GFC™ 600H

Pilot’s Guide for Bell 505

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June, 2021 190-02775-00 Rev.A 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 control
movement throughout the intended range of motion in pitch, roll, and yaw
axis. Any discrepancies must be resolved prior to operation. In addition, the
friction set from the manual cyclic friction lock must be fully removed prior
to flight.

WARNING: For safety reasons, system operational procedures must be learned

on the ground.

WARNING: The Garmin system, as installed in this rotorcraft, 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 under-
stand all aspects of the system, Pilot’s Guide documentation, the Rotorcraft
Flight Manual, and the Flight Manual Supplement. Thoroughly practice basic
operation prior to actual use.

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 harm-
ful interference, and (2) this device must accept any interference received,
including interference that may cause undesired operation.

Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
SOFTWARE LICENSE AGREEMENT

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190-02775-00 Rev. A Garmin GFC 600H Pilot’s Guide for Bell 505
 Part Number Change Summary
190-02775-00 Initial release

Rev Date Description

A June, 2021 Production Release

Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Table of Contents

Section 1 System Overview................................................................................................... 1

1.1 Basic Functions................................................................................................................... 1
1.2 HFCS Equipment................................................................................................................. 2
GMC 605H Mode Controller ................................................................................................. 3
GFS 83 Servo........................................................................................................................ 3
Attitude and Air Data Sensors................................................................................................ 4
1.3 HFCS Controls...................................................................................................................... 6
GMC 605H (3-Axis)............................................................................................................... 6
External Controls................................................................................................................... 7
1.4 System Indications............................................................................................................. 9
GMC 605H........................................................................................................................... 9
Garmin PFD HFCS Indications.............................................................................................. 12

Section 2 Helicopter Flight Control System............................................................... 13

2.1 HFCS Operation................................................................................................................. 13
HFCS Pre-Flight................................................................................................................... 13
Engaging the Helicopter Flight Control System..................................................................... 14
Disengaging the Helicopter Flight Control System................................................................ 14
Upper Modes...................................................................................................................... 15
HFCS Operation Limitations................................................................................................. 16
2.2 Basic Helicopter Flight Control System Features...................................................... 16
Attitude Hold Mode (ATT).................................................................................................... 16
2.3 Vertical Coupled Modes................................................................................................... 19
Vertical Coupled Mode Controls and Annunciations............................................................. 19
Altitude Hold Mode (ALT).................................................................................................... 20
Selected Altitude Capture Mode (ALTS)................................................................................ 21
Vertical Speed Mode (VS).................................................................................................... 22
Indicated Airspeed Mode (IAS)............................................................................................. 23
Glidepath Mode (GP).......................................................................................................... 23
Glideslope Mode (GS)......................................................................................................... 25
2.4 Lateral Coupled Modes.................................................................................................... 26
Lateral Coupled Mode Controls and Annunciations.............................................................. 26
Heading Select Mode (HDG)................................................................................................ 27
Navigation Modes (GPS, VOR, LOC)..................................................................................... 28
Approach Modes (GPS, VAPP, LOC)...................................................................................... 30
Flying An Arc With A GPS Navigator..................................................................................... 33
2.5 Helicopter Electronic Stability & Protection (H-ESP™)............................................ 33
Limit Cueing....................................................................................................................... 34
Overspeed Protection.......................................................................................................... 36
Low speed Protection.......................................................................................................... 37

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Table of Contents

Section 3 Annunciations & Alerts..................................................................................... 39

3.1 Visual Annunciations and Alerts................................................................................... 39
3-Color LED........................................................................................................................ 39
GMC 605H CAS Messages.................................................................................................. 40
GMC 605H Annunciations................................................................................................... 42
3.2 Aural Alerts........................................................................................................................ 43
Voice Alerts......................................................................................................................... 43
Flight Control System Disconnect Alert................................................................................. 44

Section 4 Abnormal Operation.......................................................................................... 45

4.1 Suspected Flight Control System Malfunction.......................................................... 45

Section 5 Terms & Conventions......................................................................................... 47

5.1 Equipment Terminology.................................................................................................. 47
5.2 System Operation Terminology.................................................................................... 47
5.3 Helicopter and System Controls................................................................................... 49
5.4 Mode Annunciations........................................................................................................ 50

Section 6 Index.....................................................................................................................Index-1
Index....................................................................................................................................Index-2

ii Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 System Overview

SECTION 1 SYSTEM OVERVIEW

The Garmin GFC 600H is an attitude-based, Helicopter Flight Control System (HFCS)
that supports an extensive set of operating modes and safety features.

CAUTION: This manual covers all functions and modes that the GFC 600H
can support; however, it is the responsibility of the user to become familiar
with the capabilities and limitations (per the Bell 505 Rotorcraft Flight
Manual Supplement).

1.1 BASIC FUNCTIONS

The GFC 600H HFCS provides the following main operating functions:
• Attitude Hold (ATT) — Attitude Hold Mode (ATT) is the lowest functional
mode of the GFC 600H system. When in ATT, the system moves the primary flight
controls to maintain a pitch and roll attitude set by the pilot. ATT can be used
throughout the entire flight envelope.
• Groundspeed Hold (GSPD) — Groundspeed Hold Mode (GSPD) is automatically
engaged when either airspeed decreases below 30 kts or groundspeed decreases
below 15 kts. While in Groundspeed Hold Mode, the FCS maintains a set
groundspeed. Groundspeed Hold Mode automatically deactivates when airspeed
exceeds 35 kts and groundspeed exceeds 20 kts.
• Level Mode (LVL) — Level Mode (LVL) controls the rotorcraft to a pitch attitude
intended to maintain steady flight under most conditions and a lateral reference
of zero bank angle. Level Mode may be engaged from any airspeed or attitude
within the GFC 600H engagement limits.
• Yaw Control (Optional) — The GFC 600H system may be optionally equipped
with a yaw axis servo. The Bell 505 uses a high torque variant of the GFS 83 servo
in order to operate the un-boosted yaw controls in this aircraft. The functionality
provided by the yaw servo is dependent upon airspeed. At low airspeeds, yaw
assists this pilot in maintaining aircraft heading. At higher airspeeds, the yaw axis
maintains coordinated flight. A yaw trim switch is mounted on the collective to
allow for lateral acceleration adjustments in cruise flight.

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System Overview

• Upper Mode Engagement — The GFC 600H system provides a means to

couple the FCS to pitch and or roll Upper Modes. Upper Modes may be selected
using the GMC 605H mode keys when above 45 KIAS. Coupled modes will
automatically disengage if the airspeed drops below 35 KIAS. Upper Mode keys
include HDG, NAV, APR, IAS, VS, and ALT.

1.2 HFCS EQUIPMENT

The basic GFC 600H system is comprised of the following equipment:

GFC 600H System

2 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 System Overview

GMC 605H MODE CONTROLLER

The panel-mounted GMC 605H serves as the primary user interface for the GFC 600H.
The GMC provides mode selection buttons and a wheel for convenient adjustment of
the Upper Mode vertical references. A backlit monochrome NVIS (night vision) friendly
LCD displays active and armed modes, reference values, alerts, and messages.
The GMC 605H has extensive I/O capabilities that support interfaces to equipment
including Primary Flight Display, Air Data Computers, FMS, VHF Nav radios, and Audio
Panel. The GMC includes internal attitude and rate sensors used to monitor the
external AHRS performance. The GMC utilizes sensor data from an external air data
computer, magnetometer and GPS receiver to provide required inputs to the internal
attitude and rate sensors.

GMC 605H

GFS 83 SERVO
The GFS 83 is a ‘smart’ servo which performs many FCS processing functions. The
GFS 83 servo actuates the flight controls of the rotorcraft and is installed in parallel
with the primary flight controls, resulting in cyclic and anti-torque pedal movement
directly proportional to servo movement. The servos are installed in pitch, roll and
optionally yaw.
The GFS 83 provides fly through capabilities, meaning that the pilot can override
the system at any time flying through any control forces which may be present. Upon
releasing the controls the system will return to its commanded references. There are
multiple variants of the GFS 83 which offer different functions.

