed for the new altitude. For example, ECON cruise Mach at FL 410 = 0.7772. ECON cruise Mach at FL 310=0.648. Mach 0.648 is unacceptably slow at FL 410.

Caution: A cruise descent may result in a new ECON speed that is unacceptably low for the current altitude. Avoid the use of cruise descent for large changes in altitude.

Question 4

Are there any additional considerations for the MAX regarding VNAV descents?

Answer 4

VNAV Descent Prediction Anomaly
-FMC performance predictions are periodically recalculated automatically to better account for changing environmental conditions. These performance prediction recalculations may result in additional computing time. As a result, an updated prediction could provide a new path when the aircraft is already in its descent phase.

-When this occurs, a 600-800 ft VNAV path discrepancy may result. Based on the prediction outcome, the aircraft can find itself below or above the idle descent path.

-If below the idle descent path, the FMC provides guidance to the enhanced Digital Flight Control System (DFCS) to command a 1,000 fpm descent until VNAV path intercept. If above the idle descent path, the FMC may find itself in late descent where the guidance mode pitch command switches to VNAV SPD. Flight Deck Crew intervention may be required to re-establish path tracking.

Question 5

What does the illumination of a flashing IRS ALIGN light indicate?

Answer 5

Alignment cannot be completed due to IRS detection of:
-Significant difference between previous and entered positions or an unreasonable present position entry.
-No present position entry.
-Excessive motion of aircraft during the alignment period. If two consecutive entries of the same position do not pass the second internal position test, the FAULT light will illuminate.

Question 6

What are the costs/benefits of a derated thrust takeoff and climb?

Answer 6

Reduced thrust takeoffs lower EGT and extend the engine life. They are used whenever performance limits and noise abatement procedures permit. Use of derated climb thrust reduces engine maintenance costs but increases total trip fuel.

Question 7

What speed does VNAV command at the all engine acceleration height if the VNAV Climb page is not manually programmed and speed intervention is not selected.

Answer 7

With VNAV armed for the climb phase, VNAV commands acceleration to the following:
-Last MCP speed (V2)+20kt until acceleration height.
-The flap placard speed minus 5 kts.
-230 kts or less, when leading-edge flaps are not fully retracted.
-250 kts with flaps retracted.
-The active target speed
-Waypoint speed restraints
-The speed restriction associated with the origin airport, whichever is more restrictive.

Question 8

You are on arrival and given holding instructions due to weather at your destination. How does entering an EFC on the FMC HOLD page affect arrival fuel?

Answer 8

Entry of the EFC time will help optimize FMC performance computations. Computation of destination fuel assumes that departure from the holding fix will occur at the EFC time.

Question 9

How does the FMC calculate Hold Available Time?

Answer 9

Displays available hold time in hours + minutes remaining if destination is to be reached with planned fuel reserves as entered on PERF INIT page.