Dynon certified install on a Cessna 172- Auto pilot roll slip and other frustrating issues...

Douglas

New Member
Joined
Sep 21, 2019
Messages
13
I recently spent a great sum of money to have an absolutely beautiful dual screen Dynon HDX panel with all the bells and whistles installed in my 1977 Cessna 172. I must say, although it is beautiful to look at and I am pleased with many of the awesome features, I have been plagued with problems from the moment we powered up the system.
First let me say I feel like I chose a reputable shop with many years of Dynon experience to do the install. In fact, I chose this particular shop not because they were on Dynon’s “certified” installers list, but because they were the biggest proponents of Dynons equipment. Their sales pitch was refreshing in that they did not try to talk me into installing Garmin equipment like two of the big “high volume installers” that were on Dynons approved list...
My objective here is not to talk poorly of anyone, but to instead just to give you some interesting background info and let you know that I was a believer in Dynons stuff after trying it out at Sun N Fun this year. After researching it online and talking to a few current experimental owners and A&P’s, I wanted a dual screen Dynon system, nothing else...
After going through the research process, I do find it odd that some of the bigger
high volume certified installers Dynons choosing to work with are not always actively promoting their equipment...It’s really kind of weird... and thinking back, I hope I made the best choice...
Anyway,
After talking to 3 different shops I chose the one that although was not the least expensive, was the most knowledgeable of the task ahead. It seems like this was the type of shop that should be a “certified dealer”. Just my opinion...
Fast forward a couple of months and the panel is in and ready to go...
So the 1st issue was a faulty com radio, after days of phone calls with dynon my tech literally built a test bench for the radio and together they came to the conclusion Dynon had sent a faulty radio...
Fine, no big deal, in my opinion poor quality control, but Dynon overnighted a new radio, problem solved.
Simultaneously my tech discovered that one of the soft keys located at the bottom of HDX screen #1 was also faulty and dynon quickly overnighted a new screen, again, come on guys, where’s the quality control? At least they were quick to respond and send a new screen. I do appreciate that...
That brings me to the auto pilot...
After carefully following Dynons calibration booklet, flying multiple flights and spending hours literally raising and lowering, torque, gain, sensitivity, and the rest, I’m still gettting the roll slip indication a couple times a minute, the auto pilot will track a course but basically methodically rocks back and forth and this is the best I’ve been able to get it to do. The high point is the vertical guidance has been good since day one.
This brings me to my biggest question...
Given my brief experience with Dynon components and what seems to be weak quality control, is it possible I’ve got a bad servo? I guess the part I don’t understand, is that Dynon has spent all this time and effort certifying this system for 172’s and Cessna 172s are all rigged basically the same, shouldn’t the pre determined settings sent to upload with the new system just work right out of the box? I’ve spent hours reading on this forum about people with RVs trying to figure out many of these same roll slip and tracking issues but it just seems like when you pay $2000 extra for an STC this stuff should be somewhat ironed out...
Anyway, has anyone on this forum experienced similar issues with a 172 install? If so any recommendations?
I apologize for the long intro but thanks in advance for taking the time to read it...
Sincerely, Doug
 

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Raymo

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Apr 25, 2016
Messages
732
Location
Richmond Hill, GA
Sorry to hear of your dilemma.

A couple thoughts. First, the radio is a re-branded Trig and are very solid. Could the shop have accidentally hit the transmit button while not connected to an antenna? If they did, it likely fried the transmitter. Second, does your plane have roll trim and does it fly level without the autopilot? It should and must for proper functionality. If it does, I'd suspect the shear pin in the servo may be broken, which could also have been caused by the shop. The shear pin can be easily replaced and Dynon's support will help.

I've had the system installed in my RV-7A for 3.5 years. It took a while and lots of flights to tweak the pitch servo settings but roll has never been a problem from day one. That said, the control forces are much greater in your plane than mine.
 

Douglas

New Member
Joined
Sep 21, 2019
Messages
13
Hey Raymo,
Thanks for the info.
No Transmit buttons installed at radio installation so no chance of a accidental transmit...
Plane flys nice and straight, so im hoping the shear pin may be the answer...
Putting it back in the shop tomorrow to examine the servo a little closer.
I appreciate your response.
 

