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AFDS / MCP (Technical Notes)

 
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K.Haroon
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Joined: 11 Dec 2005
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PostPosted: Tue Jul 31, 2012 10:06 am    Post subject: AFDS / MCP (Technical Notes) Reply with quote

Autopilot and Flight Director

Arrow When both Flight Director switches are OFF, the autopilot engages in:

• heading hold (HDG HOLD) or track hold (TRK HOLD) as the roll mode; or, if bank angle is greater than five degrees, attitude hold (ATT)

• vertical speed (V/S) or flight path angle (FPA) as the pitch mode


Arrow On the ground with both Flight Director switches OFF;

First Flight Director switch positioned ON

1) Arms the flight director in takeoff go–around (TO/GA) roll mode.

2) Arms the flight director in TO/GA pitch mode when MCP selected altitude differs more than 20 feet from displayed baro altitude.

When selected altitude is within 20 feet of displayed baro altitude, the flight director is activated in altitude (ALT) pitch mode.

If ALT mode is active, selecting an altitude more than 20 feet from displayed baro altitude and recycling the first switch arms the flight director in TO/GA roll and pitch modes.


Arrow In flight with the autopilot disengaged and both Flight Director switches OFF, the first Flight Director switch positioned to ON activates the flight director in:

• heading hold (HDG HOLD) or track hold (TRK HOLD) as the roll mode; or, if bank angle is greater than five degrees, attitude hold (ATT)

• vertical speed (V/S) or flight path angle (FPA) as the pitch mode


Arrow In flight with the autopilot engaged and both Flight Director switches OFF, the first Flight Director switch positioned to ON activates the flight director in the currently selected autopilot mode(s).


Arrow The flight director steering indications do not display with switch in OFF position, unless

• a TO/GA switch is pushed when airspeed is greater than 80 knots and flaps are out of up.


Speed Window

Arrow IAS/MACH Window

When changing from TO/GA to V/S, FPA, or ALT, the window displays:

• the flap placard speed minus 5 knots (flaps extended), or

• 250 knots (flaps up), or

• a speed value entered in the IAS/MACH window after TO/GA was pushed

- In climb, automatically changes from IAS to Mach at .840 Mach.

- In descent, automatically changes from Mach to IAS at 310 knots.


Arrow IAS/MACH Selector

Push – with VNAV active, alternately opens or closes the IAS/MACH window.

When the window is open, FMC speed–intervention is active and IAS/MACH selector may be used to set the desired speed.


Lateral Navigation

Arrow LNAV Switch

• arms, selects, or disarms LNAV as roll mode

• displays LNAV in white (armed) on both PFDs roll flight mode annunciations when armed. The previous roll mode remains active

• LNAV activates when the airplane is above 50 feet radio altitude and within 2.5 NM of the active leg

• when not within 2.5 NM of the active leg and on an intercept heading to the active leg, remains armed then activates when approaching the active leg

• when active, displays LNAV in green on the PFD roll flight mode annunciation

• selection of LNAV with the airplane not on a heading to intercept the active leg, displays NOT ON INTERCEPT HEADING in the CDU scratchpad

• selection of LNAV when an active FMC route is not available displays NO ACTIVE ROUTE in the CDU scratchpad

• LNAV maintains current heading when:

- passing last active route waypoint
- passing last waypoint prior to a route discontinuity
- passing last route offset waypoint
- activating the inactive route or activating an airway intercept and not within LNAV engagement criteria

• LNAV deactivated:

- by selecting heading hold (HDG HOLD) or track hold (TRK HOLD)
- by selecting heading select (HDG SEL) or track select (TRK SEL)
- when localizer captures
- with dual FMC failure (LNAV may be re–activated if there is an active CDU ALTN NAV route available)

• LNAV is disarmed by pushing the LNAV switch a second time, or by arming LOC or APP.


