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Boeing 757 Technical > Automatic Flight > Flashcards

Flashcards in Automatic Flight Deck (73):

What do the three FCCs control?

Three separately hydraulically powered autopilot control servos to operate the flight controls


What flight controls does the autopilot control under normal conditions and during multiple autopilot approach?

Just the aileron and elevator under normal conditions and the rudder and nose wheel steering (during rollout) on multiple autopilot approach


Do the FCCs get separate electrical power sources during a multiple autopilot ILS approach?



What do the FCCs provide the AFDS inputs to for the ADI? (2)

Operating modes to display and also the flight director commands


How can the localiser and glideslope modes be deactivated after capture? (2)

1. Disengage autopilot and turn both flight directors off
2. Select G/A mode


Two normal ways to disengage autopilot?

Either control wheel autopilot disengage switch or the MCP autopilot disengage bar


If an active AFDS mode fails what happens and is shown (4)

1. autopilot remains engaged in an attitude stabilising mode
2. amber line drawn through the mode annunciation
3. Autopilot light illuminates
4. EICAS caution message AUTOPILOT displays


When does F/D steering indication appear if the related F/D switch is off?

When the G/A switch is pushed, the airspeed is greater than 80kts, and the flaps are not retracted


What do the following ASA indications mean?
1. LAND 3
2. LAND 2
3. NO LAND 3

1. LAND 3 - 3 autopilots engaged and operating normally for an autoland
2. LAND 2 - AFDS redundancy reduced, in some cases only two autopilots available
3. NO LAND 3 - indicates a fault condition exists which results in LAND 2 condition
4. NO AUTOLAND - AFDS unable to make an automatic landing


Difference between fail operational and fail passive (LAND 3 vs LAND 2)

- LAND 3 means the level of redundancy is such that a single fault cannot prevent the autopilot system from making an autoland (fail operational)
- LAND 2 means the level of redundancy is such that a single fault cannot cause a significant deviation from the flight path (fail passive)


What happens to ASA below 200ft AGL and what does this mean?

The ASA cannot change to anything other than NO AUTOLAND. Faults not requiring crew action or awareness are annunciated after touchdown.


What thrust does autothrottle give during G/A? Also when both F/Ds and A/P are off?

2000ft per min ROC, or G/A reference thrust subject to flap and VMO limits


What distance within track does arming LNAV give immediate activation?



What heading does HDG HOLD hold?

Holds present heading or if in a turn it holds heading reached after rolling out.


Within how many degrees does the aFDS capture the LLZ?



When does G/A mode armed (2) and how can you tell it has armed?

Armed when flaps greater than up or at G/S capture. You can tell because thrust reference goes to G/A


What lateral guidance does the G/A mode give?

Maintain ground track and time of engagement


When does rollout arm and when is it active?

Armed below 1500ft AGL and activates below 5ft


When does rollout activate and what does it sue for lateral guidance?

Activates after touchdown and uses the LLZ for centreline control


How many degrees nose up does T/O mode give?

8 deg


After takeoff what does the T/O pitch bar provide? (3)

- Pitch command of greater than V2+15 or lift off speed +15
- If current airspeed remains above target speed for 5 seconds, target speed resents to current airspeed, to a maximum of V2+25
- IF IAS/MACH window speed is changed to a speed greater than target speed


Where does AFDS get V2 speed prior to takeoff for F/D T/O pitch bar?

IAS/MACH speed window


What speed is commanded on pitch bar once G/A initiated and when does it change?

- Commanded speed is either the MCP IAS/MACH window or current speed, whichever is higher
- If airspeed increases above target speed for greater than 5 seconds then it is reset to current speed up to IAS/MACH window +25kts
- If airspeed was already greater than IAS/MACH +25kts then that higher speed is maintained


When does VNAV ALT occur?

When there is a discrepancy between the NAV profile and the MCP altitude


When does VNAV SPD display?

When off VNAV path and gets its speed from either the ADI or CDU CLIMB or DESCENT pages. Also during speed intervention when MCP IAS/MACH manually sets the speed


When does RESET MPC ALTITUDE display?

When approaching TOD and MCP altitude set to current cruise altitude


When does FLARE arm, activate, and disengage?

Arms below 1500ft AGL during autoland, activates at 45ft radalt, deactivates at touchdown and the nose wheel smoothly lowers to the runway


Two systems in the automatic flight control system

1. AFDS - Autopilot flight director system
2. A/T - Autothrottle


Is there sufficient gust protection from the autothrottles when at land flap and VREF+5?



Why in turbulent conditions does the autothrottle system generally hold a higher average speed than the command speed?

Because the autothrottle is quick to power on if speed below command speed, but slow to reduce power if above. Therefore, in turbulent conditions on average it holds a higher power than needed to hold command speed


Three basic function of the Thrust Management Computer?

1. calculate thrust limits and settings or follow FMC thrust settings
2. detect and transmit autothrottle failures
3. actuate the thrust levers


If you move manually the throttles whilst the autothrottle is engaged what happens after you release the throttles?

They go back to where the autothrottles want them to comply with the engaged mode


Two ways to disconnect the autothrottles?