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System Overview

The GFS 83 contains a brushless motor and a geared drive train to provide smooth
and reliable operation. The pitch and roll servos provide a fail passive damping feature
which reduces aircraft attitude deviation in the event of servo disconnect while the
pilot’s hands are not on the controls. The yaw servo is a high-torque version of the
GFS 83 and does not provide a fail passive damping feature. The GFS 83 is installed in
the pitch, roll, and yaw axes. In the event of a mechanical jam in the servo, the pilot
must apply force to the affected rotorcraft flight control to break the shear device at
the output shaft of the servo, removing the servo from the control system and allowing
free movement of the flight control.

GFS 83 (Direct Drive)

ATTITUDE AND AIR DATA SENSORS

The GFC 600H system uses a minimum of two attitude sources and one air data
source. The GMC 605H provides one attitude solution which is used to monitor the
primary attitude solution provided by a GSU 75H ADAHRS sensor.
The GSU 75H is a remotely mounted ADAHRS which combines attitude and
rate sensors with an air data computer. The AHRS sensor includes tilt sensors,
accelerometers, and rate sensors which provides attitude, heading, and rate data to
both the G1000 and the GFC 600H system. The GSU 75H requires interfaces to the
GMU 44 magnetometer, and a GIA 63/64 GPS/SBAS receiver.
The GMU 44 magnetometer senses magnetic fields and sends the data to the AHRS
to determine the magnetic heading. The GMU 44 magnetometer is interfaced to both
the primary attitude sensor and to the GMC 605H.

4 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 System Overview

The Air Data Computer functionality of the GSU 75H connects to the existing pitot-
static system and a GTP 59 OAT probe. The GSU 75H provides pressure altitude,
airspeed, vertical speed and OAT data to the G1000 and the GFC 600H system.
The GTP is a remotely mounted temperature probe that interfaces to the Air Data
Computer for determination of OAT and true airspeed.

GSU 75H

GPS
A Garmin GPS is required as an aiding source for the GMC 605H and GSU 75H
ADAHRS and for GPS based modes including Groundspeed Hold and GPS navigation.

COLLECTIVE POSITION SENSOR

The GFC 600H collective position sensor provides collective position to the GFC
600H to improve FCS performance.

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System Overview

1.3 HFCS CONTROLS

GMC 605H (3-AXIS)

Pitch Reference
1 Roll Mode 2 Servos CAS 3
Pitch Mode Engaged Message

Lateral Mode Pitch Mode

Keys 4 5 6 Keys 7 8 9 10

GMC 605H (3-AXIS) HFCS Mode Controller

1 FCS Key Engages/disengages the Flight Control System

2 LCD Display Displays HFCS modes, references, and annunciations.
3 LVL Key Engages the Flight Control System in Level Mode (or selects Level
Mode if Flight Control System is already engaged).
4 HDG Key Selects/deselects Heading Select Mode
5 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.
6 APR Key Selects/deselects Approach Mode
7 IAS Key Selects/deselects Indicated Airspeed Mode
8 VS Key Selects/deselects Vertical Speed Mode
9 ALT Key Selects/deselects Altitude Hold Mode
10 NOSE UP/DN Adjusts the reference in Vertical Speed, Indicated Airspeed, and
Wheel Altitude Hold modes

6 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 System Overview

EXTERNAL CONTROLS
These controls provide FCS control functions but are not found on the GMC 605H.

Force Trim
Release

Cyclic Switches Collective Switches

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System Overview

Typical
Common
Control Location/ Purpose
Name
Color
Servos Disengaged: Momentary press engages
the HFCS pitch and roll axes.
Any Engaged Mode: Press and hold will reduce
the control forces for the duration of time that
the switch is depressed. After 1 second the
system will annunciate ‘FTR’ as indication that
an extended press is active.
FTR/FCS Force Trim
Cyclic (Black) ATT Mode: Press and hold reduces control
Engage Release
forces and continuously synchronizes the pitch
and roll attitude reference. Upon release
synchronizes the pitch and roll attitude
reference to current values.
CPLD Upper Modes: Upon release synchronizes
the pitch reference (VS, ALT, IAS) to the current
value as applicable.
Momentary Press: Disengages all coupled
Upper Modes. Servos remain engaged in ATT
Flight Mode.
Control Double momentary press OR press and hold for
FCS DISC Cyclic (Red)
System 1 second: Disengages the pitch, roll, and yaw
Disconnect servos.
Press and hold for 6 seconds: Toggles limit cue
ON/OFF.
Single Press: Increments the HFCS references.
Press and Hold: Slews the HFCS references.
ATT Mode: The trim switch changes the
Cyclic
TRIM Cyclic (Black) reference pitch (+/-) and roll (+/-) attitude.
Beep Trim
CPLD Upper Modes: The trim switch changes
the reference altitude, vertical speed, or
indicated airspeed, as applicable.
Engages the pitch, roll, and optional yaw axis in
LVL Level Mode Cyclic (Blue)
LVL Mode.

8 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 System Overview

Typical
Common
Control Location/ Purpose
Name
Color
Collective
YAW Yaw On/Off Engages/disengages the yaw control.
(Black)
Yaw Beep Collective In cruise, this switch allows the aircraft to be
YAW TRIM
Trim (Black) trimmed out of ball center.

External Controls Summary

1.4 SYSTEM INDICATIONS

GMC 605H
The GMC 605H provides indications to the pilot via a monochrome LCD combined
with one color LED located adjacent to the FCS key.
The left side of the LCD displays lateral Upper 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 below the active modes. The message area can display up to four messages
simultaneously.
Text can be flashed alternating between normal display and inverse video for
conditions which require the pilot’s attention.

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System Overview

Servo
Status
Active Lateral Active Vertical Mode Status Messages and
Mode Mode Reference Alerts

Armed Lateral Armed Vertical

Mode Modes
GMC 605H LCD Display

The LED adjacent to the FCS key is illuminated in conjunction with other information
on the LCD to provide status and alert information.
The FCS LED illuminates in green to indicate engagement. Manual FCS disconnect
or abnormal dropping of an Upper Mode is indicated with a flashing yellow FCS
annunciation, and red is used to indicate an abnormal disconnect or failure condition.

FCS LED

GMC 605H LED

Refer to section 3.1 for more information about specific GMC 605H messages and
LED annunciations.

SERVO STATUS
The servo status field (R=Roll, Y=Yaw, P=Pitch) indicates when the servos are
engaged. This field also provides an indication when the servos are out of detent.

10 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 System Overview

The default when turning the system on in ATT mode is pitch, roll, and (optionally)
yaw servo engagement. The yaw servo can be disengaged or re-engaged via the
collective mounted Yaw ON/OFF switch.
The Out of Detent (inverse video) annunciation indicates to the crew that an external
force (crew input) in excess of the breakout force is being applied to the servo and
the FCS is no longer controlling the aircraft in that axis. The P, R, or Y inverse video
annunciation indicates the servo is out of detent. If a servo is held out of detent for
an extended period of time a system message will also indicate the out of detent
condition.

CAUTION: When a servo indicates that it is Out of Detent the FCS is no

longer maintaining the reference in that axis and the pilot must be in
control.

Roll Servo (Out of Detent)

Yaw Servo (Engaged)
Pitch Servo (Engaged)

GMC 605H Servo Status

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System Overview

GARMIN PFD HFCS INDICATIONS

The following CAS or alert messages may be present on the PFD:

NOTE: A red FCS annunciation on the PFD indicates a system failure.

Condition Annunciation
FCS Failed - The FCS is inoperative FCS - FAIL
System is unable to provide yaw axis control FCS - YAW FAIL
PFT is in progress FCS - PFT
PFT has failed FCS - PFT FAIL
Limit Cue is off FCS - LMTQ OFF
Overspeed Protection active or Vne Limit Cue active FCS - MAXSPD
Low speed protection is active FCS - LOWSPD
A failed data path may indicate that the HFCS system has
been turned off or there is a failed communication path Failed Data Path
between the GFC 600H and the GIA 63 or GIA 64.

PFD Visual Alerts and Messages

Refer to the applicable Garmin G1000H or G1000H NXi Pilot’s Guide for detailed
information.

12 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

SECTION 2 HELICOPTER FLIGHT CONTROL

SYSTEM
NOTE: The approved Rotorcraft Flight Manual always supersedes the
information in this Pilot’s Guide.

