TruTrak Digiflight II Install Manual

DigiFlight II Series Autopilots

Installation Manual

8300-008 Rev D

TRUTRAK FLIGHT SYSTEMS

1500 S. Old Missouri Road

Springdale, AR 72764

Ph: 479-751-0250 Fax: [phone]

www.trutrakap.com

INSTALLATION MANUAL

For

DigiFlight II Series Autopilots

TABLE OF CONTENTS

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

Pitot / Static Connections..............................................................................................................................................2

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

DigiFlight II Series Ground Checkout..........................................................................................................................3

DigiFlight II Series First Flight ....................................................................................................................................6

GPSS / GPSV APPROACH PICTORIAL ...................................................................................................................8

Electrical Pin-out .......................................................................................................................................................... 9

DigiFlight II Wiring Diagram..................................................................................................................................... 10

DigiFlight II Series Block Diagram............................................................................................................................11

DigiFlight II Series with Pitch Trim Block Diagram..................................................................................................11

DigiFlight II Series with Yaw Damper Option Block Diagram .................................................................................12

GPS Setup Guide ........................................................................................................................................................13

Garmin 430W and 530W ......................................................................................................................................................... 15

Magnetic Considerations Supplement ........................................................................................................................ 17

Definitions ..................................................................................................................................................................19

RETURN MERCHANDISE POLICY AND PROCEDURE................................................................................ 21

Revision Date Description Page #

A 07/01/2008 Initial Release

B 05/20/2009 Removed Magnetic backup 2, 6, 8
C 06/16/2009 Update pictures added Magnetic supplement 3,4, 18
D 12/07/2009 Updated Warranty information 20

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. Some aircrafts mechanical primary control installations will not allow this to

occur and do not need the servo stops.

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 exceeds 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 NICO press 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).

TruTrak Flight System 1 DigiFlight II Series Auto Pilot Installation Manual
December 2009 8300-008 Rev D

PROGRAMMER INSTALLATION
Mounting Considerations

The DII programmer unit is designed to mount in the aircraft instrument panel within view and reach of the pilot. Maximum
recommended viewing angle should be no more than 20 deg

degrees longitudinal axis and 0 degrees lateral axis. The primary unit location should minimize pilot head movement when
transitioning between looking outside of the cockpit and viewing/operating the programmer unit. The location should be such
that the programmer unit is not blocked by the glare shield on top, or by the throttles, control yoke, etc. on the bottom. Use
aircraft installation standards for mounting and support of the programmer.

. The maximum mounting angle the DII can accommodate is 12

Wiring Considerations

Use AWG #24 or larger wire for all connections unless otherwise specified. The standard solder pin contacts supplied in the
connector kit are compatible with up to AWG #18 wire. In cases where some installations have more than one component
sharing a common circuit breaker, sizing and wire gauge is based on, length of wiring and current draw on units. In these cases,
a larger gauge wire such as AWG #20 may be needed for power connections. Do not attach any wires to the outside of the
programmer or route high current wires within six (6) inch of the programmer. Ensure that routing of the wiring is not exposed
to sources of heat, RF or EMI interference. Check that there is ample space for the cabling and mating connectors. Avoid
sharp bends in cabling and routing near aircraft control cables. Do not route the COM antenna coax near any autopilot
components.

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.

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 input to the
autopilot is the Control Wheel Switch input. This line should not be routed in parallel with transmitting antennas or other
sources of known RF interference. If necessary, it can be shielded with the shield connection to pin 13 of the autopilot
connector.

TruTrak Flight System 2 DigiFlight II Series Auto Pilot Installation Manual
December 2009 8300-008 Rev D

DigiFlight II Series Ground Checkout
Must be performed before first flight

Once wiring is completed the autopilot should be tested in the aircraft while on the
ground. The first step is to enter the setup mode on the autopilot and set all parameters to
their correct values. Apply power to the autopilot programmer.

The 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.

Many of the operations of the autopilot are initiated or confirmed by a press and release
of the knob (without rotating it). This is referred to as the ENTER operation.
Disengaging of the autopilot is done by holding the knob in for an extended period of
time. Any time there is an underlined field showing on the autopilot screen, rotating the
knob will cause the underlined active field to change.
Engage the autopilot by pressing ENTER. Then press and hold the MODE button in for
about three seconds until the first setup screen, showing LAT ACTIVITY is displayed.
Once the activity setup screen is on the display, rotate the knob as necessary to set the
lateral activity value to a value of 2 or 8 if High Torque servo. Push the ALT button to
move to the next setup screen.

