TruTrak DFC Install Manual

Installation Manual

For

DFC Series Autopilots

TRUTRAK FLIGHT SYSTEMS

1500 S. Old Missouri Road

Springdale, AR 72764

Ph. 479-751-0250 Fax [phone]

www.trutrakflightsystems.com

INSTALLATION MANUAL

TABLE OF CONTENTS

Mechanical Considerations.................................................................................................1

Pitot and Static Connections...............................................................................................2

Magnetic Considerations....................................................................................................2

RFI/EMI .............................................................................................................................2

FOR

DFC-Series Autopilots

Electrical Wiring.................................................................................................................3

Connecting GPS Units

Garmin 430/530..............................................................................................................4

UPS GX-50/60/65...........................................................................................................5

UPS GX-50/60/65 w/SL-30............................................................................................6

Initial Checkout..................................................................................................................7

Yaw Damper Initial Checkout............................................................................................8

First Flight..........................................................................................................................9

Magnetic Calibration........................................................................................................10

Yaw Damper In-Flight Adjustment..................................................................................11

DFC-200/250Wiring Diagram..........................................................................................12

DFC-200/250Wiring Diagram..........................................................................................13

Mechanical Considerations

The installation information in this section is extremely important and must be clearly
understood by the installer. Improper servo installation or failure to observe and diagnose
installation problems prior to flight can result in extremely serious consequences, including
loss of ability to control the aircraft. If there are any questions on the part of the installer it
is mandatory to resolve these questions prior to flight of the aircraft.

Most modern experimental aircraft use push-pull tubes to drive the primary controls. These tubes generally have a total travel
of 3” or less; therefore, it is best to connect the autopilot servo to the primary control by the same method. This connection
consists of an arm on the servo connected by a push-pull rod to the primary control. Rod-end bearings are required on each
end of the push-pull rod.

The servo arm must not rotate even near to the point called OVER CENTER, the point at which the primary
aircraft control would lock up.

This is a condition that would result from the servo being back driven when the pilot operates the controls, or
from the servo itself driving the controls to a stop. To protect against this mechanical stops are supplied with the
servos. These stops are drilled so that they can be mounted at different angles as required (18° intervals)

In addition to the proper use of the stop it is important to know the amount of travel on the primary control that
the servo can handle. With the push rod connected to the outermost hole (1 ½”) the travel on the primary cannot
exceed 2 ½”, the intermediate hole 2 1/16”, and the inner hole 1 5/8”.

It is important to note that at the neutral point of the control the SERVO ARM must be PERPENDICULAR to the
push rod, and that the stop must be mounted so as to limit travel as near as possible to equal amounts in both
directions. In certain factory-designed installations there may be well-proven exceptions.

There will be installations in which space does not permit the use of the stop. When this is done the aircraft’s primary control
stops must be positive and care must be taken to be sure that at the neutral point the servo arm is perpendicular to the push rod,
and that the travel limits of the servo arm are not exceeded.

There are installations in which the travel of the push-pull tube exceed s the allowable 2 ½”. For such installations, the drive
can be applied to a bell crank at a radius point that moves the desired 2 ½” of maximum allowed travel in the outermost hole of
the arm.

When there is no way to have a drive point of less than 2 ½” or when the primary control is cable-driven it is necessary to use
the capstan-cable servo drive. When this is done the servo should be mounted so that the 1/16” diameter cable which wraps
around the capstan when extended parallel to the primary cable is approximately 3/16” from the primary cable. If the primary
control travel does not exceed 5” the cable locking pin will be 180° away from the point at which the cable leaves the capstan.
When the primary control is at the neutral point this means the total cable wrap around the capstan is 360°. If the primary
control travel is greater than 5” the cable wrap is 720°and the pin is adjacent to the output point when the primary control is at
the neutral point.

The cable clamps when properly installed will not slip and thus get loose, but it is desirable to nicopress or swedge a fitting on
to the cable so as to provide added assurance that the cable will not become slack. If the bridle cable is not sufficiently tight
there will be lost motion in the autopilot drive. This will result in hunting (oscillation).

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Pitot and Static Connections

All multi-servo TruTrak autopilots require connections to the pitot and static lines. The preferred method of this connection
would be tee fittings near the aircraft’s altimeter. The static line for the autopilot requires due care in its construction, as
excessive lag or insufficient static orifices can cause the autopilot to oscillate (hunt) in pitch. Although there is compensation
within the autopilot sufficient to handle moderate amounts of lag, the importance of a good static port and line cannot be
overstated. In some cases problems can be caused by having a large number of devices (including the autopilot) connected to a
single, insufficient, static port. In other cases, the static line itself is adequate but there are one or more devices connected to the
same line, one of which has a large static reservoir. A simple remedy for this problem if it occurs is a tee-fitting near the static
port, and a dedicated line to the autopilot only. Obviously, an insufficiently-large orifice coupled with large static reservoirs
can aggravate the problems associated with lag.

Magnetic Considerations

Because the autopilot contains a built-in magnetometer for a backup source of heading in the event of GPS loss, it is important
to try to locate the programmer away from known sources of magnetic disturbance. Th e calibration procedure can account for a
moderate amount of fixed disturbance (for example, nearby iron objects) but it cannot adjust for changing magnetic fields such
as might be generated by certain electrical devices. One known source of such problems is the “Flag” mechanism in some older
DG or HSI devices. These units use a solenoid to hold the flag out of sight, and the magnetic field will then change when the
flags come and go. If at all possible, place the autopilot so as to be as far as possible from such devices. A hand-held compass
can be used to assist in finding such problems prior to installation of the autopilot. Even a few inches can make an appreciable
difference in the magnetic disturbance level. It should be noted also that strobe light controls generate very strong currents in
their wiring, thus they will create a periodically pulsating magnetic field disturbance. Shielding has no effect on this problem;
the only solution is to keep strobe light, landing light, navigation light, and Pitot heater wiring as far away as possible from any
electronics which can be affected by pulsating magnetic fields.

