AFCS Flashcards
What does the AFCS provide?
- autopilot functions
- yaw dampening functions
- flight director system
- altitude alerts
What powers the AFCS computer?
DC emer bus
What powers the Advisory Display Unit?
DC stby bus
ADU displays advisory and caution messages
What are the servo actuators?
Control the aircraft
Consist of an electric motor and clutch assembly that moves the respective flight control surface
Pitch and yaw actuators located in the aft portion
Roll servo actuators located on the aft side of the wing box
Control for servos powered by DC stby bus
How do you engage the autopilot?
AP pb on the AFCS control panel
This will automatically engage the yaw damper
How do you disengage the autopilot?
- Pressing the AP pb - this will only disengage AP not the yaw damper
- pressing AP quick disconnect button on control column
- using normal or standby pitch trim
- pressing YD pb on AFCS control panel
- pressing GA button on the power levers
- applying force to the rudder pedals or control column
How is the yaw damper engaged/disengaged?
The YD pb
AP will be disengaged by disengaging the YD
What mode will the AP be in if no vertical or lateral modes are selected on AFCS control panel?
Basic mode - will maintain the pitch at time of engagement and will level the wings and maintain heading at the time the wings levelled
If wings are already level, it will maintain that heading
What will the autopilot do on engagement if vertical and lateral modes are active?
It will immediately manoeuvre to follow the active commands
What happens on autopilot engagement if vertical and lateral modes are armed?
The autopilot will remain in basic mode until the flight director modes are active
What vertical modes are available?
IAS
VS
ALT - altitude hold
How can VS be changed?
By the pitch wheel
What lateral modes are available?
HDG
NAV
APP
BC - back course
What does the BANK pb do?
It will change the max bank angle between HI (27 degrees) and LO (15 degrees)
At initial system power up the max bank angle is set at 27 degrees
When will the AP and YD be disengaged together?
By applying a force on the rudder pedals
What aural and visual indications will you get on AP disengagement?
Red AP OFF light
Cavalry charge will sound
Arrows adjacent to AP pb will extinguish
RESET pb will illuminate on the ADU
AP DISENGAGED amber message on the ADU
What indications will you get on YD disengagement?
Two arrows on either side of YD pb will extinguish
ADU message will show AP/YD disengaged
How can you clear the AP disengagement warnings?
By pressing the RESET pb or by pressing the AO disconnect buttons on either control wheel
When will the AP disengage automatically?
- one of the engagement conditions for the AP or YD no longer exists
- stall warning threshold has been reached
- there is a disagreement between the two AHRS or ADCs
- there is a mismatch between the two pitch trim commands
What failures mean hand flying the rest of the flight?
PITCH TRIM FAIL
PITCH MISTRIM
AILERON MISTRIM
What does PITCH TRIM ASYM mean for the AP?
AP will automatically disengage and cannot be re engaged
Can you re engage the AP or YD after a failure?
If they disengaged due to a fault they can be re engaged by pressing the reset button but if the cause of disengagement still exists, they will disengage again
What conditions prevent AP are-engagement
- AP or YD failure
- trim inoperative monitor failure
- failure of AFCS control panel
- if an app mode was selected at the time of the failure
- if GA mode was selected at the time of the failure
- if LOC or BC mode was selected at the time of the failure
What is TCS (Touch Steering Control)?
Pilot can manually change the aircraft’s attitude, altitude, vertical speed and airspeed without disengaging the AP
Press and hold TCS button on control column
What happens to TCS if AP is in basic mode?
Pilot can reset the AP’s pitch and roll references and when TCS is released the AL will use the references that existed at the time the button was released
What are the TCS pitch limitations?
Pitch angle must be within +/- 15 degrees when TCS is released
If pitch exceeds these values, the AP will automatically reset to +/- 15
When are the flight director bars visible?
Only when an associated mode is selected
What are the Flight Director vertical modes?
