WingedFrog

WingedFrog

Well Known Member
I did my first flight in turbulence recently (the kind that will have your head hit the canopy if your seat-belt is not tight, don't ask me how I know). I found myself constantly playing with the trim tab as requested by the A/P and pulling the throttle to avoid staying in the yellow only to push it again when the airspeed got too low which only made the trim issue worse. After the flight I concluded that there is no point asking the autopilot to keep altitude when flying through strong thermals. Looking at the expert mode which I have used sparingly so far, there seems to be a possibility to use only the roll servo in order to follow a GPS track and leave the pitch servo alone. In these conditions can I operate the stick for elevator control without interfering with the roll servo? This would solve my trim problem in turbulence and let me keep my altitude with more flexibility than what the pitch servo allows based on its sensitivity calibration. I still would benefit of not having to worry about my heading.
Does all this makes sense or am I missing something?
 
Just so I have a better understanding, what AP are you running and what if anything are you driving it with? Finally, what are you flying?

Thanks
 
I flew through the conditions of which you speak yesterday. The Skyview was constantly asking for trim changes, roll and pitch slips. I tried to manually fly it in pitch only and I didn't do any better than the a/p. I finally just ignored the trim annunciations and let it ride it's way through. I found as I am sure you did if you change trim it immediately asks for trim the other way, best just ignore it. I sure was glad to get out of that airplane after 3 hours of that. I hit one big bump that bounced me off the canopy and re-arranged all the stuff in the cabin. Showed to be 2.5 positive and 1.7 negative g's
 
You will not harm the AP by turning off one axis and hand flying the other.

As the others have said, let the AP ride the bumps, if you want.

For me, when it gets really bumpy, sometimes I find it more comfortable to hand fly the plane.
 
Ignore Betty......

+1
4500 over the top of Hartsfield Saturday afternoon, could not even get a good shot of downtown out the canopy because of turbulence. I have a constant speed prop so no throttle work needed, but my auto pilot captures VS or Alt, no lateral track only option, so I couldn't set it up that way, even if I wanted.
My suggestion, just ignore Betty.....

Don Jones said:
I flew through the conditions of which you speak yesterday. The Skyview was constantly asking for trim changes, roll and pitch slips. I tried to manually fly it in pitch only and I didn't do any better than the a/p. I finally just ignored the trim annunciations and let it ride it's way through. I found as I am sure you did if you change trim it immediately asks for trim the other way, best just ignore it. I sure was glad to get out of that airplane after 3 hours of that. I hit one big bump that bounced me off the canopy and re-arranged all the stuff in the cabin. Showed to be 2.5 positive and 1.7 negative g's
Click to expand...
 
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The standard recommendation for inadvertent thunderstorm penetration (e.g., strong turbulence) is to turn altitude hold off. Try to maintain nose level attitude and let the plane go up and down, assuming terrain allows it. The idea is to minimize the stress/g-loading.
 
I flew a long cross country trip last year. Although it was not turbulent, the scattered clouds caused up and down drafts. The autopilot was constantly fighting the thermals and asking for trim changes. I eventually shut the altitude hold off, but left the AP heading on. I did not try to maintain an exact altitude, just let the plane go up and down with the thermals. I controlled the average altitude using the throttle. The ride was much more comfortable this way.
Having an autopilot is like owning a microwave oven. You wonder how you ever got along without it.
Joe Gores
 
In our 9A I installed a Trio Pro Pilot. It works well in smooth air. In turbulence I find the plane will get off altitude intermittently by a couple hundred feet or more then correct and overspeed. In roll it will track GPS well but the plane will get tossed about to 30 degree roll or more and the autopilot will not correct the unusual attitude fast enough for me to feel comfortable. Thus, in turbulence the autopilot is completely unusable.

I also have a Lancair. By its very nature it does not get bothered much by turbulence. Even with an old Navaid and Altrac it works much better in turbulence than the Pro Pilot does in the 9A.

I wondered if I was alone in these problems. I wondered if the EFIS based autopilots compensated for unusual attitudes better than a non-EFIS based autopilot. I guess not. I guess the RV in turbulence is a challenge for an autopilot.
 