RFI/EMI considerations

The autopilot programmer is shielded and does not generate any appreciable level of electromagnetic interference. Moreover,
the servo lines (except for power and ground) are low-current and cannot contribute to RF interference. The servo power and
ground lines do have switching currents through them, but so long as there are no parallel runs of servo power and ground lines
with such things as poorly-shielded antenna lines or strobe light power lines, there is no need to shield the servo harnesses.

The autopilot itself has been internally protected from RF interference and has been tested under fairly extreme conditions,
such as close proximity to transmitting antennas. However, it is always good practice to insure that such antennas are properly
shielded and not routed directly over or under sensitive panel-mounted electronic equipment. Most problems in this area are the
result of improper RF shielding on transmitting antennas, microphone cables, and the like. The most sensitive inputs to the
autopilot are the CDI, Glideslope, and Control Wheel Switch inputs. These lines should not be routed in parallel with
transmitting antennas or other sources of known RF interference. If necessary, they can be shielded with the shield connection
to pin 19 of the autopilot connector.

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Electrical Wiring

All TruTrak DFC series (DFC-200, DFC-200AS, DFC-250, DFC-250AS, DFC-300, DFC-300AS) autopilots have consistent
wiring requirements. Therefore, this manual covers all such units, with special notations covering any differences between the
units. The DFC-200 programmer is mechanically identical to the DFC-250 and differs only in its internal circuitry and
software. The DFC-300 autopilot system consists of a DFC-250 programmer and a YD-300 yaw damper module, together with
the three servos that constitute the system.

The table below provides a brief explanation of each pin function on the main 37-pin connector P101.

P101 Autopilot Rear Connector (Viewed from rear of autopilot)

P101

Pin

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Function Notes

1 Dedicated ground connection for Pitch Reverse Jumper.

Pitch Reverse Jumper,

2

present or absent, as follows:

Pin 2 open (no connect): Servo CCW (counter-clockwise) Î UP
Pin 2 Jumpered to pin 1: Servo CW (clockwise) Î UP

3 Auxiliary RS-232 Output. Presently unused, intended for future expansion.
4 LAMP1 (see also pin 18) A source of variable DC from external dimming source. Drives the

LCD backlighting circuit and six 60 mA lamps. If left disconnected, backlight will be full-on
and buttons will be unlighted. Draws approximately 500 mA at 12v, 250 mA at 28v.

5 Yaw Damper Gyro Gain. A signal from the autopilot which sets the amount of response the

yaw damper exhibits to azimuth disturbances.

6 Yaw Damper Tilt Gain. A signal from the autopilot which sets the amount of response the

yaw damper exibits to a given amount of deflection of the “ball”.

7 No Connection. Reserved for future expansion.
8 Yaw Damper Activate. A signal from the autopilot which turns on the yaw damper function. DFC-300 only
9 Analog DG/HSI Input. A zero to 5V DC signal centered at 2.5 volts from an external steering

device. An adapter specific to a given DG or HSI is required. Consult factory for details on this
adapter.

10 Pitch Servo Torque Control. A signal from the autopilot to the pitch servo which sets the

amount of torque to be delivered by the servo.

11 Pitch Servo Trim Sensor. A signal from the pitch servo to the autopilot which indicates an

out-of-trim condition and its direction.

12 Autopilot Master (+12 to +28 V DC). The autopilot itself draws less than ½ ampere. Most of

the current required by the autopilot system is used by the servos (up to 1A per servo).

13 Audio alerter signal. This pin may be wired to an unswitched input of an audio panel. The

autopilot uses various tones to denote specific events (loss of GPSS, capture Glideslope, etc).
Volume is adjustable within a setup screen of the autopilot.

14

Pitch Servo control lines. These lines cause the stepping motor in the pitch servo to run in the
appropriate direction at the desired velocity. They are small-signal lines and do not have any

15

substantial current-carrying capability or require any special shielding. Connect to pitch servo

16

as shown on wiring diagram.

17
18 LAMP2 (see explanation for pin 4, above).
19 Ground Connection. Provide #20 AWG to common grounding point.
20 Control Wheel Switch. Connect as shown in wiring diagram to a SPST momentary switch

located remotely to the autopilot for convenient engage/disengage func tion.

21

CDI LEFT

22

CDI RIGHT

Analog +/- 150 mV differential signals from Nav receiver. Pin 22 more
positive than pin 21 indicates CDI needle right-of-center.

Direction of servo arm / capstan rotation

(as viewed from face of the servo body)

for UP elevator

See note 4 on wiring
diagram

Dimmer is wired
based on supply
voltage. See note 2
on wiring diagram
DFC-300 only

DFC-300 only

not attempt to

Do
reverse servo
direction by
swapping wires

Autopilot Rear Connections to P101 (Continued)

P101

Pin

Function Notes

23

GS DOWN

24

GS UP

25 Primary Serial Input. Baud rate selectable 1200, 2400, 4800 or 9600 baud. Automatically

decodes NMEA-0183, Garmin Aviation Format, or Apollo/UPSAT Moving-Map or GPSS
format. Provides directional reference to the autopilot.

