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My 1967 M20F currently has a working PC system.  Over the years I have added Accu-Flite heading-hold, and Altitude hold.  It all works but I am getting an irrational urge to upgrade to a more modern system.  Perhaps an S-Tec 55X.  I would be interested to hear the experience of others who have gone this route.  I would be particularly grateful if someone would bring me back to my senses and talk me out of this.

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If your Brittain stuff is working great now, I'd see if you can add GPSS (I believe you can, assuming you already have WAAS) and just do that for the near-term.  There is hope (perhaps mis-placed) that the regulation relaxation/re-write might allow us to install some of the autopilots currently available only to the experimental folks.  You'd be looking well north of $20k to install a 55x I believe.  Crazy IMO.

 

For reference, I think a Garmin G3X PFD + matching autopilot system is well under $15k for everything.

https://www.gulfcoastavionics.com/products/3863-g3x-autopilot.aspx

 

Note that the G3X a/p is comparable to the GFC700 in the certified plane in terms of performance/capability.  That is far and away better than the 55x.  Check out those servo prices too!  You'd be hard pressed to get an old King servo serviced, much less overhauled, for that kind of money!  You can also change the setup/installation values via the G3X interface vs. swapping things or programming on a bench.

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I have not gone this route but have an S-TEC 55X in my Bravo, it is a wonderful piece of equipment, when  all is working properly, I'v changed trim servos, instead of listing basically all the zeros and the computer board twice..the reason for the servos was they would not honor the work on the computer board after a few occurrences and said the only way they would work on the computer again  would be if I agreed to get the new servos..I reluctantly did...and have not had any problems since getting new servos.  The s tec folks blamed Mooney for putting on bad or old servos ????  the plane was new in 2005 and they felt the servos were contaminated or something..I am clueless except have been problem free for about 4 yrs now..But the autopilot now works awesome..now Im hoping Mooney to get us guys GX models with stec in there plane a viable fix for WAAS etc.. 

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If your Brittain stuff is working great now, I'd see if you can add GPSS (I believe you can, assuming you already have WAAS) and just do that for the near-term.  There is hope (perhaps mis-placed) that the regulation relaxation/re-write might allow us to install some of the autopilots currently available only to the experimental folks.  You'd be looking well north of $20k to install a 55x I believe.  Crazy IMO.

 

For reference, I think a Garmin G3X PFD + matching autopilot system is well under $15k for everything.

https://www.gulfcoastavionics.com/products/3863-g3x-autopilot.aspx

 

Note that the G3X a/p is comparable to the GFC700 in the certified plane in terms of performance/capability.  That is far and away better than the 55x.  Check out those servo prices too!  You'd be hard pressed to get an old King servo serviced, much less overhauled, for that kind of money!  You can also change the setup/installation values via the G3X interface vs. swapping things or programming on a bench.

The Garmin looks like a great value.  The obvious question is will it be available to us any time soon.

Thanks

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The 55X is a great AP. Extremely reliable and serviceable. It's only fault is it tends to hunt and overshoot more than King and Century. Seven years ago, it ran me 24AMU's. The alt preselct is not necessary unless you are in the FL's in a 231. Most gadgets like the Aspen, etc have alt preselect and GPSS built in.

 

The Stec 30 is REALLY a great value and helps with workload while forcing the pilot to be attentive. The 55X has full functioning intercept and coupling, where the Stec 30 does not. A precision approach requires the pilot to center within 1 degree +/- before engaging. Then, you have to watch and babysit the throttle. I actually liked this better. Makes you less of an AP addict.

 

I have owned the 30 and 55X...they are both great.

 

KSMoniac is right....it may be four more years, but a Part 23 re-write may happen. My advice, all being equal? Spend 24 AMU's on an Aspen and an Stec 30 before getting the 55X. Tighter on cashish? Spend 5 fixing up the Acctrack and get an Aspen. My $.02

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Glenn -- I went the STEC 60-2 route back in 1998. I had one installation issue with the autotrim which was related to the amount of grease on the trim jack screw. Other than that (knock on wood), it has been problem free.

For the majority of the years I owned it, I used it with a straight up dual ILS/VOR Nav setup (autopilot could fly either as precision).

There is an effort to rewrite the rules for how we can maintain and what we can put in our planes without making it experimental. If that happens, many of the autopilots the experimental guys enjoy today will be available. The question is whether or not there will be limitations on the changes like the medical reform (example: you won't be able to fly IFR with the medical reform driver license approach). And an even bigger question is whether or not this rewrite will get done in our lifetime, our children's lifetime or even at all.

If you do go for the certified autopilot, some of the features you may want to consider are autotrim, rate preselect (the 55X I believe allows you to select a climb or descent at a specific rate by dialing it in, the 60-2 has this as an option), altitude preselect (I use the Aspen's altitude alert to remind me that I am reaching my assigned altitude) and GPSS. I can write a whole book on GPSS. What a wonderful addition to an autopilot. It really gave my STEC a whole new dimension of operation which includes flying procedure turns, holds and LPV approaches with unbelievable precision.

I have a YouTube video that shows an approach being flown with the STEC autopilot in GPSS mode and flying an LPVS approach. Let me know if you want the link.

