Garmin GFC 600 User Manual
GFC 600 Pilot’s Guide
™
Copyright © 2017 Garmin Ltd. or its subsidiaries. All rights reserved.
Garmin International, Inc., 1200 East 151st Street, Olathe, Kansas 66062, U.S.A.
Garmin AT, Inc.,2345 Turner Road SE, Salem, OR 97302, U.S.A.
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SO40 9LR U.K.
Garmin Corporation, No. 68, Zhangshu 2nd Road, Xizhi District, New Taipei City, Taiwan
Web Site Address: www.garmin.com
Contact Garmin Product Support at: www.flygarmin.com
For warranty information refer to:
https://fly.garmin.com/fly-garmin/support/warranty-information/
Except as expressly provided herein, no part of this manual may be reproduced, copied,
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further that any unauthorized commercial distribution of this manual or any revision hereto is
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used without the express permission of Garmin.
July, 2017 190-01488-00 Rev.B Printed in the U.S.A.
Warnings, Cautions & Notes
WARNING: Perform a thorough preflight control check to verify that there
is no excessive friction, binding, or other anomalies that prevent smooth
movement throughout the intended range of motion in pitch, roll, and yaw
axis. Any discrepancies must be resolved prior to continued operation.
WARNING: For safety reasons, system operational procedures must be learned
on the ground.
WARNING: The Garmin system, as installed in this aircraft, has a very high
degree of functional integrity. However, the pilot must recognize that providing monitoring and/or self-test capability for all conceivable system failures
is not practical.
WARNING: To reduce the risk of unsafe operation, carefully review and
understand all aspects of the system, Pilot’s Guide documentation, the Pilot’s
Operating Handbook (POH), and the Aircraft Flight Manual Supplement
(AFMS). Thoroughly practice basic operation prior to actual use. During flight
operations, carefully compare the Flight Director commands and autopilot
response to all available navigation indications, attitude displays, and air data
information. For safety purposes, always resolve any discrepancies before
continued operation.
CAUTION: The system does not contain any user-serviceable parts. Repairs
should only be made by an authorized Garmin service center. Unauthorized
repairs or modifications could void both the warranty and the pilot’s authority
to operate this device under FAA/FCC regulations.
NOTE: All visual depictions contained within this document, including screen
images of the panel and displays, are subject to change and may not reflect
the most current system and aviation databases. Depictions of equipment
may differ slightly from the actual equipment.
NOTE: This device complies with part 15 of the FCC Rules. Operation is
subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received,
including interference that may cause undesired operation.
Garmin GFC 600 Pilot’s Guide
190-01488-00 Rev. B
Part Number Change Summary
190-01488-00 Initial release
Rev Date Description
A June, 2017 Production Release
B July, 2017 Removed software version number
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Garmin GFC 600 Pilot’s Guide
190-01488-00 Rev. B
Table of Contents
Section 1 System Overview .................................................................................................. 1
1.1 Basic Functions .................................................................................................................. 1
1.2 AFCS Equipment ................................................................................................................ 2
GMC 605 Mode Controller ................................................................................................... 2
GSA 87 Servo ....................................................................................................................... 4
GI 285 Annunciator Panel ..................................................................................................... 4
1.3 Interfacing Equipment ..................................................................................................... 5
G500/G600 Integrated Glass Panel System .......................................................................... 5
Aspen EFD1000 ................................................................................................................... 6
GPS Navigators .................................................................................................................... 6
VHF Nav Radios .................................................................................................................. 7
Horizontal Situation Indicators (HSI) ...................................................................................... 7
Directional Gyros (DG) .......................................................................................................... 7
Audio Panel ......................................................................................................................... 8
GTX 335/345(R) with GPS Option ......................................................................................... 8
1.4 AFCS Controls ..................................................................................................................... 9
GMC 605 ............................................................................................................................. 9
External Controls ................................................................................................................ 10
1.5 System Indications .......................................................................................................... 11
GMC 605 ........................................................................................................................... 11
GI 285 Indications .............................................................................................................. 12
Garmin PFD AFCS Indications ............................................................................................. 13
Section 2 Automatic Flight Control System ..............................................................15
2.1 AFCS Operation ................................................................................................................15
AFCS Pre-Flight .................................................................................................................. 15
Engaging the Autopilot ....................................................................................................... 16
Flight Director Modes ......................................................................................................... 16
Disengaging the Autopilot .................................................................................................. 17
2.2 Basic Autopilot Features ................................................................................................17
Flight Director .................................................................................................................... 17
Control Wheel Steering ....................................................................................................... 19
