Operation and clarification of S-TEC 60-2 with Altitude Preselector with GTN750 and GTN650

[M20F-1968]

I have an S tech 60 – 2  autopilot with the S-Tec Altitude preselector  along the S-TEC GPSS, Garmin GTN 750 and GTN 650.   The system is working   and I am able to track both GPS and ILS/LOC  sources.  However,  if I haven't used the system for bit I find one aspect of the buttonology  confusing.   I have a button on my panel which switches between HDG and GPS (Which should probably be labeled GPSS).  There is a CDI button on each of the three Garmin boxes;  G600, GTN750, GTN650.    

 When I have not use the system for a while  I always have to go out and practice in VF are conditions to remind myself configuration of these buttons for the application intended.   In general  the  panel mounted HDG/GPS  button is placed in HDG  mode for heading only operation using the heading bug  for directional guidance.  If not using the  heading bug,  that same button should be in GPS mode.  GPS mode on the panel mounted button  will provide for GPS tracking, LPV  approaches, and ILS/LOC  approaches depending on how the CDI buttons are set on the Garmin units (G600 and GTN750/650).

 Now we start getting into the subtleties  of my configuration and other possible configurations of the Garmin installation.   When I was learning the system I made sure that the CDI button on the G 600 and the GTN unit I was using were set to the same setting, either GPS or VLOC.   In retrospect,  I am not sure whether the setting of the CDI button on the garment G 600 matters at all.   Changing the CDI  on the GTN unit changes the display from GPS to VLOC.   If my  memory serves me correctly,  Garmin stated to me  that there only needs to be one CDI button to change the configuration being used from GPS to VLOC.   When the buttons are set properly  the unit will fly the approach,  holding pattern,  and missed approach as expected.  However,  when needs to be clear what the proper button selection is and it can be forgotten or confusing if not used in the recent past.   Thus,  I question whether there can be different configurations selected which allows the units to operate with less confusion and more straightforwardly.  

 I am presently not remembering exactly the button configuration for a missed approach will hold after either an ILS or GPS approach.   As I recall,  one presses activate missed approach on the GTN 650 and it changes the display on the G 600 to  display the magenta line of the missed approach heading without vertical management,  and in order to capture that heading I need to press the HDG  button on the panel.  However,  since I have not done this in a few months I need to go out on the VFR conditions to confirm.  

 I am hoping the group has people who are operating this equipment who can tell me if there is more optimal way to configure my system to make it more intuitive and to clarify whether my memory of operations is correct,  particularly on applying the missed approach.   Is there a way  for the autopilot to climb per the missed approach  instructions?  

 As for the autopilot buttons,  I recognize that the approach must be activated near the approach,  at an angle less than about 45° and at a location below the glide slope.   Activation  is accomplished by pressing the NAV  button.  If  being vectored, a two button approach can be used, pressing both HDG and NAV.  The  autopilot will follow the heading bug until it sees the approach and then will switch to approach mode and follow the approach and bound.  On all S-TEC  autopilots,  heading mode must be selected before ALT can be selected.  Once ALT is selected,  there is no way to cancel simply the altitude  selection without canceling all functions on the autopilot and starting again by first selecting a heading mode.  The ST-360 altitude preselector is activated by pressing the VS and ALT buttons simultaneously.  

The  difficulty with the 60 – 2  autopilot is that it was designed before LPV and  GPS/GPSS steering  were invented.   The buttonology  is designed to trick the autopilot into thinking the GPS guidance looks and acts like an ILS.  The  button combinations can be confusing and I need to find a better way to remember what works,  and also learn about any possible configuration of the system,  either by hardwiring or programming that will make it more foolproof.

John Breda

[N231BN]

I think what may be confusing you is the HDG/GPS selector. That is an external input for the G600 roll steering converter. It simply swaps the HDG bug output to the autopilot with the GPSS steering commands from the GPS. It is a completely different function than the CDI selectors on the various units.

[JamesMooney]

M20F-1968 --- I had a similar (not the same, but similar) question about the STEC 60-2 and getting to arm the APR mode on RNAV (GPS) approaches. I just posted this today, here (link below). Perhaps your thread, or mine, will reveal answers to both our questions.

 

[David Lloyd]

I have a 60-2 connected to GI275s, a GNX375 and KX165.  Works great mostly, but I have had an intermittent problem capturing the glideslope/glidepath.  I have firmly established it is not operator error but a problem within the 275, the wiring from the 275 to the Stec control head or within the control head (recently repaired with new buttons, button pad and main board).  Just went out an did my 6 approaches, 3 LPV, 1 LNAV+V, 1 ILS captured the glideslope/glidepath.  One LPV captured and began to follow, then GS went out, FAIL annunciated.  No apparent reason, the 275 always show a steady glideslope indication.  I feel pretty good about answering any question about how the 60-2 works, fire away.

