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Dynon Heated Pitot..........Again!

jthocker

jthocker

Well Known Member
I reported a problem with my Dynon heated pitot well over a year ago in this thread:

http://www.vansairforce.com/community/showthread.php?t=94514&highlight=frozen+pitot+line

about 4 months after that incident my Dynon probe quit working altogether, and since it was still under warranty they cheerfully replaced it.

I received a follow up conference call by Dynon engineers and the CEO to help clarify my "frozen" issue. They were genuinely trying to understand the problem and I felt they were doing their best to find the root cause.
Because of this call I decided to go ahead and install the new Dynon probe.

Fast forward a year and I just experienced the same problem. Fly home from practice IFR through a very "wet" front, then spend over an hour in sub freezing temps, upon descent watch the airspeed decrease until ZERO, land with Groundspeed.
Pitot heat on the whole flight and confirmed amp load and warm on ground after flight.
Checked plumbing and everything runs uphill with no low spots or traps.
Think I'll spring for the new Garmin Pitot.
Good luck to Dynon, I hope they fix it!
 
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Not good news..

I hate to hear that. I've been worried about the Dynon pitot ever since your first post. They say they're working on it though. I sure hope they get it right before I'm at a point where I have to make the decision. For now, I've got the mast installed, but no pitot. I'll wait as long as I can. A friend in Wisconsin (on his 2nd RV-7) went with a Falcon due to concern about heat reliability. I'd really like a one-stop shop, but may have to follow suit.
 
I bought mine from a salvage yard. A Cessna heated pitot off something a ruther. Been on the plane for 8 years and 2k hours. The few times I ask it to do work, it does.
 
jthocker said:
I reported a problem with my Dynon heated pitot well over a year ago in this thread:

http://www.vansairforce.com/community/showthread.php?t=94514&highlight=frozen+pitot+line

about 4 months after that incident my Dynon probe quit working altogether, and since it was still under warranty they cheerfully replaced it.

I received a follow up conference call by Dynon engineers and the CEO to help clarify my "frozen" issue. They were genuinely trying to understand the problem and I felt they were doing their best to find the root cause.
Because of this call I decided to go ahead and install the new Dynon probe.

Fast forward a year and I just experienced the same problem. Fly home from practice IFR through a very "wet" front, then spend over an hour in sub freezing temps, upon descent watch the airspeed decrease until ZERO, land with Groundspeed.
Pitot heat on the whole flight and confirmed amp load and warm on ground after flight.
Checked plumbing and everything runs uphill with no low spots or traps.
Think I'll spring for the new Garmin Pitot.
Good luck to Dynon, I hope they fix it!
Click to expand...

How did Dynon respond to this recent problem?
 
Kahuna said:
I bought mine from a salvage yard. A Cessna heated pitot off something a ruther. Been on the plane for 8 years and 2k hours. The few times I ask it to do work, it does.
Click to expand...

And for what its worth, they had a bunch of them and I paid $125 for a used 12v cessna heated 12v pitot mast, mount for the skin and all. I have no idea if this was a fluke or what. I do remember at the time that the heated pitot's available were insanely expensive and I was not willing to fork over those $$. So I gave buying a used one from a salvage yard a shot. I have had other system issues RV flying in weather.. Static freezes, fuel vent freezes etc. But never a problem with the pitot system.
 
There were enough issues reported with the Dynon's lack of heat that I pulled it off my project before it was flying. Reading this report makes me glad that I did. I have zero intention of ever flying my plane into icing.....but statistics show that it does happen whether intentional or not.
 
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Ice plug for zero airspeed...

When you say "Warm on the ground" you are saying the pitot mast was warm to the touch? No sign of ice on the pitot mast? So you think the ice plug was farther up the tubing?

What did the static port look like?

Thanx!

CC


jthocker said:
Pitot heat on the whole flight and confirmed amp load and warm on ground after flight.
Checked plumbing and everything runs uphill with no low spots or traps.
Think I'll spring for the new Garmin Pitot.
Good luck to Dynon, I hope they fix it!
Click to expand...
 
comfortcat said:
When you say "Warm on the ground" you are saying the pitot mast was warm to the touch? No sign of ice on the pitot mast? So you think the ice plug was farther up the tubing?

What did the static port look like?

Thanx!

CC
Click to expand...
David,
Static ports are in standard location, no ice!
Warm means it was warm when I exited plane and checked it!
We never picked up any ice even though temps varied from slightly above freezing to below freezing. I have no idea where the plug occurred and am sick of trying to figure it all out.
Now, to get the regulated or non regulated Garmin pitot?
 