Let's keep it in the proper perspective!

It's important to keep a certain perspective and understanding about the autopilot. It is not a perfect entity. It is a tool to take out of your pilot bag and use when you would like to reduce fatigue or look at a map or look for traffic or check you flight plan etc. As far as autopilots go the Skyview AP is very elementary but it gives you a lot of bang for the buck.;)I think it is about a $2000 add on for the unit with the servos and wiring. If you were putting it into a C-182 or a A36 it would run about $15000 to $20000. Before you turn it on try to establish a cruse trimmed level condition with a fixed power setting. In continuous light chop you will see +-50 to 100 feet in ALT hold depending on what settings you have selected in its software setup. Also +-5 to 10 degrees in heading hold. But in NAV track it does a great job. If you were on a 150 NM x-country this wouldn't be bad at all.;) In continuous moderate chop or light turbulence it would be best to just leave ALT hold off. Also understand that you should try to keep you speed as close as possible to what ever it was when you turned it on with Alt hold engaged. Say +-10kts IAS.:p even in a climb or descent. Because when your speed changes you are no longer in trim, get it:rolleyes: So try not to chase the up-down trim indicator. Give it time to react to your inputs. Ever heard of CWS (Control Wheel Steering)? If you feel a really big thermal or bump coming on simple press and hold the red button (better known as the autopilot disconnect button) fly the plane through the wave then release the button and the AP will reengage in its previous selections. Or if you feel out of trim you can press and hold the red button and check the trim or adjust it then release the button bingo the AP reengages.:eek: Lets review, pressing the autopilot button quickly disconnects the AP. Pressing it for longer than a second enables CWS.;) So get out there and have fun with your AP.:D
 
To add to the comparison with the 15k to 20k autopilot, you would probably be getting the Stec which is a different animal. The Stec is a trim based unit that controls altitude by a change of pitch trim. While flying you will see the trim wheel moving to maintain the selected altitude. This is a very good system that has been around a long time. It does require a trim motor to control the trim cables, but works very well. I would like to hear from someone that has an Stec in their RV to see how well it works in that application. These units have altitude pre-select and hold that when properly working, nails it every time. As you can see though, they are pretty expensive. The efis based a/p's are quite a deal for the money.
 
Forane,
Not familiar enough with the Lancair. Why does it not respond to the tubulence like our RV's do? They are light and powered similarly.... Just wondering.
Nick
 
flightlogic said:
Forane,
Not familiar enough with the Lancair. Why does it not respond to the tubulence like our RV's do? They are light and powered similarly.... Just wondering.
Nick
Click to expand...

RV-12 wing area 127 sq. ft. Wingloading 10.4 lbs/sq. ft. Gross weight 1320lbs

Lancair Legacy wing area 82,5 sq. ft. Wingloading 23 lbs/sq. ft. Gross weight 2200lbs

MD-11 wing area 3648 sq. ft. Wingloading 173 lbs/sq. ft! Gross weight 630klbs

Wing loading affects gust response, the degree to which the aircraft is affected by turbulence and variations in air density. A small wing has less area on which a gust can act, both of which serve to smooth the ride (wiki).
 
Not wanting to pick on anybody's A/P but just adding a data point.
The Garmin integrated A/P handles trim.
 
flightlogic said:
Forane,
Not familiar enough with the Lancair. Why does it not respond to the tubulence like our RV's do? They are light and powered similarly.... Just wondering.
Nick
Click to expand...

Gagarin737 said:
RV-12 wing area 127 sq. ft. Wingloading 10.4 lbs/sq. ft. Gross weight 1320lbs

Lancair Legacy wing area 82,5 sq. ft. Wingloading 23 lbs/sq. ft. Gross weight 2200lbs

MD-11 wing area 3648 sq. ft. Wingloading 173 lbs/sq. ft! Gross weight 630klbs

Wing loading affects gust response, the degree to which the aircraft is affected by turbulence and variations in air density. A small wing has less area on which a gust can act, both of which serve to smooth the ride (wiki).
Click to expand...
I believe this is true but only part of the story. If you look at the RV it has large flat surfaces. Contrast that with a Lancair which has almost all rounded surfaces. Rounded fuselage allows for wind gusts to slip around with less sail effect on the plane. This is part of the reason landing in crosswinds is much easier in the Lancair than the RV.
Also, perhaps due to the wingloading, the thin Lancair wing does not generate lift anywhere near as well at slow speed as the thick RV wing does. Thus a gust just does not generate the lift to as great of extent. This is easily observed if both were tied down side by side - the RV will jump around with gusts while the Lancair hardly even needs to be tied down.
The trade off allows the RV to use much less runway at much lower speed.
 
