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