Yaw Damper ...................................................................................................................... 20
Manual Trim ....................................................................................................................... 21
Manual Electric Trim ........................................................................................................... 22
Autotrim ............................................................................................................................ 22
Overspeed Protection ......................................................................................................... 23
Underspeed Protection ....................................................................................................... 24
2.3 Vertical Modes .................................................................................................................. 27
Vertical Mode Controls and Annunciations .......................................................................... 27
Pitch Hold Mode (PIT)......................................................................................................... 28
Level Mode (LVL) ................................................................................................................ 30
Go Around Mode (GA) .......................................................................................................31
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Altitude Hold Mode (ALT) ................................................................................................... 32
Selected Altitude Capture Mode (ALTS) ............................................................................... 33
Vertical Speed Mode (VS) ................................................................................................... 34
Indicated Airspeed Mode (IAS) ............................................................................................36
Glidepath Mode (GP) ......................................................................................................... 37
Glideslope Mode (GS)......................................................................................................... 39
2.4 Lateral Modes ................................................................................................................... 40
Lateral Mode Controls and Annunciations ........................................................................... 40
Roll Hold Mode (ROL) ......................................................................................................... 42
Heading Select Mode (HDG) ............................................................................................... 43
Navigation Modes (GPS, VOR, LOC) .................................................................................... 45
Approach Modes (GPS, VOR, LOC) ...................................................................................... 48
Flying A DME Arc With A GPS Navigator.............................................................................. 51
Backcourse Mode (BC) ....................................................................................................... 52
2.5 Electronic Stability & Protection (ESP™).................................................................... 53
Roll Engagement ................................................................................................................ 54
Pitch Engagement .............................................................................................................. 56
Airspeed Protection ............................................................................................................ 58
Section 3 Annunciations & Alerts .................................................................................... 59
3.1 Visual Annunciations and Alerts .................................................................................. 59
3.2 Aural Alerts ....................................................................................................................... 62
Voice Alerts ........................................................................................................................ 62
Autopilot Disconnect Alert .................................................................................................. 62
Section 4 Abnormal Operation .........................................................................................63
4.1 Suspected Autopilot Malfunction ............................................................................... 63
4.2 Overpowering Autopilot Servos .................................................................................. 63
Appendices .................................................................................................................................... 64
Appendix A: Feature/Equipment Matrix ........................................................................... 64
Index ...................................................................................................................................Index-2
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Garmin GFC 600 Pilot’s Guide
190-01488-00 Rev. B
System Overview
SECTION 1 SYSTEM OVERVIEW
The Garmin GFC 600 is a high-performance, attitude-based, Automatic Flight
Control System (AFCS) that supports an extensive set of operating modes and safety
features. The system design offers the flexibility to interface with a wide variety
of avionics equipment commonly found in general aviation aircraft. The specific
functions supported by the GFC 600 vary by installation. Refer to Appendix A for more
information.
CAUTION:
This manual covers all functions and modes that the GFC
600 can support, however it is the responsibility of the user to become
familiar with the capabilities and limitations of a specific aircraft (per the
Airplane Flight Manual Supplement) which may not support all the features
described here.
1.1 BASIC FUNCTIONS
The GFC 600 AFCS provides the following main operating functions:
•Flight Director (FD) — The Flight Director function provides pitch and roll
commands needed to guide the aircraft toward the active reference selected by
the pilot. If a compatible Primary Flight Display (PFD) is installed these pitch and
rolls commands are displayed on the PFD as Command Bars. When the Flight
Director is active the pitch and roll commands can be hand-flown by the pilot.
When the Autopilot is engaged the autopilot servos drive the flight controls to
follow the commands issued by the Flight Director.
•Autopilot (AP) — The Autopilot function is provided by servo actuators which
move the flight control surfaces in response to Flight Director steering commands,
aircraft attitude, and airspeed. The optional pitch auto-trim function serves to
relieve any sustained effort required by the pitch servo to keep the aircraft in trim.
•Yaw Damper (YD) — The optional Yaw Damper function provides Dutch Roll
damping, assists in turn coordination, and provides a steady force to help maintain
directional trim. If installed the YD comes on when the autopilot is engaged. It
can be turned on/off independent of the autopilot and may be used during normal
hand-flying maneuvers.
