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FMC Preflight

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PostPosted: Fri Aug 10, 2012 10:58 am    Post subject: FMC Preflight Reply with quote


Part 1

• Ident > Pos Init > Act RTE 1

• Departures

• Nav Rad

Part 2

Perf Init > Thrust Lim > Takeoff Ref

Arrow INIT REF Key

• POS INIT page (on Ground and ADIRU Not Aligned)

• PERF INIT page (on Ground and ADIRU Aligned)

• Index Page Prompt

IDENT: Basic airplane data and navigation datbase. (777-200.2 is 777-200LR, 777-200.3 is 777-200ER with extended forward CG, 777-300.2 is 777-300ER with enhanced performance)

POS: ADIRU Initialization or SAARU Heading Initialization when ADIRU fails. Also for GPS pos inhibit and RNP etc.

PERF: Initialization of data required for VNAV operations and performance predictions.

NAV DATA: For data on waypoints, navaids, airports, and runways. Also for navaid inhibition.

ALTN: For alternate airport planning and diversions.


Page 1 - POS INIT

Page 2 - POS REF

Page 3 - POS REF


Route Page 1:

Route Page 2:


Departure (DEP) –– Other

Displays the departure page for the airport entered into this line through the scratchpad. DEP prompt for OTHER allows display of departure data about airports that are not an origin or destination. The data can be viewed but cannot be selected because the airport is not on the route.

Engine Out (EO) SIDS

Displays airline-defined single engine-out SIDs and all transitions for the selected runway. EO SID can be viewed before takeoff by line selecting and selecting the Legs page. EO SID automatically selected during takeoff if an engine-out detected prior to “flaps up”. The modification can be either executed or erased. If an EO SID does not exist, NONE displays.


VOR Frequency and Tune Status

• P (procedure autotuning) – FMC selects navaids for approach or departure procedure guidance

• R (route autotuning) – FMC selects navaids on the active route. The navaid is the previous VOR or a downpath VOR within 250nm of aircraft position

• A (autotuning) – FMC selects a navaid for best position orientation

• M (manual) – VOR is manual–tuned. Manual–tuning takes priority over FMC autotuning. Deletion of a manual–tuned frequency returns system to autotuning

When magnetic variation at the airplane and VOR locations are significantly different, the ND VOR radial and ND POS green radial do not point directly to the VOR. This difference decreases as the airplane approaches the VOR.

• RADIAL: Displays radial from left and right VOR stations to the airplane.

ADF Frequency and Tune Status

• ANT (antenna) – mode optimizes audio reception and removes ADF bearing data

• BFO (beat frequency oscillator) – mode for audio identification of stations transmitting unmodulated (CW) signals

• Default tuning mode is ADF (no indication) giving both bearing data and audio.

• Manual entry can be followed by A (ANT), B (BFO), or none, which defaults to the ADF mode.

ILS Frequency/Course and Tune Status

• PARK – the ILS is not being used and is not tuned (more than 200 NM from the T/D or less than halfway to the destination)

• XXX.XX/YYY PARK – the ILS is tuned for the selected approach but is not being used (less than 200 NM from the T/D or more than halfway to the destination, whichever is less). Line selection manually tunes ILS.

• “A” indicates autotuning under FMC control for approach guidance (less than 50 NM from the T/D or less than 150 NM from the runway threshold or FMC is in descent mode)

• “M” indicates the ILS is manually tuned

ILS autotuning is inhibited for ten minutes after takeoff and during manual–tuning.

Autotuning and manual–tuning are inhibited when:

• the autopilot is engaged and either the localizer or glideslope is captured

• only the flight director is ON and either the localizer or glideslope is captured and the airplane is below 500 feet radio altitude

• on the ground with the localizer alive, the airplane heading within 45 degrees of the localizer front course and the ground speed is greater than 40 knots.

Subsequent manual–tuning is enabled when:

• either TOGA switch is pushed

• the autopilot is disengaged and both flight directors are switched off

• the MCP approach switch is deselected when the airplane is above 1500 feet radio altitude


Any valid page data (preselected frequencies and/or frequencies/courses) may be entered for later use.



• SENSED – fuel quantity is from the totalizer. Manual entry is not possible

• CALC (calculated) – fuel quantity is from FMC calculations. Manual entry is possible

• MANUAL – fuel quantity has been manually entered. Manual entries blank totalizer on PROGRESS page 2/3. Only manual entries can be deleted.