Dr.M

New Member
Joined
Jul 25, 2019
Messages
13
Douglas - I have just finished my certified Dynon install on my C172L. So far, so good on infant mortality issues (knobs, screens, etc - I didn't use the Dynon comm). But I do agree with you on autopilot settings (gain, sensitivity, etc.). Dynon should provide those as part of their research for the STC. I, like you, had to fiddle-fart with those settings in-flight to get reasonable autopilot tracking behaviors. It is ok now...but I am not sure that my autopilot performance is optimal. Still tweaking.
 

kellym

I love flying!
Joined
Sep 29, 2013
Messages
116
Douglas - I have just finished my certified Dynon install on my C172L. So far, so good on infant mortality issues (knobs, screens, etc - I didn't use the Dynon comm). But I do agree with you on autopilot settings (gain, sensitivity, etc.). Dynon should provide those as part of their research for the STC. I, like you, had to fiddle-fart with those settings in-flight to get reasonable autopilot tracking behaviors. It is ok now...but I am not sure that my autopilot performance is optimal. Still tweaking.
I agree that default settings from the certification aircraft should be supplied. However, recognize that the fleet of C-172s varies widely on force and travel needed in the controls...both by model and age/wear/tear. Earlier models needed much less force and IIRC somewhat less travel than later models. Later models had significantly higher forces required as options and weight increased. Control cable tensions and pulley condition all affect what is needed. In the mid-70s flight schools often had both old high time early model C-172s and some brand new ones. Moving between them from day to day as availibility dictated would be eye opening as to the differences. Thus it is not surprising that some tweaking is required for the calibration.
 

Douglas

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Joined
Sep 21, 2019
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13
Douglas - I have just finished my certified Dynon install on my C172L. So far, so good on infant mortality issues (knobs, screens, etc - I didn't use the Dynon comm). But I do agree with you on autopilot settings (gain, sensitivity, etc.). Dynon should provide those as part of their research for the STC. I, like you, had to fiddle-fart with those settings in-flight to get reasonable autopilot tracking behaviors. It is ok now...but I am not sure that my autopilot performance is optimal. Still tweaking.
Dr. M,
Thanks for your reply!
Just an update...
Dynon has agreed to send my shop a new roll servo. I hope that this solves the problem. Hey Doc, once you get your system all dialed in, I would love to know what your final settings turn out to be? It would be interesting to publish that data and useful to other Dynon customers too. I’ll do the same if I ever get a system that works as advertised!
Thanks,
Doug
 

Douglas

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Joined
Sep 21, 2019
Messages
13
I agree that default settings from the certification aircraft should be supplied. However, recognize that the fleet of C-172s varies widely on force and travel needed in the controls...both by model and age/wear/tear. Earlier models needed much less force and IIRC somewhat less travel than later models. Later models had significantly higher forces required as options and weight increased. Control cable tensions and pulley condition all affect what is needed. In the mid-70s flight schools often had both old high time early model C-172s and some brand new ones. Moving between them from day to day as availibility dictated would be eye opening as to the differences. Thus it is not surprising that some tweaking is required for the calibration.
Kellym,
I agree with your analysis of the 172 fleet and the differences in control force and travel. Ive owned both a 1963 D model and a 1977 N model and both had there own feel and slight differences in control tension ect...However, I think Dynon should help the consumer understand that a larger servo may be needed in some older models. Their STC specifically states it’s suitable for Cessna 172 models F-S. Its my understanding that these models are all rigged basically the same with very slight differences. Anyway, with the exception of excessive wear, it certainly seems that they could publish basic settings and values that would cover the STC‘D aircraft and the their consumers could save a massive amount of time, energy and confusion...
Thanks, Doug
 

Dr.M

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Joined
Jul 25, 2019
Messages
13
Dr. M,
Thanks for your reply!
Just an update...
Dynon has agreed to send my shop a new roll servo. I hope that this solves the problem. Hey Doc, once you get your system all dialed in, I would love to know what your final settings turn out to be? It would be interesting to publish that data and useful to other Dynon customers too. I’ll do the same if I ever get a system that works as advertised!
Thanks,
Doug
Here are the autopilot parameters that seem to be working for my C172L, so far:
 

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Douglas

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Sep 21, 2019
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Dr. M,
Thank you so much for sharing these!
Once we have the new roll servo installed,
I‘ll also post my autopilot parameters.
Hopefully others will do the same and we can reach a consensus.
 