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System Overview
•Manual Electric Trim (MET) — The optional Manual Electric Trim uses the same
servo as the auto-trim function and allows the pilot to command trim via a trim
switch when the autopilot is not engaged. The MET function does not preclude
the use of the aircraft’s basic mechanical trim system.
•Electronic Stability & Protection (ESP) — The ESP function provides a soft
barrier to keep the aircraft within the desired operating envelope when the autopilot
is not engaged. When the GFC 600 senses that the aircraft is near the defined
operating limit in pitch attitude, roll attitude, high airspeed, or low airspeed, the
ESP function will automatically engage one or more servos to nudge it back to the
nominal operating envelope. While ESP utilizes the same sensors, processors, and
actuators as the GFC 600 autopilot it is a separate mutually exclusive function.
ESP can be easily overpowered by the pilot and can be disabled using the AP
DISC / TRIM INT button.
1.2 AFCS EQUIPMENT
The basic GFC 600 system is comprised of the following equipment:
GMC 605 MODE CONTROLLER
The panel-mounted GMC 605 serves as the primary user interface for the GFC 600.
The GMC provides autopilot and Flight Director mode selection buttons and a wheel
for convenient adjustment of the pitch, airspeed, and vertical speed references. A
backlit monochrome LCD displays active and armed modes, reference values, alerts,
and messages.
The GMC 605 contains internal sensors which calculate the aircraft attitude, allowing
the GFC 600 to operate without relying on any external source of attitude. Flight
Director mode logic as well as some autopilot management functions are performed
within the GMC 605 main processor.
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Garmin GFC 600 Pilot’s Guide
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System Overview
The GMC 605 has extensive I/O capabilities that support interfaces to a large variety
of equipment including Primary Flight Displays, Air Data Computers, GPS navigators,
VHF Nav radios, Audio Panels, HSIs, and Directional Gyros (DGs). The GMC requires
airspeed and altitude information, therefore if it does not have an interface to an Air
Data Computer, a small Air Data Module must be attached to the back of the GMC’s
mounting tray to provide basic air data information to the AFCS.
The GMC 605 features a covered USB port on the front face of the unit, allowing a
convenient means of updating software and downloading diagnostics information to
aid in troubleshooting.
CAUTION:
The USB port is not designed to provide power or data to external
consumer devices such as smart phones, cameras, or tablet computers and
should not be used in flight.
GMC 605
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System Overview
GSA 87 SERVO
The GSA 87 servos provide control surface actuation as part of the autopilot, yaw
damper, electric trim, and ESP functions. The GSA 87 is a ‘smart’ servo which performs
most of the autopilot processing functions and offers many inherent safety features.
The brushless motor and electronic torque and speed sensing capabilities provide
smooth, reliable operation. The GSA 87 design incorporates an internal engagement
solenoid and a gear train that allows the motor to be backdriven by the pilot in case
the solenoid fails to disengage. This eliminates the need for a mechanical slip clutch
along with the associated performance limitations and maintenance requirements.
GSA 87
GI 285 ANNUNCIATOR PANEL
The GI 285 Annunciator Panel provides basic AFCS status and mode annunciation
for GFC 600 installations where the GMC 605 cannot be mounted within the pilot’s
primary field of view and there is no PFD capable of providing the annunciations.
GI 285
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Garmin GFC 600 Pilot’s Guide
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System Overview
1.3 INTERFACING EQUIPMENT
The GFC 600 is capable of interfacing with a wide variety of equipment including
the following:
G500/G600 INTEGRATED GLASS PANEL SYSTEM
The GDU 620 Primary Flight Display (part of the G500/G600 Glass Cockpit system)
can provide AFCS mode annunciation and alerts, Flight Director command bar display,
Altitude Preselect (ALTS) capability, Heading (HDG) reference selection, and bank limit
indications for the ESP function. The PFD displays AFCS reference values and bugs for
Vertical Speed (VS) and Indicated Airspeed (IAS) modes. Nav source selection can be
performed on the PFD and the GFC 600 will couple to the selected source for guidance.
The G500/G600 systems include an Air Data Computer which provides airspeed and
baro-corrected altitude to the AFCS. This is particularly beneficial when operating in
Altitude Hold (ALT) mode because the autopilot will automatically synchronize to small
changes resulting from an updated altimeter setting.
GDU 620
Reference the latest G500/G600 Pilot’s Guide for more detail about features related
to AFCS.
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Garmin GFC 600 Pilot’s Guide
System Overview
ASPEN EFD1000
The Aspen EFD1000 can provide Flight Director command bar display, Heading (HDG)
reference selection, and Nav source selection functions. The GFC 600 will couple to
the selected nav source for guidance including when the EFD1000 is operated in GPSS
mode.