WARNING: Refer to the approved Rotorcraft Flight Manual Supplement for

GFC 600H specific emergency procedures.

2.1 HFCS OPERATION

HFCS PRE-FLIGHT
The pilot is expected to perform all pre-flight aircraft control checks required by the
Rotorcraft Flight Manual. Refer to the Bell 505 RFM and associated Flight Manual
Supplements for additional details regarding required checks. Any discrepancies must
be resolved before flight.
Upon power-up the GFC 600H will automatically perform a Pre-Flight Test (PFT) to
check internal GMC 605H functions, interfaces, and servo status. While the test is in
progress the GMC displays the message PFT. The GMC’s status LED is illuminated in
yellow for 1 second and then in red for 1 second. The servos will engage and move
each control over a small range of motion. Any failed LED annunciators on the GMC
605H should be noted and addressed by the operator. The Pre-Flight Test will not
complete until the ‘Continue’ button is pressed. HFCS functions are not available until
after the PFT has been successfully completed.
When PFT is complete, the AUTOPILOT TEST OK 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, the AUTOPILOT TEST FAILED
aural is played, and the FCS LED illuminates in red.
If PFT does not pass or complete, refer to the RFMS for further action.

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HFCS

GMC 605H Pre-Flight Test

ENGAGING THE HELICOPTER FLIGHT CONTROL SYSTEM

The Helicopter Flight Control System is engaged by pressing the FCS key on the GMC
605H or the FTR (cyclic mounted switch). The pitch, roll, and yaw axes (if installed)
will engage. On the ground or at low speeds, the system will engage in GSPD or HOV
Mode.
Another way to engage the Helicopter Flight Control System is by selecting the
LVL key or switch. This will engage the pitch, roll and yaw servos with the attitude
references set to a level flight attitude which will not result in any further deceleration
for most weight & balance conditions.
The rotorcraft must be within the GFC 600H engagement limits in order to engage
the Helicopter Flight Control System. Refer to the Bell 505 RFMS for engagement
limits.

DISENGAGING THE HELICOPTER FLIGHT CONTROL SYSTEM

The Helicopter Flight Control System is manually disengaged by pressing the FCS
key on the GMC 605H or by a double momentary press or press and hold of the FCS
DISC switch on the cyclic. Manual disengagement is indicated by an aural alert and
the FCS LED on the GMC 605H flashing yellow for five seconds. The aural alert and
flashing annunciations can be canceled by an additional press of the FCS DISC switch.
Automatic disengagement is indicated by an aural alert and the FCS LED on the
GMC 605H flashing red. The aural alert and flashing annunciations continue until
acknowledged by pressing the FCS key, the FTR / FCS ENG, or the FCS DISC switch on
the cyclic. Automatic disengagement may occur due to a failure within the GFC 600H
system, loss of all GPS and air data inputs, or exceeding the engagement attitude
limits.
14 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

UPPER MODES
Upper Modes (ALT, VS, IAS, APR, HDG, and NAV) are normally selected independently
for the pitch and roll axes using the keys on the GMC 605H bezel. Unless otherwise
specified, all mode keys are alternate action (i.e., press on, press off). In the absence
of specific mode selection, the Upper Mode reverts to the default vertical and/or lateral
modes.
Active modes are annunciated on the GMC 605H’s screen in large text. Armed
modes are annunciated in smaller text below the active modes and will automatically
become the active mode as soon as capture criteria are 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. An aural is also played whenever an
automatic mode change occurs.
If the information required to compute an active Upper Mode (such as navigation
data) becomes invalid or unavailable, the Upper Mode automatically reverts to ATT for
that axis. The affected mode annunciation on the GMC 605H flashes. 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.
An aural is also played whenever a mode automatically reverts.
The Upper Mode is automatically disabled if the information required to compute
the modes becomes invalid or unavailable.
The GFC 600H system supports coupled flight in the pitch and/or roll axes. When
coupling a single axis, the remaining axis operates in ATT. This state is indicated on
the GMC by showing ‘ATT’ in the corresponding mode field. The cyclic beep trim
switch will provide control of the function currently in the mode field. When an axis
is coupled to ALT/IAS/VS, the up/down cyclic beep trim switch will directly control the
mode reference. When ATT is the active mode, the cyclic beep trim provides direct
control of the reference attitude. Some system operations will require an Upper Mode
to be present. As an example, an approach cannot be armed under ATT. Selection
of the APR key with ATT present in the pitch or roll field will automatically select the
default Upper Mode (HDG / IAS) and arm the navigation mode or force capture to the
appropriate navigation guidance if all capture criteria are met.

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HFCS

HFCS OPERATION LIMITATIONS

The maximum commanded pitch/roll attitudes and minimum airspeed values are
established during HFCS certification. Maximum commanded pitch and roll rates are
also limited. Reference the Bell 505 RFMS for HFCS limits.

2.2 BASIC HELICOPTER FLIGHT CONTROL SYSTEM

FEATURES

ATTITUDE HOLD MODE (ATT)

Attitude Hold Mode (ATT) is the lowest available flight control mode for the GFC
600H system. This mode of operation is available throughout the entire airspeed
envelope of the aircraft, but operation is altered based on phase of flight.
While in ATT, the HFCS provides attitude retention and rate stabilization. The servos
installed in parallel with the primary flight controls provide an artificial force trim, or
detent, required to maintain the set pitch and roll references. If the pilot overrides
the controls and moves out of the detent, the servos will resist the movement away
from the detent with a force that increases proportionally as the rotorcraft’s attitude
deviates from the set pitch and roll references. The pilot may temporarily remove this
force trim, or detent, by pressing and holding the FTR (Force Trim Release) Button on
the cyclic control. When the FTR Button is released, the HFCS will maintain the new
pitch and roll attitude that existed when the button was released and restore the force
trim. The FTR Button may also be momentarily pressed and released while at a new
pitch and roll attitude to maintain the new attitude references.
With the optionally installed yaw axis engaged, during cruise flight the yaw servo
will provide yaw damping as well as ball centering for coordinated flight. While at low
speeds or in GSPD, the yaw axis will provide heading hold. The heading hold reference
for yaw is adjusted via the FTR Button the same way it is used to adjust the pitch and
roll attitude references. The primary objective of the yaw axis is to provide coordinated
flight. The detent for the yaw axis is set accordingly. Refer to the Bell 505 RFMS for
yaw axis cruise to hover transition speeds.

16 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

GROUNDSPEED HOLD MODE (GSPD)

Below a configurable ground speed threshold, the system will transition to Ground
Speed (GSPD) Hold Mode. Ground Speed Hold Mode is a sub-mode of Attitude Hold
Mode in which the control of attitude is augmented to maintain lateral and longitudinal
ground speed. Entry into and out of Ground Speed Hold Mode is automatic and
requires a valid GPS solution.
See the Bell 505 RFMS for entry and exit conditions for Groundspeed Hold (GSPD)
Mode.
While in Ground Speed Hold Mode the beep trim increments or slews the reference
lateral and longitudinal ground speed. Ground Speed Hold can be trimmed to maintain
backward or sideward flight.

GMC 605H Annunciating Automatic Transition to Hover (Ground Speed Hold Mode - GSPD)
GSPD mode is available from take-off, or upon reducing the aircraft’s groundspeed
below the hover transition threshold. If the optional yaw axis is installed and engaged,
the yaw axis will maintain a constant heading while in GSPD. The pilot adjusts the
forward/aft and left/right GPS velocity using the cyclic beep trim. During hover or
air taxiing while in GSPD, the HFCS will maintain the set lateral and longitudinal
groundspeed references relative to the rotorcraft’s current ground track. This allows
the pilot to adjust the rotorcraft’s heading and have the HFCS follow the turn while
taxiing over a center line.

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HFCS

HOVER ASSIST (HOV)

The HFCS automatically enters Hover Assist mode when the GSPD reference is set
to 0 kts and the actual groundspeed falls below 1 kt. Hover Assist is a sub-mode of
GSPD. When active, Hover Assist is annunciated by ‘HOV’ on the GMC 605H display
and maintains the rotorcraft’s position over a fixed point on the ground. The hover
position is updated whenever the pilot overrides the cyclic controls out of detent or
when the Force Trim Release (FTR) Button is depressed. Hover Assist is entered and
exited automatically. A valid GPS position is required for Hover Assist to function.

