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Thread: AHRS Periodically goes crazy

  1. #1

    AHRS Periodically goes crazy

    The AHRS connected to our AF-5500 periodically has the horizon at a severe tilt and will sometimes spin as we are flying straight and level. Then it comes back to normal. What should we check into?

  2. #2
    Sounds like a magnetometer going out. Are there any associated error messages on the EFIS? What AHRS unit do you have? Post a picture of your SET --> CAL --> Admin Settings page if you don't know.

  3. #3
    Name:  AHRS_2.jpg
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Size:  14.7 KB Here is a photo of the AHRS unit. There were no error messages. We don't think it is the magnetometer since our compass headings are correct. We had to move the AHRS away from the original mount on the airplane behind the pilot seat on the airframe because it was right next to the magnets of the landing gear motor and the compass headings were off by up to 20 degrees in random directions.

    We ended moving it as far back as possible onto the plastic gas tank (no metal, no ferrous) but now we get the pitch/roll going crazy. We are wondering if we lost the grounding we had when it was bolted to the chassis. Right now the only ground it has is via the multipin connector.

    We are going to try to add a beefy ground strap from where is was mounted to behind the pilot to its current location.
    Last edited by Harold Roberts; 09-16-2021 at 02:16 PM.

  4. #4
    Advanced Flight Systems Shawn McGinnis's Avatar
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    Grounding is probably not the issue. I would suspect vibration would be the bigger factor at that location. Can you include a picture of the mount?
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

  5. #5
    Quote Originally Posted by Shawn McGinnis View Post
    Grounding is probably not the issue. I would suspect vibration would be the bigger factor at that location. Can you include a picture of the mount?
    I will when we go to airport next. Vibration is not something we considered. Unfortunately the most solid place to mount the AHRS is where it used to be, next to the gear motor. I just conferred with my partner and we think we could create a more solid mount off the spar of the plane rather than the plastic gas tank.
    Last edited by Harold Roberts; 09-17-2021 at 01:11 PM.

  6. #6
    Shawn, we moved the AHRS to the spar and it seems to have solved the problem. You can see the adjustable leveler we used since we found that when we did calibration pitch and roll adjustments in the settings menu that they would be 'forgotten' over time. Therefore we are simply leveling the AHRS to perfection. Name:  AHRS_Spar_Mount.jpg
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Size:  20.4 KB

  7. #7
    Advanced Flight Systems Shawn McGinnis's Avatar
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    Looks like it should work and as long as the MAG CAL runs you should be good.

    Quote Originally Posted by Harold Roberts View Post
    ...since we found that when we did calibration pitch and roll adjustments in the settings menu that they would be 'forgotten' over time...
    You might double check your software version. That sounds like a bug of the past.
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

  8. #8
    Quote Originally Posted by Shawn McGinnis View Post
    Looks like it should work and as long as the MAG CAL runs you should be good.

    "You can see the adjustable leveler we used since we found that when we did calibration pitch and roll adjustments in the settings menu that they would be 'forgotten' over time. Therefore we are simply leveling the AHRS to perfection."
    You might double check your software version. That sounds like a bug of the past.
    We have software V16.6.2, installed Feb 2021 which had the bug fix you mention. We found it reduced the number of times we had to reset the pitch settings but did not eliminate the 'forgetfulness'. So we used this infinitely adjustable nut/screw mount instead. This also allowed us to follow the manual's suggestion to 'mount closely aligned to the aircraft.

    Question: The install manual says to use aluminum or brass screws, we used stainless steel, I assume that is OK as stainless should be non-magnetic. Even if it isn't, will the screws really make a difference?

    Finally: You might get a kick out of where the manufacturer mounted the AHRS, when your install manual says at least 2' away from 'landing gear or motor'. As you can see it is right next to the landing gear motor!
    Name:  mount location.jpg
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  9. #9
    Shawn, is there a manual for the AHRS P/N: 72010 available to download?

  10. #10
    Advanced Flight Systems Shawn McGinnis's Avatar
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    Quote Originally Posted by Harold Roberts View Post
    ..I assume that is OK as stainless should be non-magnetic. Even if it isn't, will the screws really make a difference?
    Stainless should be fine, brass aluminum is one way to ensure non-magmatic. As long as the MAG CAL is successful anything is ok.

    Quote Originally Posted by Harold Roberts View Post
    Shawn, is there a manual for the AHRS P/N: 72010 available to download?
    https://www.advancedflightsystems.co...al%20V15.1.pdf Pages 29-31
    Shawn McGinnis

    Advanced Flight Systems
    support@advanced-flight-systems.com

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