Reference the Aspen EFD1000 Pilot’s Guide for operational details about features
related to autopilot interfaces.
GPS NAVIGATORS
The GFC 600 can accept guidance from a variety of panel mount GPS navigators
including those that provide Roll Steering and Glidepath commands and older models
that provide only basic lateral course deviation for guidance. The WAAS-enabled
Garmin GNS and GTN series navigators also provide an interface to the GMC 605 that
supports improved aircraft attitude computation, thereby enhancing AFCS performance
and increasing the availability of basic modes in the event of an air data failure.
The GTN 650 is an example of a compatible GPS Navigator:
GTN 650
Reference the applicable Pilot’s Guide for more information about operating the
GPS navigation equipment installed in an aircraft.
NOTE:
If there is more than one navigation source (GPS and/or VHF Nav)
installed it is the responsibility of the user to understand the nav source
selection mechanism and ensure that the GFC 600 is coupled to the
intended source guidance.
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Garmin GFC 600 Pilot’s Guide
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System Overview
VHF NAV RADIOS
The GFC 600 can accept VOR/Localizer and Glideslope guidance from a variety of
VHF Nav receivers including stand-alone radios and those that are included as part of
a Nav-Com or GPS-Nav-Com integrated navigator.
The GNC 255 is an example of a compatible VHF Nav receiver:
GNC 255
Reference the applicable Pilot’s Guide for more information about operating the VHF
Nav equipment installed in an aircraft.
HORIZONTAL SITUATION INDICATORS (HSI)
The GFC 600 can accept Heading commands and Course inputs from a variety of
HSIs including mechanical instruments such as the Bendix King KI 525A and Century
NSD360A and electronic HSI displays such as the Sandel SN3500/4500.
DIRECTIONAL GYROS (DG)
If GFC 600 is installed in an aircraft without an HSI, the system can accept Heading
commands from a variety of popular DGs that have a compatible interface. These
installations do not provide a Course input to the GFC 600, therefore whenever the
user selects a NAV or APR mode on the GMC 605 the Heading bug must be manually
set to align with the Course pointer on the CDI.
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Garmin GFC 600 Pilot’s Guide
System Overview
AUDIO PANEL
The GFC 600 can interface to a wide variety of audio panels to provide aural alerts
including the AP Disconnect tone and low Airspeed warning. The AFCS aural alerts
cannot be muted or deselected via the audio panel controls. In addition to the audio
panel interface, a Sonalert aural tone generator must be included with most GFC 600
installations to ensure the AP Disconnect aural is heard by the pilot if the audio panel
fails or suffers a loss of power.
The GMA 345 is an example of a compatible audio panel:
GMA 345
GTX 335/345(R) WITH GPS OPTION
The GTX 335/345(R) transponders with GPS Option can provide an interface to the
GMC 605 that supports improved aircraft attitude computation, thereby enhancing
AFCS performance and increasing the availability of basic modes in the event of an air
data failure.
GTX 345
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Garmin GFC 600 Pilot’s Guide
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1.4 AFCS CONTROLS
GMC 605
System Overview
NOTE:
1
2
3
1
AP Key Engages/disengages the autopilot
2
FD Key Activates/deactivates the Flight Director only. Pressing once turns
VNAV support is a future growth function.
4 5
7 8
9 10 11 12 13
GMC 605 AFCS Mode Controller
on the director in the default vertical and lateral modes. Pressing
again deactivates the Flight Director and removes the Command
Bars. If the autopilot is engaged, the key is disabled.
3
YD Key Engages/disengages the yaw damper (if installed).
4
LCD Display Displays AFCS modes, references, and annunciations.
6
14
5
LVL Key Engages the autopilot in Level Mode (or selects Level Mode if
autopilot is already engaged).
6
ALT Key Selects/deselects Altitude Hold Mode
7
HDG Key Selects/deselects Heading Select Mode
8
NAV Key Selects/deselects Navigation Mode. Cancels GS Mode if LOC
Mode is either active or armed. Cancels GP Mode if GPS Mode is
either active or armed.
