Auto pilots and bumps

AuntPeggy

AuntPeggy

Final Approach
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Oklahoma
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Today I picked up the C-172 from Sky Acres where its annual was completed. I played with it a little bit, then settled in to fly home. I turned on the autopilot, but the wind was choppy and we started bumping along so I turned off the autopilot and flew by hand.

We had the autopilot motor burn out a couple of years ago and I have been convinced that it was turbulence that caused it to fail. So, now I'm asking you all. Do you turn off the autopilot in mild turbulence?
 
I tend to leave the autopilot on. The manual claims smoother flight with the autopilot and I tend to agree with the manual so far. Sure, it'll be more wear-n-tear but so far I just accept it. Heck, I had all that work done on the autopilot to use it, not just look at the switches and dials and say that it's a neat thing that I can't afford to use.
 
Clark1961 said:
I tend to leave the autopilot on. The manual claims smoother flight with the autopilot and I tend to agree with the manual so far. Sure, it'll be more wear-n-tear but so far I just accept it. Heck, I had all that work done on the autopilot to use it, not just look at the switches and dials and say that it's a neat thing that I can't afford to use.
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I agree. I leave my single axis on in mild to moderate turbulence.
 
I leave it on in turbulence but then I'm a renter. If I owned the airplane I think I'd still use the AP in turbulence. I would think the drive servos are designed to handle loads imposed by at least a moderate level of turbulence.
 
Depends on the autopilot and what it is certified to do. Consult the autopilot manual and check it's limitations and recommended use.
 
Nav8tor said:
I leave it on in turbulence but then I'm a renter. If I owned the airplane I think I'd still use the AP in turbulence. I would think the drive servos are designed to handle loads imposed by at least a moderate level of turbulence.
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It depends upon the autopilot. My 337 has a Cessna 400A autopilot and the servos have shear pins that will shear if overloaded. Some other makes of autopilots use clutches on the servos.
 
With an attitude based autopilot, I generally leave it on in the mild bumps. Rate based autopilots generally don't react as well, particularly in pitch, so they go off.

In the G1000/GFC700, it's "what turbulence?" Well, not really, but close. That system is practically as good in turbulence as my hand flying.
 
Always on. I'm also used to having a yaw damper, so that of course stays on, too.

In some airplanes that are rather slow and slippery, like the DA-40, I'd turn the AP off in turbulence. Otherwise, it's very easy to overspeed....

-Felix
 
Rotor&Wing said:
It depends upon the autopilot. My 337 has a Cessna 400A autopilot and the servos have shear pins that will shear if overloaded. Some other makes of autopilots use clutches on the servos.
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And have the shear pins in your 400A ever failed as a result of turbulence?
 
TMetzinger said:
With an attitude based autopilot, I generally leave it on in the mild bumps. Rate based autopilots generally don't react as well, particularly in pitch, so they go off.
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I agree with your comment on rate based autopilots with a caveat, I will turn off the altitude hold but leave on the roll axis.
 
When I flew a plane with autopilot (AP) for IFR training in turbulance I would turn the AP on for a few minutes then turn it off to practice responding to the instruments. The AP would do a better job of trimming the airplane in bumpy conditions than I could for level flight.
 
Rotor&Wing said:
It depends upon the autopilot. My 337 has a Cessna 400A autopilot and the servos have shear pins that will shear if overloaded. Some other makes of autopilots use clutches on the servos.
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AFaIK, the autopilots with shear pins in the servos are designed to limit control forces electrically to something less than that necessary to shear a pin and only an electrical failure should result in a broken pin. This may not always be true though, I'd refer to the POH supplement for the particular autopilot for guidance. Aside from that, in some conditions I find I can deliver a smoother ride if I take over from the autopilot but I wouldn't be concerned about hurting the servos beyond the slightly higher wear rate in turbulent conditions.
 
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