Automatic Flight Control System (AFCS)

AFCS General (22-00-00)

• The Automatic Flight Control System (AFCS) provides Flight Director (FD), yaw dampening, autopilot (AP), Tactile Control Steering (TCS), and automatic pitch trim functions.

• The system offers dual Flight Director, single autopilot, and single yaw damper capabilities.

• The AFCS provides all-weather approach capability to Category I limits for MLS, if optional MLS receivers are installed, and Category II limits for ILS operation

• The AFCS handles non-precision VOR, front and back course localizer, FMS, and optional MLS Azimuth approaches

• The AFCS consists of one Flight Guidance Control Panel (FGCP), two Flight Guidance Modules (FGM), one Yaw Damper Actuator Unit (YDAU), and two Autopilot Actuator Units (APAU).

• Cockpit switches dedicated to the AFCS include two Autopilot Control Wheel Quick Disconnect Switches, two Tactile Control Steering (TCS) Switches, two Go Around (GA) Switches, and two Autopilot Disengage Warning Lights

AFCS System Compoment Location (22-00-01)

• The Flight Guidance Control Panel (FGCP) is at the center of the glareshield and uses four DZUS fasteners for installation.

• The FGCP's front contains knobs, switches, and two independent processing channels.

• The processing channels are located on two separate circuit boards and are energized by two separate power sources, use the same control knobs and switches, and each channel of the FGCP has a digital data output and discrete signals to its related FGM and the flight data processing system (FDPS).

• The FGPC has heading, course selector, navigation source selector, altitude pre-selector rotary knobs and NOSE DN and UP pitch thumb wheel.

• The FGPC has Indicated Airspeed, Vertical Speed, Vertical Navigation, Altitude Hold, and Altitude Select vertical FD modes, and Heading, Navigation, Approach and Back Course Localizer lateral FD modes.

• The Flight Guidance Modules (FGM1, FGM2) are installed in their related Integrated Flight Cabinets (IFC1 and IFC2) located in the avionics rack between the pilot's bulkhead and the wardrobe installation in the forward left hand fuselage. IFC1 is in the lower avionics rack and IFC2 is located in the upper avionics rack.

• Each IFC has an Input Output Module (IOM), Input Output Processor (IOP), FGM a Stall Protection Module (SPM), a Primary Power Supply Module (PPSM) and Aircraft Configuration Module (ACM).

• Mechanical keying ensures correct FGM insertion into the IFC, secured by a front locking lever for tool-free insertion and extraction.

• The Yaw Damper Actuator Unit (YDAU) uses FGM electrical commands for linear mechanical input to the rudder control system.

• The YDAU inputs sum in series with pilot inputs from rudder pedals via a fork end on the motor side and rod end with bearing on the ram side.

• The YDAU includes a housing, brushless DC motor, reduction gearing, mechanical torque limiter, irreversible screw and nut mechanism, mechanical stops, a dual potentiometer, and electronic circuits

• No brake or engagement clutch allows irreversible output to the rudder.

• A torque limiter protects the motor and gear train during mechanical travel limit stops.

• The YDAU receives position commands from FGM1, and outputs two position values to each FGM.

• FGM2 inhibits the YDAU by supplying an inhibit-discrete.

• Identical Autopilot Actuator Unit (APAU) assemblies are used for roll and pitch axes, roll APAU is attached to the aileron forward quadrant and the pitch APAU being in the vertical stabilizer and attached to the pilot's elevator control circuit.

• The APAU consists of paired APAU actuator connected to an APAU capstan.

• The APAU capstan has a override slip clutch to ensure the turning of the cable drum

• The APAU actuator components are housing, brushless DC motor, electromechanical engage clutch, two gearing stages, a power electronics assembly, output shaft, electronic board, and dual potentiometers.

• The APAU receives position commands from FGM1 and back to the two FGMs.

• FGM1 connects the APAU by commanding the clutch and FGM2 can prevent APAU operation by supplying an inhibit-discrete signal to the electrical power from the motor.

• The APAU actuators measure applied torque and send two torque values to each FGM.

• Control wheel red AP disengage pushbutton supplies discrete inputs to the Flight Guidance Modules (FGM1/2).

• The red AP disengage pushbuttons manually disengage the autopilot, alongside resetting both automatic AP disengage and yaw damper disengage warnings.