LEVEL MODE (LVL)

Level mode is a sub-mode of ATT and is annunciated as both the vertical and lateral
modes when active. Pressing the LVL key or cyclic mounted switch engages the
Helicopter Flight Control System (if the Helicopter Flight Control System is disengaged)
in level vertical and lateral modes. Any active lateral or vertical Upper Modes are
cancelled. Level mode does not track altitude or heading but instead establishes a
pitch attitude intended to maintain steady flight under most conditions and a lateral
reference of zero bank angle. The aural alert “Leveling” will sound upon engagement.
To exit Level Mode the following actions may be taken:
• Use the cyclic trim switch to change the pitch or roll attitude reference.
• Activate a Upper Mode.
• Disengage the FCS.

NOTE: Level Mode may be helpful if the rotorcraft is inadvertently flown

into IMC conditions.

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 HFCS

GMC 605H Annunciations

The GMC 605H annunciates ‘LVL’ in both the vertical and lateral sections.

GMC 605H Annunciating Level Mode

2.3 VERTICAL COUPLED MODES

VERTICAL COUPLED MODE CONTROLS AND

ANNUNCIATIONS
The table below lists the vertical coupled modes with their corresponding controls and
annunciations. The mode reference is displayed next to the active mode annunciation
on the GMC 605H for Altitude Hold, Vertical Speed, and Indicated Airspeed modes.
The NOSE UP/DN wheel can be used to change the vertical mode reference while
operating in VS, IAS, or ALT modes and the cyclic trim switch can be used to change the
vertical mode reference when coupled. Refer to the Bell 505 RFMS for increments of
change and limits for each of these references.

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HFCS

Vertical Mode Description Control Annunciation

Selected Altitude
Captures the Selected Altitude * ALTS
Capture
Altitude Hold Holds the current altitude ALT nnnn ft
Maintains the current rotorcraft
Vertical Speed vertical speed; may be used to climb/ VS nnnn fpm
descend to the Selected Altitude
Maintains the current rotorcraft
Indicated Airspeed
airspeed; may be used to climb/ IAS nnn kt
(IAS)
descend to the Selected Altitude
Captures and tracks the SBAS
Glidepath GP
GPS glidepath on approach
Captures and tracks the ILS
Glideslope GS
glideslope on approach
* When the GFC 600H is receiving a Selected Altitude value from the PFD, ALTS is armed automatically
when VS or IAS modes are active.

Helicopter Flight Control System Vertical Mode Summary

ALTITUDE HOLD MODE (ALT)

Altitude Hold mode can be activated by pressing the ALT key; the HFCS synchronizes
the current rotorcraft altitude (to the nearest 10 feet) with the Altitude Reference.
Altitude Hold mode is also automatically activated by Selected Altitude Capture
mode when capturing a preselected altitude set on the PFD. In this case, the Selected
Altitude becomes the Altitude Reference. If the barometric correction is changed on
the PFD the HFCS will slowly climb or descend to recover the reference altitude.
When operating in Altitude Hold mode, the displayed altitude reference can
be adjusted by using the cyclic beep trim switch or the NOSE UP/DN wheel. The
reference altitude can only be moved a maximum of 250 ft from the current rotorcraft
altitude; each click changes the reference altitude by 10 ft.

20 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

GMC 605H ANNUNCIATIONS

The GMC 605H annunciates ‘ALT’ for Altitude Hold mode. If a Garmin PFD is
installed, the GMC also shows the reference altitude in the mode reference section.

GMC 605H Annunciating Altitude Hold Mode

SELECTED ALTITUDE CAPTURE MODE (ALTS)

Selected Altitude Capture mode is a transitional mode used in conjunction with other
vertical modes. It is not directly selectable by the GMC 605H panel or other equipment.
Instead, Selected Altitude Capture is automatically armed if a valid altitude is present
in the altitude preselector on the PFD upon activation of the following modes:
• Vertical Speed • Indicated Airspeed

The Altitude Preselect function on a Garmin PFD allows the pilot to adjust the
altitude bug to a target Selected Altitude for the HFCS to capture and subsequently
track in Altitude Hold mode.
The GMC 605H will annunciate ‘ALTS’ as the armed vertical mode while the active
vertical mode is VS or IAS.

GMC 605H Altitude Select Indications (ALTS Armed)

As the rotorcraft nears the Selected Altitude, the HFCS automatically transitions
to Selected Altitude Capture mode with Altitude Hold mode armed. This automatic
transition is indicated by the ‘ALTS’ annunciation flashing for up to 10 seconds and the
appearance of the ‘ALT’ annunciation. The Selected Altitude is shown as the Altitude
Reference.
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HFCS

Upon capturing the Selected Altitude, the HFCS automatically transitions from
Selected Altitude Capture to Altitude Hold mode and holds the reference altitude. As
Altitude Hold mode becomes active, the ‘ALT’ annunciation moves to the active vertical
mode field and flashes for 10 seconds to indicate the automatic transition.

GMC 605H Annunciating Selected Altitude Capture Mode

Changing the Selected Altitude on the PFD while Selected Altitude Capture mode is
active causes the HFCS to revert to ATT in the pitch axis.
If the Altitude Select bug is set to ‘---’ on the PFD, any engagement of IAS or VS
will not result in ALTS being armed until the Altitude Select bug is set to a valid value.
Likewise, capturing the selected altitude and reselecting IAS or VS when the Altitude
Select bug is within +/- 500 feet of the current operating altitude will not rearm ALTS.
Once the aircraft deviates or the bug is moved beyond that limit, ALTS will rearm.

VERTICAL SPEED MODE (VS)

Vertical Speed mode is activated by pressing the VS key. Upon activation the
VS reference synchronizes to the current rotorcraft vertical speed and subsequently
maintains that vertical speed. The Vertical Speed Reference may be changed by using
the cyclic beep trim switch or the NOSE UP/DN wheel.

GMC 605H ANNUNCIATIONS

The GMC 605H annunciates ‘VS’ for Vertical Speed mode. Additionally, the GMC
605H annunciates the Vertical Speed Reference in the mode reference section.

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 HFCS

GMC 605H Annunciating Vertical Speed Mode

INDICATED AIRSPEED MODE (IAS)

Indicated Airspeed mode is activated by pressing the IAS key. Upon activation
the IAS reference synchronizes to the current rotorcraft airspeed and subsequently
maintains that airspeed. The IAS reference can be changed using the beep trim switch
or NOSE UP/DN wheel.

GMC 605H ANNUNCIATIONS

The GMC 605H annunciates ‘IAS’ for Indicated Airspeed mode. Additionally, the
GMC 605H displays the Airspeed Reference value in the mode reference section.

GMC 605H Annunciating Indicated Airspeed Mode

GLIDEPATH MODE (GP)

Glidepath mode is used to track a glidepath generated by the FMS.
Selecting Glidepath Mode:
1) FMS: Ensure a GPS approach with vertical guidance (LPV, LNAV/VNAV,
LNAV+V, LP+V) is loaded and activated into the active flight plan.
2) Ensure that GPS is the selected navigation source on the PFD.
3) GMC 605H: Press the APR key. The HFCS maintains the current mode but
arms Glidepath mode. If the current vertical mode is ATT then IAS mode
will become the active mode with GP armed.

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HFCS

4) Upon reaching the glidepath, the HFCS vertical mode transitions to

Glidepath Mode and begins to capture and track the glidepath.
Once the following conditions have been met, the glidepath can be captured:
• GPS must be the active lateral mode.
• Vertical deviation is valid.
• The CDI is at less than full-scale deviation.
• Automatic sequencing of waypoints has not been suspended (no ‘SUSP’
annunciation on the HSI).
• Must be captured from below the glidepath.

NOTE: Some RNAV (GPS) approaches provide a vertical descent angle

as an aid in flying a stabilized approach. These approaches are NOT
considered Approaches with Vertical Guidance (APV). Approaches that are
annunciated on the HSI as LNAV or LNAV+V are considered Nonprecision
Approaches (NPA) and are flown to an MDA even though vertical glidepath
(GP) information may be provided and the HFCS will capture and track the
vertical guidance.

WARNING: When flying an LNAV approach (with vertical descent angle)

with the Helicopter Flight Control System coupled, the rotorcraft will not
level off at the MDA even if the MDA is set in the altitude preselect.