The next setup screen is LAT TORQUE. Insure that the value displayed is somewhere
close to the maximum value of 12. Once that is done, press the ALT button to advance
to the next setup screen.

Rotating the knob, select a value for BAUD which is compatible with the GPS receiver
connected to pin 17. The value of 9600 is the most commonly used rate. Once baud rate
selection is done, press the ALT button to advance to the next setup screen.

The next setup screen is the BANK ANGLE screen. Select an initial setting of MED.
Once this is done, press the ALT button to advance to the next setup screen.

The next setup screen is the MICRO ACTIVITY screen. This setting should be set
initially to a setting of 0. Once the micro activity is set to 0, press the ALT button to
advance to the final lateral setup screen.

The next setup screen is the GPS GAIN screen. This setup is used to increase the bank
angle that the autopilot will fly in GPS Steering mode. Increase the value to increase the
allowable bank angle. Press the ALT button to advance to the next setup screen.

The next setup screen is the YAW DAMPER screen. Set to Y if a yaw damper is
installed, otherwise, select N and Press the ALT button to advance to the next setup
screen.

Press the knob to exit, and return to the main flight screen.

Then press and hold
screen, showing PITCH AXIS is displayed. (NOT USED IN DII) The default of ON
will always be selected after a power cycle. To turn the pitch axis off, select OFF, and
click the knob to exit. To advance to the next setup screen, press the ALT button to
advance to the next setup screen.

TruTrak Flight System 3 DigiFlight II Series Auto Pilot Installation Manual
December 2009 8300-008 Rev D

the ALT button in for about three seconds until the first setup

The VRT ACTIVITY is displayed. Rotate the knob as necessary to set the vertical activity
value to a value of 2. Push the ALT button to move to the next setup screen.

The next setup screen is VRT TORQUE. Insure that the value displayed is set to the
maximum value of 12. Once that is done, press the ALT button to advance to the next setup
screen.

The next screen allows a MIN AIRSPD to be set. The minimum airspeed value is the
slowest indicated airspeed the autopilot will fly, independent of what it is commanded to do.
Rotate the knob to adjust this airspeed to a value safely above a stall but lower than normal
approach or climb out speeds. Select the desired value, and then press the ALT button to
advance to the next setup screen.

The next screen allows a MAX AIRSPD to be set. The maximum airspeed value is the
fastest indicated airspeed the autopilot will fly, independent of what it is commanded to do.
Rotate the knob to adjust this airspeed to a value safely below the red line airspeed, but
above the normal cruise speed. Select the desired value, and then press the ALT button to
advance to the next setup screen.
The next screen allows an adjustment for the amount of delay, or “lag” in the aircraft static
system. Start with a value of zero (0) until the first flight test of the autopilot. Having
verified this selection and set it to zero, press the ALT button to advance to the next setup
screen.

The next setup screen is MICRO ACTIVITY for the pitch axis, as with the lateral micro
activity this setting should be set initially to a setting of 0. Once the micro activity is set to
0, press the ALT button to advance to the final setup screen.

The final setup screen is the HALF-STEP setup screen. This screen is to change the
resolution of the pitch servo. Initially this setting should be set to N (No). Once this is
done, press the knob to exit and return to the main flight screen.

The next step in the check-out procedure is to verify that the servos run, and in the correct direction. At this point, the display
differs depending on autopilot model.

DigiFlight II DigiFlight IIVS

The screen will show that the
altitude portion of the
autopilot is still disengaged.
Press the ALT button to
engage the altitude hold
function.

Ø

In both cases, the selected heading will be underlined on the bottom left of the display, and the autopilot will be in the altitude
hold mode. Both the pitch and roll servos should stop, or move only very slowly.