Vertical Navigation

Arrow VNAV Switch

• arms, selects, or disarms VNAV as the pitch mode

• displays VNAV in white (armed) on both PFD pitch flight mode annunciations below 400 feet

• VNAV activates 400 feet above runway elevation

• When VNAV selected and the FMC has insufficient data to provide VNAV guidance (such as the gross weight is invalid or there is no end–of–descent point in descent) displays PERF/VNAV UNAVAILABLE in the CDU scratchpad

• VNAV SPD, VNAV PTH, or VNAV ALT pitch mode displays in green (active) on the PFD pitch flight mode annunciation

• in VNAV SPD pitch mode, AFDS commands pitch to hold target airspeed. The autothrottle operates in the THR REF, THR, IDLE, or HOLD mode, as required by phase of flight

• in VNAV PTH pitch mode, the AFDS commands pitch to maintain FMC target altitude or VNAV path; autothrottle operates in speed (SPD) mode

• in VNAV ALT pitch mode, AFDS commands pitch to maintain MCP selected altitude; autothrottle operates in speed (SPD) mode

• when selecting VNAV and VNAV commands a descent with the MCP altitude window above the current airplane altitude, the autopilot maintains the altitude at which VNAV was selected. When on an instrument approach using VNAV, selecting the missed approach altitude does not interfere with the VNAV descent

• when selecting VNAV and VNAV commands a climb with the MCP altitude window below the current airplane altitude, the autopilot maintains the altitude at which VNAV is selected

• With the VNAV PTH pitch mode active, the autothrottle operates in the following modes:

- for climb or cruise – operates in the speed (SPD) mode
- for descent – operates in the IDLE, HOLD, or speed (SPD) mode

• VNAV pitch guidance available with one engine inoperative


•VNAV deactivated by:

- selecting TO/GA, FLCH SPD, V/S, FPA, ALT or G/S pitch mode
- dual FMC failure


•VNAV is disarmed by:

- pushing the VNAV switch a second time, or
- arming APP


Localizer (LOC) Switch

Arrow When Pushed:

• arms, disarms, or captures localizer (LOC) as the roll mode

• displays LOC in white (armed) on the PFD roll flight mode annunciation before localizer capture; current roll mode remains active until LOC capture

• displays LOC in green (active) on the PFD roll flight mode annunciation after localizer capture

• arms AFDS to capture and track inbound on front course

• capture point varies based on range and intercept angle

• localizer capture can occur when intercept track angle is within 120 degrees of the localizer course

• The localizer mode can be disarmed before localizer capture by:

- pushing the localizer switch a second time, or
- arming or activating LNAV

• The localizer mode can be deactivated after localizer capture by:

- selecting a roll mode other than LNAV, or
- pushing a TO/GA switch, or
- disengaging the autopilot and turning both Flight Director switches off, or
- pushing the localizer switch a second time above 1,500 feet radio altitude (reverts to the default roll mode)


Approach (APP) Switch

Arrow When Pushed:

• arms, disarms, or captures localizer (LOC) as roll mode and glideslope (G/S) as pitch mode

• displays LOC and G/S in white (armed) on PFD roll and pitch flight mode annunciations prior to localizer and glideslope capture

• displays LOC and G/S in green (engaged) on PFD roll and pitch flight mode annunciations after each one is captured

• AFDS captures and tracks localizer and captures the glideslope upon interception

• localizer captures when intercept track angle is within 120 degrees of localizer course

• glideslope captures when intercept track angle is within 80 degrees of localizer course. Glideslope capture is inhibited before localizer capture.

• The approach mode can be disarmed or deactivated for any status of localizer and/or glideslope by disengaging the autopilot and turning both Flight Director switches off.

• When both localizer and glideslope are armed, the approach mode can be disarmed by selecting APP, LOC, LNAV, or VNAV.

• The approach mode deselects:

- by pushing APP when above 1,500 feet radio altitude, or

- with localizer captured and glideslope armed, by selecting heading select (HDG SEL) or heading hold (HDG HOLD), or

- after localizer and glideslope are captured, by selecting TO/GA mode


Takeoff/Go-around (TO/GA) Switches

Arrow When Pushed On the ground:

• below 50 knots and flaps out of up, activates autothrottle in THR REF mode at reference thrust limit selected on THRUST LIMIT page. If not pushed below 50 knots, autothrottle operation is inhibited until reaching 400 feet altitude

• pushing either switch above 80 knots disarms LNAV and VNAV


Arrow When pushed in flight (after lift-off with takeoff reference thrust limit displayed):

• removes takeoff and climb derates and assumed temperature thrust reduction

• A/T in HOLD, activates A/T in THR REF mode

• disarms LNAV and VNAV, if armed

• between 50 feet and 400 feet, selects TO/GA roll mode

• above 400 feet, selects TO/GA roll and pitch modes


Arrow When pushed (on approach with flaps out of up or glideslope captured):