26

ARINC-A

27

ARINC-B

28 Roll Servo Torque Control. A signal from the autopilot to the roll (aileron) servo which sets

the amount of torque to be delivered by the servo.

29 Localizer mode signal. When floating or at power supply potential, the autopilot will assume

CDI signal represents a VOR deviation. When grounded, the autopilot will assume that CDI
represents a localizer signal with different flight dynamics, and in addition will allow coupling
to the glideslope as well for an ILS approach. Some Nav receivers refer to this as the “ILS
Energize” function.

30 Auxiliary RS-232 Input. Presently unused, intended for future expansion.
31 No Connection. Reserved for future expansion.

Roll (aileron) Servo control lines. These lines cause the stepping motor in the roll servo to run
in the appropriate direction at the desired velocity. They are small-signal lines and do not have

32

any substantial current-carrying capability or require any special shield ing. Connect to roll

33

servo as shown on wiring diagram.
34
35

Wiring to roll servo J201

J101 Pin 32 Pi n 33
Standard J201-4 J201-5 Servo CCW (counter-clockwise) Î RIGHT
Reversed J201-5 J201-4 Servo CW (clockwise) Î RIGHT

36 No Connection. Reserved for future expansion.
37 No Connection. Reserved for future expansion.

Analog +/- 150 mV differential signals from Glideslope receiver. Pin 24 more
positive than pin 23 indicates GS needle above center.

Digital differential signals from Garmin, Sierra, or other panel-mount receiver
which provide directional steering commands (GPSS) to autopilot

Direction of servo arm / capstan rotation

(as viewed from face of the servo body)

for RIGHT aileron

Reverse servo
direction if necessary
by swapping wires on
pin 32 and 33. See
note 3 on wiring
diagram.

Specific connections for certain commonly-used in-panel GPS units

Note that the information in the tables is based upon the best information available from each manufacturer’s documentation at
the time of publication. Please consult the appropriate installation manual for confirmation of wiring information.

Garmin 430 and 530 connections to TruTrak autopilot

P4001 [P5001] on
Garmin 430 [530]

21 MAIN +LEFT CDI LEFT 21
22 MAIN +RIGHT CDI RIGHT 22
27 MAIN +UP GS UP 24
28 MAIN +DOWN GS DOWN 23
56 GPS RS 232 O UT 1 Primary Serial Input 25
46 GPS ARINC 429 OUT A ARINC-A 26
47 GPS ARINC 429 OUT B ARINC-B 27
14 ILS / GPS APPROACH Localizer Mode 29

Garmin 430/530 setup instructions:

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Signal Name

(Garmin)

Signal Name

(TruTrak)

P101 on

TruTrak Autopilot

Power 430/530 up and turn it on while holding down the ENT key. Release the ENT key when the display activates. After the
data base pages, the first page displayed is the MAIN ARINC 429 CONFIG page. While in Configuratio n m ode, pages can be
selected by ensuring the cursor is off and rotating the small right knob. To change data on the displayed Configuration Page,
press the small right knob (CRSR) to turn on the cursor. Turn the large right knob to chang e be tween data fields. Turn the large
or small right knob to change a field that the cursor is on. Once you have made the desired selection, press the ENT key to
accept the entry.

With the MAIN ARINC 429 CONFIG page display e d , on the ro w la bel ed OUT, select SPEED Î Low
and DATA ÎARINC 429.

Advance to the MAIN RS232 CONFIG page.
On the row labeled CHNL1, select OUTPUT Î Aviation.
Note that for the Garmin units, the autopilot will need to be set for 9600 baud.

.

UPSAT GX-50/60/65 connections to TruTrak autopilot

37-Pin Connector

on UPSAT

GX-50/60/65

Signal Name

(UPSAT)

Signal Name

(TruTrak)

P101 on

TruTrak Autopilot

14 CDI +L CDI LEFT 21
13 CDI +R CDI RIGHT 22

5

or

22

Use pin 5 – TxD1 – if GX has no

GPSS

Use pin 22 – TxD2 – if GX has

GPSS

Primary Serial

Input

25

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UPSAT GX-50/60/65 + SL30 connections to TruTrak autopilot

GX

50/60/65

14 CDI +L CDI LEFT 21
13 CDI +R CDI RIGHT 22
30 GSI +UP GS UP 24
31 GSI +DOWN GS DOWN 23
33 ILS ENERGIZE Localizer Mode 29

SL30 Signal Name

(UPSAT)

Signal Name

(TruTrak)

P101 on

TruTrak Autopilot

5

or

22

GX-50/60/65 setup instructions:
Power the GX-50/60/65 up and turn it on while holding down the leftmost and rightmost “smart keys.”
Rotate the LARGE knob to the Serial Interface Configuration “CH RX TX” page. Press SEL (the selection fields will start

flashing), rotate the LARGE knob to select the port, rotate the SMALL knob to select the desired configurations, then press
ENT when complete.

If the GX unit has no GPSS capability, select “MOVING MAP” For CH 1, Tx column and wire to pin 5 of the GX unit;
if the GX unit does have this feature, select “GPSS” for CH 2, Tx colum n, an d wi re to pi n 2 2 inst ead.

To restore the GX-50/60/65 to normal operation, switch its power off, then back on.
Note that for the GX-50/60/65 units, the autopilot will need to be set for 9600 baud. The autopilot’s ARINC-A and ARINC-B

inputs should be left unconnected, as steering information in the case of UPSAT units is sent over the serial RS232 line along
with the ground track and ground speed information the autopilot needs.

