Autopilot off in turbulent air?

[Tommy]

Turning off autopilot in moderate turbulent condition in order to preserve the servos? 

Urban legend or some element of truth in it? 

[rbridges]

I've started doing it because mine will disengage anyway.  I don't know if that's normal, but I figured it couldn't be good for them.  btw, it's an stec50.  

[Jerry 5TJ]

Related -- I've felt it better to switch from GPSS to heading mode in turbulence as the autopilot doesn't make so many small heading changes. It makes passengers a bit happier. I'm referring to my  KFC225 system. 

The KFC325 has a "soft ride" mode  used in turbulent air.  That mode does reduce ride harshness & perhaps it reduces servo strain.

 

[RobertGary1]

Never heard that. I do it because they aren’t very good in turb. Even in the G1000 with the Garmin 700 autopilot I’ve had to exaggerate rolls in turb. That’s about the best autopilot I’ve flown  And a rate based autopilot would be hopelessly lost in turb 

-Robert

[Piloto]

I have the Century 31 and use it in turbulence all the time. Have not seen any unusual behavior. 

José

[gsxrpilot]

My KFC150 seems to do fine in turbulence. 

[kortopates]

Mine comes off in turbulence for two reasons. Foremost I can do a much better job flying the plane in turbulence than my very capable KFC150. If you ever experience the variety of bad turbulence we can get from the Sierra's you'll know what I mean. Secondly when mountain wave activity may be a possibly (its not always by any means and more likely to just be vertical gust) I don't want the AP trying to maintain altitude either; again I can do a much better job minimizing the stress on the airplane and I am more concerned about that than the servo's. If its just light chop where the AP can keep up, I can still do a better job giving a smoother ride than with the AP on and will do so.  Although the KIng AP's do pretty decent job in turbulence, many of the lesser capable AP's do a pretty terrible job keeping the wings level. 

[Bartman]

Unless if its very uncomfortable I leave my Century IIb on, but have it in Hdg mode.  If it is continuous moderate then I turn it off.  I have only experienced mountain wave over KAVL Mount Mitchell area and although it has been very smooth the STEC 30 Alt Hold could not keep up so I turned it off.  I'm not concerned about the servo because if it fails it was weak and needed attention anyway.  I have asked for and used block IFR altitude to my advantage on more than a few occasions.

years ago someone told me to try an occasional pump of the rudder L-R-L in moderate turbulence and it does seem to soften the ride if I do this, especially when its just the occasional jolt but I'm not gonna keep that going. Then again, maybe it just feels smoother because I am fooled into thinking I have some control.

[Yooper Rocketman]

I was always taught the reason you disconnect the A/P in turbulence (serious stuff, not light) was to avoid over-stressing the air frame.  Like Paul, I find I can provide a better ride by hand flying.

Tom

[AndyFromCB]

5 hours ago, Jerry 5TJ said:

Related -- I've felt it better to switch from GPSS to heading mode in turbulence as the autopilot doesn't make so many small heading changes. It makes passengers a bit happier. I'm referring to my  KFC225 system. 

The KFC325 has a "soft ride" mode  used in turbulent air.  That mode does reduce ride harshness & perhaps it reduces servo strain.

 

I also like to turn off altitude hold, ask for a block and switch to pitch mode and just maintain 0 degree pitch (or whatever is required for level). This way it's not chasing the altitude so much.

[RobertGary1]

3 hours ago, gsxrpilot said:

My KFC150 seems to do fine in turbulence. 

Interesting. When I had the kfc 140 it was terrible in the Sierras. A rate based autopilot seems worthless when the tc is sloshing all over  

-Robert

[RobertGary1]

2 hours ago, Skmoore63 said:

My rate-based S-Tec 30 handles turbulence just fine. Apparently it hadn't heard it was worthless. 

That is very interesting. The reason you pay for an expensive attitude based autopilot is because when a big bump knocks the ball out a tc incorrectly indictes a deep turn. I wonder what type of external reference  your has. When crossing The Sierras a tc just flops around. 

-Robert

[gsxrpilot]

The only time I've been in a situation in an airplane that I wished I wasn't was in some pretty bad turbulence in solid IMC over the White Mountains of Vermont/New Hampshire this last summer. It was a bit convective and while we were staying clear of the large cells, there was several minutes that were pretty rough. As we were IMC, and the KFC150 was handling everything well enough, I thought it best to let it continue flying the plane. I threw out the speed brakes and slowed everything down while we braced ourselves in the cockpit. It only lasted a few minutes, but with hindsight, I'd have diverted further around the weather.

All in all, I was very happy with the way the KFC150 handled the rough air.

[carusoam]

Training in bumpy IMC, Dec in NJ... (rented Cessna)

TC flopping around uncontrollably...

quick question...

What do you use to keep the clean side up, if the attitude indicator goes on vacation...?

i haven't seen the TC do this in my O.  But it doesn't see a lot of bumpy IMC anymore either...

Looks like a good back-up AI is in order...

Best regards,

-a-

[RobertGary1]

31 minutes ago, carusoam said:

Training in bumpy IMC, Dec in NJ... (rented Cessna)

TC flopping around uncontrollably...

quick question...

What do you use to keep the clean side up, if the attitude indicator goes on vacation...?

i haven't seen the TC do this in my O.  But it doesn't see a lot of bumpy IMC anymore either...

Looks like a good back-up AI is in order...

Best regards,

-a-

It could be very difficult to keep the dirty side down in turbulent IMC if the vacuum goes out. Notice that the military, airlines etc never ask a pilot to fly IMC on a t c. Their procedure is to look at a different attitude indicator. Personally I think the G5 is the deal of the decade in aviation.

 

-Robert,CFII

[gsxrpilot]

55 minutes ago, RobertGary1 said:

Personally I think the G5 is the deal of the decade in aviation.

 

[Tommy]

When you disengage A/P (specifically KFC 200), does it stop the servos from running? I was told that they kept spinning regardless. If that's the case then I might as well use it instead of trying to preserve the servos during turbulent flight. 

[xcrmckenna]

 

Im pulling the trigger on one. I’ll be glad to see the vac pump go bye bye.


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[RobertGary1]

2 hours ago, xcrmckenna said:

Im pulling the trigger on one. I’ll be glad to see the vac pump go bye bye.


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I"m keeping mine as a backup. Even the Cessna G1000's still come with a vac pump to drive the standby.  It doesn't hurt anything to keep it unless you need the panel space.

-Robert

[xcrmckenna]

I"m keeping mine as a backup. Even the Cessna G1000's still come with a vac pump to drive the standby.  It doesn't hurt anything to keep it unless you need the panel space.
-Robert

I thought about keeping it. But I want to keep the panel open for the 900 coming. The G5 has a 4 hour battery back up. Between it and the compass. I should be able to get out of a cloud in that amount of time as long as I keep my head in the game. My vac pump is starting to get long in the tooth, I notice the vac gauge fluctuates every now and then. I will like adding some useful load as well.


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