DYNON AP Performance

Over the months there have been multiple posts regarding the performance of DYNON?s AP system. Several of the posts have complained about the AP not being able to hold altitude or course without significant deviations. Others report poor performance in all but extremely smooth air yet some, including the DYNON Beta testers claim the performance is rock solid. In an attempt to quantify the AP performance I think it would be interesting to poll those who have installed and have flown the DYNON AP in their RVs.

Joe,

Your poll is not going to give you good info as the software version people are using along with the servos will have a big impact on how the AP works.

For instance, I can now say the Dynon AP is rock solid in my installation but as a Beta Tester my software and hardware versions are ahead of what has been released. Also I have over 100 hours flying with the Dynon AP and know how to tune it to MY plane. This tuning is not trivial and it took me some time to get it "right". Even then I still play around with the settings.

Some of those posting on this forum have talked about going to the mid-size SV42 servos, those have a higher torque setting the SV32's. Thus if someone is flying with the SV32's and they are slipping a good bit, their AP will not be able to control the aircraft as well as the exact same aircraft with the SV42's that do not slip. Even then, it is possible to tune the SV42's so they put out less torque than the SV32's.

The other challenge is what is “rock solid”. Other than Jamie Painter, very few of us have flown with different AP’s in the same aircraft. Some might feel that one AP is rock solid while AP Brand X is wondering all over the place but in reality Brand X may do a better job of holding heading and altitude.

For example, your last option "Acceptable performance only in smooth air", who has flown a TT, Dynon, and Trio and can compare them? Maybe the Dynon does better in rough air than the others but it is still unacceptable to the user.

Subjective polls such as this are very difficult to derive useful data from.

to me rock solid would be like setting the cruise on my truck. It holds the speed, when I go up a hill it speeds up but not past the speed I have set, lets say 55mph or just plain maintains the speed. It approaches the speed and lets up and settles right on 55 or like mentioned just maintains the speed throughout. My AP(dynon) is like a little kid is flying, it needs to make a change and goes up lets say in altitude and than goes past and says hay, we went past and than drops back down and hay we missed again. This is in calm no turbulance flying. Very anoying. I see NO slip, I assume that's a yellow indication on the lower left of the screen for pitch. I think the software needs some help, lots of help. I do find the only time I can use the AP is when I need to pluck in a new waypoint and I need to take my attentions away from flying, it does ok to keep me from diving and losing everything so to speak. When I'm done doing this, I cancel AP.

You need to check it

allbee said:

to me rock solid would be like setting the cruise on my truck. It holds the speed, when I go up a hill it speeds up but not past the speed I have set, lets say 55mph or just plain maintains the speed. It approaches the speed and lets up and settles right on 55 or like mentioned just maintains the speed throughout. My AP(dynon) is like a little kid is flying, it needs to make a change and goes up lets say in altitude and than goes past and says hay, we went past and than drops back down and hay we missed again. This is in calm no turbulance flying. Very anoying. I see NO slip, I assume that's a yellow indication on the lower left of the screen for pitch. I think the software needs some help, lots of help. I do find the only time I can use the AP is when I need to pluck in a new waypoint and I need to take my attentions away from flying, it does ok to keep me from diving and losing everything so to speak. When I'm done doing this, I cancel AP.

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Dude, something is wrong. Mine will pulse a little now and then but it never does what you are describing. Well it did once and checked the shear screw. Guess what, that was the problem. Fixed it and the AP went right back to working fine. You need to check 1) That the shear screw is tight 2)that you don't have excessive play in your control path and 3)that the servo is mounted solidly with little to no flex. I regularly fly 2.5 to 3 hour sorties and I fly abut a .1. Dynon does the rest including the climb and descent.

For anyone that's not getting the performance they're expecting from our autopilot, please give us a call at 425-402-0433 or send an email to [email protected].

I agree this is a bit of an unfair poll for the reasons Bill R. stated.

In my case, I have an RV-8 with a Dynon AP that is controlled by an AP74. There is also an HS34 in the set up. I started out with SV32 servos, but particularly with the pitch servo, was seeing an unacceptable amount of servo slip (and was seeing some slip on the roll servo). Dynon, being the great folks that they are, shipped me two SV42's that I installed. I went flying and went through their set up routine for the AP. I am very pleased with the performance. The altitude is within 20' of the set point, with no twitchiness or altitude excursions. If the airplane climbs by 10 or 20 feet as it would in an mild updraft, it will gently track back down to the set point. The same is true for the roll servo. Heading is within a degree or two, no twitchiness, and tracks a GPS course very well. I have yet to fly it in major turbulence with lots of updrafts and downdrafts. Those conditions are a challenge for any GA autopilot. I once flew with a $40k King KFC-200 AP in a Beech, and on those gusty days, it had a hard time keeping up. On those days you're better off uncoupling and hand flying anyway.