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I forgot one other thing. You may want to check with an avionics shop about the difference between the 55X and the 60-2. Chris from Penn (now Agape) Avionics told me that the 60-2 was far superior in performance than the 55X. Based on the comments John presents above, he may be right.

My 60-2 is rock solid, no hunting of any kind. I also like the ability of the STEC to set the intercept angle for a coupled approach. This comes in handy if ATC is vectoring you to the final approach course. You press the HDG & NAV buttons together and you can use the heading bug to fly the vectors and it will intercept at some rather steep angles.

I have another video of that. In that case, it was close to a 80 degree intercept. It flew a little bit through the course, but not worse than I would have done :)

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To me replacing old equipment that works well enough and is cheap to fix IS irrational. If nothing else you'll lose the use of the plane the week that the work is being done and have to drive while it's being installed. And on an old F panel just getting up and behind and working is going to break something else. It's tight back there a lot of that stuff is old and stiff and doesn't like to be jostled. If you're flying hard IFR single pilot maybe the additional utility might be worth the trade-offs.

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My only experience with the PC is from things I have read. I have an Stec 30 with no alt hold and I must say I really like it. It fly's the heading bug or the NAV really well my avionics guy said the alt hold is an easy upgrade but my plane trims out real well and requires little attention to stay on altitude. It's fun to let it make my waypoint turns keeps the ball dead center. The only thing I find is when I hit rough air it starts to struggle to keep up don't know if that's normal when that happens I just put it into standby until back in smoother air.

Knowing the cheap sucker I am I don't think I would spend the money for it but I am glad it's there. On a long cross country the smoke was so thick we got into zero zero and between the Stec and the I pad we were just fine I just let Snoopy fly himself while I sorted things out to get back into visible air.

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If you do decide to up-grade, I suspect there are people on Mooneyspace who would like your PC accuflite, etc.  Make sure your shop uses care when removing the PC to save every piece and part!   :mellow:

Good advice.  Thanks

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Glenn -- I went the STEC 60-2 route back in 1998. I had one installation issue with the autotrim which was related to the amount of grease on the trim jack screw. Other than that (knock on wood), it has been problem free.

For the majority of the years I owned it, I used it with a straight up dual ILS/VOR Nav setup (autopilot could fly either as precision).

There is an effort to rewrite the rules for how we can maintain and what we can put in our planes without making it experimental. If that happens, many of the autopilots the experimental guys enjoy today will be available. The question is whether or not there will be limitations on the changes like the medical reform (example: you won't be able to fly IFR with the medical reform driver license approach). And an even bigger question is whether or not this rewrite will get done in our lifetime, our children's lifetime or even at all.

If you do go for the certified autopilot, some of the features you may want to consider are autotrim, rate preselect (the 55X I believe allows you to select a climb or descent at a specific rate by dialing it in, the 60-2 has this as an option), altitude preselect (I use the Aspen's altitude alert to remind me that I am reaching my assigned altitude) and GPSS. I can write a whole book on GPSS. What a wonderful addition to an autopilot. It really gave my STEC a whole new dimension of operation which includes flying procedure turns, holds and LPV approaches with unbelievable precision.

I have a YouTube video that shows an approach being flown with the STEC autopilot in GPSS mode and flying an LPVS approach. Let me know if you want the link.

Please send a link.  I would love to see it.  Thanks

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+1 on the 55X as that is what I installed this summer.  Yeah, way too much money, but I'm spending my kids inheritance.  Just compare the s-tec 30 + GPSS cost to the 55x that has it included.  I love to have the heading bug set or GPS setup before take-off and just punch the button and set the VS to climb at and off we go.  Still trying to learn the other features.  

 

Don

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I did from the 30 to 55X. They all share the same servos. The high ticket item in the upgrade is the auto trim. Stec provides a reasonable means of upgrading.

The 60-2 fits in the same hole, same wiring harness I would think, so I would expect a simpler and much less expensive install.
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I'm sure there would be much interest in your Brittain Altitude Hold. Like me!

The AccuTrak and AccuFlite are hard to beat. One runs off a heading bug, the other has a switch do go either to my G430W for flight path including approaches, or to Nav2. There is no separate GPSS with Brittain. It flies nice approaches, but I still have to do the altitude changes and follow glide slopes by hand. Thus my interest in your Altitude module.

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  I will inform you of the outcome.  I am leaning toward the upgrade.  The Brittain all works, and the altitude module was back at the factory for overhaul last year.  It is a neat install that takes little panel space.

 

Thank you all for the thoughtful input.

post-7559-0-30721800-1417662638_thumb.jp

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Thanks, Glenn.

My Altitude Hold (aka Trim Wheel) works fairly well most of the time for that (mostly just the first), but is easily upset by leaning forward looking for traffic, or my wife reaching into the back seat for something, to say nothing of what happens if I have my head down looking at charts/plates for too long. At least I don't drift off course very much (usually, unless I set the heading bug to correct for wind drift and forget to take it out.

P.S.--I usually climb at constant speed, but descend with cruise power settings and let the speed build to make up for my slow climb. Holding 500 fpm, backing off throttle and pushing mixture richer as I come down will put me right around 170 mph, just inside the green line (yellow starts at 175).

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