TruTrak install in C177B Cardinal

Discussion in 'Avionics and Upgrades' started by Dbarbee, Jan 3, 2018.

  1. Dbarbee

    Dbarbee Pre-Flight

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    The avionics shop wrapped up the installation of the TruTrak Vizion autopilot in my C177B Cardinal last weekend and I braved the cold to go try it out on New Years Day.

    Installation:
    The install took about 2 weeks but that included the shop taking a few days off around Christmas, a couple of unexpected events that took them away from it, connecting my 430 gps output to my EDM830, and some rearranging of my circuit breakers. Overall the progress was steady and uneventful. The installer commented that the illustrations in the manual for the roll servo were a little hard to match up to what they could see through the inspection covers but they eventually concluded that it could only go one way. The roll servo pushrod was missing from the kit but TruTrack sent one promptly and it didn't slow the progress. The shop originally estimated "around $2,000" for the install but I haven't gotten the final bill yet. I expect it to be a little higher but not too much. With the cost of the TruTrak ($5,000), STC ($140 including $40 EAA membership), and installation (~$2,000) the total cost should be under $7,500.

    Test Flight:
    Track Select Mode (TRK): Roll control was very firm and responsive and rolled out right on the selected track and held it very well.

    GPS Steering Mode (GPSS): Followed a flight plan and a GPS approach from the 430w flawlessly, including 90 degree turns, and kept the CDI dead center. Turn anticipation, procedure turns, hold entries, and holds all worked perfectly.

    Vertical Speed Mode (SVS)
    : Vertical speed control was about what I expected for an autopilot without auto electric pitch trim. There seemed to be a delay between the time I put in a new VS command and the time that the AP responded and the pitch control seemed mushy. Occasionally when asking for a climb or descent, the trim indicator would initially ask for pitch trim in the opposite direction. It also didn't seem to be able to nail the VS on the VSI as well as the lateral modes did. When the AP asks for a trim adjustment it's difficult to tell if it needs a little or a lot. I expect this to get better as I learn to use the AP and learn how it responds.

    Altitude Hold Mode (ALT HOLD)
    : Worked reasonably well with minimal deviations, even in light turbulence. The up/down pitch trim indicators came on a lot in the light turbulence, which I expected since the Cardinal can take quite a bit of pitch pressure to hold the nose up/down during down/up drafts.

    Vertical Approach Mode (GPSV): The vertical approach mode didn't work. I set up for an LPV approach on the 430w with the AP in GPSS Mode and ALT HOLD. I never saw GS ARM or GS CPLD on the display and the AP stayed in ALT HOLD mode as the airplane passed through the glideslope. I tried it a second time with the same results. (I didn’t try it in zero vertical speed mode but suspect the results would be the same) After reviewing the setup procedure I verified the 430w ARINC 429 configuration and everything looked right. Hopefully this will turn out to be just a configuration setting somewhere in the 430w or the Vizion.

    Any suggestions on things I can check?

    Missed Approach Mode: supposed to command a climb at 500 fpm on the current track when activated during an LPV approach. I was not able to test this mode since the AP would not enter approach mode.

    Control Wheel Steering Mode (CWS): I tested the control wheel steering from TRK mode by holding the CWS button on the yoke and changing the heading and releasing the button. The AP locked onto the new track as expected. (I don’t anticipate using the feature very much)

    Emergency Level Mode (AP LVL): I put the airplane into a nose high bank and pushed the AP LVL button. The roll servo firmly engaged and gently leveled the wings. The pitch servo engaged but the AP was much slower to bring the nose down than it was to level the wings. I repeated this with a nose low bank with the same results. Even though the pitch seemed a little sluggish, it did stabilize the airplane in straight and level flight.

    Automatic Envelope Protection Mode (AEP): Over-bank protection kicked in around 40 degrees of bank and firmly nudged the yoke back below 40 degrees. I tried the Minimum Speed Protection by slowing to stall speed. I couldn't get a full stall break so the AP must have been trying to lower the nose but it didn't have the same positive feel that the bank protection did. I didn't want to fly the airplane close to VNE so I didn't try the Maximum Speed Protection.

    Gyro Bank Mode (BANK): I haven’t tested the gyro bank mode yet which is basically roll mode if the AP loses GPS input.

    Summary:
    Overall I'm very happy with the TruTrak's lateral control (TRK & GPSS) which is primarily what I wanted. Without automatic electric pitch trim I think the VS and Altitude Hold are working about as well as they can, especially considering the high pitch force needed in the Cardinal sometimes during turbulence. Don't get me wrong, the vertical modes did OK and will probably perform better once I get more familiar with using them, they just didn't feel as firm and positive as the lateral modes.

    By the end of the 2 hour flight I was getting the hang of the buttonology and after a few more flights I'm sure I'll have it down. One issue I discovered was the location of the control unit in the old ADF indicator hole right above the flap handle. Several times I inadvertently put in 10 degrees of flaps while trying to adjust the autopilot. I'll probably swap places with the intercom during my next upgrade.

    The TruTrak Vizion was a good fit for my needs, expectations, budget, and mission. I'm confident the GPSV issue will be resolved eventually so I'm not too concerned about that. I'd highly recommend it to someone looking for a low budget AP with lots of features but you've got to do your homework and understand it's limitations.
     
