ALTRAK Altitude Hold problem

I bought this ALTRAK Altitude hold system from another member some time ago and am installing it in my RV-9A build.

During installation, I was not aware that the 470 Ohm resistor in the LED Engage wiring, was not in the wiring that was sent. As a result, when I powered up the system the first time, the LED blew out in quite dramatic fashion.

I was able to find a replacement LED and then wired in the 470 Ohm resistor.

In subsequent testing of the system now, the "ALT" button light stays on all the time.. I believe I may have damaged the light logic function in the controller. The unit does change on-off state when the button is pressed.

I have tested the altitude hold function by "tilting" the controller fore and aft, and the servo does move the elevator. It's pretty rough/raspy motion but I was advised that since it's a step function control, that's probably how the system operates. Maybe someone can comment.

I was wondering is anyone may have an ALTRAK controller unit (only, my servo is fine) that they'd be willing to sell. I'm pretty sure that the push button light shouldn't be on all the time, only when the system is engaged.

I've asked a VAF Forum Honeywell Engineer if he could supply any schematics or advice on how the repair the controller, but he wasn't sure what info he could locate and/or share. So not sure if it's repairable.

Any advice or guidance would be appreciated!

Tnx,
Andy C.

Andy,

As someone who also fried his Altrak LED/switch I can sympathize. Don't remember exactly how, but I think I had the multimeter set for amps instead of volts, or something like that. Anyway, one new switch later all was fine. That was about 8 years ago. All is well since then.

My system is a combined Digitrak (roll control, GPS steering) and Altrak (altitude hold) system. I have an A/P master switch that controls power to the entire system, both A/P controllers and the servo motors. When powered up the Digitrak flashes "---" on the display until it comes ready, then displays "OFF" until I do something further to engage it. At the same time during power up the Altrak button flashes, about 4 times.....never really counted. Once the Altrak comes ready the button is unlit, until I later engage it.

To engage the A/P system after it is powered on, I press and hold the "control wheel steering" button. The Digitrak will alternately display magnetic heading and "-F-" (assuming I have entered a flight plan in the GPS....usually have). Once the Digitrak is set, I can toggle the ALT button to engage altitude hold.

Now to your questions:

First: Is your Altrak combined with a roll control autopilot, or is it a stand alone system? Reason I ask is mine is a combined system, and there is a connection between the Digitrak and Altrak controllers......result is the Altrak will not engage until the Digitrak is engaged first. Reading the Altrak installation instructions, seems like a stand alone system ALT button should act the same as mine during power up.

Second: servo "rough/raspy" motion. Yep, that's just the way they feel and sound. It work fine when altitude hold is engaged. Assuming the airplane is reasonably trimmed, I don't think the servo hardly ever moves. If it does, it isn't more than 1 step.

Your Altrak controller mounting looks OK, like the installation instructions I have.

Sorry, I don't have a spare Altrak controller, only the one I'm flying. Controller schematics....nope, it is a black box as far as I am concerned.

Let me know if you need any other info such as installation photos, or my system schematic. Might help. Also if your system is not flying yet and you'd like to do a full up flight test, I could be persuaded to run your controller in my airplane to see if it works the same as mine. I'm not convinced yours is totally dead. PM me if you need anything.

Hey, one other thought. You didn't by chance put the diode in backwards did you? Might make it be ON after power up, instead of OFF. Should be easy to check out with a multimeter.

Steve thanks for the replies. My system is a stand alone installation.

I do not get the 3 light flashes, just as I mentioned, the light turns on and stays on when I power the system.

I appreciate the offer to try my control module, that would rule out any wiring problem I believe, although I'm using the harness that presumably worked in the sellers installation.

I really triple checked the LED installation when I replaced it, I'm sure it's installed with the correct polarity.

I still think I hurt whatever controls the light logic in the controller... I wish the previous owner had alerted me to it....

AC

KazooRV-9A said:

.... although I'm using the harness that presumably worked in the sellers installation.
AC

Click to expand...

Andy,
Maybe you've already done this, but here goes anyway. Might be worth crawling through the existing wire harness you got with the system to verify everything is wired correctly, especially the switch/LED assembly. There are three connections on the switch, but only the normally open and common ones are used. The normally closed pin does not get used.

Just a thought. Shouldn't take too long to verify the harness.