Dynon

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Jan 14, 2013
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Woodinville, WA
So first, thanks for choosing us. We really do hope you feel you've made the right choice when we have you all sorted out.

Second, we're sorry that you've experienced a couple of early failures. It's hard to read experiences like yours. They're rare, but they do happen. We're proud of our equipment's overall reliability, but occasionally, there are failures. Rarely, experiences like yours happen. We're also proud of ths support we provide when things go less than perfectly. We'll work hard to help get you flying and troublefree quickly.

As for the AP - there are settings specific to the C172 that can be downloaded in both PDF form and via loadable configuration files. I wouldn't recommend using the latter at this point, as things have probably been tailored to your airplane. But in case the AP settings weren't applied at installation time, it might be worth using the PDF version, which has a list of the recommended settings. Here's a link to the certified documentation. You're interested in the "Cessna 172 F-S" folder, and then the "103527-000 - Rev A - SkyView HDX System Configuration Manual - Cessna 172 F-S" document, which has the AP settings that we found flew 172s well.
 

Dr.M

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Jul 25, 2019
Messages
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Dynon,
I misread that part of the Config Manual...I thought you were merely showing how to navigate the screens, but your screen shots actually contain the parameters that you recommend setting. My bad.

Your pitch numbers are very close to what I discovered by test flights. I'll test your roll parameters tomorrow (even though I think 30 degree roll limit may cause whiplash from my early flight experiences). Will update after some test flights how your numbers work within next couple of days Thanx
 

Dr.M

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I tried the Config Manual parameters for roll and pitch. Because they don't appear to be coupled to each other, the 30 degree bank and other parameters make the plane dive significantly during the turn (normal), announce "trim up", complete the turn, then announce "trim down". Reducing max roll to 15 degrees eliminates the roller coaster ride and allows the pitch servo to keep up. Additionally, with the Config Manual settings, the plane "wallows" and hunts trying to hold heading, track, etc. Long story, short; I have flight tested the below "tightened up" parameters and they fly much better than Config Manual settings (my plane is C172L, 180hp, light loading).
 

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Douglas

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Sep 21, 2019
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Dr M,
Thanks for the info! I’m hoping to flight test my new Servo Monday. I think Ill start with your settings and see how it goes. I’m in a 172n, 180 hp as well.
Thanks again for your response!
 

Dr.M

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Jul 25, 2019
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Douglas,
I look forward to your results (Dynon probably does, too). Gathering autopilot settings results from several of us "early adopters" will help us all troubleshoot (rigging, slippage, servo performance, etc.) and refine the ride.
Thanx
 

TOMI

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Oct 24, 2019
Messages
1
We have been installing Dynon equipment since 2007 and have the upmost confidence in Dynon Avionics. Their customer support and tech lines are instrumental in delivering the best avionics on the market in our opinion.

Though we have beat our heads against the wall on these few items that failed, we have never been left out in the cold by Dynon. Things happen and mistakes get made. So be it... no one is perfect. I am the best example of a non-perfect person.

The frustration is on both sides of the fence. The customer and our shop spent many hours ringing out wires and triple checking everything before picking up the phone for tech help. This goes for the manufacture as well. The last thing they want to hear is how their equipment failed right out of the box. Indeed it is very rare to have these kind of gremlins, but every now and then we have to eat a soup sandwich.

My hat is off to Dynon for their support but mainly to the customer for being so understanding through this process. When this kind of money is spent it changes peoples attitudes but this was not the case with this customer. The professionalism and courtesy has been greatly appreciated.

