Vertical Card compass install

Hi all, I got a Precision flat card compass to install. I am confused on whether I can install it myself. The September 2018 article on installation says I can install it and calibrate it without paying a shop. My I/A friend said he did some digging and found that a compass trained, certified repair station A/P is needed to do the calibration on a surveyed compass rose. Can someone please advise.


  • This project is very simple. I wrote an article on step by step install I think in 2018 or 2019 and you'll find it in our archives. You can also do the alignment, it's very easy. You can have your A&P sign off on your work.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.

    Need help? Let me know!

  • Scott, thanks for the reply and I agree that your article is detailed and excellent. I was surprised my I/A friend who has signed off on and overseen my other projects thought that way. The instructions for calibration are included with the unit and should be easy to perform if I can find a compass rose.

  • For any other members who may be struggling with this process as well, Scott's article can be found in the September 2018 issue of PIPERS:

    Katie Holliday-Greenley
    PIPERS magazine editor

  • edited September 2020

    Calibrating the compass on a compass rose is not as easy as it sounds. Over the years, I have had my compass calibrated many times by others, with me assisting, and by myself. A good avionics shop will do an awesome job at minimal cost.

    First, the surveyed area (compass rose) must be current! Markings laid down 20 years ago will be in error as the Earth’s magnetic pole wanders.

    Second, You have to do the calibration with the engine running!! Shutting down, hopping out, realigning the aircraft, climbing back in and starting back up is not so easy as you will be repeating this at least 4 to 8 times. You can avoid this by having a helper outside the aircraft, sighting aircraft alignment with a calibrated surveying compass but this must be done in an area free of other magnetic influence.

    Third, to create the required compass card, you will need to “jog” the airplane, engine running, around a circle, stopping every 10 degrees to record the error, using your DG as a reference that has been set to north within the past few minutes or so if it is a standard gyro.

    Once, an Air National Guard avionics tech did it for me with a “magic box.” Inside the airplane, he was able to dial in the headings he wanted and, believe it or not, the compass would turn to those headings for adjustment!! I’m still pondering that one. But usually, it is a two person job.

    A suggestion would be to have a good avionics shop or an A&P who has the experience do it, and ask to observe the process. It’s an eye opener.



  • When I got my airplane it had a vertical card already in it. After flying it a few times it seemed that I had to re-adjust the DG quite often especially after making several turns. I thought the DG was going to need to be serviced soon! Then I noticed it was more a heading specific error, DOH! Time for the compass rose!!
    My home airport has a compass rose painted in the runup area and it is usually very busy on the weekends when I am able to be there so I had been putting it off for some time. Well, last winter came a Saturday and the airport was IFR! I headed out to the airport and sure enough, I was all by myself except for a few guys working in their hangars. I spent about an hour following the instructions for the VCC until I got it about as good as I could then another trip around the Rose to record the final correction factors and it's as close to perfect as any airplane I have flown. Plus as a bonus, my DG does not need an overhaul after all!

  • Thanks for all the comments. I am told that the compass rose on our field has too many metal hangars around it and it is also outdated for accuracy. No one knows of another compass rose option in our area. I plan to have some avionics work done in the next few months and will have them swing the compass at that time. I am told that it should be done after changing equipment anyway due to changing interference. I am sure the avionics shops use a master compass rather than a rose.

  • I am surprised Scott would say you could do it and end his comments by suggesting to get your A& P to sign it off. In other words You cannot do it.

  • I have a very good relationship with my AI. He knows me and my plane. This relationship works very well for me.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.

    Need help? Let me know!

  • Caution when adjusting the PAI-700. This is a great unit but when I was selling these, I had more than one customer who got too aggressive with the adjusting process, turning the adjusting screws too far and damaging the unit. I think there is a comment in the instructions about this. FYI!

  • Good point Bob.
    Each adjustment can go 180 degrees plus or minus from their respective neutral position and no more!
    It is pointed out in the instructions!

    If you have more mag interference that can be compensated for with the internal adjustment they have external add ons to help compensate.

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