Problems with a G1000/WAAS/STEC 55X setup not working, help please!

[Steve Parker]

I bought a 2006 M20R Ovation with G1000 and a 2014 WAAS upgrade and a STEC 55X autopilot.  We flew it down to Missouri and I just got my instrument proficiency check.  I have an STEC 55X user guide that came with the aircraft, I downloaded another more recent one, and I found a better focused manual for the old G1000 + STEC 55X setup in Cirrus aircraft when their G1000 had the legacy configuration with the same controls as mine.  I studied the manuals to walk through step by step.

In shooting approaches, I first noticed every time I followed the procedures to engage the GPSS, it showed "GPSS FAIL" on the STEC and the command steering bars disappeared.  Even following each of the manuals step by step in flight, no luck.  So, after being unable to engage GPSS, we tried to shoot regular ILS and VOR approaches.  I initiated the approaches as specified and it followed it for a bit then it commanded turns and climbs/descent that threw the approach out the window.  I had to disconnect the autopilot and hand-fly using the CDI and glideslope marker. I'm following the manual and G1000/GPSS guidebook procedures to the letter so it's not me not "activating" approaches or not knowing the difference in selecting "Vectors" or "specific entry point".

I need to 1) get the ILS/VOR/etc. approaches working as coupled approaches, 2) get the STEC to engage GPSS mode without failing, and 3) get GPS approaches working. 

Any suggestions?  I'd also like to find a course or instructor for learning the G1000.  I have the Max Trescott G1000 handbook and it's helpful on G1000 procedures but not on the STEC 55X at all.

I think I need an instrument expert to sort out my STEC 55X-G1000 link.  Help me, Obi Wan! 

[Mooney in Oz]

10 hours ago, Steve Parker said:

I bought a 2006 M20R Ovation with G1000 and a 2014 WAAS upgrade and a STEC 55X autopilot.  We flew it down to Missouri and I just got my instrument proficiency check.  I have an STEC 55X user guide that came with the aircraft, I downloaded another more recent one, and I found a better focused manual for the old G1000 + STEC 55X setup in Cirrus aircraft when their G1000 had the legacy configuration with the same controls as mine.  I studied the manuals to walk through step by step.

In shooting approaches, I first noticed every time I followed the procedures to engage the GPSS, it showed "GPSS FAIL" on the STEC and the command steering bars disappeared.  Even following each of the manuals step by step in flight, no luck.  So, after being unable to engage GPSS, we tried to shoot regular ILS and VOR approaches.  I initiated the approaches as specified and it followed it for a bit then it commanded turns and climbs/descent that threw the approach out the window.  I had to disconnect the autopilot and hand-fly using the CDI and glideslope marker. I'm following the manual and G1000/GPSS guidebook procedures to the letter so it's not me not "activating" approaches or not knowing the difference in selecting "Vectors" or "specific entry point".

I need to 1) get the ILS/VOR/etc. approaches working as coupled approaches, 2) get the STEC to engage GPSS mode without failing, and 3) get GPS approaches working. 

Any suggestions?  I'd also like to find a course or instructor for learning the G1000.  I have the Max Trescott G1000 handbook and it's helpful on G1000 procedures but not on the STEC 55X at all.

I think I need an instrument expert to sort out my STEC 55X-G1000 link.  Help me, Obi Wan! 

Hello Steve. I can only try to help with the problem you are experiencing with the GPSS failing. Although it’s been years since I’ve operated a G1000, I don’t know if your problem is exclusive to that same setup, but here goes. I used to have a 55X, an Aspen and 2 IFD’s that I retained. 

I discovered that on the ground, after switching on the avionics master if I switched on the 55X without allowing the navigators to complete initialisation before the 55X fully initialised, the 55X GPSS would not engage after takeoff. Recycling the 55X off then back on and following reinitialisation, the 55X GPSS would work.

Following this discovery I made sure the navigators fully initialised on the ground first before switching on the 55X and never had the problem again. This was not written in any manual and even my installer was unaware of this solution.

Although I am unsure if the brand of navigators contributed to the problem or you have a deeper issue, it still might be worth a try.

[LANCECASPER]

3 hours ago, Steve Parker said:

I bought a 2006 M20R Ovation with G1000 and a 2014 WAAS upgrade and a STEC 55X autopilot.  We flew it down to Missouri and I just got my instrument proficiency check.  I have an STEC 55X user guide that came with the aircraft, I downloaded another more recent one, and I found a better focused manual for the old G1000 + STEC 55X setup in Cirrus aircraft when their G1000 had the legacy configuration with the same controls as mine.  I studied the manuals to walk through step by step.