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  2. Dbarbee

    Dbarbee Pre-Flight

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    Update if anyone is interested...

    The AIRINC 429 data out configuration in the 430W was set to "AIRINC 429" instead of "GAMA 429". Made the change and tried another approach and it followed the LPV glideslope perfectly with the glideslope and localizer centered all the way to DA. The Missed Approach mode worked exactly as advertised too; engaged at DA, AP went to 500 fpm climb on current track, I added power, and away we went. Out of curiosity, I tried it again on a non-LPV RNAV approach (LNAV+V) to see if it would follow the advisory glideslope. I've heard of other experimental autopilots that would follow the advisory glideslope but this one does not.

    The vertical modes worked much better in the smoother air last night. I think it also helped that I'm getting a better feel for adding/removing power to help the autopilot climb/descend without needing a lot of trim adjustments. During the LPV descent I learned that I can just leave the pitch trim alone and reduce power, like I would when hand flying, then just make small power adjustments when the autopilot asks for up or down trim. (Up trim = add power, down trim = reduce power)

    Overall I couldn't be happier and it's performing up to my expectations.
     
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  3. Ravioli

    Ravioli En-Route PoA Supporter

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  4. Dbarbee

    Dbarbee Pre-Flight

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    Here ya go...
    Installation Kit: Installation Kit.JPG
    Pitch Bracket and rod: Pitch Bracket & Rod.jpg
    Pitch Bracket: Pitch Bracket.jpg
    Pitch Servo and rod: Pitch Servo & Rod.jpg
    Roll Bellcrank and rod: Roll Bellcrank & Rod.jpg
    Roll Servo and rod: Roll Servo & Rod.jpg
    Panel Center Stack: Center Stack.jpg
    Full Panel: Full Panel (After).jpg
    Autopilot Control Unit: Intercom & Autopilot.jpg
     
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  5. Ravioli

    Ravioli En-Route PoA Supporter

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    BTDT. That big ole paddle drops to 10 whenever I reach over to touch the STEC. Soon it will be second nature to double check it.
     
  6. Ravioli

    Ravioli En-Route PoA Supporter

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    Older pic of ours, but you see what I mean... the STEC is directly above the Flap switch.

    This old pic doesn't even have the 430 and GTX327. Oh well, fresh pics after the fresh checks get cut. :)

    Cardinal panel.jpg
     
  7. idahoflier

    idahoflier Pre-Flight

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    Thanks for the post! I was curious about TruTrak...
     
  8. gwav8or

    gwav8or Filing Flight Plan

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    And a wonderful flight it was, Dbarbee! :)
     
  9. bnt83

    bnt83 Final Approach

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    This autopilot is a great option if you (owner) can use your mechanical knowledge and swing it as an owner assisted project. Hopefully your mechanic(s) is willing to help.
     
  10. Dbarbee

    Dbarbee Pre-Flight

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    Indeed it was, and good company! :)
     
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  11. Dbarbee

    Dbarbee Pre-Flight

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    Very true and I seriously considered attempting the install myself with A&P supervision, and the shop probably would have let me help. The installation looked to be fairly straightforward and the kit came with everything needed (including hardware) with the exception of a breaker, master switch, yoke switch, & optional audible alarm.

    In the end though with work, cold weather, etc., I decided my airplane probably would have been down for a lot longer than two weeks if I’d tried to do it myself. The shop was completely OK with me stopping by every day to see the progress and took the time to and explain the process.
     
  12. wayne

    wayne Line Up and Wait

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    Love the write-ups. Thanks!

    I was reading about this AP just last night. I don't see anything about it doing LOC/ILS. Does it do that, or just GPS & heading bug?
     
  13. Dbarbee

    Dbarbee Pre-Flight

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    It’s a strictly GPS based autopilot so it won’t follow VOR, LOC/ILS, or a heading bug. It follows only a selected GPS ground track, GPS NAV from a portable GPS, or GPS steering from a panel mounted IFR GPS (and GPS vertical steering for LPV approaches if it’s a WAAS IFR GPS)

    As long as you monitor the approach on a second VOR, I see no reason you can’t leave the GPS in GPS mode during an approach, allowing the GPS to continue providing GPS Steering to the TruTrak.

    Setting the desired track to give a specific heading for a vector shouldn’t be a problem either.
     
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  14. wayne

    wayne Line Up and Wait

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    Ouch. I get a lot of "heading xxx" in IFR flight. Oh, I see, it will do that sort of in Track mode, but it's not following your heading bug. If it will do that then it's fine. The bulk of my flying is GPS flight plan, which often turns into "direct destination".

    Hand flying the LOC/ILS is not a big deal, a bummer, but not a big deal. I'd love to have that like I do with most autopilots, but I can do it by hand.
     
  15. Skyrys62

    Skyrys62 Cleared for Takeoff

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    Thanks for sharing and the great write-up. :thumbsup:
     
  16. Radar Contact

    Radar Contact Line Up and Wait

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    Most airports I've seen with an ILS also have an LPV to the same runway. Even if cleared for the ILS you could have that on the backup and let the autopilot fly the LPV with the same outcome.
     
  17. Baron62

    Baron62 Pre-Flight

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    Nice detailed report! Thank you so much. Enjoy the new automation. :)