Cost Index

Cost Index 0 = Maximum range cruise speed (minimum fuel schedule)

Cost Index 140 (approx) = LRC speed (approx .84 at optimum altitude)

Cost Index 9999 = Maximum flight envelope speed (minimum time schedule). Thrust limits or maximum speed limits are generally encountered with cost index entries of 5000 or more.

Increasing from .84 to .855 (approx 10 knots) increases trip fuel by 4-5%.

Min Fuel Temp

Displays minimum fuel operating temperature (3 degrees C warmer than the fuel freeze temperature for a given fuel). Default value from the AIRLINE POLICY page displays in small font. Flight crew entered value displays in large font.

Cruise Center of Gravity (CRZ CG)

Used by FMC to compute maximum altitude and maneuver margin to buffet.

Displays default value selected in AMI (Airline Modifiable Information).

If the default CRZ CG value in AMI is blank, the CHECK AIRLINE POLICY message displays.

777-200ER (AP-BGJ - AP-BGL, AP-BHX) - Displays default value of 30.0% in small font and may not be deleted.

777-200LR (AP-BGY, AP-BGZ) - Displays default value of 14.0% in small font and may not be deleted.

777-300ER (AP-BHV, AP-BHW, AP-BID) - Displays default value of 7.5% in small font and may not be deleted.

Step Size

Displays the climb altitude increment used for planning the optimum climb profile.

• "0" to inhibit predicted step climbs

• Altitudes from 1000 to 9900 in 100 foot increments

• "I" for ICAO

• "R" for RVSM

In-flight entries are inhibited. In-flight step size changes are made on the CRZ page


Assumed Temperature (SEL)

Entry of temperature followed by “F” displays assumed temperature in degrees F; otherwise, assumed temperature displays in degrees C.

APU-to-Pack for 777-200LR and 777-300ER (AP-BGY - AP-BHW, AP-BID)

“SEL-APU” displays in the header when the APU is running.

Selection of “APU” from the scratchpad displays “APU” in the data line in small font representing the ARMED state.

Approximately one minute after the second engine start, “APU” displays in large font representing the ACTIVE state.

Entry of an assumed temperature, shutting down the APU, selecting another TO rating, or deleting the entry; deletes the APU selection.

Note: If only cooling air from ground air conditioning cart is supplied (no pressurized air from the APU or ground external air), then the TAT probe is not aspirated. Because of high TAT probe temperatures, the FMCs may not accept an assumed temperature derate. Delay selecting an assumed temperature derate until after bleed air is available... (SP.16.14)

Thrust Reference Mode

Displays selected takeoff thrust mode (top right corner)

D - Displays when an assumed temperature derate is active.

A - This prefix is added to the line title TO when APU-to-Pack takeoff is selected.

Against LSK 1R is the takeoff N1 calculated by the thrust management computer

TO 1 and TO 2

Selects percentage derate for takeoff thrust limit and arms the associated climb thrust. Default thrust derate can be modified on the AIRLINE POLICY page.

Derated Climb Performance In Large Civil Aircraft




Valid entries are 5, 15, or 20

Entry of 5 when FLAPS 5 is the climb thrust reduction point displays the scratchpad message INVALID ENTRY.

Runway/Position (RWY/POS)

• Displays the selected takeoff runway, and TO/GA push distance from the runway threshold or runway intersection identification.

• Flight crew may enter or uplink runway and intersection data. Runway entry does not change runway entered on RTE or DEPARTURES page.

• Valid position entry is a one or two numeric in the range 0-30 and must be followed by two zeros.

• Preceding the entry with a “-” means a longer takeoff distance is available e.g. -0300 is 300 meters before the runway threshold).

• RWY/POS update inhibited when GPS is primary FMC navigation source.

Takeoff Data Request

Transmits a data link request for takeoff data uplink. Flight crew can enter RWY, intersection or position shift, CG, TOGW, or OAT to qualify the request.

V Speeds (V1, VR, V2)

• 777-200ER (AP-BGJ - AP-BGL, AP-BHX)

Manually entered speeds less than V1MIN, VRMIN, or V2MIN are indicated by display of “MINV1”, "MINVR", or "MINV2" in the line title and the value of V1MIN, VRMIN, or V2MIN in the data line.