I could probably get by with an SV32 for roll, but I like the SV42 as it gives me options since the torque is not cranked up to 100%. Going from memory, but I think my torque on the pitch servo is 85% (more torque than the SV32 can provide), and the roll is either 60 or 65%. It is important to take your time doing the setup. If you can't dial it in and the plane is hopping all over the place, something is wrong: loose shear screw, servo needs to be upsized due to too much slippage, control linkage slop, servo mount flexing. Any of these issues (or combination thereof) will significantly degrade AP performance.

dynonsupport said:

For anyone that's not getting the performance they're expecting from our autopilot, please give us a call at 425-402-0433 or send an email to [email protected].

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You can't ask for anything more than that.

Before builders post their "issues" here give Dynon the courteous of trying to work out the problems you are having. All vendors have issues from time to time. Is your plane perfect? Dynon seems to be one of those vendors that is willing to work with us, infact they bend over backwards to make things happen. Don't screw it up for the rest of us, work with them first. The AP world need the compedtition.

I concur with the comments about working with Dynon, and the subjective nature of the poll, but will say enthusiastically that Dynon worked with me diligently throughout my install and troubleshooting, and I am pleased with the results.

I answered B.) Good performance in all weather conditions, but would modify it to say that it is very solid in smooth air, and descent in light turbulence and up/downdrafts, such as I have seen over the mountains at times. I did have some pitch oscillations early on, and did the servo screw and castellated nut adjustment per the Dynon instructions, and have been pleased with the results. I also recently uploaded the 5.1.1 software update...waited a bit as I heard that some were having issues with 5.1, but the fix was put out by Dynon very rapidly, and I've had no issues with 5.1.1. No extensive experience with other similar GA AP's but will say that it flies my airplane well.

I have an RV-6 (Super Six, so it's a bit heavier overall, but FWIW has light controls, per my experience and that of my seller, an experienced Rocket builder/flyer). AP-74 and 2 SV-32 Servos. Torque (both) set at 100%. Sensitivity set at 15 pitch, 8 roll seems to be the sweet spot for smooth air, and the ability to adjust those values in flight in bumpy air makes for acceptable performance there (another subjective comment, of course). Quantitatively, I see +/- 10-20' in ALT hold with smooth corrections most of the time, and good 500 fpm climbs/descents with an occasional bump, and pretty good level offs. Roll control is very solid in NAV, and +/- a couple degrees in HDG, with just the occasional bump. I personally think roll control is a little more solid in NAV, but only lightly less so in HDG. If the roll bumps get more noticible it's usually due to fuel burn/balance, and a tweak of the airleron trim alleviates them. Pitch and roll trim are key to good performance (probably an obvious statement ), but that's likely true for all similar units.

A good example of the performance would be a X-C this past week from Reno to San Luis Obispo and back to do a dynamic balance on my prop. I flew on AP and took "before and after" vibration readings with an app on my iPhone (a separate post for later). AP made the task easy, held HDG and ALT quite well and made very smooth turns between runs. It's been very comfortable on the X-Cs I've taken since installation.

Overall a very nice piece of gear, with lots of nice features that are even nicer with the AP-74.

Cheers,
Bob

Second guessing?

In 2007 I hitched a ride to the Copperstate fly-in with Ken Holcomb in his RV7. Ken has a pair of Dynon's and it was my first time flying behind a glass panel, I was impressed. I spoke with the Dynon representative at Copperstate as well as a few follow up phone calls to Dynon.

I am currently working on the fuselage but while working on the wings I made the decision to go with Dynon. I purchased and installed their roll servo and heated pitot. I was feeling good about my decision but the first few post in this string had me second guessing myself.

I'm feeling better after the last few positive post but I'm following this discussion with interest so please keep the comments coming.

Thanks!

For 1500 bucks (approx) it doesn't get any better than this.

Generally speaking, I fly my 9A in smooth air and it holds alt & course quite well. My XC is monthly round trips Tucson to Long Beach. I had two problems with the AP but in both cases Dynon worked with me to resolve them.

One issue was the rebooting of the D180 I use to control the AP74. Dynon first RMA'd the D180 but when that didn't resolve the issue, they brought in one of the software people to examine their code and determine what could be causing the fault. Turns out the software indicated the only device that could reboot a D180 (with internal battery backup) was the magnetometer. Dynon suggested I disconnect the questionable compass (I have two) and test for a few hours. The D180 quit rebooting so then Dynon sent me a new magnetometer. Three hours later, no more reboots.