Use pin 5 – TxD1 – if GX has no

GPSS

Use pin 22 – TxD2 – if GX has

GPSS

Primary Serial

Input

25

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Initial Checkout

Once wiring is completed the autopilot should be tested in the aircraft while on the ground. The first step is to enter the setup
modes on the autopilot and set all parameters to their correct values. Apply power to the autopilot programmer. Its initial
screen should be displayed, along with the words PWR UP in the lower-right of the display. After approximately ten seconds,
the autopilot is ready to be set up for operation, indicating AP OFF on the display.

Press and hold MODE on the autopilot for about three seconds until the first setup screen, showing LAT ACTIVITY and LAT
TORQUE is displayed. Rotate the encoder knob as necessary to set the lateral activity value to a value of 1 or 2. Press and
release the knob to enter that value and advance to the lateral torque field. Insure that the value displayed is somewhere close to
the maximum value of 250. Once that is done, press ENTER to enter that value and advance to the next screen.

Rotating the encoder knob, select a value for BAUD RATE which is compatible with the panel-mount GPS receiver connected
to pin 25. The value of 9600 is the most commonly used rate. Once baud rate selection is done, press and release the encoder
knob to enter that value and advance to the next screen.

Rotating the encoder knob, select a value for AUDIO VOLUME (0 to 16) which results in a comfortable listening level. This
adjustment varies the audio level of the alerter signal output on pin 13 of the programmer and wired into an audio panel.
Having selected a comfortable level, press and release the encoder knob to enter that value and advance to the next screen.

Rotating the encoder knob, select Y (yes) or N (no) to the EXT DG/HSI? question. If no external device is connected to pin 9
on the connecter, answer N. The EXT DG flight mode will be present or absent when operating the autopilot based on the
answer to this question. Having made this choice, press and release the encoder knob to enter that value and advance to the
next screen.

Rotating the encoder knob, select Y (yes) or N (no) to the NAV RCVR? question. If no CDI inputs are connected to pins 21
and 22 on the connector, answer N. The NAV and LOC flight modes will be present or absent when operating the autopilot
based on the answer to this question. Also insure that pin 29 is wired to an appropriate signal. Having made this selection, press
and release the encoder knob to enter that value and advance to the next screen.

If “Y” (yes) was selected on the NAV RCVR? question the autopilot will then ask whether a glideslope receiver is connected.
If no Glideslope deviation inputs are connected to pins 23 and 24 on the conn ector, answer N. If the question is answered “N”
the autopilot will not attempt to couple to a glideslope during localizer approaches. Having made th is choice, press and release
the encoder knob to enter that value and advance to the next screen.

Rotating the encoder knob, select Y (yes) or N (no) to the YAW DAMPER? question. If no YD-300 module is connected to
pins 5,6 and 8 on the connector, answer N. If the programmer is part of the DFC-300 system which includes the yaw damper
module, answer Y. Having made this choice, press and release the encoder knob to enter that value and advance to the next
screen.

To the MAG CALIBRATE? Question, answer N (no) at this time. This operation can be done at a later time. Press and release
the encoder knob to advance to the next screen.

If “Y” (yes) was selected on the YAW DAMPER? question the autopilot will display a setup screen for yaw damper centering
and activity settings. At this time, select 0 for YD TILT and 0 for YD ACTIVITY, pressing the knob after setting each value.

Once all the initial lateral setup of the autopilot is complete, the pitch axis initial setup should be done.
Press and hold ALT on the autopilot for about three seconds until the first pitch setup screen is displayed. Rotate the encoder

knob as necessary to set the vertical activity value to a value of 1 or 2. Press and release the knob to enter that value and
advance to the vertical torque field. Insure that the value displayed is somewhere close to the maximum value of 250. Once
that is done, press and release the encoder knob to enter that value and advance to the next screen.

The next screen allows a minimum airspeed to be set, as well as (DFC-250 only) a default value of climb airspeed for use by
the altitude selector. Using the encoder knob, set the minimum airspeed to the slowest airspeed the autopilot should ever fly the
aircraft. This should be safely above stall airspeed for the aircraft. This is also the speed (DFC-300 system only) at which the
yaw damper will automatically disengage prior to landing. If the system being set up includes a yaw damper, it is necessary to
set minimum airspeed to 0 at this time, to allow the yaw damper to be tested properly before the first flight. After selecting the
appropriate value(s) press and release the encoder knob to advance to the next screen.

The STATIC LAG field is used to accommodate aircraft with delay in the static line. Start with a value of 0 until the first flight
test of the autopilot. Select 0, then press and release the encoder knob to complete the setup mode.

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The next step in the check-out procedure is to verify that all servos run, and in the correct direction. Power up the autopilot and
wait approximately ten seconds for AP OFF to be displayed in the lower right portion of the screen. Then press and release the
ON OFF button to engage the autopilot. At this point, the selected heading will be underlined on the botto m left of the display,
while the selected vertical speed (“SVS”) will be shown on the bottom right. Use the VS UP and VS DN buttons to set
selected vertical speed to zero. The pitch servo should stop, or move only very slowly. Then press VS UP repeatedly until
several hundred feet per minute is showing on the lower right SVS field. At this point the pitch servo should be moving the
control yoke or stick back, in an effort to raise the nose of the aircraft. Similarly, using VS DN to select a negative selected
vertical speed, the pitch servo should be moving the controls in such a way as to lower the nose of the aircraft. If direction is
incorrect, install or remove the jumper between pins 1 and 2 of the autopilot connector.