• activates autothrottle in THR mode with GA reference thrust limit displayed

• selects TO/GA roll and pitch modes

• with no A/P or F/D active, activates A/T in THR REF


Arrow Second push (go-around active with flaps out of up, LNAV armed, TO/GA roll and pitch mode)

• activates autothrottle in THR REF using GA reference thrust


Arrow Second push (go-around active with flaps out of up, LNAV active, TO/GA pitch mode)

• activates autothrottle in THR REF using GA reference thrust, roll mode remains LNAV


Arrow Second push (go-around active with flaps out of up, HDG SEL or HDG HOLD active, TO/GA pitch mode)

• activates autothrottle in THR REF using GA reference thrust, selects TO/GA roll and pitch modes.


Autothrottle Modes

Arrow Autothrottle annunciations are:

• THR – autothrottle applies thrust to maintain the climb/descent rate required by the pitch mode

• THR REF – thrust set to the reference thrust limit displayed on EICAS

• IDLE – displays while the autothrottle moves thrust levers to idle; IDLE mode is followed by HOLD mode

• HOLD – thrust lever autothrottle servos are inhibited. The pilot can set thrust levers manually

• SPD – autothrottle maintains command speed. Speed can be set using the MCP IAS/MACH selector or by the FMC, as displayed on the CDU CLIMB, CRUISE, or DESCENT page. The autothrottle will not exceed the operating speed limits or the thrust limits displayed on the EICAS. If only one thrust lever is active, "L-" or "R-" displays in front of SPD for the active thrust lever


Arrow Autothrottle Disconnect

The autothrottle system can be disconnected manually by pushing either autothrottle disconnect switch, except during conditions that cause the autothrottle to automatically activate.

The autothrottle can also be disconnected manually by:

Positioning both A/T ARM switches to OFF, or individually by positioning the left or right A/T ARM switch to OFF.

Positioning one or both A/T ARM switches to OFF prevents activation of all autothrottle modes for the affected autothrottle.

Autothrottle disconnect occurs automatically:

• if a fault in the active autothrottle mode is detected

• when either reverse thrust lever is raised to reverse idle

• if the thrust levers are overridden during a manual landing, after the autothrottle has begun to retard the thrust levers to idle

• when both engines are shut down


Roll Modes

Arrow ATT – (active):

• When the autopilot is first engaged or the flight director is first turned on in flight, AFDS holds a bank angle between 5 and 30 degrees and will not roll to wings level.

• When the bank angle is less than 5 degrees, AFDS rolls to wings level (HDG HOLD or TRK HOLD).

• When the bank angle is greater than 30 degrees, AFDS rolls to 30 degrees of bank.


Arrow TO/GA

• On the ground, TO/GA annunciates by positioning either flight director switch ON when both flight directors are OFF; or, by pushing either TO/GA switch with airspeed greater than 80 KTS. TO/GA roll guidance becomes active at lift–off

• In flight, TO/GA is armed when flaps are out of up or glideslope is captured. There is no flight mode annunciation for TO/GA armed. TO/GA is activated in flight by pushing a TO/GA switch. The roll steering indication provides guidance to maintain the ground track present at mode engagement


Arrow ROLLOUT:

• ROLLOUT (armed) – displayed below 1500 feet radio altitude and activates below 2 feet

• ROLLOUT (active) – after touchdown, AFDS uses rudder and nosewheel steering to steer the airplane on the localizer centerline


Pitch Modes

Arrow TO/GA:

On the ground, TO/GA annunciates by positioning either flight director switch ON when both flight directors are OFF; or, by pushing either TO/GA switch with airspeed greater than 80 knots. The flight director PFD pitch bar indicates an initial pitch of eight degrees up. TO/GA pitch guidance becomes active at lift-off.

After lift-off, the AFDS commands a pitch attitude to maintain:

• a target speed of V2 plus 15 knots or the airspeed at rotation (pitch attitude greater than two degrees) plus 15 knots, whichever is greater

• if current airspeed exceeds the target speed for 5 seconds, the target speed is reset to the lesser of the current airspeed or V2 plus 25 knots

• the IAS/MACH window speed if the window speed is changed to a speed greater than the target speed

Note: AFDS uses the speed set in the IAS/MACH window for V2.