Mich48041 said:
I flew a long cross country trip last year. Although it was not turbulent, the scattered clouds caused up and down drafts. The autopilot was constantly fighting the thermals and asking for trim changes. I eventually shut the altitude hold off, but left the AP heading on. I did not try to maintain an exact altitude, just let the plane go up and down with the thermals. I controlled the average altitude using the throttle. The ride was much more comfortable this way.
Having an autopilot is like owning a microwave oven. You wonder how you ever got along without it.
Joe Gores
Click to expand...

Thanks Joe, this is the confirmation I was hoping for. From now on I will use the A/P in expert mode.
 
Jetguy said:
It's important to keep a certain perspective and understanding about the autopilot. It is not a perfect entity. It is a tool to take out of your pilot bag and use when you would like to reduce fatigue or look at a map or look for traffic or check you flight plan etc. As far as autopilots go the Skyview AP is very elementary but it gives you a lot of bang for the buck.;)I think it is about a $2000 add on for the unit with the servos and wiring. If you were putting it into a C-182 or a A36 it would run about $15000 to $20000. Before you turn it on try to establish a cruse trimmed level condition with a fixed power setting. In continuous light chop you will see +-50 to 100 feet in ALT hold depending on what settings you have selected in its software setup. Also +-5 to 10 degrees in heading hold. But in NAV track it does a great job. If you were on a 150 NM x-country this wouldn't be bad at all.;) In continuous moderate chop or light turbulence it would be best to just leave ALT hold off. Also understand that you should try to keep you speed as close as possible to what ever it was when you turned it on with Alt hold engaged. Say +-10kts IAS.:p even in a climb or descent. Because when your speed changes you are no longer in trim, get it:rolleyes: So try not to chase the up-down trim indicator. Give it time to react to your inputs. Ever heard of CWS (Control Wheel Steering)? If you feel a really big thermal or bump coming on simple press and hold the red button (better known as the autopilot disconnect button) fly the plane through the wave then release the button and the AP will reengage in its previous selections. Or if you feel out of trim you can press and hold the red button and check the trim or adjust it then release the button bingo the AP reengages.:eek: Lets review, pressing the autopilot button quickly disconnects the AP. Pressing it for longer than a second enables CWS.;) So get out there and have fun with your AP.:D
Click to expand...

Great tutorial John, I did not expect so much but I will take it, and intend to have fun, yes! Thanks!
 
Dave12 said:
To add to the comparison with the 15k to 20k autopilot, you would probably be getting the Stec which is a different animal. The Stec is a trim based unit that controls altitude by a change of pitch trim. While flying you will see the trim wheel moving to maintain the selected altitude. This is a very good system that has been around a long time. It does require a trim motor to control the trim cables, but works very well. I would like to hear from someone that has an Stec in their RV to see how well it works in that application. These units have altitude pre-select and hold that when properly working, nails it every time. As you can see though, they are pretty expensive. The efis based a/p's are quite a deal for the money.
Click to expand...


Don't know anything about the Stec, but Pre-select operation is possible in the Dynon. I have the creaky old D-180 and AP74 and in the Dynon default setup mode the AP-74 captures the current heading and altitude when the auto pilot is engaged, not a pre-selected heading or altitude. However, that is the default ON ENGAGE mode. In the SETUP>AP>AP74 SETTINGS menu you can change the engage mode to ON MODE ARM, and when the autopilot is engaged, the bug settings are not modified. That allows you to pre-select a desired heading and/or altitude prior to engaging the AP and when you push the engage button the AP initiates a turn and climb to your preselected heading and altitude. For instance, you can be on the ground, power up the AP but not engaged, arm the heading and altitude buttons, set the bugs for your desired heading and altitude. After takeoff, engage the AP and it will fly to your pre-selected hdg and alt. Betty warns you when passing within 500' of your set altitude and the Dynon is spot on too, when capturing the altitude, mine within 10' or so. and the SkyView modes must be similar and even better. I don't know how much better than that the Stec could be.
 
