Autopilot Upgrade

[Marauder]

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.

Nice panel. Whatcha got stashed in the center? Looks like a 650 and something else...

[Glenn]

Nice panel. Whatcha got stashed in the center? Looks like a 650 and something else...

 

I redid the panel a little too soon to take advantage of all of the new stuff.  The current set-up has been adequate to keep me from getting lost.

 

[1964-M20E]

I have the 30 with ALT hold and like it very much it was in the plane when I bought it and factored in my decision to buy this plane. This was the first autopilot I had the pleasure to fly behind.

 

As for upgrading:

1. How much do you fly the plane? 70+ hours a year on long cross country
2. Under what conditions? flights with varying IMC
3. Does it provide more utility with it?
4. Would the 24k be better invested in another system on your plan to give you more versatility and safety? (Aspen pro 1000)
5. Resale values you will probably be able to get 25% of what you spend but if you fly often, and keep the plane for a while it doesn’t matter if it adds joy and safety to the flight.

 

 

I know mostly questions not many suggestions but you have to answer those for yourself.

[rbridges]

I've got an stec50 with ALT hold.  I linked it with GPSS to my 430W and I love it.  I don't use the altitude hold much b/c it has a tendency to "hunt" for it.  I've read other posts with similar experiences.  I basically trim for altitude and let the AP steer.

[Bob_Belville]

I've got an stec50 with ALT hold.  I linked it with GPSS to my 430W and I love it.  I don't use the altitude hold much b/c it has a tendency to "hunt" for it.  I've read other posts with similar experiences.  I basically trim for altitude and let the AP steer.

My STEC50 ALTHLD works perfectly. Even in our area on the lee side of the mountains where there are always up or down drafts from mountain wave effect. I only disengage ALTHLD to adjust for BARO changes. (I have an Aspen and a GTN 750 so I have GPSS but that should not affect the ALTHLD function.)

[Marauder]

I've got an stec50 with ALT hold. I linked it with GPSS to my 430W and I love it. I don't use the altitude hold much b/c it has a tendency to "hunt" for it. I've read other posts with similar experiences. I basically trim for altitude and let the AP steer.

My STEC50 ALTHLD works perfectly. Even in our area on the lee side of the mountains where there are always up or down drafts from mountain wave effect. I only disengage ALTHLD to adjust for BARO changes. (I have an Aspen and a GTN 750 so I have GPSS but that should not affect the ALTHLD function.)

I agree with Bob, something is not right with your altitude hold. Mine is rock solid as well. Even in turbulence.

[Marauder]

I redid the panel a little too soon to take advantage of all of the new stuff. The current set-up has been adequate to keep me from getting lost.

Right panel.JPG

Dude! You been holding out on us! Nice panel!

[Bob_Belville]

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).

I descend @ redline (164kcas), or just under, unless it is very turbulent. 180 ktas is really good for the soul.

[ArtVandelay]

I agree with Bob, something is not right with your altitude hold. Mine is rock solid as well. Even in turbulence.

I second that, you do have to be stable before enable the alt hold but haven't had a problem, haven't tried higher altitude yet (>10000)

[rbridges]

I guess mine needs to be tweaked.  I can be flying level and trimmed perfectly.  Activate ALT and it slowly oscillates.  Usually it will settle down, but after a few cycles, I get tired of waiting.  It's a minor inconvenience, so I haven't put a lot of effort into researching the problem.

[Marauder]

I guess mine needs to be tweaked. I can be flying level and trimmed perfectly. Activate ALT and it slowly oscillates. Usually it will settle down, but after a few cycles, I get tired of waiting. It's a minor inconvenience, so I haven't put a lot of effort into researching the problem.

How much oscillation are we talking about? Enough to see the altimeter to change or just a slight up and down. On a real calm flight, I may feel very minor oscillations, but not enough to change altitude.

[rbridges]

How much oscillation are we talking about? Enough to see the altimeter to change or just a slight up and down. On a real calm flight, I may feel very minor oscillations, but not enough to change altitude.

 

mine is at least a few hundred feet above and below.  that's why I described it as "searching."   There are several hits on google about this problem.  I need to put a little time into fixing it.

[Marauder]

mine is at least a few hundred feet above and below. that's why I described it as "searching." There are several hits on google about this problem. I need to put a little time into fixing it.

There is a pressure transducer under your panel that is plumbed into the static system. That could be failing or the pitch computer is having an issue.

Hundreds of feet is definitely a problem.

[Hank]

I descend @ redline (164kcas), or just under, unless it is very turbulent. 180 ktas is really good for the soul.

180 Ground speed is good for my soul, but Vne = 200 mph = 174 knots.

But 500 fpm descent often pushes ground speed above 200 mph; faster descent makes for faster air & ground speeds.

[rbridges]

There is a pressure transducer under your panel that is plumbed into the static system. That could be failing or the pitch computer is having an issue.

Hundreds of feet is definitely a problem.

 

thanks.  It really gets annoying, that's for sure.

[Browncbr1]

180 Ground speed is good for my soul, but Vne = 200 mph = 174 knots.

But 500 fpm descent often pushes ground speed above 200 mph; faster descent makes for faster air & ground speeds.

Bob was talking about 180kts true, up high coming down

[Bob_Belville]

Bob was talking about 180kts true, up high coming down

Yes, it is possible to do 180 ktas without exceeding 164 kcas. @ 75% power my E cruises @ over 155 ktas, well into the ASI's yellow arc in level flight. I need one more mod... a J model ASI. 

[schule]

I had a similar altitude hunt issue with a King AP. It ended up being solved by a pitch servo rebuild. AP Central sent it out to a shop in the Dakotas to fix 30+ years of wear and corrosion. It was effectively hanging up do to corrosion and then over loading trying to move. It created some very creative pitch oscillations.

Again, different system with a similar problem.