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Thread: TruTrack autopilot

  1. #11
    Senior Member randylervold's Avatar
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    Default Re: TruTrack autopilot

    I just test flew the 2nd customer install we've done, #129, this morning. We had smooth morning air and so I was able to sense any anomaly. It flew absolutely flawlessly. It held altitude to within 10', in TRK mode it flew dead straight with no percieveable weaving, tracked to a GPS waypoint correctly, and performed commanded climbs and descents as it should with no scalloping. There was no "wallowing" whatsoever. There are user settings for "MIN A/S" and "MAX A/S". I recommend you set the MIN AS at 85 mph and the max at around 125.

    Not just my word, Pete Dougherty, the technician that does the installs, was riding pax and witnessed the entire test. I'd say any bugs are worked out. ;-)
    Randy Lervold

  2. #12
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    Default Re: TruTrack autopilot

    Randy
    Thanks for the report on the #3 TruTrack installation.
    I am sure mine will work as well with the new controller.

    Question ---Why do you recomend such a high minimun airspeed?
    85 mph seems very close to normal cruse and does not allow much room for climbs with the autopilot on.
    Normal long range cruse settings (low power) at altitude may well be below 85 mph indicated making the autopilot unusable when needed most.
    I would think that at least as low as Vy would be better or maybe Vx?
    Is there some aircraft aerodynamic reason or some problem with the autopilot response at low airspeeds?
    Just trying to get an engineering sense of the reasons for your recomending 85 mph.
    125 mph sounds good for Vmax.
    I am going to install my new controller today and hope to get in a test flight.
    I'll let you know how it works.
    Bill
    Last edited by seastar; 06-04-2010 at 05:53 AM.

  3. #13
    Senior Member randylervold's Avatar
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    Default Re: TruTrack autopilot

    Quote Originally Posted by seastar View Post
    Randy
    Question ---Why do you recomend such a high minimun airspeed?
    85 mph seems very close to normal cruse and does not allow much room for climbs with the autopilot on.
    Normal long range cruse settings (low power) at altitude may well be below 85 mph indicated making the autopilot unusable when needed most.
    I would think that at least as low as Vy would be better or maybe Vx?
    Is there some aircraft aerodynamic reason or some problem with the autopilot response at low airspeeds?
    Just trying to get an engineering sense of the reasons for your recomending 85 mph.
    125 mph sounds good for Vmax.
    I am going to install my new controller today and hope to get in a test flight.
    I'll let you know how it works.
    Bill
    My 85 mph LOW AS recommendation has no engineering basis, just trying to make the autopilot's assignment achievable. When the airplane gets slow it is harder for the AP to fly it, not as much response available due to the low AS, and it takes longer for corrections which the software might struggle with. I'm sure it could fly it at 75 mph no problem in smooth air, in turbulence however it might be a bit of a challenge. It's easy to change the setting so go up and try it at various slower speeds in 5 mph increments and let us know how it does.
    My approach is to start with a speed envelope that we know the AP can handle, then incrementally expand it so we arrive at a reasonable range that works.
    Randy Lervold

  4. #14
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    Default Re: TruTrack autopilot

    I installed a new TruTrack autopilot controller yesterday and had my first test flight today.
    This controller works much much better.
    I still have a small "wallow" but only about 10 degree banks at a very slow rate rather than the violent 30/40 degree banks of the earlier unit.
    TruTrack has suggested a new setting that they think will take care of the remaining problem.
    Additionally, this unit holds altitude very well while the first unit did not.
    In light turbulance the altitude varied by only 10-20 feet today with the new controller.
    I think the problem is close to being solved.
    This is the kind of bank angle I was getting with the autopilot on.
    Carbon Cub 010.jpg
    Last edited by seastar; 06-08-2010 at 09:15 AM.

  5. #15
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    Default Re: TruTrack autopilot

    My second TruTrack autopilot started acting like the first one - severe banks left and right - a wallow.
    TruTrack sent me a third unit and I now, finally, have an autopilot thazt works.
    At least part way.
    As of yet, I can not get the autopilot to accept a flight plat and follow it.- It may be my fault.
    Bill

  6. #16
    Senior Member randylervold's Avatar
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    Default Re: TruTrack autopilot

    Quote Originally Posted by seastar View Post
    As of yet, I can not get the autopilot to accept a flight plat and follow it.- It may be my fault.
    Bill
    Once the AP is engaged, and with a waypoint or flight plan in the GPS, push the mode button and it will change from "hdg" mode to "gps" mode and track the current waypoint. The GPS is sending NMEA data to the AP so when in GPS mode it really has no choice but to follow it.
    Randy Lervold

  7. #17
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    Default Re: TruTrack autopilot

    Randy
    So far, that does not work for my unit(s).
    It is not quite that simple.
    Not all GPS's send all of the NMEA string and that may be the problem.
    I'm sure it will work somehow. I just need some time to figure it out.
    The autopilot is working very well in heading and altitude hold.
    Bill

    PS
    Back in the early 80's I was on the committee that developed the standard for the National Marine Electronics Association.
    If anyone is interested in a good, simple writeup of how it works then look at this.
    http://www.gpsinformation.org/dale/nmea.htm#nmea

  8. #18
    Administrator Pete D's Avatar
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    Default Re: TruTrack autopilot

    The new control heads I have gotten and installed here at the factory I have had to change the baud rate setting from 9600 to 4800. It sounds like you are pretty familiar with this type of thing but you might double check that...its usually those simple things that'll get ya!

    Pete D.

  9. #19
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    Default Re: TruTrack autopilot

    Pete
    You are correct.
    TruTrack shipped both replacement units set to 9600 baud.
    That's one of the first things I checked and changed.

    Are you still setting the low airspeed to 85 MPH?
    The autopilot works fine much lower than that.
    Try it on your next installation at 60 MPH.

    When I get a chance I'll let you know what I do to fix my "follow a flight plan" problem.
    Bill
    Last edited by seastar; 07-01-2010 at 12:51 PM.

  10. #20
    Administrator Pete D's Avatar
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    Default Re: TruTrack autopilot

    Yes, we currently are setting the low speed at 85, though I think maybe 70 might be a better number.

    I would be interested in hearing what it is that you find to get it working again, as we had the original unit driving the plane to a way point when it was here, sure seems that it should work with multiple way points assembled into a flight plan.

    Pete D.

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