Last year, flying home from Idaho to Texas I was very glad to have at least a 1 axis autopilot to help fly through mountain turbulence. I only had to hand-fly the pitch. There were moments of barely keeping the plane under control, but the autopilot did a wonderful job at keeping the wings mostly level through the roughest spots. If I would have had to hand-fly both axis, it would've been very much more fatiguing to do that.
 
Dave12 said:
To add to the comparison with the 15k to 20k autopilot, you would probably be getting the Stec which is a different animal. The Stec is a trim based unit that controls altitude by a change of pitch trim. While flying you will see the trim wheel moving to maintain the selected altitude. This is a very good system that has been around a long time. It does require a trim motor to control the trim cables, but works very well. I would like to hear from someone that has an Stec in their RV to see how well it works in that application. These units have altitude pre-select and hold that when properly working, nails it every time. As you can see though, they are pretty expensive. The efis based a/p's are quite a deal for the money.
Click to expand...

I'll agree with you that the new crop of A/P's are fantastic, but totally disagree on the operation of the typical S-Tec....it's works in no way how you describe it above. Don't confuse "automatic pitch trim" which will move the trim in order to keep forces on the flight controls in balance, with the misconception that the autopilot is actually using the trim to fly it. S-Tec's have huge servos that connect to the flight control system. No flame intended, just wanted to make sure we didn't mislead someone. Almost every experimental autopilot is leaps better than the older certified counterparts, that I will agree on! :)

Cheers,
Stein
 
In the early 2000s, I flew co-pilot in an Aztec from Iowa to Las Vegas. There were six of us on board.

We skirted South of an area of severe thunderstorms near Kansas City. From that point on, the airplane was all over the place, in moderate to severe turbulence. The tail was wagging, the nose was bobbing up and down, and it was extremely uncomfortable. Of the six people aboard, I was the only one who did not get sick. Most of them got sick multiple times, including the pilot.

We filled 23 sick-sacs that day. 23! It has henceforth been known as the Vomit Comet.

It was only near the end of the flight that the pilot disengaged his STEC autopilot -- and almost instantly the ride became MUCH smoother. Apparently that danged thing had been fighting the turbulence, and throwing in control inputs that were a half-cycle out of sync with the turbulence. In other words, it was INDUCING turbulence, making it worse.

That was a forehead-smacking day. Had he only known to disengage that autopilot, we could have made a lot of people happy.

So, moral of the story: Autopilots aren't always the best method of flight in turbulence.
 
In the advanced mode, you also have the ability to choose a vertical speed of zero, instead of a specific altitude. This will reduce the amount it fights thermals, but will lead to a slow drift of your altitude.

We've actually done a lot of work in the AP to make it more comfortable in turbulence. Our original AP fought REALLY hard to stay on altitude, even in turbulence. Did a fine job at that. Also made people sick. We learned a lot and now the AP is a bit looser in turbulence, but a lot more comfortable.

Jetguy said:
As far as autopilots go the Skyview AP is very elementary but it gives you a lot of bang for the buck.
Click to expand...

Jetguy, the Dynon AP can do altitude intercepts, IAS holds, sequenced approaches, and fully coupled approaches with sequencing. Some of our customers tell us it's as capable as the one in the 767 they fly. You are likely using the AP in simplified mode, which does reduce your options while making it a bit easier to use, but the AP itself has the capability to be one of the most advanced autopilots around.
 
Jetguy, the Dynon AP can do altitude intercepts, IAS holds, sequenced approaches, and fully coupled approaches with sequencing. Some of our customers tell us it's as capable as the one in the 767 they fly. You are likely using the AP in simplified mode, which does reduce your options while making it a bit easier to use, but the AP itself has the capability to be one of the most advanced autopilots around.
Click to expand...

