· The AP can be engaged by the AP ENGAGE pushbutton at the FMP. When the AP is engaged with no FD modes selected, the AP will command heading hold and pitch hold. When the AP is

GENERAL

The Automatic Flight Control System (AFCS) controls the aircraft around the pitch, roll, and yaw axes. The system consists of:

• Two Flight Directors (FD).

• Autopilot (AP).

• Flight Augmentation System (FAS).

• Flight Mode Panel (FMP).

• Autopilot control panel.

• AFCS status panel.

• Additionally, AP cut-out, Touch Control Steering (TCS), and Go-Around (GA) buttons are provided.

• Each FD provides, dependent on the FD mode(s) selected, pitch and/or roll steering guidance by means of command bars at the onside Primary Flight Display (PFD). The AP provides dual channel pitch and roll attitude stabilization. Additionally, HDG hold stabilizations is provided. The AP follows pitch and roll commands as selected by the pilots at the autopilot control panel or supplied by the selected FD for automatic flight path control. The FAS provides dual channel turn co-ordination and yaw damping. Single channel elevator trim, which is controlled from both AP pitch channels, is also provided by the FAS.

• Failures will be detected and the relevant alerts are presented.

Fokker 50 - Automatic Flight Control System

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FLIGHT DIRECTOR

Description

Each FD is provided with data from: Aircraft with one ADC Aircraft with two ADC’s Onside AHRS Onside AHRS ADC Onside ADC Captain’s altimeter Captain’s or first officer’s altimeter via FMP NAV sources as selected at the onside ECP NAV sources as selected at the onside ECP

• Each FD provides the onside PFD with guidance, by means of command bars, for manual steering purposes.

The command bars will not be displayed when:

• The FD COMMAND pushbutton is depressed at the onside EFIS control panel.

• There is a source failure affecting the mode.

• The FD fails. The roll command bar will not be displayed when:

• The TURN knob is moved out of center with the AP engaged.

• A new NAV source is selected at the onside EFIS control panel (except when the onside FD is the HDG mode).

The following FD modes are available: Heading select HDG Go-around GA VOR/LOC NAV Back course BC VOR approach VAPP Radio navigation modes. Glide slope GS FMS LNAV Altitude pre select ASEL Altitude hold ALT Air data modes. Vertical speed hold VS Indicated airspeed hold IAS All modes (except the GA mode) are selected by mode select pushbuttons at the FMP. The GA mode is selected by depressing the GA button at either POWER lever. All modes are selected simultaneously for both FD’s. The radio navigation and air data modes can only be selected if the corresponding sources are available. If the selected mode does not correspond with the NAV source selected at EFIS, the FD will not accept that mode. The captured and armed modes of each FD are displayed at the onside PFD. The FMP annunciates the modes of the FD, which is used to command the AP.


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For detailed information on the various FD modes, see subsection FLIGHT DIRECTOR MODES. All FD modes are cancelled when:

• The FD fails.

• Standby (SBY) is selected at the FMP.

• The onside SG fails.

• ALTN SG is selected at the AVIONICS panel.

• EFIS self test is initiated. All radio navigation modes are cancelled when a new NAV source is selected at the onside EFIS control panel. For aircraft equipped with one ADC

All air data modes (except the ASEL mode) are cancelled when the ADC fails. The ASEL mode is cancelled when the captain’s altimeter or the altitude pre-select function of the FMP fails. For aircraft equipped with two ADC’s

All onside air data modes (except the ASEL mode) are cancelled when the onside ADC fails. The ASEL mode is cancelled when the onside altimeter or the altitude pre-select function of the FMP fails. A heading data failure from the onside AHRS affects the HDG, NAV, BC, VAPP, and FMS modes, and:

• The roll command bar disappears.

• FMA remains on; and

• AP reverts to basic roll (if coupled to the FD). A NAV source failure after a radio navigation mode selection and prior to capture causes the FD to continue the arm phase of the mode. After capture, the FMA and the relevant command bar disappears, and AP steering in the affected axis is not available. When this failure disappears, mode operation will be resumed. When an attitude data failure from the onside AHRS occurs:

• The command bars disappear.

• FMA remains ON.

• AP steering in the affected axis is not available.

When this failure disappears, mode operation will be resumed.