GMC 605H ANNUNCIATIONS

The GMC 605H annunciates ‘GP’ for Glidepath mode. Since Glidepath mode relies
on GPS positioning, the ‘GPS’ lateral mode is also annunciated.

24 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

GMC 605H Annunciating Glidepath Mode

GLIDESLOPE MODE (GS)

Glideslope mode is available for ILS approaches to capture and track the glideslope.
Selecting Glideslope Mode:
1) GIFD NAVIGATION: Tune and activate the desired localizer frequency.
2) Ensure that LOC is the selected navigation source on the PFD and the
course selector has been properly set to the inbound course.
3) GMC 605H: Press the APR key. This simultaneously arms LOC and GS
(Glideslope) modes. If the current vertical mode is ATT then IAS will
become the active mode with GS armed.
Once the localizer has been captured (LOC is annunciated as the active lateral
mode), the glideslope can also be captured.
Once the following conditions have been met, the glideslope can be captured:
• LOC must be the active lateral mode.
• Vertical deviation is valid.
• The CDI is at less than full-scale deviation.
• Must be captured from below the glideslope.

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HFCS

GMC 605H ANNUNCIATIONS

The GMC 605H annunciates ‘GS’ for Glideslope mode. Since Glideslope mode relies
on LOC lateral guidance, the ‘LOC’ lateral mode is also annunciated.

GMC 605H Annunciating Glideslope Mode

2.4 LATERAL COUPLED MODES

LATERAL COUPLED MODE CONTROLS AND

ANNUNCIATIONS
The table below lists the lateral modes with their corresponding controls and
annunciations. Refer to the Vertical modes section for a detailed description of Level
mode.
Lateral Mode Description Control Annun.
Captures and tracks the Selected
Heading Select HDG
Heading
Navigation, GPS GPS
Navigation, VOR Enroute
VOR
Capture/Track
Captures and tracks the selected
Navigation, LOC navigation source (GPS, VOR, LOC)
Capture/Track LOC
(No Glideslope)

26 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

Lateral Mode Description Control Annun.

Approach, GPS Capture/

Track (Glidepath mode GPS
automatically armed)
Captures and tracks the selected
Approach, VOR Capture/
approach navigation source (GPS, VOR, VAPP
Track
LOC)
Approach, LOC Capture/
Track
LOC
(Glideslope mode
automatically armed)
Helicopter Flight Control System Lateral Coupled Mode Summary
Lateral modes utilize bank angles consistent with standard rate turns up to a
maximum of 25 degrees angle of bank. At high altitudes, the HFCS automatically will
limit bank angles to a lower value. Refer to the Bell 505 RFMS for more information.
GPS navigation may use bank angles up to 30 degrees in some cases.

HEADING SELECT MODE (HDG)

Heading Select mode is activated by pressing the HDG key. Heading Select mode
tracks the Selected Heading on the PFD and can be adjusted using the HDG Knob on
the PFD.
Turns are commanded in the same direction as the initial Selected Heading Bug
movement, even if the Bug is turned more than 180˚ from the present heading (e.g.,
a 270˚ turn to the right). However, Selected Heading changes of more than 340˚ at a
time result in turn reversals.

GMC 605H ANNUNCIATIONS

The GMC 605H displays the HDG annunciation when Heading Select mode is active.

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HFCS

GMC 605H Annunciating Heading Mode

NAVIGATION MODES (GPS, VOR, LOC)

NOTE: LOC Mode is only available as an armed or captured mode when the
aircraft heading is aligned within a 105 degree intercept of the approach
course. If the heading exceeds this limit, LOC will automatically be dropped
as the active or armed mode.

NOTE: The selected navigation receiver must have a valid VOR or LOC
signal or active GPS course to enter or arm Navigation Mode.
Pressing the NAV key selects Navigation mode. Navigation mode acquires and
tracks the navigation source (GPS, VOR, LOC) currently selected for use on the PFD.
When GPS is the selected navigation source the HFCS will follow GPS Roll Steering
commands from the FMS.
Navigation mode can also be used to fly non-precision GPS and LOC approaches
where vertical guidance is not required.
If the Course Deviation Indicator (CDI) shows greater than half scale when the NAV
key is pressed, then the selected NAV mode is armed. If the lateral HFCS mode is ATT
when the NAV key is pressed, HDG will automatically become the active lateral mode.

NOTE: If the CDI shows greater than 1/2 scale deflection while in ATT,
ensure the heading bug is either set to the present heading or the intended
heading to prevent unwanted deviations in the flight path upon HDG
becoming the active mode.

28 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

GMC 605H Annunciating GPS Navigation Mode Armed

If the CDI is less than half scale, Navigation mode will immediately become the
active mode.
If Navigation mode is active and any of the following occur, the HFCS lateral axis
reverts to ATT Hold mode with a level roll reference:
• Different VHF Nav frequency tuned while in VOR or LOC Navigation mode (Note:
Navigation mode may remain engaged if there is still valid deviation after the
frequency changes from VOR to VOR, or from LOC to LOC)
• Navigation source switched (e.g. GPS to VOR/LOC, or VOR to LOC)
• Loss of navigation signal
If NAV is the active mode and the course is changed the FCS will establish an
appropriate track up to 45 degrees to capture the new course. Large course changes
at other than over the VHF station should be in HDG mode with a manually established
intercept angle and the NAV mode re-armed.
If VOR or VAPP is the active mode and the course is changed while in the cone of
confusion over the station the FCS will turn to a heading appropriate to capture the
new course and recapture the guidance upon exiting the cone of confusion.

GMC 605H ANNUNCIATIONS

The GMC 605H annunciates the appropriate lateral mode as GPS, VOR, or LOC
depending on the selected navigation source when the NAV key was pressed.

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HFCS

GMC 605H Annunciating Various NAV Modes

APPROACH MODES (GPS, VAPP, LOC)

NOTE: The selected navigation receiver must have a valid VOR or LOC
signal or active GPS course to enter or arm Approach Mode.
Approach mode is selected by pressing the APR key. Approach mode acquires and
tracks the navigation source (GPS, VOR, or LOC) selected on the PFD. This mode uses
roll steering for GPS approach guidance or the selected navigation receiver deviation
and selected course inputs to fly the approach. Pressing the APR key when the CDI
deflection is greater than half scale will arm the approach mode. If ATT is active when
the APR key is pressed, HDG becomes the active mode.

GMC 605H Annunciating GPS Approach Mode Armed

If the CDI deflection is less than half scale, the approach mode immediately becomes
the active mode when the APR key is pressed.

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 HFCS

GPS APPROACH MODE

When GPS Approach mode is armed, Glidepath mode is also armed.
Selecting GPS Approach Mode:
1) FMS: Ensure a GPS approach is loaded and activated into the active flight
plan. The active waypoint must be part of the flight plan (cannot be a
direct-to a waypoint not in the flight plan).
2) PFD: Ensure that the GPS navigation source is selected and a valid CDI is
displayed on the HSI. If the CDI is more than 1/2 scale ensure the heading
bug is set to intercept the final approach course.
3) GMC 605H: Press the APR key.

VOR (VAPP) APPROACH MODE

VOR Approach mode (VAPP) provides greater sensitivity for signal tracking than VOR
Navigation mode.
Selecting VOR Approach Mode:
1) GIFD NAVIGATION: Ensure a valid VOR frequency is tuned
2) PFD: Ensure that VOR is the selected navigation source, the appropriate
course is set, and a valid CDI is displayed on the HSI. If CDI indication is
more than 1/2 scale ensure the heading bug is set to intercept the selected
course.
3) GMC 605H: Press the APR key.

LOCALIZER (LOC) APPROACH MODE

LOC Approach mode allows the HFCS to fly an ILS approach with a glideslope.
When LOC Approach mode is armed, Glideslope mode is also armed automatically.
LOC captures are inhibited if the difference between rotorcraft heading and localizer
course exceeds 105°.

