TruTrak Digitrak Install and User Guide - Manual (Page 10)

TruTrak flight systems DigiTrak Installation Manual
October 2009 8 8300-009 Rev B
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. Lost motion in the linkage can best be observed by temporarily clamping the servo arm and gently moving
an aileron back and forth, while observing how much aileron movement takes place against the clamped servo.
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 receiver and the autopilot. After the GPS receiver
acquires its position, the autopilot display will change from “ – – – ” to “OFF” indicating that valid position data is available.
If the word “OFF” is not 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,
ƒ Pin 3 on the connector is not wired to a source of RS-232 serial data. Check wiring.
ƒ The GPS receiver’s baud rate disagrees with that selected within the autopilot. Match up Baud rates.
ƒ The GPS receiver’s serial output port has not been properly configured to provide RS 232 output. See GPS documents for
proper configuration.
Summary:
ENGAGE AUTOPILOT WITH FLIGHT CONTROL CENTERED, TAP
RIGHT BUTTON SEVERAL TIMES. FLIGHT CONTROL MUST
MOVE TOWARD RIGHT. TAP LEFT BUTTON SEVERAL TIMES,
FLIGHT CONTROL MUST MOVE BACK TOWARD LEFT.
DigiTrak First Flight
THE FIRST FLIGHT SHOULD BE DONE AFTER HAVING COMPLETED 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 “OFF” when it is disengaged and valid GPS data is present.
If this does not occur, it is best to diagnose and fix the problem prior to first flight of the autopilot.
The activity adjustment (setup screen 1) determines how briskly the autopilot responds to roll disturbances. The setting can be
adjusted, in flight, over a wide range; thus the autopilot can be tailored to adapt to any aircraft installation.
The activity adjustment 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 (0) 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. Engage the autopilot by pressing . Observe that
the display now shows the captured GPS ground track as the selected direction of flight.
Press and hold the and buttons simultaneously until the first setup screen is shown on the display. The digit “1”
will be flashing, followed by the activity value that was set earlier during pre-flight setup. Use to select the value zero
(0), and observe the resulting control movement. Using , 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 (rapidly move
the stick back and forth)and over-active. Back the setting down using
until the autopilot is responsive but not over-
active. It is best if these adjustments are made in conditions of light to 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 activity level is established, press to store the value and move to the second setup screen.