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Controls and indicators


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AUTOPILOT AND YAW DAMPER

General

The Autopilot (AP) provides heading and attitude stabilization. The AP is manually controlled by steering inputs from the PITCH wheel and TURN knob. Automatic control is realized by steering inputs from either Flight Director (FD). The AP and Flight Augmentation System (FAS) provide automatic elevator trim control. The Yaw Damper (YD) provides yaw damping and turn co-ordination. The pitch and roll attitude stabilization channels of the AP, and the yaw channels of the YD are fully duplicated. AP and YD are internally monitored so that failures are detected and localized. System controls

AP COMMAND buttons are provided at the FMP. These buttons determine which FD supplies steering commands to the AP. AP and YD engagement

The AP can be engaged by the AP ENGAGE pushbutton at the FMP. When the AP is engaged with no FD modes selected, the AP will command heading hold and pitch hold. When the AP is engaged with a roll and/or pitch mode as selected at the FMP, the AP roll and/or pitch axes are automatically coupled to these modes. AP engagement is not possible if one of the automatic AP and YD disengagement conditions apply, or if the TURN knob is out of center. The YD is automatically engaged whenever the AP is engaged. NOTE: While the aircraft is on the ground, automatic YD engagement is inhibited for

test purposes. An YD ENGAGE pushbutton is provided at the autopilot control panel toe engage the YD independent of the AP. AP and YD disengagement

The AP en YD are manually disengaged by:

• Depressing the AP cut-out button on either pilot’s control wheel, or by

• Depressing the go-around button on either power lever.

• A manual AP and YD disengagement is confirmed by a single cavalry charge. If only the YD was engaged, no alert will be generated.

The AP and YD are automatically disengaged when:

• The stick shaker is activated.

• The flight control lock is on; or when

• A data fault from both AHRS’s occurs. When the AP is not engaged, and the landing gear is selected down, the YD is automatically disengaged.


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Automatic AP disengagement is announced by a continuous cavalry charge tone. Automatic YD disengagement is announced by a single chime. Automatic disengagement can be generated by AP or YD failures as described below. An automatic AP or YD disengagement failure is announced by a continuous cavalry charge. Touch control steering

To momentarily override the AP, a Touch Control Steering (TCS) button is provided on each control wheel. When this button is depressed the aircraft can be manually maneuvered in roll and pitch, without disengaging the AP. When the TCS button is released, the AP will maintain this new attitude and heading. If the bank angle exceeds more than six degrees at TCS release, the existing roll attitude will be maintained. When the TCS button is released and FD modes where selected then the modes are affected as follows:

• Air data modes (ALT, IAS, and VS) will hold the new data.

• HDG select, NAV, BC, VAPP, FMS and GS will resume tracking according the old data.

• It is not possible to use TCS if the turn knob is out of the center position. Pitch wheel

Rotating of the PITCH wheel, located at the autopilot control panel, will change the pitch attitude and will cancel ASEL capture and ALT mode. For VS and IAS mode, rotation of the wheel will change the air data hold reference (only with AP engaged) as displayed at the PFD. PITCH wheel operation is inhibited during glide slope capture. Turn knob

A TURN knob is provided at the autopilot control panel. Rotation out of center will result in a bank angle proportional to the turn knob angle. This will cancel any selected FD roll mode. After glide slope capture TURN knob operation is inhibited.


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Failure monitoring and warning

AFCS status panel

An AFCS status panel is installed to indicate the operational status of the AP and YD. For maintenance and test purpose, two TEST buttons are provided. Roll and pitch pushbutton’s

These pushbuttons are blank during normal operation. When an OFF light illuminates, with the AP engaged, it is an indication that the respective AP channel has been disengaged automatically. The other AP channel remains operational. When the AP is not engaged, depressing the pushbutton disengages the respective channel and the OFF light illuminates. Disengagement of the AP cancels single channel operation. Yaw pushbutton’s

These pushbutton’s are associated with the YD. Operation is the same as described at the roll and pitch pushbutton. Trim light

The trim light indicates that the AP has been out of trim for longer than twelve seconds. UP or DN indicates the direction in which trim is insufficiently applied. AP/YD monitors

The AP and YD are provided with monitors to detect and localize failures. Failures, which are detected and localized in a specific channel in the pitch, roll, or yaw axis result in a single channel reversion in that axis. Single channel reversion occurs when:

• The monitors localize a failure to a specific channel, or when

• There is a data fault from AHRS 1 or 2. A single channel reversion is presented at the AFCS status panel and does not result in flight path deviations or out of trim situations. However the affected axis is no longer fail passive. The AP remains engaged. NOTE: Actuation of the TEST pushbutton, associated with the remaining operating

channel of AP and/or YD, will automatically disengage the AP and/or YD.


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When failures are detected but cannot be localized in a specific channel in the pitch or roll axis, or when a single channel reversion is not successfully completed in the AP, the result is:

• Automatic AP disengagement.

• Continuous cavalry charge.

