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Ian

Autopilot in Turbulence

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A question for the wiser and more experienced heads than me on here.

 

If you encounter turbulence what are the limits (or even are there any limits) to using the autopilot?

 

To date, if I've been flying on autopilot then run into turbulent air I've always gone back to hand flying it, not too sure why, but just a bit of uneasiness over what the servos can cope with - am I being unduly worried?

 

Thanks

Ian

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Hi Ian,

 

I don't believe the AP will have any issues, but I hear many prefer flying by hand in bad turbulence because a person seems to do a better job over all.

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Hi Ian,

 

The autopilot handles light to moderate turbulence just fine, I tend to turn mine off when I have to chase it with throttle a lot, meaning when the autopilot is making large pitch excursions to try and maintain altitude causing me to throttle down to prevent overspeed or up to keep from loosing airspeed. In these cases which I would consider constant moderate turbulence its less frustrating to hand fly.

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When flying into turbulence it is important to fly at your maneuvering speed. In a CTLS that is 98 kts CAS.

 

You can fly on the autopilot but if hand flown one can probably make corrections in a more timely fashion. Also I'm not sure if the Autopilot can make as large a correction as one can hand flying.

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From the TruTrak website: "Trutrak autopilots fly very well in turbulence. It is not necessary to turn off a Trutrak autopilot in any amount of turbulence." (see fourth question at TT FAQ page http://www.trutrakap.com/faq.html). Probably best to ask them directly on their Customer Forum web page.

 

My TT AP flies well in turbulence, but I do slow to below Va. But, your turbulence may be my stay on the ground conditions.

 

fg

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My experience in turbulence with the autopilot is that it makes for a very "nervous" ride with instant corrections to turbulence and handflying (although more tiring) makes for a much smoother ride.

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Thanks for your thoughts. I think this year I'll do a bit of experimentation when it gets bumpy

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I've had to recently reset my TruTrak A/P after getting it back from the factory for repair. The new software and internals seemed to change the response of the A/P and I had to crank up the sensitivity to prevent "hunting" in still air. In doing this, I found that the unit can become overly responsive if cranked too high. The good thing is that there is a large range of settings and the TruTrak is capable of sensing very small changes in attitude. My thought on those who feel that their A/P is correcting too much or too fast in turbulence is to look at their settings and try lowing the vertical and/or latteral sensitivities to a point where the A/P is not overreacting to the conditions. I've not done this so I do not know if doing so may result in under correction in still air. I would suggest that all settings are recorded before making any changes because there is no way to go back to previous settings other than manually doing so. Of course, there is always the TruTrak experts like Lucas and others who are there to answer questions such as these.

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Dick, when you say "sensitivity", do you mean "activity" on the AP menu? (sensitivity is not a bad description of what the activity parameter does)

fg

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Yep! He means activity. There actually is no one set of settings that will work for every aircraft of the same type. A set of "stock" settings will get you close. But tune the autopilot to YOUR comfort, not what the airplane is "suppsoed" to use. If it seems a little jumpy in turblulence, reduce the activity setting a little bit. My suggestion is to make small changes. Adjsut the value by one number at a time and allow 1-2 minutes for the autopilot to adjust. Although the change is instantaneous as far as the setting adjustment goes, the effect on the flight dynamics usually takes a little longer. Continue making adjustments until you're comfortable. MOST airframes have a happy medium point where you can acheive a set of settings that flies well in smooth or rough air. HTH. Thanks!

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Didn't some autopilots have a turbulence setting that was a little slower to respond? I assume you can't make any of these changes in situ, but must choose which setting makes you happy and live with it from one flight to the next?

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I'd be curious what Lucas says - I have adjusted my TT AP parameters (activity, micro activity, and static lag) in flight with no ill effects.

fg

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Adjustment can be done "in situ" with the TruTrak. While flying, hold in the "VERT" or "LAT" button until the menu comes up and continue with the changes. Just let it settle for a few seconds and stabilize before evaluating the change. It is possible to have unique settings for various conditions if this suits one's needs. Besides VERT ACTIVITY and LAT ACTIVITY there is also MICRO ACTIVITY and HALF STEP to play with so the changes can take some time to work thru. While finding the best settings, personally I prefer to have someone fly the airplane and watch for traffic while I tweak the TruTrak. I'm not sure how well one can tune the system while flying in turbulence due to the variability of the conditions preventing consistent results from the changed settings. I have found that adjustment of the system in very still air has worked best as the settings seem to also provide good aircraft control in gusty or turbulent conditions. Due to the amount combinations possible for the various settings, it is recommended that one record initial settings before adjustment if one wishes to return to baseline and bring along a notebook to record comments and settings made during the flight.

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Dic,

 

Thanks for the info. Any way to pre-program a couple of different settings so you invoke them with a key stroke or two, depending on the situation?

 

 

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I'd be curious what Lucas says - I have adjusted my TT AP parameters (activity, micro activity, and static lag) in flight with no ill effects.

fg

 

Definitely. You really ONLY want to make adjustments in the air. Making the adjustments on the ground is stabbing in the dark. Smooth air works better as another poster said, it's difficult to sense any result in turbulent air.

 

 

Dic,

 

Thanks for the info. Any way to pre-program a couple of different settings so you invoke them with a key stroke or two, depending on the situation?

 

There is not a quick change for the settings. I do not know of any digital autopilots that have this function.

 

Thanks!

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From the time that my plane was new, if a tried to engage the autopilot as I was climbing after takeoff, the plane would drop the nose and turn to the right. I called Lucas today and we went through my setting and found that the min. speed was set at 89 kts. That has been my problem as most of the time, my climb out would probably be 78 kts. or more, but less than 89. Anyone know what the min. speed should be?

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From the time that my plane was new, if a tried to engage the autopilot as I was climbing after takeoff, the plane would drop the nose and turn to the right. I called Lucas today and we went through my setting and found that the min. speed was set at 89 kts. That has been my problem as most of the time, my climb out would probably be 78 kts. or more, but less than 89. Anyone know what the min. speed should be?

Minimum controllable airspeed plus a little margin is a good ball park. I think mine is set to 60kt. At that speed the AP can make a level turn at its maximum rate (I think mine is set to max out around 25 degrees bank) and never get close to the stall.

 

If it gets slower than that I want to be hand flying. In reality I don't think I have turned on the AP below 80kt or so.

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Here are the Dynon Autopilot settings for Pitch Axis.

 

Torque                                 10%                 100%              100%

Sensitivity                              1                      24                    10

                                        

Default Climb Vert SPD     100 ft/min        3000 ft/min      500 ft/min

Default Descent Vert SPD 100 ft/min        3000 ft/min      500 ft/min

Max Airspeed                      1.30*Vs1         .95*Vne           .95*Vne

Min Airspeed                       1.30*Vs1         .95*Vne          1.30*Vs1

 

Roll Axis have no speed settings, they are Roll Gain and Bank Angle Limit only.

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