The roll servo should also be responding at this time, moving the controls in such a way as to turn the aircraft from the
heading (shown as a 3-digit number after the word MAG in the upper-left of the display) to the

selected heading (shown as a 3-

current

digit number after the word SEL in the lower left of the display). The initial value of the selected heading is the current heading
of the aircraft at the moment of engagement, but the encoder knob can be used to modify the selected heading. When the
heading shown as SEL agrees with the heading of the aircraft shown in the top line as MAG, the roll servo should stop or run
only very slowly. If the knob is rotated clockwise, to a selected heading
should move in such a way as to roll the aircraft to the right. Conversely, a selected heading to the

right of the current heading, the control yoke or stick

left of the current heading
will move the controls in the opposite direction to attempt a roll towards the left. If servo direction is not correct, the wires
going to pins 4 and 5 of the roll servo (pins 32 and 33 on the main connector) must be reversed to achieve the correct response.
If the servos do not move at all, double-check the LAT TORQUE or VRT TORQUE setting as appropriate. If a servo jitters but
does not actually rotate, check the wiring on the four servo drive lines to that servo for continuity and correctness. If the servo
does not seem to have any torque, check the relevant torque control line for continuity and correctness.

At this time, check that the servo arm or capstan is properly operating the controls. For servo installations using an arm, check
that as the controls go from limit to limit the arm of the servo remains in the operating range of the servo (a maximum of 100
degrees total rotation) and that when the controls are centered, the connecting pushrod is approximately perpendicular to the
arm of the servo. For capstan systems, insure that the cabling remains at proper tension and is properly secured as the servo
moves the controls from stop to stop. Insure that the servo remains secure in its mounting and does not flex its mounting
bracket as it drives the control to its stops. For installations using an arm, insure that as the servo moves the control towards
the end of control travel it does not cause the main control’s torque tube to flex in any way that could cause control system
lockup at the extremes of servo travel. Insure that any “lost motion” in the linkages is eliminated or minimized, in order to
maximize the performance of the autopilot. Lost motion (dead zone) will result in wandering or slow “hunting” behavior in
flight.

The next step in the check-out procedure is to verify that the serial input from the GPS receiver is being properly received and
interpreted. With the aircraft outside of any building, power up the GPS panel-mount recei ver and the autopilot. After the GPS
receiver acquires its position, the autopilot will begin to flash the “*” character once per message from the GPS unit showing
that valid position data is available. The display will still show MAG followed by a flashing “*” character, followed by the
present approximate magnetic heading. If no “*” is displayed ev en after it is known that the GPS unit has a position fix, the
problem must be diagnosed. Possible reasons for such a problem are,

 Pin 25 on the connector is not wired to a source of RS-232 serial data
 The GPS receiver’s baud rate disagrees with that selected within the autopilot
 The GPS receiver’s serial output port has not been properly configured to provide the information

For a DFC-300 system, the next step in the checkout procedure is to verify operation of the yaw damper. Before this test,
remove the yaw damper module from its mounting location (a vertical bulkhead) so that it can be manually tilted. Verify the
direction strap is correctly wired on pins 16 and 17 of J501, the 25-pin yaw damper connector. If the unit is to be mounted on
the rear side of a bulkhead, the strap between pins 16 and 17 of J501 must be absent; if the unit is to be mounted on the front
side, the jumper must be present.

Having verified the strap, manually center the rudder and then engage the yaw damper by pressing the MODE key on the
autopilot programmer. (Any time the autopilot is off; the yaw damper may be toggled on and off using this key, so long as the
aircraft is not flying slower than the preset minimum airspeed). Hold the yaw damper module in the same position it will
occupy when mounted on the bulkhead in an approximately level position that stops the servo rotation. Tilt the module to
simulate the aircraft banking to the right. The yaw damper should respond by commanding the rudder to move towards the
right, and conversely a bank to the left should move the rudder towards the left. If the ser vo moves in the wrong direction
during this test, double-check the correct jumper setting on pins 16 and 17 and if found to be correct, interchange the wires on
the yaw damper servo connector (pins 4 and 5 of J401) or at the connector on the yaw damper module (pins 12 and 13 of J501).
Re-check the direction after exchanging the wires.

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Having verified the correct direction of response to the tilt sensor, secure the yaw damper module to the bulkhead. Re-engage
the yaw damper and adjust the leveling potentiometer (which protrudes from the face of the yaw damper module) to stop the
movement of the servo. The aircraft should be on a level surface (with its “ball” centered) for this adjustment. Once the proper
adjustment is done, press the MODE key to disengage the yaw damper, re-enter the lateral setup using the MODE button, and
set YD ACTIVITY value to zero. This insures that the yaw damper adjustments do not complicate the first test flight of the
autopilot. Holding down the ALT button to enter the setup mode, and repeatedly pressing ENTER to advance to the MIN
AIRSPD field, set the minimum airspeed to the desired value for actual flight. This should be an indicated airspeed (in knots)
which is safely above the stall but not below normal approach or climbout speeds.

The remaining adjustments relate to the dynamics of flight and compensation of the magnetic backup system in the autopilot.

