TruTrak problem

Hi All,

I have TruTrak Autopilot Vision 380 bought new around 5 years ago. The set is installed on RV7A and worked perfectly first 2 years after installation.

Approximately 1 year ago the roll servo stopped working properly. I supposed the problem was in servo and I bought a new one and replaced the original one.
Unfortunately it didn’t help and the problem is the as described below.

1. All altitude functions of AP work properly. Also roll servo works good on ground - the result of ground test described in the manual is OK.
2. In the air the roll servo works in the way like it would be “to weak” to do it's job.
3. Usually the initiation of turn (new heading) is done properly but due to “weak” signal or torque servo cannot stop the turn in the indicated hedging and the aircraft continues it.
4. If I keep the steering wheel I can feel soft movements but not strong enough to stop the initiated turn or keep requested heading.
5. In case of direct flight - is continued till the aircraft is moved by stronger turbulence.

Could you please help me to identify the problem? Thank you.
Witold

The first thing I'd check is the torque setting for the roll servo. Try increasing the torque if that doesn't make a difference you'd want to check the wire from the auto pilot to the servo that controls the torque, if that wire isn't connected you won't have enough torque. You should be able to find the pin out for your auto pilot online, that will tell you which wire controls the torque.

Contact Andrew Barker at Honeywell (Bendix King). He used to own TruTrac. I’ve found him quite helpful with this type of question.

His email address is: [email protected]

I suspect you have sheared the drive pin on the servo. Take off the pivot arm from the servo to see. It will have just enough friction to act like you describe. I might take the whole servo out to check it completely. If it is sheared, then find out why. Check aileron stop to stop relative to the swing range of the servo.

Then, email Andrew with more information for help.

Many thanks to all of you.

Drive pin is Ok. Checked it in the first step. I will check all cables and connections. If this is not the reason will contact Andrew.

thanks for emailing me directly, sometimes I'm a little slow to check in here!

First thing is always verify the wiring / torque output to the servo.

Pin 6 at the servo should have about 5 volts when the AP is engaged.

If the servo has a good torque on the ground, but not in flight, verify the ground / power connections. I have seen very strange things happen with intermittent connections to ground!

Many thanks for your support. The problem has been solved. I reworked the connector before the servo and all is good. Very likely pin 6 was soft and the connection was broken.
The scale of knowledge on this form is exceptional for me. I have solved a lot of problems thanks advises I got here. At least one problem which could be fatal in consequences.
Thank you.
Witold