In flight, TO/GA is armed when flaps are out of up or glideslope is captured. When a go–around is initiated, the command speed is the MCP IAS/MACH window or current airspeed, whichever is higher, to a maximum of the IAS/MACH window speed plus 25 knots. GA displays as the thrust limit on the primary EICAS engine display.


Arrow VNAV:

• VNAV SPD (active) – AFDS maintains the FMC speed displayed on the PFD and/or the CDU CLIMB or DESCENT pages. If speed intervention is selected, the MCP IAS/MACH selector is used to manually select the speed

• VNAV PTH (active) – AFDS maintains FMC altitude or descent path with pitch commands. If the MCP altitude window remains set to the current cruise altitude and the airplane is within two minutes of the top of descent, the CDU scratchpad message RESET MCP ALT displays

• VNAV ALT (active) – when a conflict occurs between the VNAV profile and the MCP altitude, the airplane levels and the pitch flight mode annunciation becomes VNAV ALT. The airplane maintains altitude. To continue the climb or descent, change the MCP altitude and push the altitude selector or change the pitch mode

• If an early descent is desired, FLCH, V/S, or FPA may be selected to descend below the VNAV descent path. If, during the decent, VNAV is armed and the airplane descent path subsequently intercepts the VNAV descent path, VNAV activates in VNAV PTH


Arrow FLARE:

• FLARE (armed) – during autoland, FLARE displays below 1500 feet RA.

• FLARE (active) – during autoland, flare activates between 60 and 40 feet RA.

• FLARE deactivates at touchdown and smoothly lowers the nosewheel to the runway.


Arrow ALTITUDE SELECTOR AND ALTITUDE INTERVENTION




CLIMB

• In climb or descent, with altitude constraints, each push of the altitude selector deletes the next waypoint constraint between the airplane altitude and the altitude window setting.

• In climb, with no altitude constraints, and the altitude window set above the FMC cruise altitude, the cruise altitude is changed to the altitude window setting when the altitude selector is pushed.



Whenever the airplane levels off at an MCP altitude not in the FMC, VNAV ALT annunciates. For example, FMC cruise altitude is FL250 and the clearance altitude, FL190, is set in the MCP. Pitch maintains altitude and thrust maintains FMC target speed. In the example, the speed after the temporary level off would be ECON CLB SPEED. Setting the clearance altitude in the MCP window and pushing the altitude selector continues the climb. VNAV SPD activates. Pitch maintains FMC speed and thrust increases to the armed reference thrust limit. In the example, the airplane climbs to FMC CRZ ALT and then levels at FL250 in cruise.


CRUISE

• In cruise, with the altitude window set above or below FMC cruise altitude, pushing the altitude selector resets the FMC cruise altitude to the altitude window altitude.

• In VNAV PTH or VNAV ALT pitch mode, pushing the altitude selector initiates a climb or descent toward the altitude window altitude. When a conflict occurs between the VNAV profile and the MCP altitude, the airplane levels and the pitch flight mode annunciation becomes VNAV ALT. The airplane maintains altitude.

To continue the climb or descent, change the MCP altitude and push the altitude selector.


DESCENT

• Within 50 NM of the top–of–descent:

With the altitude window set below cruise altitude, pushing the altitude selector (VNAV enaged) initiates the descend now (DES NOW) feature.

(DES NOW): The DES NOW prompt is shown on the descent page when the cruise phase is active. Selecting the DES NOW prompt and executing initiates a VNAV SPD descent of approximately 1250 feet per minute at ECON speed.

Within 50 NM of the top of descent point, VNAV starts an early descent and captures the idle descent path.




• More than 50 NM from top–of–descent:

With the altitude window set below cruise altitude, pushing the altitude selector causes the VNAV to begin a cruise descent to the new cruise altitude. VNAV may not capture the idle descent path since the target airspeed is economy cruise and the descent path is based on idle thrust and economy descent airspeed.

The CRZ page displays ACT ECON CRZ DES. If the altitude set in the altitude window is below the speed transition (SPD TRANS) or restriction (SPD RESTR) altitude displayed on the DES page, those altitudes and speeds are deleted. Transition or speed restrictions must be maintained by flight crew action.



Last edited by K.Haroon on Fri Oct 12, 2012 6:30 am; edited 2 times in total
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