In shooting approaches, I first noticed every time I followed the procedures to engage the GPSS, it showed "GPSS FAIL" on the STEC and the command steering bars disappeared.  Even following each of the manuals step by step in flight, no luck.  So, after being unable to engage GPSS, we tried to shoot regular ILS and VOR approaches.  I initiated the approaches as specified and it followed it for a bit then it commanded turns and climbs/descent that threw the approach out the window.  I had to disconnect the autopilot and hand-fly using the CDI and glideslope marker. I'm following the manual and G1000/GPSS guidebook procedures to the letter so it's not me not "activating" approaches or not knowing the difference in selecting "Vectors" or "specific entry point".

I need to 1) get the ILS/VOR/etc. approaches working as coupled approaches, 2) get the STEC to engage GPSS mode without failing, and 3) get GPS approaches working. 

Any suggestions?  I'd also like to find a course or instructor for learning the G1000.  I have the Max Trescott G1000 handbook and it's helpful on G1000 procedures but not on the STEC 55X at all.

I think I need an instrument expert to sort out my STEC 55X-G1000 link.  Help me, Obi Wan! 

I understand that the S-Tec 55x is not certified to fly WAAS approaches with the G1000.

[MatthiasArnold]

Hello Steve,

Some hints on how to get a better understanding of the root cause.
Performance wise the 55X is miles behind the GFC700 - but it's the AP you and I have installed in our planes.
A lot of basic stuff you most probably already checked.

• What is the SW version installed 0401.30, 0401.34?
• Stupid question: is the elevator trim switch (always) enduring usage of the AP?
• Basic lateral - HDG mode engaged 
  • Fly around and set the AP to HDG mode
    • How good does it track when flying straight ahead (qualitative)?
    • How high is the deviation between selected heading (heading bug) and the resulting heading (value on top of HSI)?
      • Check the the deviation for several headings.. (should be below +/- 3degrees or so).
      • If its higher than some degrees you must recalibrate it (long thin flathead screwdriver required).
    • How good does it roll-in and roll out on heading changes (qualitative)?
    • What is the resulting turn rate when doing a 180 or 360degrees turn?
      • Check the magenta turn rate indicator arc on top of the HSI?
      • Check the bank angle on top to the AI if you see something like 20° bank at 140TAS (TAS/10 + 7)
      • Make a 180/360360degrees turn and use a stop watch.
      • Often the 55X is pretty slow in turning, less than standard rate turn of 3degrees/s.
      • If the resulting turn rate is 2degrees/s or below the STEC TC which sits behind the MFD needs some TLC form a capable avionics shop (its a gyro based instrument showing turn rate and forwarding this analog signal to the 55X -> rate based AP)
• Basic vertical - any lateral (e.g. HDG) plus ALT mode
  • How good is the alt hold functionality (stable/oscillating)?
  • Engage the VS mode and set it to different values (e.g. +/-500/1000fpm)
    • How good does the resulting VS match the selected VS (see VSI on the RHS of the PFD altitude band) 
  • When flying straight and level, select a different altitude on the G1000 (e.g. 1000ft higher), press the ALT/VS buttons on the G1000 and select a VS, e.g. 800ft/min. 
    • Are (top of the PFD) the modes ALT armed (white color), VS engaged (green color)?
    • Does the AP reduce VS and level of automatically when reaching the selected altitude?
    • Does the AP switch to ALT mode automatically?
• Basic lateral NAV tracking
  • select some VOR track/radial close to your current position, select the NAV1/2 source in the HSI and intercept it (in HDG mode)
  • engage NAV mode (push once)
    • Does the AP intercept and track?
    • Is there a remaining offset on the CDI (all the time some degrees to the left or right))?
    • If yes you still have a problem with the HDG offset calibration..
  • select some GPS track, e.g. direct to (might be followed b OBS mode and choosing a specific) track and select the GPS source (magenta) in the HSI.
    • BTW: what GPS/HSI sensitivity is displayed in the HSI (ENR/TRM/DPR/0.3/1.0/..)? If its set to a numeric mode someone played around in the user settings. It should be set to AUTO
    • Fly towards the track and press NAV only once (yes only once)!
      • Is NAV mode engaged (green) in the PFD?
      • Does it somewhat intercept and follow the track (although sluggish)?
    • Once on the track select GPSS adjust HDG back, go back to HDG mode and press NAV twice?
      • Is GPSS mode engaged (green) in the PFD?
      • Does it somewhat intercept and follow the track?
      • Does it go into error mode or stay OK (Elevator trim switched on???)
    • (Per my understanding the main difference between NAV/GPSS on the 55X are just different gain factors, the selection of the NAV source (VOr, GPC, LOC) is solely with the G1000)

If all of the above works satisfactory you are ready to try some ILS/RNP approaches ..
Otherwise you most probably need the support of some good avionics shop to check the STEC TC, servos, ..?

G1000 Training
For G1000 (and IFR) training I utilized the X-Plane 11 flight sim with Realsimgear G1000 and M20 collection models.
Right now I'm checking out the new X-Plna 12 (still in beta, for nerds only) and awaiting the Torquesim M20R model (which will replace the M20 collection).

Best,
Matthias

 

This images show flying M20R in X-Plane 12 beta at home - pretty close IMHO..