Well, having flown the 767 for many hours I guess we will have to agree to disagree on this particular subject. ;)
 
I'd say turn it off in turbulence, and f you don't like the ride turn it back on. For my preference I leave it off in turbulence.
 
RFSchaller said:
I'd say turn it off in turbulence, and f you don't like the ride turn it back on. For my preference I leave it off in turbulence.
Click to expand...

Rich, I am not going to give up that soon! I am the kind of guy who always drives with the cruise control on and I am a techie, this is fertile ground to indulge in my worse foibles! :eek::rolleyes:;):D
 
dynonsupport said:
In the advanced mode, you also have the ability to choose a vertical speed of zero, instead of a specific altitude. This will reduce the amount it fights thermals, but will lead to a slow drift of your altitude.

We've actually done a lot of work in the AP to make it more comfortable in turbulence. Our original AP fought REALLY hard to stay on altitude, even in turbulence. Did a fine job at that. Also made people sick. We learned a lot and now the AP is a bit looser in turbulence, but a lot more comfortable.



Jetguy, the Dynon AP can do altitude intercepts, IAS holds, sequenced approaches, and fully coupled approaches with sequencing. Some of our customers tell us it's as capable as the one in the 767 they fly. You are likely using the AP in simplified mode, which does reduce your options while making it a bit easier to use, but the AP itself has the capability to be one of the most advanced autopilots around.
Click to expand...

But to do that, don't you have to feed it with nav....and/or a waas gps like the 430w to do LPV approaches?

Most 12s only have a comm....no nav source.
 
Dynon vs TruTrac

So, Dynon Support Guy, I'm a big fan of Dynon in general, but not your autopilot. i know your tech team considers the TruTrac product line to be the 'gold standard', and have compared your product's performance to it as you worked to improve your own. How do you think your product rates now, and why? What capability did you improve, and how did you do it? A technical answer would be appreciated.
Thanks...and thanks for great products!
 
gossend said:
So, Dynon Support Guy, I'm a big fan of Dynon in general, but not your autopilot. i know your tech team considers the TruTrac product line to be the 'gold standard', and have compared your product's performance to it as you worked to improve your own. How do you think your product rates now, and why? What capability did you improve, and how did you do it? A technical answer would be appreciated.
Thanks...and thanks for great products!
Click to expand...

Dynon Avionics is constantly working to improve our products, so we value any and all feedback on them. Knowing what is and isn't working for our customers is key to engineering the best products we possibly can. In both SkyView and our D10/D100-series products, our autopilot has been through a few different iterations. So, it would help to know what models and version of software you are referencing so we can get you better information.

Our engineering approach in all our products is a delicate balancing act between (1) adding features/flexibility, (2) keeping it easy to use, and (3) in the case of the AP, making it comfortable. We feel we've made great strides since the autopilot was first released in 2008. While we don’t want to give away the store, we can say a few things about the improvements we’ve made (in both D10/D100 and Skyview):

  • Great heading and track hold performance both in still air and in turbulence, even if you have the ball off center.
  • Gust alleviation capability in vertical gusts.
  • Transitions from altitude hold to climbs and descents, and altitude capture with no overshoot.
  • Turns to heading in both heading and track modes

The advanced autopilot in Skyview adds several more features, including:
  • Smooth 1 knot/second airspeed control.
  • Separate vertical speed hold.
  • No difference in altitude capture from either vertical speed or airspeed.
  • An optional dedicated autopilot interface control panel to simplify workflow.
  • VNAV, IAS Hold, mode sequencing, fully-coupled approaches
  • Flight Director with single cue (v-bars) or dual cue (crosshairs) presentation

Over the last few months, we’ve been tweaking some of the more subtle aspects of the autopilot’s performance - for example, how it annunciates pitch trim needs. We’ve been quietly but publicly testing these improvements in our own support forum.