First Flight

The first flight should be done after having c ompleted all the setup and testing on the ground. For the first flight, it is important
that the GPS unit is properly functioning with the autopilot, so that the dynamics of flight can be set without consideration of
the calibration of the magnetic backup system. As discussed earlier, when there is proper connection to the serial input of the
autopilot, the display will show a flashing asterisk “*” in the display to the right of the word MAG; once taxi speed exceeds 10
knots, the display will change from MAG to TRK if the GPS unit has achieved a position fix and sufficient groundspeed. If this
does not occur on fast taxi speeds, it is best to diagnose the problem prior to first flight of the autopilot.

The two activity adjustments (LAT ACTIVITY and VRT ACTIVITY) determine how briskly the autopilot responds to roll and
pitch disturbances. They can be adjusted, in flight, over a wide range; thus the autopilot can be tailored to adapt to any aircraft
installation.

Each of the two activity adjustments covers a numeric range of 0 to 12. Unless the value for a particular aircraft is provided by
TruTrak, it is advisable to start with a setting of zero and work up from there. Most installations would ultimately require
somewhat higher settings.

Prior to takeoff on the first flight, synchronize the autopilot’s altimeter to the aircraft’s primary altimeter value. With the
autopilot off press the ALT button once, to show the ALTIMETER SYNC screen (take care not to accidentally enter the ALT
SELECT screen by mistake). Use the encoder knob to adjust the altitude reading to agree. Each click of the knob gives 100
foot increments; to get ten-foot increments, push in on the knob and rotate it. Having set the autopilot’s altimeter to agree with
the primary altimeter, press ENTER to record this value.

On the first flight, manually fly the aircraft to a suitable area for testing. Engage the autopilot using the ON OFF switch.
Observe that the SEL field now shows the captured present ground track (shown after TRK on the display) and the SVS

selected vertical speed) field shows the approximate present rate of climb or descent in feet per minute. Use the VS UP or VS

(
DN buttons to set the selected vertical speed to zero. Press and hold the MODE button for a few seconds until LAT ACTIVITY
is shown on the display, along with an underlined value. Rotate the knob to select the value zero (0), and observe the resulting
control movement. Increase the value one setting at a time, taking time to observe an increasing level of control response. At
some point, if too high a setting is chosen, the autopilot will be jittery and over-active. Back the setting down until the autopilot
is responsive but not over-active. It is best if these adjustments are made in conditions of moderate turbulence (the TruTrak
loves turbulence) so as to make it easy to observe the response of the autopilot to disturbances. It will be noted that a fairly
limited range of activity setting will be acceptable; too low a value will result in sluggish response, while too high a value will
result in nervous, inappropriate response. Within this acceptable range there is room for individual preference; some people
prefer a more aggressive autopilot than others. It should be noted that any builder can accomplish this adjustment procedure
and no professional is required.

Once the desired LAT ACTIVITY level is established, press ENTER to store the value.
Next, the LAT TORQUE field is adjusted. Again, it is best that this be done in light to moderate turbulence. The reason is that

more torque is required of the autopilot in turbulence than is the case in still air, because the velocity of the servo is greater as
turbulence requires more rapid servo movement. This means that when activity is set to the high end of the acceptable range, a
higher torque setting will be required.

The reason for setting LAT TORQUE to a setting less than its maximum (250) is to reduce the current draw of the servo and to
make it easier to override the autopilot should the need arise. Manual override is not normally required, as using the control­wheel switch or the ON OFF button will disengage the autopilot, but it is best to have a setting of torque which can be
comfortably overridden if necessary.

Once the desired LAT TORQUE level is established, press ENTER to store the value.

TruTrak Flight Systems DFC Autopilot Installation Manual
9 May 2006 Printing

Having set the autopilot for its proper roll response, it is time to move to the pitch axis adjustments. Press and hold the ALT
button until VRT ACTIVITY is shown on the display, along with an underlined value. In the same manner as was done for the
roll axis, use the knob to find a setting which results in the appropriate response. Again, too high a value will be jittery or
oscillatory and too low a setting will be sluggish and unresponsive. Having found the desired VRT ACTIVITY setting, press
ENTER to store the value and move to the VRT TORQUE field.

In a manner similar to the lateral axis, rotate the knob to choose a torque setting sufficient to fly the aircraft in light to moderate
turbulence without slipping the servo, yet not so high as to be difficult to override manually. Having selected this value, press
ENTER to store the value.

The next screen shows selections for MIN AIRSPD and NORM CLIMB. The minimum airspeed value is the slowest indicated
airspeed the autopilot will fly, independent of what it is commanded to do. This airspeed value should be safely above stall
speed (knots IAS) yet slower than normal approach or climbout speeds. Select the value, and press ENTER to confirm it. The
NORM CLIMB field is the airspeed (knots IAS) which would be normally used in a climb, typically the cruise climb airspeed
for the aircraft. This value shows up as the default airspeed (which can be changed as desired while climbing) in the altitude
selector function. Select the normal climb airspeed with the knob and press ENTER to confirm and store the value.

The next screen is the STATIC LAG field. It is set to 0 at the factory but can vary between 0 and 2 to suit a particular static
system. The value 0 assumes a static system with very little “lag”; the value 2 assumes a fairly large amount of lag. To
diagnose the lag of a particular system, it is necessary to be in the altitude hold mode of the autopilot, so prior to setting this
field, simply press the ALT button, cycling the vertical mode display until the ALTITUDE HOLD screen shows, then press
ENTER. This puts the autopilot into altitude hold mode at the current altitude.