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Garmin GFC 600 Pilot’s Guide
System Overview
9
APR Key Selects/deselects Approach Mode
10
BC Key Selects/deselects Backcourse Mode
11
VNV Key Selects/deselects Vertical Path Tracking Mode for Vertical
Navigation flight control (growth function)
12
IAS Key Selects/deselects Indicated Airspeed Mode
13
VS Key Selects/deselects Vertical Speed Mode
14
NOSE UP/DN
Wheel
Adjusts the vertical mode reference in Pitch Hold, Vertical Speed,
Indicated Airspeed, and Altitude Hold modes
EXTERNAL CONTROLS
These controls are used for important Flight Director and autopilot functions but are
not found on the GMC 605.
Control
AP DISC/
TRIM INT
button
GA button
(optional)
MET switch
(optional)
CWS switch
(optional)
10
Common
Name
Autopilot
Disconnect
Typical
Location Purpose
Pilot control
yoke/stick
Go Around Power lever
or instrument
panel
Manual
Electric Trim
Control Wheel
Steering
Pilot control
yoke/stick
Pilot control
yoke/stick
Garmin GFC 600 Pilot’s Guide
Disengages the autopilot, yaw
damper, and interrupts pitch trim
operation; or, acknowledges an
autopilot disconnect alert and mutes
the associated tone.
Holding the AP DISC / TRIM INT
button down for five seconds will
also disable Electronic Stability &
Protection.
Selects Go Around mode.
Commands manual electric pitch
trim.
Temporarily disengages the pitch
and roll servos. Upon releasing CWS
the servos re-engage and may be
synchronized to a new reference
(depending on mode).
190-01488-00 Rev. B
System Overview
Control
Dimmer knob
(optional)
Common
Name
Panel Lighting
Dimmer
Typical
Location Purpose
Instrument
Panel
Adjusts the brightness of the GMC
605 LCD backlight, keypad, and
LED annunciators. If dimmer is not
connected the GMC lighting will
be adjusted automatically using its
photocell.
1.5 SYSTEM INDICATIONS
GMC 605
The GMC 605 provides indications to the pilot via a monochrome LCD combined
with three color LEDs that are located adjacent to the AP, FD, and YD keys.
The left side of the LCD displays lateral Flight Director modes, the center portion of
the display provides vertical modes and references, and the right side of the display
serves as a message area for status and alerts. Active modes and references are
depicted in large letters along the upper portion of the display, with armed modes
in a smaller font along the lower portion. The message area can display up to four
messages simultaneously.
Text can be flashed alternating between normal display and inverse video when
needed to get the pilot’s attention.
Active Lateral
Mode
Armed Lateral
Mode
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Active Vertical
Mode
Armed Vertical
Mode
GMC 605 LCD Display
Mode
Reference
Garmin GFC 600 Pilot’s Guide
Status Messages and
Alerts
System Overview
The LEDs adjacent the AP, FD, and YD keys are illuminated in conjunction with
other information on the LCD to provide status and alert information.
The AP, FD, and YD LEDs are illuminated in green to indicate that they are engaged.
Manual autopilot and yaw damper disconnect is indicated with flashing yellow AP
and YD annunciations, and red is used to indicate an abnormal disconnect or failure
condition.
The FD LED flashes yellow to indicate when an active mode is dropped automatically
by the AFCS.
The AP LED is illuminated in yellow when a trim failure has occurred or when a
mistrim condition has developed.
AP (Autopilot) LED
FD (Flight Director) LED
YD (Yaw Damper) LED
GMC 605 LEDs
Refer to section 3.1 for more information about specific GMC 605 messages and
LED annunciations.
GI 285 INDICATIONS
The GI 285 Mode Annunciator is required in installations where the GMC 605 is
located outside of the pilot’s primary field of view and there is no Garmin PFD to
provide mode annunciations and alerts. The left side of the GI 285 displays lateral
Flight Director modes, the center portion of the display provides status information for
the autopilot, yaw damper, and trim system, and the right side displays vertical modes.
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Garmin GFC 600 Pilot’s Guide
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System Overview
The GI 285 can illuminate indications in multiple colors and also supports flashing
annunciations when needed to get the pilot’s attention. Active modes are depicted in
green and armed modes in white. Yellow is used to indicate when an active mode is
dropped automatically by the AFCS.
The AP and YD annunciations are illuminated in green to indicate that they are
engaged. Manual autopilot and yaw damper disconnect is indicated with flashing
yellow AP and YD annunciations, and red is used to indicate an abnormal disconnect
or failure condition.
The TRIM annunciation is illuminated in yellow when a trim failure has occurred or
when a mistrim condition has developed.
The pilot should reference the GMC 605 message area for more information
regarding failures and mistrim conditions.