It is an engineering challenge to design an autopilot which provides a stable, comfortable ride in the huge range of Experimental and LSA aircraft. The autopilot is highly tunable to allow for the range of airplanes it may find itself in. While the out of the box setup works for many planes, we know that every plane is different. Even 2 RV8s, built by 2 different people can have slightly different flight characteristics which make it difficult to have a one-size-fits-all approach. We now provide a comprehensive "Autopilot In-Flight Tuning Guide”, which provides a step-by-step process for both tuning our autopilot from scratch, as well as troubleshooting specific issues.

We find that the vast majority of customers who methodically follow the Tuning Guide wind up with an excellent ride in a wide variety of conditions.

We have a full-time autopilot & aeronautical engineer, who obsesses over data logs from AP flights in a wide variety of aircraft. He and our team of pilots and software engineers are always looking for ways to improve the autopilot experience. Specific feedback on both user interface and ride quality gives them something to chew on.

If you have other specific questions or feedback, please don't hesitate to ask.

Paul Dunscomb
VP Engineering
Dynon Avionics
 
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Thanks for the well constructed and insightful response. Much appreciated. I'll pursue it further with the reference materials you provided.
Thanks again
DG
 
PaulD said:
Dynon Avionics is constantly working to improve our products, so we value any and all feedback on them. Knowing what is and isn't working for our customers is key to engineering the best products we possibly can. In both SkyView and our D10/D100-series products, our autopilot has been through a few different iterations. So, it would help to know what models and version of software you are referencing so we can get you better information.

Our engineering approach in all our products is a delicate balancing act between (1) adding features/flexibility, (2) keeping it easy to use, and (3) in the case of the AP, making it comfortable. We feel we've made great strides since the autopilot was first released in 2008. While we don?t want to give away the store, we can say a few things about the improvements we?ve made (in both D10/D100 and Skyview):

  • Great heading and track hold performance both in still air and in turbulence, even if you have the ball off center.
  • Gust alleviation capability in vertical gusts.
  • Transitions from altitude hold to climbs and descents, and altitude capture with no overshoot.
  • Turns to heading in both heading and track modes

The advanced autopilot in Skyview adds several more features, including:
  • Smooth 1 knot/second airspeed control.
  • Separate vertical speed hold.
  • No difference in altitude capture from either vertical speed or airspeed.
  • An optional dedicated autopilot interface control panel to simplify workflow.
  • VNAV, IAS Hold, mode sequencing, fully-coupled approaches
  • Flight Director with single cue (v-bars) or dual cue (crosshairs) presentation

Over the last few months, we?ve been tweaking some of the more subtle aspects of the autopilot?s performance - for example, how it annunciates pitch trim needs. We?ve been quietly but publicly testing these improvements in our own support forum.

It is an engineering challenge to design an autopilot which provides a stable, comfortable ride in the huge range of Experimental and LSA aircraft. The autopilot is highly tunable to allow for the range of airplanes it may find itself in. While the out of the box setup works for many planes, we know that every plane is different. Even 2 RV8s, built by 2 different people can have slightly different flight characteristics which make it difficult to have a one-size-fits-all approach. We now provide a comprehensive "Autopilot In-Flight Tuning Guide?, which provides a step-by-step process for both tuning our autopilot from scratch, as well as troubleshooting specific issues.

We find that the vast majority of customers who methodically follow the Tuning Guide wind up with an excellent ride in a wide variety of conditions.

We have a full-time autopilot & aeronautical engineer, who obsesses over data logs from AP flights in a wide variety of aircraft. He and our team of pilots and software engineers are always looking for ways to improve the autopilot experience. Specific feedback on both user interface and ride quality gives them something to chew on.

If you have other specific questions or feedback, please don't hesitate to ask.

Paul Dunscomb
VP Engineering
Dynon Avionics
Click to expand...

This is the reason why I chose SkyView displays with the integrated autopilot for my newly acquired airplane.

Keep up the good work and thank you for your informative post, Paul.
 
A great read. A great team. Thank you Dynon....
Happy 4th to all Americans. Thanks be to modern weaponry and trees to hide behind... that we are not British... And that we eat our toast hot.
 
Question to Dynon guy

"You are likely using the AP in simplified mode"

Can you explain your statement about "simplified" or "advanced" mode. I didn't realize we have these different modes.
Thanks
 
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