• 777-200LR and 777-300ER (AP-BGY - AP-BHW, AP-BID)

Manually entered speeds equal or greater than V1MIN - 5 knots, VRMIN - 5 knots, or V2MIN - 5 knots are allowable.

“MINV1”, "MINVR", or "MINV2" do not display in the line title and speeds do not display on data lines.

Speeds less than V1MIN-5 knots, VRMIN - 5 knots, or V2MIN - 5 knots result in V1MIN, VRMIN, or V2MIN display in the line title; the values display in large font on data lines.

V–SPEEDS UNAVAILABLE – For certain high thrust/low gross weight takeoff conditions, FMC V–speeds are not calculated. Adjust gross weight and/or takeoff thrust limit to enable V–speed calculations.

The FMC will protect for minimum control speeds by increasing V1, VR and V2 as required.

However, the FMC will not compute takeoff speeds for weights where the required speed increase exceeds the maximum certified speed increase.

This typically occurs at full rated thrust and light weights.

In this case, the message "V SPEEDS UNAVAILABLE" will appear on the FMC scratchpad and the takeoff speed entries will be blank.

Takeoff is not permitted in this condition as certified limits have been exceeded.

The options are to select a smaller flap setting, select derate thrust and/or add weight (fuel).

Selecting derate thrust is the preferred method as this will reduce the minimum control speeds.

Note that the assumed temperature method may not help this condition as the minimum control speeds are determined at the actual temperature and therefore are not reduced.

Incase of 777-200 LR: The FMC will not compute takeoff speeds for weights below those shown in the Minimum Weight for FMC Takeoff Speeds Calculation table.

In those cases where the required speed increase exceeds the maximum speed increase built into the FMC, the message "V SPEEDS UNAVAILABLE" will appear on the FMC scratchpad and the takeoff speed entries will be blank. This typically occurs at high rated thrust, high flaps setting and light weights.

To obtain speeds for the takeoff in these situations, the options are to use available performance software, or select a smaller flaps setting, or use reduced takeoff thrust and/or add weight.

Selecting derate thrust is the preferred method of reduced takeoff thrust as this will reduce the minimum control speeds.

Reference Speeds (REF SPDS)

Enables or disables display of the FMC calculated reference (V) speeds in the center column for comparison with the V speeds in the right column.


Alternate Thrust (ALTN THRUST)

Display is active if a TAKEOFF REF uplink has been accepted which includes alternate thrust data. Selects alternate thrust or alternate thrust/flaps for takeoff.

Runway Wind (RWY WIND)

Displays the calculated headwind/tailwind and crosswind components for the takeoff runway and surface wind.

Speed displays in knots and: H for headwind, T for tailwind, R for right crosswind, L for left crosswind.

Flight crew entry is limited to headwind/tailwind entry. Two digit number followed by H or T.

Speed entry without a letter defaults to a headwind component.

A flight crew entry clears the WIND line.

Acceleration Height (ACCEL HT)

Displays acceleration height in Height Above Airport (HAA) for flap retraction. EO is Engine Out.

The FMC adds airport elevation to entered HAA acceleration height causing acceleration at an MSL altitude. For example, for an airport elevation of 1000 feet, an entry of 2000 acceleration height causes acceleration at 3,000 feet MSL.

Climb Thrust and Thrust Reduction (THR REDUCTION) Altitude

Displays armed climb thrust rating and HAA height for reduction from takeoff thrust to climb thrust. Default value is from the AIRLINE POLICY file.

Manual entry can be an HAA height or 1 for flaps 1 and 5 for flaps 5.

Limit Takeoff Gross Weight (LIM TOGW)

Displays takeoff gross weight limit for the uplinked data. Manual entry not allowed.

Prefix ALT or STD is added to line title when alternate or standard takeoff data is pending.


• Valid runway slope entries are 1 or 2 digit numbers between 0.0 through 2.0 in percent gradient.

• Slope entries may be proceeded by U (for uphill) or D (for downhill). Entries without a U or D are assumed to be uphill.

• Valid runway condition is “D” or “DRY” for dry or “W” or “WET” for wet.

• Entry of “S” or “WET SK-R” displays “WET SK-R” and FMC computes V1 for a skid resistant runway.
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