Once the autopilot is in altitude hold mode, re-enter the vertical setup mode by holding the ALT key. Use the knob ’s ENTER
function to cycle over the choices already made until the STATIC LAG display is again on the screen. In still air, straight and
level flight, in altitude hold mode, observe whether the altitude appears to oscillate, or “hunt” up and down. If this is the case, it
may be caused by several factors, one of which is the amount of lag in the static system. Increasing the STATIC LAG value to
a 1 or a 2 may cure the problem; however this should be set to the smallest value that satisfactorily flies the aircraft in the pitch
axis, as the larger the value the less responsive the autopilot will be to vertical commands or altitude erro r. Other po ssible
causes of hunting in altitude hold are “lost motion” in the aircraft controls or too low a level of vertical activity setting.
Excessive lag in the static system itself can be caused by undersized static ports, improperly placed ports, long static lines, or
especially by attached equipment with large static reservoirs. The autopilot can be adapted to cover a wide range of static
systems, but in truly extreme cases it may be necessary to provide a separate static line for the autopilot so that other equipment
attached to the port does not degrade the autopilot’s performance.

Magnetic Calibration

The DigiFlight autopilot contains a built-in magnetometer which is used to maintain gyro centering and slaving for the built-in
Electronic DG of the autopilot in case of GPS loss. This magnetometer is calibrated at the factory in a disturbance-free
environment, but once installed in the aircraft it may be necessary to account for any magnetic disturbances in the aircraft
itself.

Once satisfactory results are obtained in flight dynamic settings, the back-up magnetometer of the autopilot should be
calibrated. For best results, this operation should be done on a day when the winds are relatively calm, so that air is still and
heading and ground track are approximately the same in all directions. The operation should be deferred until such flight
conditions exist. For this operation the autopilot will fly four legs of approximately half a minute each, first north, then east,
then south, then west. Prior to the calibration sequence, fly the aircraft to an area where this can suitably be done. Engage the
autopilot and select the altitude hold mode at an appropriate altitude. Press and hold MODE until the setup screen appears.
Press ENTER to cycle through the previously-done settings until MAG CALIBRATE? Appears on the screen. Rotate the knob
to select Y (yes) and press ENTER. The autopilot screen will announce “CALIBRATING… TURNING NORTH”. It will fly
to a ground track of 000 degrees, then say “HOLDING NORTH”. For approximately twenty seconds, the unit will obtain data
from the magnetometer for this heading. It will then announce “TURNING EAST”, then “HOLDING EAST” and so on, until
it has flown a twenty-second leg in all four directions, ending up flying towards the west. Having completed this operation, the
display will change to “CALIBRATION COMPLETE” “PRESS ENTER”. Confirm the calibration sequence by pressing
ENTER. At this point, the autopilot will revert back to its normal flight mode with a direction selector, but the upper-left
display will show MAG rather than TRK, indicating that the autopilot is in its
be confirmed in flight. Rotate the knob to select various headings and observe the flight of the autopilot in the magnetic backup
mode. If problems or inaccuracies occur with various headings, it is possible that these problems are due to excessive
turbulence or winds on this particular flight, and it may be necessary to repeat the operation at a different time. Once the
check-out of the backup mode is finished, disengage and then re-engage the autopilot to return to normal Track (TRK) mode.

magnetic backup mode. This allows the mode to

DFC Autopilot Installation Manual TruTrak Flight Systems
May 2006 Printing 10

DFC-300 systems require adjustment of the yaw damper parameters. With the autopilot disengaged, level the aircraft and hand­fly the aircraft in still air. Press MODE to engage the yaw damper (the lower-left part of the display will indicate YD ON).
Then press and hold MODE to enter the setup screen. Cycle through the settings already done until YD LEVELING and YD
ACTIVITY show on the display. Centering is adjustable from -8 to 8 and has enough authority to move the ball approximately
one and one half times the width of the ball in either direction. (Coarse adjustment was made using the potentiometer in the
yaw damper module during the earlier Initial Checkout Procedure.) The next field, YD ACTIVITY, determines how
aggressively the yaw damper responds to yaw disturbances. Yaw damper activity can range from 0 (off) to 12 (extremely
aggressive). For this purpose it is best to find light to moderate turbulence so the effects can be properly observed. Having
found suitable conditions, use the knob to gradually increase the value of YD ACTIVITY in order to obtain an appropriate
level of response to yaw disturbances. Too high a value will result in rapid oscillation, while too low a value will essentially
disable the quick response of the yaw damper to turbulence. Within the acceptable range of operation, there is still room to
account for personal preferences. So long as the yaw damper’s YD ACTIVITY value is not so high as to cause oscillation, the
response is simply set according to preference and comfort.

The normal operation of the autopilot will turn the yaw damper on any time the autopilot is engaged, and the yaw damper will
stay on after the autopilot is disengaged. During final approach and the diminishing of the airspeed below the MIN AIRSPD
setting, the yaw damper will automatically disengage. To disengage the yaw damper prior to that point, simply use the MODE
button to toggle the yaw damper off. When the autopilot is in the Off mode, the MODE button acts as a yaw damper on/off
toggle function and the display will indicate YD ON or YD OFF.

This concludes the in-flight setup of the TruTrak digital autopilot.

TruTrak Flight Systems DFC Autopilot Installation Manual
11 May 2006 Printing

D

INST

ALLATIONNOTES:
USE #20 AWG FOR POWER AND GROUND WIRES TO SERVOS

1.

(PINS 1 AND 9 ON 9-PIN CONNECTORS J201 AND J301)
AND WIRE TO AUTOPILOT MASTER AND SINGLE-POINT GROUND.
ALL OTHER WIRING #20 TO #24 AWG.