Tad and Justin
 

Douglas

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Sep 21, 2019
Messages
13
I tried the Config Manual parameters for roll and pitch. Because they don't appear to be coupled to each other, the 30 degree bank and other parameters make the plane dive significantly during the turn (normal), announce "trim up", complete the turn, then announce "trim down". Reducing max roll to 15 degrees eliminates the roller coaster ride and allows the pitch servo to keep up. Additionally, with the Config Manual settings, the plane "wallows" and hunts trying to hold heading, track, etc. Long story, short; I have flight tested the below "tightened up" parameters and they fly much better than Config Manual settings (my plane is C172L, 180hp, light loading).
Dr.M
I’m sorry that it took me so long to post results, but after the failure of the roll servo it took a while to get it replaced and to return my plane to service.
At any rate, I flew 2 fully coupled Rnav approaches tonight and the entire system worked perfectly. It’s been a long road getting this aircraft to a satisfactory point and I still have a bit further to go, but I‘m starting to see the light at the end of the tunnel.
Doug
 

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Dr.M

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Jul 25, 2019
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Doug,
Sounds like things are working well. I continued to tweak my settings a bit more. Compared to yours, my current Pitch settings are (Sensitivity = 15) and (Pitch Gain = 3.0). Roll settings (Roll Sensitivity = 24) and (Bank Angle Limit = 15). My changes to pitch are intended to help keep up with altitude during banks. The changes to roll are intended to smooth out turns. My plane is currently in the paint shop so I won't be testing for a while. Happy Thanksgiving.
 

Douglas

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Sep 21, 2019
Messages
13
Thanks for the update Dr M.
I hope the paint job turns out well.
Happy Thanksgiving to you too!
 

GlastarJohn

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Joined
Dec 11, 2019
Messages
2
I recently spent a great sum of money to have an absolutely beautiful dual screen Dynon HDX panel with all the bells and whistles installed in my 1977 Cessna 172. I must say, although it is beautiful to look at and I am pleased with many of the awesome features, I have been plagued with problems from the moment we powered up the system.
First let me say I feel like I chose a reputable shop with many years of Dynon experience to do the install. In fact, I chose this particular shop not because they were on Dynon’s “certified” installers list, but because they were the biggest proponents of Dynons equipment. Their sales pitch was refreshing in that they did not try to talk me into installing Garmin equipment like two of the big “high volume installers” that were on Dynons approved list...
My objective here is not to talk poorly of anyone, but to instead just to give you some interesting background info and let you know that I was a believer in Dynons stuff after trying it out at Sun N Fun this year. After researching it online and talking to a few current experimental owners and A&P’s, I wanted a dual screen Dynon system, nothing else...
After going through the research process, I do find it odd that some of the bigger
high volume certified installers Dynons choosing to work with are not always actively promoting their equipment...It’s really kind of weird... and thinking back, I hope I made the best choice...
Anyway,
After talking to 3 different shops I chose the one that although was not the least expensive, was the most knowledgeable of the task ahead. It seems like this was the type of shop that should be a “certified dealer”. Just my opinion...
Fast forward a couple of months and the panel is in and ready to go...
So the 1st issue was a faulty com radio, after days of phone calls with dynon my tech literally built a test bench for the radio and together they came to the conclusion Dynon had sent a faulty radio...
Fine, no big deal, in my opinion poor quality control, but Dynon overnighted a new radio, problem solved.
Simultaneously my tech discovered that one of the soft keys located at the bottom of HDX screen #1 was also faulty and dynon quickly overnighted a new screen, again, come on guys, where’s the quality control? At least they were quick to respond and send a new screen. I do appreciate that...
That brings me to the auto pilot...
After carefully following Dynons calibration booklet, flying multiple flights and spending hours literally raising and lowering, torque, gain, sensitivity, and the rest, I’m still gettting the roll slip indication a couple times a minute, the auto pilot will track a course but basically methodically rocks back and forth and this is the best I’ve been able to get it to do. The high point is the vertical guidance has been good since day one.
This brings me to my biggest question...
Given my brief experience with Dynon components and what seems to be weak quality control, is it possible I’ve got a bad servo? I guess the part I don’t understand, is that Dynon has spent all this time and effort certifying this system for 172’s and Cessna 172s are all rigged basically the same, shouldn’t the pre determined settings sent to upload with the new system just work right out of the box? I’ve spent hours reading on this forum about people with RVs trying to figure out many of these same roll slip and tracking issues but it just seems like when you pay $2000 extra for an STC this stuff should be somewhat ironed out...
Anyway, has anyone on this forum experienced similar issues with a 172 install? If so any recommendations?
I apologize for the long intro but thanks in advance for taking the time to read it...
Sincerely, Doug
I had a servo slipping problem on my experimental installation. It was solved by going to the next beafier servo. There were three strengths of servos at the time. In Pitch if I remember correctly
 
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