GI 285 Annunciator
Refer to section 3.1 for more information about specific AP, YD, and TRIM
annunciations on the GI 285.
GARMIN PFD AFCS INDICATIONS
A Garmin PFD (if installed) can display Flight Director command bars, active and
armed mode annunciations, references, autopilot and yaw damper engagement
status, and AFCS alerts. Bugs are displayed along with digital references for Selected
Heading, Vertical Speed, Selected Altitude, and Indicated Airspeed (when GFC 600 is
in IAS mode).
Refer to the G500/G600 Pilot’s Guide for more detailed information.
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Garmin GFC 600 Pilot’s Guide
System Overview
Active
Armed
Command
Navigation
Lateral Modes
Bars
GPS is
Selected
Source
Auto-
pilot
Status
Yaw
Damper
Status
AFCS Status Annunciations
Vertical Modes
Active
Armed
Selected
Altitude
14
Autopilot info on Garmin GDU 620 PFD
Garmin GFC 600 Pilot’s Guide
190-01488-00 Rev. B
AFCS
SECTION 2 AUTOMATIC FLIGHT CONTROL SYSTEM
NOTE:
Manual (AFM) always supersedes the information in this Pilot’s Guide.
NOTE:
for GFC 600 specific emergency procedures.
The approved Pilot’s Operating Handbook (POH) or Airplane Flight
Refer to the approved Airplane Flight Manual Supplement (AFMS)
2.1 AFCS OPERATION
AFCS PRE-FLIGHT
The pilot is expected to perform a standard pre-flight control check by moving the
flight controls through their full range of motion in pitch, roll, and yaw axis to verify
smooth and unrestricted operation. Any discrepancies must be resolved before flight.
Upon power-up the GFC 600 will automatically perform a Pre Flight Test (PFT) to
check internal GMC 605 functions, interfaces, and servo status. While the test is in
progress the GMC displays the message PFT. The GMC’s three LEDs are illuminated
in yellow for 1 second and then in red for 1 second. The GI 285 (if installed) will
illuminate all lateral mode annunciations in yellow for 1 second, followed by the AP
YD/TRIM annunciations in yellow for 1 second, then the vertical modes in yellow for
1 second, and finally the AP/YD/TRIM annunciations in red for 1 second. Any failed
LED annunciators on the GMC 605 or GI 285 should be noted and addressed by the
operator.
When PFT is complete the AP Disconnect aural is played through the audio panel. If
everything passed the PFT message is removed from the GMC display. If there are any
failures detected the GMC displays PFT FAIL and illuminates the AP LED in red. The AP
annunciation on the GI 285 will also be illuminated red.
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Garmin GFC 600 Pilot’s Guide
AFCS
ENGAGING THE AUTOPILOT
The autopilot is engaged by pressing the AP key on the GMC 605. If the Flight
Director is already on the autopilot will begin following the active Flight Director
commands. If the Flight Director is not on when the AP key is pressed, the Flight
Director will come on with autopilot engagement in the default PIT and ROL modes.
Another way to engage the autopilot is by selecting the LVL key. This will engage
the autopilot in Level mode.
The aircraft must be within the GFC 600 engagement limits (+/-50 degrees pitch
and +/- 75 degrees roll attitude) in order to engage the autopilot.
FLIGHT DIRECTOR MODES
Flight Director modes are normally selected independently for the pitch and roll axes
using the keys on the GMC 605 bezel. Unless otherwise specified, all mode keys are
alternate action (i.e., press on, press off). In the absence of specific mode selection,
the Flight Director reverts to the default pitch and/or roll modes.
Active modes are annunciated on the GMC 605’s screen in large text. Armed modes
are annunciated in smaller text below the active modes and are queued to take effect
as soon as capture criteria is met. Automatic transition from armed to active mode is
indicated by the armed mode annunciation moving up to the active mode field and
flashing for 10 seconds.
If the information required to compute an active Flight Director mode (such as air data
or navigation data) becomes invalid or unavailable, the Flight Director automatically
reverts to the default mode for that axis. The affected mode annunciation on the GMC
605 flashes in conjunction with the FD LED in yellow. The affected GI 285 annunciation
also flashes in yellow. When such a loss occurs, the system automatically begins to
roll the wings level (enters Roll Hold mode) or maintain the pitch angle (enters Pitch
Hold mode), depending on the affected axis. The flashing annunciation stops when
the affected mode key is pressed or another mode for the axis is selected. If after 10
seconds no action is taken, the flashing annunciation stops.
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