2.

INSTRUMENT LAMP DIMMER CONTROL IS OPTIONAL.
12V SYSTEMS: CONNECT J101 PIN 4 TO DIMMER CONTROL AND J101 PIN 18 TO GROUND.
28V SYSTEMS: CONNECT J101 PIN 18 TO DIMMER CONTROL ( J101 PIN 4 NO CONNECT ).

ROLL SERVO ONLY:

3.

REVERSAL OF SERVO DIRECTION CAN BE
ACCOMPLISHED IF NECESSARY BY SWAPPING
WIRES AT PINS 4 AND 5 OF THE SERVO
CONNECTOR (J201).

4. PITCH SERVO ONLY:
REVERSAL OF SERVODIRECTION CAN BE ACCOMPLISHE
AS NECESSARY BY INSTALLING OR REMOVINGA JUMPER
BETWEEN PINS 1 AND 2 OF THE 37-PIN CONNECTOR
( CUSTOMER'S J101 MATING PROGRAMMER P101 ).

PITCH SERVO

J301 9-PIN FEMALE

D-SUBMINIATURE

AIRCRAFT
ELECTRICAL
GROUND(-)

INSTRUMENT LAMP
DIMMER (See Note 2)

AUDIO ALERTER OUTPUT
EXT DG/HSI INPUT

NOTE 4

162738495

AUX RS-232

( FUTURE EXPANSION )

CONTROL WHEEL SWITCH

FROM NAV RECEIVER

CDI LEFT
CDI RIGHT
LOC MODE

FROM GLIDESLOPE RECEIVER

GS DOWN
GS UP

FROM GPS RECEIVER

PRIMARY SERIAL INPUT
ARINC-A
ARINC-B

12345678910111213141516171819

20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

PROGRAMMER MODULE

J101 37-PIN FEMALE

D-SUBMINIATURE

(View Facing Rear of unit)

NOTE

3

162738495

ROLL SERVO

J201 9-PIN FEMALE

D-SUBMINIATURE

DFC-200/250 EXTERNAL WIRING DIAGRAM

DFC Autopilot Installation Manual TruTrak Flight Systems
May 2006 Printing 12

INSTALLATION NOTES:

1.

USE #20 AWG FOR POWER AND GROUND WIRES TO SERVOS
(PINS 1 AND 9 ON 9-PIN CONNECTORS J201, J301 AND J401)
AND WIRE TO AUTOPILOT MASTER AND SINGLE-POINT GROUND.
ALL OTHER WIRING #20 TO #24 AWG.

..

2.

INSTRUMENT LAMP DIMMER CONTROL IS OPTIONAL.
12V SYSTEMS: CONNECT J101 PIN 4 TO DIMMER CONTROL AND J101 PIN 18 TO GROUND.
28V SYSTEMS: CONNECT J101 PIN 18 TO DIMMER CONTROL ( J101 PIN 4 NO CONNECT ).

3.

ROLL AND YAW DAMPER SERVOS ONLY:
REVERSAL OF SERVO DIRECTION CAN BE
ACCOMPLISHED IF NECESSARY BY SWAPPING
WIRESATPINS4AND5OFTHERESPECTIVE
SERVO CONNECTOR (J201 OR J401).

4.

PITCH SERVO ONLY :
REVERSAL OF SERVO DIRECTION CAN BE ACCOMPLISHED
AS NECESSARY BY INSTALLING OR REMOVING A JUMPER
BETWEENPINS1AND2OFTHE37-PINCONNECTOR
( CUSTOMER'S J101 MATING PROGRAMMER P101 ).

5.

YAW DAMPER UNIT MUST BE MOUNTED ON A VERTICAL
TRANSVERSE BULKHEAD. JUMPER IS INSTALLED ONLY IF
MODULE IS MOUNTED ON BULKHEAD FRONT SIDE.

PITCH SERVO

J301 9-PIN FEMALE

D-SUBMINIATURE

AIRCRAFT
ELECTRICAL
GROUND ( - )

INSTRUMENT LAMP
DIMMER (See Note 2)

AUDIO ALERTER OUTPUT
EXT DG/HSI INPUT

NOTE 3

NOTE 4

162738495

YAW DAMPER SERVO

J401 9-PIN FEMALE

D-SUBMINIATURE

CONTROL WHEEL SWITCH

AUX RS-232

( FUTURE EXPANSION )

FROM NAV RECEIVER

CDI LEFT
CDI RIGHT
LOC MODE

FROM GLIDESLOPE RECEIVER

GS DOWN
GS UP

FROM GPS RECEIVER

PRIMARY SERIAL INPUT
ARINC-A
ARINC-B

1142153164

5678910111213

17 18 19 20 21 22 23 24 25

NOTE 5

YAW DAMPER MODULE

J501 25-PIN FEMALE

D-SUBMINIATURE

PROGRAMMER MODULE

J101 37-PIN FEMALE

D-SUBMINIATURE

(View Facing Rear of unit)

DFC-300 EXTERNAL WIRING DIAGRAM

1 2 3 4 5 6 7 8 910111213141516171819

20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

162738495

NOTE

3

162738495

ROLL SERVO

J201 9-PIN FEMALE

D-SUBMINIATURE

TruTrak Flight Systems DFC Autopilot Installation Manual
13 May 2006 Printing

TruTrak Flight Systems, Inc.

1500 S. Old Missouri Rd.

Springdale AR 72764

[phone]

FAX [phone]

www.trutrakflightsystems.com