• Both channel OFF lights of the particular axis flashing. In the YD, the result is:

• Automatic YD disengagement

• Single chime; and

• Both YAW channel OFF lights flashing The AP remains engaged. In case of failure of the automatic AP or YD disengage circuitry; a continuous cavalry charge tone will be generated. This cavalry charge tones can be cancelled by depressing either AP cut-out or either go-around button.


Page 8

Controls and indicators


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NOTE: The first officers control wheel is a mirror of the captains control wheel.


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Page 11


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Alerts

AP OUT OF TRIM

2

AURAL MWL/MCL CAP LOCAL CONDITION(S) / LEVEL

CAUTION

TRIM

UP

OR

DN

AP OR YD SINGLE CHANNEL FAILURE

1

ROLL 1 (2)

OFF

AND/OR

OFF

AND/OR

YAW 1 (2)

OFF

YD AUTOMATIC DISENGAGEMENT (WITH AP ENGAGED)

1

YAW 1

OFF

YAW 2

OFF


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AURAL MWL/MCL CAP LOCAL CONDITION(S) / LEVEL

YD AUTOMATIC DISENGAGEMENT (WITHOUT AP ENGAGED)

1

YAW 1

OFF

YAW 2

OFF

AP AUTOMATIC DISENGAGEMENT

-

ROLL 1

OFF

ROLL 2

OFF

AND/OR

PITCH1

PITCH 2

OFF

OFF

CONTINOUOS

CAVALRY CHARGE

AUTOMATIC AP OR YDDISENGAGEMENT FAILURE

1

CONTINOUOS

CAVALRY CHARGE


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FLIGHT DIRECTOR MODES

Roll modes

Heading select mode (HDG)

The HDG select mode provides guidance to the selected heading as indicated by the heading bug at the onside ND. When HDG is selected, NAV, VAPP, BC, FMS and GS modes are cancelled. Navigation mode (NAV)

The NAV mode provides guidance to intercept and track:

• VOR radials, when tuned to a VOR frequency and DME distance to station is greater than 20 NM. For DME distances less than 20 NM use VAPP mode.

• Localizer signals, when tuned to an ILS frequency. Prior to capture the HDG mode is active. Passing overhead a VOR station, course changes up to 90 degrees can be made by selecting a new course at the ND. Back course mode (BC)

The Back Course mode operates in the same way as the NAV (LOC) mode with the course select and deviation signals reversed. If there is a valid glide slope on the back course, the glide slope mode can be selected after BC mode selection. VOR approach mode (VAPP)

This mode is basically identical to the NAV (VOR) mode, but intercept and tracking are optimized for distances within 20 NM of the VOR station. FMS mode (LNAV)

The FMS provides roll steering commands to fly along a selected flight plan. It is not possible to select LNAV at the FMP without FMS selection at the EFIS control panel. Pitch modes

Pitch hold mode

Whenever a roll mode is selected without a pitch mode, the pitch command bar will display a pitch-attitude-hold command. The pitch command bar will be synchronized to align with the aircraft symbol when the TCS button is depressed or when the AP is engaged. Altitude hold mode (ALT)

When ALT is selected, GS capture, GA, IAS, VS, ASEL capture, and pitch-hold modes are cancelled. TCS operation will synchronize the altitude-hold reference to the new altitude.


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Altitude pre-select mode (ASEL)

The desired altitude can be set by the altitude selector at the FMP. ASEL can be armed while using the GA, ALT, pitch-hold, VS, or IAS mode. When approaching the selected altitude, the system automatically switches to ASEL capture and the previous pitch mode is cancelled. ALT mode will engage upon reaching the selected altitude, which will cancel ASEL capture. Changing the selected altitude during the ASEL capture phase will reset the FD to ASEL armed. Glide slope mode (GS)

When the NAV receiver is tuned to an ILS frequency (localizer and glide slope signals are available) and the GS mode is selected, NAV and GS modes are armed. With the GS mode armed, the pitch axis can be in any of the pitch modes (except the GA mode). Capture can be made from above or below the beam. Glide slope capture is interlocked so that the localizer must be captured prior to glide slope capture. If the localizer or glide slope receiver fails prior to capture, the system will remain in the annunciated roll and/or pitch mode. Vertical speed hold mode (VS)

When VS is selected, GS capture, GA, ALT, IAS, ASEL capture, and pitch-hold modes are cancelled. TCS operation win synchronize VS hold reference with the new VS. When the VS mode is engaged the existing vertical speed becomes the hold reference and is displayed at the PFD. The VS reference may be changed by rotating the PITCH wheel when the AP is engaged. Indicated airspeed hold mode (IAS)