[EarthboundMisfit]

14 hours ago, Steve Parker said:

I bought a 2006 M20R Ovation with G1000 and a 2014 WAAS upgrade and a STEC 55X autopilot.  We flew it down to Missouri and I just got my instrument proficiency check.  I have an STEC 55X user guide that came with the aircraft, I downloaded another more recent one, and I found a better focused manual for the old G1000 + STEC 55X setup in Cirrus aircraft when their G1000 had the legacy configuration with the same controls as mine.  I studied the manuals to walk through step by step.

In shooting approaches, I first noticed every time I followed the procedures to engage the GPSS, it showed "GPSS FAIL" on the STEC and the command steering bars disappeared.  Even following each of the manuals step by step in flight, no luck.  So, after being unable to engage GPSS, we tried to shoot regular ILS and VOR approaches.  I initiated the approaches as specified and it followed it for a bit then it commanded turns and climbs/descent that threw the approach out the window.  I had to disconnect the autopilot and hand-fly using the CDI and glideslope marker. I'm following the manual and G1000/GPSS guidebook procedures to the letter so it's not me not "activating" approaches or not knowing the difference in selecting "Vectors" or "specific entry point".

I need to 1) get the ILS/VOR/etc. approaches working as coupled approaches, 2) get the STEC to engage GPSS mode without failing, and 3) get GPS approaches working. 

Any suggestions?  I'd also like to find a course or instructor for learning the G1000.  I have the Max Trescott G1000 handbook and it's helpful on G1000 procedures but not on the STEC 55X at all.

I think I need an instrument expert to sort out my STEC 55X-G1000 link.  Help me, Obi Wan! 

We don’t have WAAS, but had this same issue on our 2005 Ovation 2GX with G1000/Stec55X when it was new to us 5 years ago. GPSS would not engage after 2 presses of the NAV button. Would get the GPSS Fail annunciation.  NAV mode (1 press of NAV button) worked normally with CDI guidance from GNSS or VOR.  

From memory, I think the issue was resolved after we did a continuity test on all the pins in the connector at the back of the AP. I recall our avionics guy removing and reseating all the pins during his troubleshooting process. GPSS magically began working again. 

Later down the road we had to replace the AP main board (twice) when a servo died, but GPSS has worked ever since.  All lateral and vertical modes work as expected, including coupled ILS, VOR, and 2D GNSS.  

Edited October 1, 2022 by EarthboundMisfit

[GeeBee]

I have a G1000 WAAS with an S-Tec and it all works fine. GPSS works good, flies WAAS approaches fine including LPV.  You can't fly a lot of LPV approaches to minimums engaged, the last 200' you are below minimum engagement altitude of 400' so you have to hand fly below 400' which you want to do anyway in the event of go around. You have some issues which need to be sorted out by a good avionics shop. I can find no paperwork that prohibits the S-Tec from flying WAAS approaches. It will not fly VNAV in any regime so you have to V/S that, but if you have a magenta G/S in the approach mode, couple it up with G/S. 

As to learning the G1000 the King Ground School course is a good one. I would recommend it. 

[Steve Parker]

10 hours ago, Mooney in Oz said:

Hello Steve. I can only try to help with the problem you are experiencing with the GPSS failing. Although it’s been years since I’ve operated a G1000, I don’t know if your problem is exclusive to that same setup, but here goes. I used to have a 55X, an Aspen and 2 IFD’s that I retained. 

I discovered that on the ground, after switching on the avionics master if I switched on the 55X without allowing the navigators to complete initialisation before the 55X fully initialised, the 55X GPSS would not engage after takeoff. Recycling the 55X off then back on and following reinitialisation, the 55X GPSS would work.

Following this discovery I made sure the navigators fully initialised on the ground first before switching on the 55X and never had the problem again. This was not written in any manual and even my installer was unaware of this solution.

Although I am unsure if the brand of navigators contributed to the problem or you have a deeper issue, it still might be worth a try.

Thanks for the advice.  My Mooney doesn't have an avionics master switch, just a master switch so the G1000 initialize even before engine start which gives me engine readouts during engine start.  I've delayed turning on the autopilot power switch until established in cruise climb and yet, unlike yours, it gives all the problems I described.  Recycling the autopilot power doesn't correct it either.  I'm glad you solved your problem without having to incur instrument repair.  Sadly, mine seems not so easy to fix.

[Steve Parker]

9 hours ago, LANCECASPER said:

I understand that the S-Tec 55x is not certified to fly WAAS approaches with the G1000.

I'll recheck the POH, but mine had the WAAS upgrade in 2014 and apparently three levels were certified.  Mine was the middle level which gave WASS upgrade and could fly coupled approaches.  Thanks for the advice. I'll make sure.

[GeeBee]

The G1000/S-Tec cannot fly LNAV+VNAV (because there is no VNAV function, you need to use V/S) It can fly LPV in G/S. 

You need to find a good avionics shop to repair your autopilot.