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HFCS

Selecting LOC Approach Mode:

1) GIFD NAVIGATION: Ensure a valid localizer frequency is tuned.
2) PFD: Ensure that LOC is the selected navigation source, the appropriate
course is set, and a valid CDI is displayed on the HSI.
3) GMC 605H: Press the APR key.
If Approach mode is active and any of the following occur, the HFCS reverts the
lateral axis to ATT with the roll reference set to level:
• Different VHF Nav frequency tuned while in VOR or LOC Approach mode (Note:
Approach mode may remain engaged if there is still valid deviation after the
frequency changes from VOR to VOR, or from LOC to LOC)
• Navigation source switched (e.g. GPS to VOR/LOC, or VOR to LOC)
• Loss of navigation signal

GMC 605H ANNUNCIATIONS

The GMC 605H will annunciate VOR Approach mode as VAPP, LOC Approach mode
as LOC and GS, and GPS Approach mode as GPS and GP. The annunciation displayed
is based on the selected navigation source when the APR key is pressed.

GMC 605H Annunciating Various Approach Modes

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 HFCS

FLYING AN ARC WITH A GPS NAVIGATOR

The HFCS will intercept and track an arc that is part of the active flight plan provided
that GPS Navigation mode is engaged, GPS is the active navigation source on the PFD,
and the arc segment is the active flight plan leg. It is important to note that automatic
navigation of arcs, including DME arcs is based on GPS. If the final approach segment
will be flown as a VOR or Localizer approach the pilot must manually change the
navigation source from GPS to VOR/LOC when the arc segment is completed. The
HFCS will revert the lateral axis ATT mode and the pilot must press the APR key to
capture and track the VOR or Localizer approach.
If the pilot decides to intercept the arc at a location other than the published IAF (i.e.
ATC provides vectors to intercept the arc and subsequently selects Heading mode or
ATT, the HFCS will not automatically intercept or track the arc unless the pilot activates
the arc leg of the flight plan and arms GPS Navigation mode.

2.5 HELICOPTER ELECTRONIC STABILITY &

PROTECTION (H-ESP™)

WARNING: Do not assume H-ESP will provide protection in all circumstances.

There are in-flight situations that can exceed the capabilities of H-ESP
technology.
Helicopter Electronic Stability and Protection (H-ESP) feature is a collection of
functions which monitor rotorcraft operating parameters and provide control inputs
and pilot feedback when necessary to prevent or discourage operating the rotorcraft
in a potentially unsafe manner.
H-ESP consists of the following functions:
• Limit Cueing
- Pitch Attitude Threshold
- Roll Attitude Threshold
- Overspeed Protection
- Low-G Protection

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HFCS

• Overspeed Protection (Coupled to Upper Mode)

• Low Speed Protection (Coupled to Upper Mode)
Limit Cueing provides resistance to pilot inputs which would result in exceeding
attitudes, accelerations, or speeds associated with safe flight.
Overspeed Protection is provided as a limit cueing function when ATT is the engaged
mode on pitch. Additionally overspeed protection provides automated reduction of
airspeed when the HFCS is coupled to an Upper Mode (ALT, VS, GS, or GP). Each
condition provides an aural and visual annunciation to the pilot to alert them to the
condition.
Low Speed Protection prevents inadvertent entry into the low speed flight regime
while in ALT, VS, GS, or GP modes thus reducing the possible risk of loss of control. Low
Speed is annunciated to the pilot with both a visual and aural annunciation.

LIMIT CUEING
Limit Cueing engages automatically when the rotorcraft approaches or exceeds one
or more predetermined airspeed, attitude, or Low-G limitations. The system provides
increasing resistance to control inputs that would exceed the configured limits. This is
perceived by the pilot as resistance to control movement in the undesired direction.
As the rotorcraft deviates further from the normal attitude, airspeed, and/or Low-G
limit the force increases proportionally (up to an established maximum) to encourage
control movement in the direction necessary to return to the normal attitude, airspeed,
and/or G-Loading range.
If the FCS is engaged and the pilot is flying out of detent the limit cue forces will be
felt as an additional force beyond that required to hold the cyclic out of detent. Upon
retreating from limit cue thresholds control forces will return to normal out of detent
levels.
If the FCS is disengaged then the servo in the axis exceeding limits will engage
and resistance will be felt. Upon retreating from limit cue thresholds the servo
will disengage and control forces will return to normal levels associated with servo
disengaged operation.
When limit cueing is active the pilot can press the FCS DISC switch to remove limit
cue forces.

34 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

If the pilot desires to prevent Limit Cueing from engaging the FCS DISC switch can
be pressed and held for 6 seconds to disable the function. When disabled a “LMTQ
OFF” message is displayed on the GMC and a “FCS - LMTQ OFF” PFD advisory is
displayed. Turning off limit cueing does not disable speed protections.
Pressing and holding the FCS DISC switch for 6 seconds or power cycling the FCS
will re-enable Limit Cueing functions.
Attitude, airspeed, and Low-G limits are specified in the Bell 505 RFMS.
The servo torque limit is configured such that when Limit Cueing is active the pilot
can always overpower the servo to control the rotorcraft.
Minimum
Configured
H-ESP Torque
Limit
Configured
Bank Limit

Maximum
Configured
H-ESP Torque
Limit

H-ESP Roll Operating Range When Engaged (SEE RFMS FOR ACTUAL LIMITS)
(Force Increases as Roll Increases & Decreases as Roll Decreases)

Limit Cue is automatically disengaged if the rotorcraft reaches the HFCS roll
engagement attitude limit.

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HFCS

H-ESP Pitch Operating Range When Engaged (SEE RFMS FOR ACTUAL LIMITS)
(Force Increases as Pitch Increases & Decreases as Pitch Decreases)

OVERSPEED PROTECTION
NOTE: Overspeed Protection is not active in Indicated Airspeed Hold (IAS)
mode.

NOTE: While Overspeed Protection is active, the rotorcraft will deviate from
the selected reference.
While Vertical Speed, Altitude Hold, Glideslope (GS), Glidepath (GP), or Selected
Altitude Capture mode is active, airspeed is monitored by the system. Overspeed
protection is provided in situations where the system cannot acquire and maintain the
mode reference for the selected pitch mode without exceeding the maximum HFCS
airspeed. The maximum HFCS airspeed is 10 knots below the current computed Vne
as determined by altitude and temperature.

36 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 HFCS

CAUTION: The GFC 600H system computes the current Vne based on
altitude and/or temperature. The GFC 600H does not adjust Vne based on
aircraft weight, configuration, or operation. It is the pilot’s responsibility to
know the current applicable Vne for the rotorcraft and operate within the
Vne limit regardless of FCS mode of operation.
When the six second airspeed trend exceeds the maximum HFCS airspeed, the system
will command the aircraft to deviate from the active pitch reference and produce a
pitch up command to prevent the rotorcraft from exceeding the current maximum
HFCS airspeed, a visual MAX SPEED annunciator will be displayed, a single aural MAX
SPEED will be played, and the previously active mode will become the armed mode.
Resolving an overspeed condition:
• Reduce the collective.
• Adjust the vertical mode reference NOSE UP using the cyclic trim switch or
GMC 605 NOSE UP/DN wheel.
• Change the engaged mode to ATT or IAS.

GMC 605H Overspeed Indication

When the overspeed condition is resolved the MAXSPEED message is removed and
the armed vertical mode becomes active again.

LOW SPEED PROTECTION

NOTE: While Low Speed Protection is active, the rotorcraft will deviate from
the selected reference.

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HFCS

CAUTION: While Low Speed Protection is active the rotorcraft will deviate
from the selected reference resulting in a possible loss of altitude and/or
terrain separation.
Low Speed Protection is designed to prevent inadvertent deceleration into low speed
flight, which could result in high descent rates or inadvertent loss of control, and is
available when coupled in ALT, VS, GP, or GS.
When the FCS is coupled in ALT, VS, GP, or GS modes and the rotorcraft is decelerating
to within six seconds of reaching a predetermined minimum airspeed (specified in the
AFMS):
• The LOW SPEED aural will sound every 15 seconds.
• A visual low speed annunciation is displayed.
• The active mode will change to IAS with a reference set to the minimum
engagement speed for Upper Modes.
• The previously active mode will become the armed mode.
A LOW SPEED mode condition is resolved when the pitch attitude required to
maintain the previously active mode (ALT, VS, GS, or GP) is less than the pitch attitude
required to hold the IAS reference commanded by LOW SPEED mode.
Resolving a low speed condition:
• Increase the collective sufficiently to allow the previously active mode to be
satisfied at a speed greater than the LOW SPEED commanded IAS value.
• Adjust the trim NOSE DOWN using the TRIM or GMC 605 NOSE UP/DN
wheel (decrease VS or ALT).
• Change the FCS vertical mode to IAS or ATT.
• Disengage the HFCS.