ALT SEL
ALT
VS
IAS
What are the flight director lateral modes?
HDG
NAV
BC
What are the flight director combined modes?
APP
GA
What flight director modes are not selectable?
ALT SEL - automatically armed, both an AP and FD mode
GA - armed by pressing one of the GA buttons on the power leavers, a FD mode only
What will the flight director command in GA mode?
The lateral bars will command the present heading
The vertical bars will command a safe pitch altitude based on flap setting and SE performance
What mode stays active in GA mode?
ALT SEL - upon reaching a preset altitude it will be captured as normal
Where are armed modes indicated?
On the third line of the ADU in white
Where are captured modes indicated?
On the fourth line of the ADU in green
What vertical modes have an armed status?
ALT
GS
What lateral modes have an armed status?
VOR
LOC
BC
How are captured modes displayed?
Displayed in green with an Asterisk
Contained within a box which lasts for five seconds
Where will the AP ENG be displayed?
On the bottom right of the EADI in green
What is the AP caution message on the EADI?
AP MSG in amber to tell crew to check ADU
What is the AFCS normally coupled to?
Coupled to the captains side at initial power up and uses data from the associated ADC and SGU
How can you change which side the AFCS is coupled to?
Press the CPL button on the AFCS control panel
The side it’s coupled to is indicated by a green arrow displayed on left side of the EADI, arrow will point in the direction of the coupling
The arrow next to the CPL pb will also indicate direction of coupling
What modes will disengage after changing coupling?
NAV
BC
APP
When does dual coupling occur?
Occurs automatically when the localiser and glideslope are captured provided both ILS receivers are turned to the same ILS frequency
Dual coupling will be indicated by illumination of both arrows either side of CPL pb
What will the flight director be coupled to when approach mode is cancelled?
Flight director will remain coupled to the side selected at the time dual coupling occurred
When will the GUIDANCE light illuminate?
In the event of excessive deviation during a dual approach or if CAT II engagement conditions are lost
What happens if a sensor fails on the selected coupled side?
The AFCS can still be coupled but the FD mode that uses that failed sensor cannot be selected or engaged
What does the STBY pb do on the AFCS control panel?
Cancels all armed and engaged flight director modes
If the AP is engaged it will revert to basic mode
When is the altitude select mode automatically armed?
When the aircraft is climbing or descending towards a selected altitude
Altitude is set by rotating the ALT rotary switch
Selected altitude is displayed on the ADU
What are the altitude select mode phases?
Armed phase - crew can use vertical speed hold, IAS hold or pitch hold to perform the climb or descent
Capture phase - mode used to fly the selected altitude is cancelled and AFCS will provide guidance to capture the selected altitude - indicated by ALT SEL CAPTURE on ADU and green ALT message on EADI
Altitude hold phase - once altitude has been captured. ALT message on ADU and green ALT message on the EADIs
What is pitch hold mode?
Will automatically default to pitch hold mode if the selected altitude is changed during the capture phase
What will happen when selecting the ALT pb?
The aircraft will round out the climb or descent to return and hold the altitude existing at the time the altitude hold mode was selected
What happens when you press the VS mode?
Aircraft is placed in vertical speed hold mode
Action cancels any other active flight director vertical modes
What will happen when the IAS pb is pressed?
The AFCS will provide guidance to maintain the indicated airspeed existing when the IAS pb was pressed
Airspeed will be displayed in green on the ADU
What is over station mode?
When the aircraft is in the cone of confusion
AFCS will provide steering command based on heading only
What will be displayed when the AFCS is tracking the localiser?
ADU and EADI will display a green LOC message
How is the go around mode cancelled?
- selecting another vertical mode
- engaging the TCS
- pushing the STBY pb
- engaging the autopilot
What is the altitude alerts?
Visual alert is an amber light on the two altimeters and an aural C chord tone
When will the altitude alert light illuminate?
When the aircraft is within 1000 ft to 250 ft of the selected altitude