Anyway, for the GS to arm and capture, several things must take place. Stec needs to be both in NAV and ALT mode.  Navigation signal must be on a recognized localizer frequency or GPS approach (a energize signal is sent from either the GPS or ILS radio to the 275 and 275 to the Stec).  The CDI must be less than 1/2 full scale.  There is another hurdle or two in the background for a GPS approach.  APR will annunciate.  If 60% below the appropriate glideslope/glidepath, in 10 seconds after APR lights, the GS will light showing the glideslope/glidepath is armed.  When the glideslope/glidepath needle centers, it should capture and the ALT light extinguishes.

If using GPSS to fly to an approach fix the Stec must be in HDG mode.  Rolling out on the final approach course, switch from HDG to NAV and if the CDI is within 1/2 scale APR should annunciate and 10 seconds later, GS.

[JamesMooney]

Hey David - this is helpful and touching on the questions I asked in my own thread (link is in this thread, above). I'm going to invite you there to get your thoughts (and to keep the threads clean in terms of focus). Thx.

[carusoam]

Inviting @midlifeflyer may be interesting…

Best regards,

-a-

[midlifeflyer]

  On 10/31/2021 at 3:55 PM, M20F-1968 said:

The  button combinations can be confusing and I need to find a better way to remember what works, 

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Customized checklist. In your own airplane, doing it will eventually imprint it on your psyche, but until then, checklist.

I fly and teach in so many combinations of GPS and autopilot, it would be impossible for me to remember what works without a combo-specific checklist. Personally, I don't want to clutter up my normal ops checklist with that stuff and I no longer need it with some combos, so it's on a separate page. (Sample)

Edited November 1, 2021 by midlifeflyer

[M20F-1968]

On missed approach, should the S-TEC be in HDG mode or NAV mode.  Is there a vertical climb component to the S-TEC on missed approach?  Does the position of the GPSS (HDG v. GPS) switch on the panel make any difference on a missed approach?

John Breda

 

[Sheriff23]

  On 11/1/2021 at 12:05 PM, midlifeflyer said:

Customized checklist. In your own airplane, doing it will eventually imprint it on your psyche, but until then, checklist.

I fly and teach in so many combinations of GPS and autopilot, it would be impossible for me to remember what works without a combo-specific checklist. Personally, I don't want to clutter up my normal ops checklist with that stuff and I no longer need it with some combos, so it's on a separate page. (Sample)

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This is money....did you make this yourself or is there a source for similar products?  I have a STEC 60-2, GNS-430W and dual G-5s.  Definitely need something like this/may have to build one.

[N231BN]

  On 11/4/2021 at 8:55 AM, M20F-1968 said:

On missed approach, should the S-TEC be in HDG mode or NAV mode.  Is there a vertical climb component to the S-TEC on missed approach?  Does the position of the GPSS (HDG v. GPS) switch on the panel make any difference on a missed approach?

John Breda

 

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Initially it should be HDG and HDG, your bug should be on runway heading or whatever is specified for the initial climb. When at a safe altitude, make sure the GPS is sequenced to the MAP point and then select GPSS while in HDG mode to fly the missed procedure.

[midlifeflyer]

  On 11/4/2021 at 1:28 PM, Sheriff23 said:

This is money....did you make this yourself or is there a source for similar products?  I have a STEC 60-2, GNS-430W and dual G-5s.  Definitely need something like this/may have to build one.

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It's all me. Been writing my own checklists since a student and using the general format (tweaking from time to time) for at least 20 years  Started doing the equipment pages when equipment became more complex. I try to limit it to "here's what's different about this one!" So it's always a work in progress. If I needed more room on the page, I'd probably get rid of the pre-flight check since that's pretty standard.

[Marauder]

  On 11/4/2021 at 8:55 AM, M20F-1968 said:

On missed approach, should the S-TEC be in HDG mode or NAV mode.  Is there a vertical climb component to the S-TEC on missed approach?  Does the position of the GPSS (HDG v. GPS) switch on the panel make any difference on a missed approach?

John Breda

 

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John - I feel your frustration. The STEC manual for the 60-2 hasn't been updated since 2007 and there is no mention of any GPS interfacing! I don't have an altitude pre-select but this is how I initiate a missed approach on a RNAV approach:

> Upon reaching the MAP, I disconnect the AP and begin the climb

> I hit the "Activate GPS Missed Approach" button on the GTN

> I activate the STEC in "HDG" mode and if I am flying the missed per the GTN, activate GPSS (otherwise, I stay in "HDG" mode and use the bug to begin the miss)

> Once I am at the correct pitch and power for the climb, I activate the "VS" mode.