User guide

TruTrak Flight System 6 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
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 the ALT button to advance to the next setup screen.