With respect to its ability to hold course, flying thru LAX Class B near Disneyland is not the easiest assignment. As soon as I'm off LGB, I bank a hard right, engage AP, and it takes me directly to the first WAYPOINT and then onto the next. If ATC clears me to 9500, I set AP for 9,500, leave it at 500 fpm climb, and sit back and relax as we cruise home.

During the last trip the wife said, "I'm gonna take a nap" to which I replied: "Me first" (kidding of course). Workload is down by at least 80%. On two occasions ATC asked me if I had an autopilot installed given the dead bang straight line course and little to no deviation from assigned alt.

For 1500 bucks (approx) it doesn't get any better than this. Hopefully, this answers the survey.

My airplane (not an RV) while very maneuverable and fun to fly VFR, however is a handful IFR . My Dynon auto pilot adds the stability need, so I can easily fly my plane in IMC. Yes, it is rock solid.
You should see my flight aware trip logs and flight data recorded down loaded from the Dynon?it is truly there in all weather conditions. I would agree with others that this performance is highly dependent on the set up and installation. I have over 100 hours flying it. It a takes a while to get the thing set up properly. I was a beta tester for Dynon on this product and I have quite a bit of experience working with it. Yesterday I took my bother in law up for a flight (he designs auto pilots for Honeywell) his comments ?.not bad at all, but when I told him the price, he was truly amazed by this product.

I'm not certain if I need to make the shear-pin repair (my servo is supposedly not affected by the production problems Dynon reported) -- for those of you who are getting good performance, how much play at the aileron do you have with the AP engaged?

The trailing edge of my (9A) ailerons can move 1/2" up and down, AP engaged on the ground. This movement is not due to play in the control system -- the servo itself is allowing this movement. In smooth air, it does ok, though it's easy to put it off course when I make altitude adjustments (I have a roll servo only). In what feels like light-to-moderate turbulence to me, it's all over the place. Have tried different sensitivity, torque, etc.

Haven't upgraded to the 5.1.1 software yet.

Paul Eastham said:

The trailing edge of my (9A) ailerons can move 1/2" up and down, AP engaged on the ground. This movement is not due to play in the control system -- the servo itself is allowing this movement.

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If the aileron is moving more than 1 degree up or 1 degree down with the servo engaged (SETUP->AP->TEST will hold the servo in position for this test), that's excessive play.

If the servo arm is moving relative to its shaft, something is loose and needs attention. Give us a call at 425-402-0433 or send an email to [email protected].

Just wanted to post our results on the Dynon AP.

System is D100/D180/HS34/AP74......and would be the AP76

Nav is provided by a GNS530W.

Heading mode. Pretty Good, not 100% but 98% and maybe another compass cailbration might help.

Track Mode. 99.9% Does this beautifully.

Nav VOR. Could be a bit better in rough conditions however overall its excellent performance. There may be parameters in the GNS530W that I have not found yet for tuning the VOR outputs, but essentially its fine.

Nav GPS. 100%.....Perfect!

Altitude Hold. Long story here but we did have a shear screw that needed replacing and Loctite 271 treatment. We did the mod on the first servo which was a much earlier shipment (due to a stuff up the second one was a 32 sent) so when we received the second one well after the SB, we believed it was factory done. It was not and it was sloppy. Also one of the rod ends had an amazing amount of slop in it, which I did not notice during the installation. Now that its all sorted its rock solid. The sensitivity setting has beedn reduced to 16 and its great!

All we need now is the vertical Nav option, and this will be the best bang for buck AP on the planet!...... and its pretty dran ood now!

DB

For what it is worth guys, watching these threads over the year I see person after person getting their problems resolved working with Dynon.

Remember that this product is still only (or less than) a year old. The competitors have had a decade or more of time to fine-tune their products, and all cost more. Keep working with them and they will get it sorted out.

breister said:

For what it is worth guys, watching these threads over the year I see person after person getting their problems resolved working with Dynon.

Remember that this product is still only (or less than) a year old. The competitors have had a decade or more of time to fine-tune their products, and all cost more. Keep working with them and they will get it sorted out.

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Bill, good observation.

I have also tried to pay close attention to the thread (concerns that it may turn into a vendor bashing session), and like you I am pleased to see the outcome.

Good Job, Dynon.

If any of you would really like to see the AP76 come to life in the future, please send me your details via a PM and encourage your mates to as well.

I am going to start a big push to co-operate with Dynon on getting this one to market. I will need your support.

If we can get this over the line, Dynons Skyview and "Classic view" will be the best AP on the market!

So all the lurkers out there, put your hand in the air and be counted!

DB