GMC 605H Underspeed Protection

38 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Annunciations & Alerts

SECTION 3 ANNUNCIATIONS & ALERTS

3.1 VISUAL ANNUNCIATIONS AND ALERTS

The GFC 600H provides visual annunciations and alerts to notify the pilot of system
status, failures, degraded operation, and conditions requiring specific pilot action. The
table below summarizes the messages that may appear on the GMC 605H’s display
along with any associated LED illumination, and a brief description. Refer to other parts
of this Pilot’s Guide for more information about the functions and modes associated
with the annunciations and alerts.

3-COLOR LED
Next to the system engagement key is a 3-color (red, yellow, and green) LED which
supports solid and flashing states.
The following image depicts a change in state from coupled to decoupled. The FCS
status light flashes yellow and the modes flash between normal text and inverse video
to depict a change in state. An aural “Decoupled” is played.

GMC 605H Annunciating Decoupling

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Annunciations & Alerts

GMC 605H CAS MESSAGES

GMC 605H Description

Message
YAW FAIL System is unable to provide yaw axis control.
FCS has failed - The FCS is inoperative. The red FCS LED will flash until
FCS FAIL the pilot acknowledges with the FCS Key or FCS DISC Button. Once
FCS FAIL is acknowledged, the LED is illuminated steady red.
Air Data inputs to the GMC 605H have failed. If the FCS was engaged,
ADC FAIL it will disengage automatically. The FCS cannot be engaged while the
air data inputs are failed.
AHRS DGRD The AHRS is not receiving aiding sources (either GPS or air data).
Collective position sensor has failed. Yaw axis performance during
COLL FAIL collective changes will be degraded. ALT, VS, IAS, GS, and GP
performance during collective changes will be degraded.
GPS DATA The FCS is not receiving valid GPS AGL, velocity, ground speed, or track.
TRK MODE GPS track is being used for heading mode.
NO ATT The FCS is not receiving attitude data from the external AHRS.
ON GROUND The FCS state is on ground.
MAXSPEED Overspeed protection or Vne limit cueing is active
LOWSPEED Lowspeed protection is active
The Limit Cue function has failed. The pilot should not expect tactile
LMTQ FAIL feedback for pitch/roll, low-G, and Vne exceedances. Upper Mode
Overspeed and Lowspeed protection remains operational.
Limit Cue is off. The pilot should not expect tactile feedback for
LMTQ OFF pitch/roll, low-G,and Vne exceedances. Upper Mode Overspeed and
Lowspeed protection remains operational.
PFT Preflight test is in progress
Preflight test has failed. The FCS is inoperative. The FCS LED
PFT FAIL
illuminates steady red.

40 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Annunciations & Alerts

GMC 605H Description

Message
MANIFEST Incorrect software manifest versions. Maintenance is required.
P DETENT Cyclic has been Out of Detent (OOD) on pitch axis for > 30 seconds
R DETENT Cyclic has been Out of Detent (OOD) on roll axis for > 30 seconds
Y DETENT Pedals have been Out of Detent (OOD) for > 30 seconds.
The ‘pitch’ beep trim switch has seen an active signal for > 30 seconds.
PIT BEEP
The switch is disabled when this message is displayed.
The ‘roll’ beep switch input has seen an active signal for > 30 seconds.
ROLL BEEP
The switch is disabled when this message is displayed.
The ‘yaw’ beep switch input has seen an active signal for > 30
YAW BEEP
seconds. The switch is disabled when this message is displayed.
LVL SWITCH The LVL switch is active for longer than 15 seconds.
CYC FTR The cyclic FTR switch is active for longer than 60 seconds.
AP SWITCH The FCS DISC switch is active for longer than 15 seconds.
The GMC 605H key selected by the user is disabled because the
DSBLD KEY
associated function is not supported in a particular installation
FCS KEY The FCS key on the GMC 605H is stuck in the active state

HDG KEY The HDG key on the GMC 605H is stuck in the active state
NAV KEY The NAV key on the GMC 605H is stuck in the active state
APR KEY The APR key on the GMC 605H is stuck in the active state
IAS KEY The IAS key on the GMC 605H is stuck in the active state
VS KEY The VS key on the GMC 605H is stuck in the active state
ALT KEY The ALT key on the GMC 605H is stuck in the active state
LVL KEY The LVL key on the GMC 605H is stuck in the active state

CAS Messages

190-02775-00 Rev. A Garmin GFC 600H Pilot’s Guide for Bell 505 41
Annunciations & Alerts

GMC 605H ANNUNCIATIONS

System Description GMC 605H ‘FCS’ LED GMC 605H

‘R’ and ‘P’
FCS Engaged Steady green
illuminated
Yaw Axis Engaged ‘Y’
Normal (Optional) illuminated
Mode Flashing amber for 10 seconds, then
FCS Disconnect
extinguished
Yaw Axis
Disengaged
Abnormal Change in state
Flashing amber for 10 seconds, then
Upper from coupled to
extinguished
Mode decoupled
Abnormal
FCS Disconnect Continuous flashing red
Disconnect
Continuous flashing red until
System FCS Fail FCS FAIL
acknowledged, then steady red
Failure
Yaw Axis Failure YAW FAIL

42 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Annunciations & Alerts

3.2 AURAL ALERTS

The GFC 600H outputs aural annunciations and alerts to provide enhanced
awareness to the pilot of several key HFCS conditions.

VOICE ALERTS
Voice alerts are played through the rotorcraft audio panel and are heard through the
pilot and co-pilot ICS. The alerts cannot be muted. The voice alerts include:
Annunciation Description
Announces a low indicated airspeed condition and is played
“Low Speed” in conjuction with the Underspeed Protection function.
Repeats every 15 seconds while LOW SPEED mode is active.
Announces when the Flight Control System state is changed
“Decoupled”
from coupled to decoupled.
“Leveling” Announces when Level Mode is engaged.
Overspeed Protection active or VNE Limit Cue active. Plays
“Max Speed”
once.
“Yaw Fail” Yaw axis has failed and disconnected.
Automated mode transitions are annunciated with a double
“Double Chime”
chime.
“Autopilot Test Okay” PFT has passed.
“Autopilot Test Failed” PFT has failed.
“Limit Cue Enabled” Limit Cue has been enabled.
“Limit Cue Disabled” Limit Cue has been disabled.

Aural Annunciations

190-02775-00 Rev. A Garmin GFC 600H Pilot’s Guide for Bell 505 43
Annunciations & Alerts

FLIGHT CONTROL SYSTEM DISCONNECT ALERT

Flight Control System disengagement is accompanied by an aural two-tone alert
which is played through the audio panel.
Manual Flight Control System disengagement plays the alert two times. After it is
played once the pilot may elect to press the FCS DISC button again to silence the alert.
Abnormal (automatic) disengagement results in the alert being played continuously
until silenced by the FCS DISC or FTR button.

44 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Abnormal Operation

SECTION 4 ABNORMAL OPERATION

4.1 SUSPECTED FLIGHT CONTROL SYSTEM

MALFUNCTION
Refer to the Bell 505 RFMS for abnormal operations.

190-02775-00 Rev. A Garmin GFC 600H Pilot’s Guide for Bell 505
45
 Blank Page

Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Terms & Conventions

SECTION 5 TERMS & CONVENTIONS

5.1 EQUIPMENT TERMINOLOGY

Term Description
Digital Helicopter Flight Control Mode Controller. This piece of
GMC 605H equipment also houses 1 of 2 attitude solutions used in the flight
control system.
Garmin Force-Trim Servo. This is a “smart” servo that is installed
in parallel with the helicopter primary flight controls. Parallel
GFS 83
means that the servo is attached to the existing controls such than
when these servos move, the pedals and cyclic move with them.
Air Data and Attitude Heading Reference System. The GSU 75H
GSU 75H ADAHRS ADAHRS is the primary attitude and air data source for the GFC
600H system.
Flight Control System or Helicopter Flight Control System. This
FCS or HFCS
terminology is used rather than autopilot.
Equipment Terminology

5.2 SYSTEM OPERATION TERMINOLOGY

Term Description
A state of an Upper Mode that allows the pilot to select a mode
of control, however, the necessary criteria to initiate the mode
Armed
of control have not been satisfied. An armed mode provides an
automatic transition to a future active mode.
A term used to describe an Upper Mode which is currently
Active
providing an HFCS control input to achieve a control objective.
A state of the flight control system where the pitch and roll servos
use calculated Upper Mode commands to drive servo deflections.
CPLD (Coupled)
The coupled mode achieves a reference flight trajectory without
pilot input.
Engaged A state used to define whether a servo is on and active.

