stec autopilot question

Discussion in 'Avionics and Upgrades' started by DKirkpatrick, Feb 1, 2021.

  1. DKirkpatrick

    DKirkpatrick Pre-takeoff checklist

    Joined:
    May 18, 2011
    Messages:
    191
    Display Name:

    Display name:
    DKirkpatrick
    Hello. Looking at a plane advertised as having an S-tec20 with altitude hold. Does that mean it's an S-tec 30 now? ... so it's now a two axis autopilot? Will this autopilot have GPSS capability?
    input appreciated.
     
  2. Ryan Klems

    Ryan Klems Pre-takeoff checklist

    Joined:
    May 21, 2018
    Messages:
    341
    Location:
    Tucson, AZ
    Display Name:

    Display name:
    Rowat
    It could just have an altitude hold add on. As far as GPSS, unless they have G5s, an ST-901 or GDC 31 or some sort of system providing the GPSS roll steering emulation on the heading signal, it definitely doesn't have GPSS built-in. Do you have a link to the listing or a picture of the panel?
     
  3. DKirkpatrick

    DKirkpatrick Pre-takeoff checklist

    Joined:
    May 18, 2011
    Messages:
    191
    Display Name:

    Display name:
    DKirkpatrick
    i have a super low res image — only shows the STEC20 control turn/bank in the panel, and I can't make out a push button for altitude hold... EXCEPT that it has a thumb connect/disconnect for altitude on the yoke.
    thanks Ryan
     
  4. Hang 4

    Hang 4 Cleared for Takeoff

    Joined:
    Aug 18, 2017
    Messages:
    1,103
    Display Name:

    Display name:
    Hang 4
    I have an STEC 20 that was converted to a 30 with Alt hold. There is no alt hold button on the control head, it's on the yoke. There's a blue light that illuminates when in alt hold. That light is in the control head. Mine has GPSS, through a G500/GTN. There is no GPSS module in mine, but one is available to allow it to use other inputs.
     
  5. DKirkpatrick

    DKirkpatrick Pre-takeoff checklist

    Joined:
    May 18, 2011
    Messages:
    191
    Display Name:

    Display name:
    DKirkpatrick
    Thanks for the help!
     
  6. Arrow76R

    Arrow76R Pre-takeoff checklist

    Joined:
    Jan 27, 2015
    Messages:
    308
    Location:
    Colorado Springs
    Display Name:

    Display name:
    Arrow76r
    I went that same route; i.e. started with the STec 20/30 that did have "altitude hold" although it really demanded very frequent manual trim action as the STec would beep and flash demanding manual intervention when it could no longer hold the altitude. The next step was to add auto-trim (including a new dedicated trim servo) that would run the trim wheel when the tension it was using on the yoke exceeded some fixed value. This is what STec calls the "60 PSS" system. That add-on consisted of a panel mounted control for manual trim, glide slope tracking and altitude hold enabling functions. I also added the ST-901 that gave me roll steering thus allowing the STec to follow "the magenta line" course from my GNS 530W. That was accompanied by another panel "push-button" that selected GPSS (roll steering) or "heading" which then reverted to the mechanical DG (with heading output) for STec input rather than the GPS box. The next upgrade was to add 2 G-5 units, one of which was the new HSI. This allowed the ST-901 to be removed along with the DG/GPSS push-button since the G-5 HSI provides roll steering for the STec. It took me a number of years to accomplish this but it is worth it BECAUSE STec has no plans for an STC approval to put their 3100 digital autopilot into the Piper PA28 series. And, to go to Garmin, would require throwing out all the STec boxes and servos and re-installing Garmin servos, etc. So... this is essentially a dead-end for the STec capability I have.