When IAS is selected, GS capture, GA, ALT, VS, ASEL capture, and pitch-hold modes are cancelled. TCS operation will synchronize the IAS-hold reference with the new IAS. When the IAS mode is engaged the existing airspeed becomes the hold reference and is displayed at the PFD. The IAS reference may be changed by rotating the PITCH wheel when the AP is engaged. Go-around mode (GA)

When GA is selected, all other modes are cancelled and the command bars show wings level and a fixed pitch-up attitude command of eight degrees. In addition to the GA mode any roll mode may be selected, which cancels the wings level command. Selecting GA disengages AP and YD. The GA mode is cancelled by selecting another pitch mode, selecting TCS, or by engaging the AP. Stand-by selection (SBY)

This selection cancels all FD modes in both FD’s simultaneously; causing the command bars at both PFD’s to disappear.

• Failures will be detected and the relevant alerts are presented.


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SYSTEM OPERATION

General

It is recommended to use the FD during all phases of the flight except when flying a visual approach and during landing. Before flight the PF should select the onside FD to be in command for the AP by pressing the appropriate AP command button at the FMP. The AP may be engaged from 400 feet height after take-off until 50 feet height on an ILS approach or 200 feet on other approaches. The PF will have the FD display on the PFD when the AP is engaged. However, when the TURN knob is used, the FD command bar is automatically removed. The PNF may switch the FD display off, if required, unless an instrument approach is executed. The FD mode status is shown by the Flight Mode Annunciator (FMA) at the LH and RH PFD. Take-off, climb-out, and cruise

After lift-off rotate to align the aircraft symbol with the command bar. When aircraft is cleaned up and above 400 feet AGL the AP can be engaged, this will automatically cancel the GA mode. The AP will be in the pitch-hold mode. The climb-out can be executed in this mode, IAS mode or VS mode. Selection of IAS mode or VS mode before engagement of the AP will also cancel the GA mode. NOTE: • The primary means to control speed remains the pitch attitude.

• The FD pitch command in GA as used during take-off should be regarded ads a guidance only.

When the VS mode is selected at the FMP, the AFCS will maintain the existing vertical speed. When the IAS mode is selected at the FMP, the AFCS will maintain the existing indicated airspeed. The VS or IAS data can be changed by operating the PITCH wheel at the autopilot control panel. TCS may be used to steer to a new reference datum for the affected mode (pitch hold, IAS or VS). When the desired pitch attitude, speed or vertical speed is attained, releasing the TCS button will reset the FD in the original mode with the new reference datum.


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When cleared to continue climb set cruise altitude at the FMP and select ASEL mode. Continue climb in the existing mode until the ASEL capture point is reached. At this point the original vertical mode is cancelled. The aircraft will level off at the selected altitude and the ALT mode will capture automatically. NOTE: If the PITCH wheel is operated during the ASEL capture phase the ASEL

mode will be cancelled and the aircraft will continue the climb through the selected altitude.

Descent

Select the new altitude at the FMP before starting descent and select ASEL. A descent can be executed using the pitch hold mode, the VS mode or IAS mode. If the engaged mode was ALT, the pitch hold mode can be engaged by operating the PITCH wheel at the autopilot control panel. Any time the ALT mode is cancelled either by selecting VS, IAS, or pitch mode, select ASEL to ensure leveling off at the selected altitude. Navigation modes

NAV capture and tracking

The VOR operation in the NAV mode features automatic capture and tracking of a radial. Use the HDG mode to fly an intercept heading. Any pitch mode can be used. Tune the NAV receiver to the desired VOR. Select this navigation receiver at the ND in command. Set the course at the ND as desired, using the respective course selector at the FMP. Select NAV mode, green HDG and white NAV arm are shown at the FMA indicating that the system is flying the intercept heading and is armed for NAV capture. At VOR radial capture, the green HDG annunciator will go out and the green NAV cap will be shown, indicating that airplane will intercept and track the radial with crosswind compensation. If the VOR flag comes into view while tracking the VOR radial, the AP will hold heading but the command bar will go out of view, and the NAV cap annunciator will go out while the flag is in view. The system includes a VOR over-station sensor, which inhibits response to the beam signal when in the cone of silence above the VOR station. When beam rate becomes excessive, the AP automatically maintains selected VOR course only, providing stable station passage. If desired, a different outbound radial may be selected while over the station when the TO-FROM pointer changes direction. Moving the respective course selector while still tracking the beam signal can cause the system to switch to the over-station passage mode. To optimize interception and tracking, the computer uses DME distance as an input. If the DME HOLD feature is used, the computer disregards the DME information.


