Performance of Digitrak Autopilot by TruTrak

The Digitrak autopilot by TruTrak keeps the plane level and on the selected true course. We have used that autopilot for several months and are impressed by its performance.

Two situations have come up where the autopilot took a strange action. In both cases, we had caused the problem. Below, we describe the two problems and appropriate remedial action.

Case 1

The autopilot is engaged in flight, holding a specified true course. My passenger asks for something in the baggage compartment. Turning around, I grab the item and give it to the passenger.

He suddenly says, “Look, we are turning.” Indeed, we are in a gentle left turn. I disengage the autopilot and go back to the original course.

Engaging the autopilot again, it immediately begins a left turn again. Once more, I disengage the autopilot. Something must be wrong with the autopilot, right?

Just then I look down and see that the ball is out of center. Apparently, when I turned around to grab the item in the baggage compartment, I inadvertently pushed the left rudder pedal, causing uncoordinated flight.

I center the ball with the rudder and engage the autopilot. Presto, it works perfectly again.

Case 2

Taking off after a refueling stop, I engage the autopilot. It immediately goes into a gentle turn. I disengage, then try once more. Again, the plane goes into a turn.

Then I remember that, upon starting the engine, I had to roll forward and turn the plane so that the propeller would not blast air into the adjacent parking lot. As a result, the plane was rolling forward in a turn when the autopilot was initialized.

Guessing that the turn on the ground during initialization is causing the problem, I turn off the autopilot, fly the plane straight and level as smoothly as possible, and turn on the autopilot. Within a few seconds it is initialized.

From then on, the autopilot performs perfectly. 

Conclusions
 
  • In flight with the autopilot engaged, make sure that the ball is not pushed out of center by inadvertent rudder action.
  • Initialization of the Digitrak autopilot on the ground requires that the plane is not in motion. If that is not possible, or when the plane is in the air, a straight ahead motion must be maintained during the initialization phase.

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