1. A/T arm switch to off
2. Pushing the A/T disconnect switch on the thrust lever


When does A/T automatically disconnect? (2)

1. If a fault occurs
2. When reverse thrust lever is raised to reverse idle


At what speed does A/T go to THR HLD during takeoff?



When does THR HLD remain until after takeoff? (3)

When either a pitch mode, A/T mode, or thrust reference mode is selected.


When do the remaining two autopilots arm for a multiple autopliot approach?

When the APP mode is armed


What does the runway align sub mode do? Ho does it operate? (3)

- Reduces the crab angle established during crosswind conditions prior to automatic landing
1. actuated at 500ft when in LAND 2 or 3
2. initiates a slip with a max bank angle of 2deg when crab angle exceeds 5deg
3. wing levelling initiated when ROLLOUT mode is engaged


How does FLARE submode operate? (2)

- At 45ft FLARE engaged
- At 25ft thrust levers go to IDLE


What do you need to note when operating in LAND 2 and the autopilots get disengaged at low level? In a go-around?

In LAND 2 at 330ft an amount of nose up trip is automatically added to help the FLARE mode. If the autopilots are disengaged then 20-30lbs of forward control column force may be needed to counteract the auto trim.
If a G/A is initiated the trim is automatically taken out so no force needed


When does ROLLOUT engage?

Below 5ft


When does A/T disengage automatically on ROLLOUT? How tell?

When thrust levers moved to reverse idle position. A/T DISC caution light and EICAS message and aural warnings are not activated


Do the flight director bars come on when G/A activated and F/D switches are off?



When does the G/A remain armed until?

2 sec after going below 5ft


What happens if G/A pushed but aircraft been floating off the ground for more than 2 seconds?

Pitch mode will remain in FLARE and A/T go-around mode will engage


If aircraft is on the ground but but has been less than 5ft for less than 2 seconds what happens when G/A pushed?

G/A pitch mode will engage but A/T will remain at idle


How does flap setting affect thrust mode selection during a go-around?

For flaps 20 or less another thrust mode can be selected.


What is the note regarding single autopilot go-arounds and elevator authority?

Elevator authority during a single autopilot go-around is limited (to reduce effects of autopilot malfunction) so there may be insufficient elevator authority to counteract pitch up caused by rapid application of full go-around thrust


What does AFDS provide for pitch and roll modes in windshear recovery?

Normal roll mode as per G/A (ground track), and either 15deg nose up or pitch limit whichever is lower


What limits are monitored automatically by the AFDS and TMC in all modes except V/S? (3)

1. Flap limit speeds (FLAP LIM)
2. Max angle of attack (ALPHA)
3. Max speed (SPD LIM)


What mode does the F/D first engage when F/D switch cycled to off then on in flight?



Speed range of IAS/MACH window? (IAS and MACH)

Speed = 100-399kts, MACH = 0.40-0.95


When does IAS/MACH change between IAS and MACH in climb and descent?

Climb = approx 0.80 Mach
Descent = approx 300KIAS


What does LNAV do if it reaches the last active waypoint, passes the last waypoint in a DISCO, or passing last route offset waypoint?

Maintains current heading


What automatically happens to HDG window on LLZ capture?

Goes to ILS front course


What does AUTO bank angle selector do? (deg limit?)

Adjusts bank angle between 15-25deg depending on TAS (slow = 25, high = 15)


Range of V/S display? (ft)

-8000fpm to +6000fpm


Altitude window range?



What does pushing the altitude button during climb or descent do - with altitude constraints?

deletes the next waypoint constraint between the airplane altitude and the MCP altitude


What does pushing the altitude button during climb - no altitude constraints and the MCP altitude window is above cruise altitude?

Changes cruise altitude to MCP altitude window value (i.e. new cruise alt)


What altitude is flown when the ALT HOLD button is pushed?

The altitude at the time the button was pushed


What is the note regards A/P roll manoeuvres after LLZ capture?

May compare inconsistent with F/D roll commands for 1-2 minutes after LLZ capture


How can you disarm LLZ mode before it is captured? (2)

1. push the LLZ switch a second time
2. arm LNAV


How deactivate LLZ mode after LLZ capture? (3)

1. Select a roll mode other than LNAV
2. Push G/A switch
3. Disengage A/P and turn both F/Ds off


Angle must be within LLZ to get G/S capture?

Within 80 deg


When do the other A/Ps automatically arm on APP?

Through 501500ft radalt and LLZ and G/S captured


When does LAND 2 or 3 appear automatically?

When both LLZ and G/S are captured and below 1500ft radalt


How long does the green box appear around AFDS and A/T mode changes?

10 sec


What 3 warnings does a second push of the A/P disengage switches cancel?

1. Master Warning
2. EICAS Warning
3. Aural warning


What does amber AUTO PILOT light indicate? How extinguish?

1. A degraded operating condition exists in engage autoplilot
2. Extinguished when condition is corrected or alternate autopilot is connected (provided fualt is not common to alternate autopilot)


Why is min height for A/P engagement at 200ft?

Proved in testing that 200ft is min height to manually recover from an A/P hard nose over


Max overshoot/undershoot allowed in RVSM airspace?



When operating in RVSM airspace and within 5nm and 2000ft of other traffic what should you do during climb and descent to minimise generation of TAs and RAs?

Reduce vertical speed to 1000fpm and below