• Selection of TCS mode uses two black TCS pushbutton switches attached to the pilot's and co-pilot's hand wheel with selection supplies discrete input to the Flight Guidance Modules (FGM1, FGM2).

• Activating the GA FD mode uses 2 black power lever GA pushbutton switches that then supply a discrete input to the FGMs.

• Glare shield mounted AP-disengage warning lights come on to indicate an automatic AP-disengage condition.

Flight Director General (22-10-00)

• The Flight Director (FD) provides aircraft lateral and vertical guidance that is displayed on the PFDs for manual control, or coupled to the Autopilot for automatic control.

• Each Flight Guidance Module can independently control Flight Director functions, however, Flight guidance Module #1 is master and Flight Guidance Module #2 is slave where if 1 fails, then 2 automatically becomes the master.

• Pilots remain able to select lateral and vertical guidance modes when at least one Flight Guidance Module can perform the FD function. The Flight Director commands from the Flight Guidance Module #1 are only coupled to the Autopilot.

• The PFD will show "L" or "R FD FAIL" if the director function has failed based on the related FGM. And “AFCS FAIL", if both flight directors are disabled based on the failures of both flight guidance modules.

• Since either FGM can independently provide FD function, both modules process FD mode selections compute commands for display display, sensor selection, and monitoring, where if one FGM fails, then AP and yaw damper can not be engaged!

• Activated through inputs from the FGCP and GA select switches.

• FD modes can be both active and/or armed, active modes provide for guidance, armed acts as a standby.

• FGMs send pitch and roll for display, alongside displaying active AP disengage messages.

• In single FD mode for ILS approaches, both PFDs show Command bars and annunciation of current mode

• Data from Flight Guidance Module #2 passes to both PFDs only if Module #1 has Failed.

• PFD#1 shows Flight Director command bars and mode annunciation coming from Module#1,

• PFD#2 displays the same bars coming from 2/2 if in Dual FD mode

• Either a single cue or across bar or can be shown can be configured by changing settings

• When not in Dual FC mode, FGMs use data being shown on one of the PDFs. Data displayed on the PFD#1 is by default used, but there the HSI select switch to alter this is set to the other hand

• FGM uses air data, attitude, heading data, select information alongside, heading, and of course, the select from the pilot

Yaw Damper (22-10-04)

• Yaw damper uses rudder to provide damping of the aircraft dutch roll mode and turn coordination
• The authority the yaw damper has 4.5 degs on either side and commands are limited by a software function.
• The Yaw damper engagement is allowed in air and on ground, and is triggered automatically when the pilot is engaged.
• YD is disengaged by, AP, failure or stuck button on the FGCP or caused disengagement. When its automatic the PVD shows either the YD or AP/Yd disengage is shown alongside amber
• YD is recordered following a manual, YD disengagement, so that it is ready to be reengaged automatically

Autopiliot (22-10-05)

• Autopilot is engaged by selecting P switch on FGCP alongside disengaging AP switch on the same module. Yaw Damper engagement is also activated this will only occur if the yaw damper is fully engaged
• Autopilot deactivates the AP and reset it
• The two main conditions are : that Aircraft is above 1Vsr alongside below 290 knots. That the altitude is above 27000 feet.
• The pitch trim on board the aircraft disengages the switch on the same control will also deactivate the AP
• The system AP is automatically recentering with a safety consideration to protect the circuit

Tactile Control Steering (22-10-06)

• AP is the TCs which is enabled by pressing on what of the control steering switches, allows for de-clutch of a pitch and roll at the same time and they can be changed individually
• FD command bars are disabled and AP is enabled with the letters TCS in white. The system mains will also give alerts

Automatic Pitch Trim (22-10-07)

• AP pitch trim engages during a AP being controlled, flap AP trim which does not trigger, if the AP is disconnected, a

• Functions all occur via flight control

• AP is engaged in two mode slow and high the high occurs with a value of 180 knots or lower the low occurs when higher them this speed.

• Manual trim is given more importance . An important state if the aircraft is engaged then will turn off system AP with automatic disengage

• Pitch trim failure gives amber “pitch term fail” warning will give the indicator will show the issue.

• Pitch rim. If there is a state in which trim is disengage then it may not be showing and system failure with the FCECU will.

Overview of the Automatic Flight Control System (AFCS) functions, including Flight Director, autopilot, and yaw damper. Covers system components such as the Flight Guidance Control Panel and Autopilot Actuator Units. Details all-weather approach capabilities and cockpit switches.