The lower right of the
screen will show the
present value of s

ertical speed, (SVS)

v
which will be
approximately zero. If it
is not zero, press the
ALT button to move the
cursor to the SVS field,
and then use the knob to
set the value to 0. The
display will change to
show altitude hold
mode.

elected

Ø

TruTrak Flight System 4 DigiFlight II Series Auto Pilot Installation Manual
December 2009 8300-008 Rev D

DigiFlight II DigiFlight IIVS

The autopilot programmer unit needs to be out of the panel, so
that it can be gently
and nose-down flight. If the autopilot is tipped in a nose-down
maneuver, the control should move in such a way as to
attempt to move the control yoke or stick back, in an effort to
raise the nose of the aircraft. Similarly, a nose-up tipping of
the autopilot should push the yoke or stick forward in an
effort to lower the nose of the aircraft.

Using the ALT button will toggle the altitude hold on and off.
When the altitude hold is off, the pitch servo is electrically
disconnected and will not move in response to disturbances.

If the direction of movement of the pitch servo is incorrect, install or remove the jumper between pins 1 and 2 of the autopilot
connector and repeat the setup to verify correct results up to this point.

The roll servo should also be responding at this time, moving the controls in such a way as to turn the aircraft from the current
heading (shown as a 3-digit number after the word HDG in the upper-left of the display) to the selected
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 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 HDG, the roll servo should stop or run only very
slowly. If the knob is rotated clockwise, to a selected heading right
move in such a way as to roll the aircraft to the right. Conversely, a selected heading to the left
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 20 and 21 on the main connector) must be reversed to achieve the correct response. If a
servo does 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.

tipped fore-and aft to simulate nose-up

With the cursor in the SVS field, rotate the knob clockwise
until several hundred feet per minute is showing in the 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, rotating the knob counter-clockwise to select a
negative vertical speed (descent) the pitch servo should be
moving the controls in such a way as to lower the nose of the
aircraft.

Using MODE and ALT buttons will toggle the cursor back
and forth between the SVS field and the SEL (selected
heading) field. The cursor will revert back to the selected
heading field after a few seconds of inactivity.

heading (shown as a 3-

of the current heading, the control yoke or stick should

of the current heading will

At this time, check that each 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 each 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 or push-pull 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.

Summary:

ENGAGE AUTOPILOT WITH FLIGHT CONTROL CENTERED,
ROTATE KNOB CLOCKWISE. FLIGHT CONTROL MUST MOVE
TOWARD RIGHT. ROTATE KNOB COUNTER CLOCKWISE,
FLIGHT CONTROL MUST MOVE BACK TOWARD LEFT.

DII VS: TAP “ALT” BUTTON TO MOVE CURSER TO “ALT” SIDE.
ROTATE KNOB CLOCKWISE. FLIGHT CONTROL MUST MOVE
TOWARD BACK. ROTATE KNOB COUNTER CLOCKWISE,
FLIGHT CONTROL MUST MOVE TOWARD FRONT.

TruTrak Flight System 5 DigiFlight II Series Auto Pilot Installation Manual
December 2009 8300-008 Rev D

DII ONLY: TAP “ALT” BUTTON TO ENGAGE ALT HOLD. MOVE
TAIL UP AT LEAST A FOOT AND ELEVATOR MUST MOVE UP
AT SAME TIME. MOVE TAIL DOWN AT LEAST A FOOT AND
ELEVATOR MUST MOVE DOWN AT SAME TIME.

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, Apply power to the GPS panel-mount receiver 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 HDG followed by the present approximate magnetic
heading, with a flashing “*” character beneath HDG. If no “*” is displayed even 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 17 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

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

DigiFlight II Series First Flight

The first flight should be done after having completed all the setup and testing on the ground. The calibration of the magnetic
backup system does not affect the first flight with GPS input! 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 beneath the word HDG; once taxi speed exceeds 10 knots, the display will change from
HDG 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 24. 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.

On the first flight, manually fly the aircraft to a suitable area for testing. Press the knob to engage the autopilot. Observe that
the SEL field in the lower-left now shows the captured present ground track (shown after TRK in the upper-left of the display).

DigiFlight II DigiFlight IIVS

Press ALT to engage Altitude Hold The SVS field will be showing the approximate rate of

climb or descent in feet per minute.
Press ALT to move the cursor to the SVS field,
select the value 0 ( which will engage altitude hold).

Press and hold MODE button 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
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.

turbulence) so as to make it easy to observe the response of the

Once the desired LAT ACTIVITY level is established, press the ALT button to advance to the next setup screen.

TruTrak Flight System 6 DigiFlight II Series Auto Pilot Installation Manual
December 2009 8300-008 Rev D