190-02775-00 Rev. A Garmin GFC 600H Pilot’s Guide for Bell 505
47
Terms & Conventions

Term Description
A servo function which maintains aircraft pitch and/or roll
attitude. This function moves the rotorcraft flight controls to
ATT (Attitude Hold) maintain the attitude. When the pilot moves the controls, the
servo provides a spring feel which helps the pilot move the
controls to achieve the reference attitude.
A hands on controls function which provides an increased force
LMTQ (Limit
gradient or control force cue to deter additional pilot control
Cueing)
inputs which would exceed configured rotorcraft limits.
An attitude hold sub-mode used to return the aircraft to a level
LVL (Level)
pitch and roll attitude.
Groundspeed Hold Mode is a sub-mode of Attitude Hold Mode in
GSPD
which the control of attitude is augmented to achieve a control
(Groundspeed Hold
objective of constant lateral and longitudinal ground speed.
Mode)
Entry into and out of Ground Speed Hold Mode is automatic.
Hover Assist is a sub-mode of GSPD. When active, Hover Assist is
HOV (Hover Assist) annunciated by ‘HOV’ on the GMC 605H display and maintains
the rotorcraft’s position over a fixed point on the ground.
The control position at which the pitch and roll control objectives
have been achieved. Moving the controls away from this position
Detent
will provide resistance to the pilot. Upon release of the controls
they will return to the detent position.
A function that provides pitch and roll commands to the pilot or
servos, based on the pilot-selected mode(s) on the GMC (HDG,
Upper Modes
NAV, IAS, ALT, etc.). Modes are classified as either “Active” or
“Armed”.
A state of the flight control system where the servos are not
engaged. H-ESP (Limit Cue protection) is still active when the
STBY (Standby)
system is in standby to protect the pilot from exceeding the
operating limits of the helicopter.
System Operation Terminology

48 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Terms & Conventions

5.3 HELICOPTER AND SYSTEM CONTROLS

Control Description
A rotorcraft primary control which controls the pitch of the tail
rotor blades or alternative anti-torque system. This control is used
Anti-Torque Pedals
to control rotorcraft movement about the yaw axis. The yaw servo
drives the pedals of the helicopter.
A rotorcraft primary control which alters the pitch angle of the
Cyclic main rotor blades cyclically. This control input is used to control
the rotorcraft’s pitch and roll attitude.
The collective is used to make changes to the pitch angle of all
Collective the main rotor blades simultaneously, or collectively, as the name
implies.
This input increments or decrements the control reference in pitch
Beep Trim (or Trim or roll. When the system is in ATT, beep trim adjusts the attitude
Reference) hold reference. When the system is coupled to an Upper Mode,
the beep trim adjusts the active mode references.
Slewing a beep trim reference is a means to press and hold the
Slew
Cyclic TRIM Switch to make larger changes in the control reference.
FCS DISC (FCS A switch input that allows the pilot to disengage the servos. A
Disconnect) momentary press also returns the system to ATT Hold Mode.
A four way switch input which provides pilot control of the active
TRIM
FCS pitch and roll references.
A switch input which resets the FCS Reference. This switch is
used in ATT to set the attitude reference. In coupled flight, this
switch will also sync the coupled Upper Mode reference to the
FTR (Force Trim current aircraft condition (i.e., if the system is telling the aircraft to
Release) fly a vertical speed descent of 100 feet per minute and the pilot
manually increases the descent rate, pressing the FTR will reset the
vertical descent to the new condition. While pressed the forces
required to move the controls out of detent are reduced.
Helicopter and System Controls

190-02775-00 Rev. A Garmin GFC 600H Pilot’s Guide for Bell 505
49
Terms & Conventions

5.4 MODE ANNUNCIATIONS

Mode Description
Allows the aircraft to capture the altitude selected on the PFD.
ALTS (Selected
When activating the Airspeed Mode or Vertical Speed Hold Mode,
Altitude Capture
the system will fly to the selected altitude, and maintain that
Mode)
altitude by transitioning to Altitude Hold Mode.
ALT (Altitude
Capture Hold Maintains the target altitude.
Mode)
Arms the appropriate lateral and vertical navigation guidance for
APR (Approach the approach phase of flight. Navigation receiver sources include
Mode) VOR, LOC/GS, or GPS/SBAS guidance. The GMC APR Key is used
to Arm/Activate this mode.
GP (Glide Path
Tracks a GPS approach profile.
Mode)
GS (Glide Slope
Tracks a ILS navigation glide slope receiver signal.
Mode)
HDG (Heading
Maintains a selected heading on the PFD.
Mode)
IAS (Indicated
Maintains the indicated airspeed.
Airspeed Mode)
USP (Under Speed Provides protection against coupled pitch modes from exceeding
Protection) the minimum allowed Upper Mode airspeed.
OSP (Overspeed Provides control saturation and adjustments to prevent overspeed
Protection) of the rotorcraft.
VS (Vertical Speed
Maintains vertical speed.
Hold Mode)
Upper Modes

50 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Index

SECTION 6 INDEX
A Indications 9
GP 23
Alerts 39 GPS. See Navigation Modes or Approach
ALT 20 Modes
Altitude Hold Mode 20 GS 25
Altitude Reference 21 GSA 87 Servo 3, 4
ALT Key 6
ALTS 21 H
Annunciations 39. See also Vertical
HDG. See Heading Select Mode
Modes or Lateral Modes
HDG Key 6
AP. See Autopilot
Heading Select Mode 27
Approach Mode 30
Helicopter Flight Control System 13
APR Key 6
Features 16
Aural Alerts 43
Operation 13
Autopilot 1, 2
HFCS. See Helicopter Flight Control
Disengaging 14
System
Engaging 14
HSI. See Horizontal Situation Indicators
Features 16
Overspeed Protection 34, 36 I
Underspeed Protection 37
Flight Director 16, 34, 36 IAS 23
Malfunction 45 Indicated Airspeed Mode 23
Autopilot Disconnect Alert 44 L
D Lateral Modes 26
DG. See Directional Gyros Approach, GPS 27
Approach, LOC 27
E Approach Modes (GPS and LOC) 30
Approach, VOR 27
ESP. See Electronic Stability & Protection
Heading Select Mode 27
G Navigation Modes (GPS, VOR, LOC)
28
Glidepath Mode 23, 31 LCD Display 6
Glideslope Mode 25 Line Replaceable Unit (LRU) 1, 2
GMC 605 3, 6

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Index

LOC. See Navigation Modes or Approach V

Modes
LVL Key 6 Vertical Modes 19
Glideslope 20
M Indicated Airspeed 20
Selected Altitude Capture 20
MAXSPEED annunciation 37, 41
Vertical Speed 20
MET. See Manual Electric Trim
Vertical Speed Mode 21, 22
N VNV Key 6
VOICE ALERTS 43
Navigation Modes (GPS, VOR, LOC) 28 VOR. See
NAV Key 6 VS 22
NOSE UP/DN Wheel 6
Y
O
YD. See Yaw Damper
Overspeed Protection 34, 36
P
PFD
Annunciations 39, 45, 47, 49, 50
PFD HFCS Indications 12
R
ROL. See Roll Hold Mode
S
Selected Altitude 21
Selected Altitude Capture Mode 21
Selected Heading 27
System
Controls 6
U
Underspeed Protection 37

Index-2 Garmin GFC 600H Pilot’s Guide for Bell 505 190-02775-00 Rev. A
 Index

190-02775-00 Rev. A Garmin GFC 600H Pilot’s Guide for Bell 505 Index-3
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