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ILS approach

On an ILS approach, the localizer and glide slope are automatically captured. The localizer is captured first from the HDG mode in the same way as a VOR radial. The glide slope can be captured with any vertical mode previously selected and from either above or below the beam. Localizer capture is required before automatic glide slope capture is possible. To fly an ILS approach, perform the following. Pre-select both NAV receivers to the ILS frequency. Use the active NAV frequency on a local VOR/DME for position monitoring in this phase. If so required, select DME hold before transfer to ILS; set the localizer course on both left and right ND. Fly the HDG mode to the desired intercept heading. When on the interception heading and approaching the ILS localizer:

• Select both NAV receivers to ILS.

• Arm GS and NAV by selecting the GS mode at the FMP.

• Conform the FMA shows GS and LOC armed (white) and HDG green. As the airplane approaches the localizer beam, the green HDG annunciator goes out and the green LOC will annunciate localizer capture. The airplane will intercept the localizer. The expanded localizer pointer at the bottom of the PFD will appear when the localizer deviation is a third of a dot or less. After localizer capture, select the missed approach heading using the heading bug on the FMP. When the glide slope is captured, the white GS arm annunciator goes out and the green GS capture FMA will illuminate. Any previously selected vertical mode will automatically release at glide slope capture. The AP will track the center of the localizer and glide slope beams with wind corrections. NOTE: For CAT 1 ILS approaches the decision altitude should be based on pressure

altitude. The AP should be disengaged at:

• 50 feet RA minimum. The DH will always be above this radio altitude.

• If a go-around is executed, at DA/DH, by pressing either power lever mounted GA button. If, on the ILS, the localizer or glide slope signal to the FD becomes invalid (flag showing), the command bar(s) will go out of view, and the FMA will go out. The AP will maintain attitude in that axis. NOTE: After localizer capture the HDG mode cannot be re-engaged unless SBY is

selected first. After GS capture the TURN mode and the altitude exit alert are inhibited.


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Go-around

A missed approach may be executed by pressing a GA button on either power lever. The autopilot will disengage, GA will be shown on the FMA and alert tone will sound. The command bar(s) will show a wings-level 8 degrees pitch-up attitude command. HDG mode can be engaged after GA has been selected to fly GA pitch attitude and HDG for a missed approach. After the gear and flaps are retracted, re-engage the autopilot and go-around is automatically cancelled. The missed approach departure is made using HDG with the climb being performed using pitch hold, IAS mode, or VS mode. The go-around mode can be selected at any time with any mode previously selected, but it will disengage the AP. Back-course approach

Tune NAV 1 to the LOC frequency. Select the NAV 1 to the LOC frequency. Select the NAV 1 at the ND to the front localizer course. Set the desired intercept heading with the heading with the heading selector at the FMP. Select Back Course (BC) to arm the system for automatic back-course localizer capture. ALT mode may be selected to maintain approach altitude. As in a front course approach, the localizer is captured automatically. When the aircraft approaches the back localizer, automatic capture will occur. The course deviation bar as well as the localizer deviation display have the proper sensing (follow the needle). After BC is selected, GS may be selected if there is an operation glide slope on the back course. After localizer tracking has started, the descent phase of the approach should be initiated. Select the VS mode and adjust the commanded rate of descent using air-data command display by rotating the PITCH wheel. For a missed approach, go-around operation is as previously described. VOR approach

To fly a typical VOR approach, track to the station in the VAPP mode with the NAV receiver tuned to a VOR frequency. After entering the cone of silence, set the course pointer to the outbound track. After station passage, the system will track the new outbound course. If the VOR is approached from a heading that requires maneuvering to the outbound leg, select HDG mode and use the heading selector at the FMP. Adjust the heading bug 135 degrees or less in the direction of the 180 degrees turn. Select VAPP. Set the course to the inbound track. After completing 45 degrees of the turn, adjust the heading bug to the desired heading. The aircraft will automatically capture and track the inbound radial with automatic crosswind compensation. For the descent, use the IAS or VS mode with the air data command display. Select MDA at the FMP and ASEL mode for automatic altitude capture. NOTE: After VOR radial capture, the HDG mode cannot be re-engaged unless SBY

is selected first. Electrical power transients

If a generator fails or a propeller is feathered, the electrical power transient will have the following effects on the AFCS:

• The AP will revert to single channel operation.

• The onside FD will revert to the SBY mode.


Page 20

Documents

· The AP can be engaged by the AP ENGAGE pushbutton at the FMP. When the AP is engaged with no FD modes selected, the AP will command heading hold and pitch hold. When the AP is