Complexity sells better. Just look inside many of our RV's or new cars. I like simplicity, but that is why we each build differently.
 
jthocker said:
Fly home from practice IFR through a very "wet" front, then spend over an hour in sub freezing temps, upon descent watch the airspeed decrease until ZERO, land with Groundspeed.
Click to expand...

:eek:

In an airplane NOT equipped to fly into icing conditions? You have more "guts" than I will ever have.

:cool:
 
GalinHdz said:
:eek:

In an airplane NOT equipped to fly into icing conditions? You have more "guts" than I will ever have.

:cool:
Click to expand...

Galin,

I figured that when I posted this you would chime in and chastise me.
Not guts, just experience in safe air travel and I don't feel like debating you.:)

Best regards,
 
There are a lot of Dynon heated pitots in the fleet (thousands), and there have been a few reports by pilots who have experienced a degradation in their airspeed indications with their heated pitots in operation. This has been a difficult issue to reproduce and drive to root cause. However, we take these reports very seriously. Dynon is actively working to determine the root cause and any potential improvements to installation recommendations, best practices, or the product itself.

This winter someone with a SkyView system experienced this issue and we obtained good data from his datalog. Part of engineering a solution is reproducing it and capturing data. We are very much in the midst of doing that.

That work is ongoing, and we do not yet have any conclusions or recommended actions.
-Dynon Support
 
jthocker said:
Galin,

I figured that when I posted this you would chime in and chastise me.
Not guts, just experience in safe air travel and I don't feel like debating you.:)

Best regards,
Click to expand...

;)

All kidding aside, I am glad to hear nothing "serious" happened.

:cool:
 
I have one of these pitot tubes, and am anxious to hear a resolution of this issue. Here are my observations:

The drain holes (2, I presume one is for the AOA line) are very small. Smaller than in other pitots?
The drain holes are only half way back, not at the aft end.
When I apply heat, the front half gets hot, but from the drain holes aft it is less hot. It seems to me that the heating elements are in the front half.
The very bottom, aft end is a different piece (the front part is screwed into the aft part) and does not get particularly warm at all.

So, not knowing the internal construction, I think the question is: Can liquid water get further aft than the drain hole location? If it can accumulate in the very aft end of the pitot then is there sufficient heat to keep it from freezing there?
 
I'm wondering the same thing Bob is. Maybe a change to the drain system in the pitot tube would help. If the drains are freezing up or are too small to allow adequate drainage, water could move up past the heated area of the tube and freeze in an unprotected area? I have the Dynon heated pitot and will keep it for now, and see if there is a fix. I haven't experienced any problems, haven't flown in weather yet, but will be soon. I've only actually turned my PH on a couple times to see if it was working.
 
5 times for me...

I have had the Dynon heated pitot AOA for 800+ hours and have experienced degrading failures five times... twice in clear air.

My observations of the system have been reasonably consistent each time.

Generally it goes like this: Autopilot is on and you are doing your thing when suddenly you notice that the airplane is getting a bit pitchy... the airspeed is a tad low but steady... the pitchy response degrades quickly and becomes dramatic as the airspeed degrades further and the system becomes very unstable... you must disengage the AP and fly by another reference at this point. Heat on the whole time does not help... heat on with the first indication does not help... once the pitot signal is degraded (presumably from ice formation with the pitot) the heat WILL NOT clear. Only a decent into warm above freezing will clear the pitot.

If the airspeed degrades to zero (fully obstructed) the SkyView system switches to a GPS assist mode that is awesome... VERY flyable in any condition. I have forced this mode to test fly by plugging the pitot and it is great. Unfortunately there is no way to force it in flight as routine. As soon as some airspeed is restored the great GPS assist mode is replaced with a completely unreliable pitot driven display.

I have relayed this information to Dynon over the past several years... I believe that they will resolve it as it becomes a priority and they are able to target changes.

From my experience the pitot does not get hot enough, regulates to soon, or does not provide heat in the right place... and there might be an issue with the drain hole... There has been some suggestion that there might be accumulated moisture within the pitot lines in the wing well away from the pitot that freeze... but that does not match my observations of extended flight in below freezing conditions prior to having a pitot failure and blowing out the lines after one event did not reveal any visible moisture.

4 of the times there was NO visible ice on the wings or windshield... once there was a bit of very light ice on the windshield... twice there was no obvious moisture...not in clouds and not raining... all of the times the air was moist though. One time it appeared that the application of pitot heat actually initiated the problem.

Quite frustrating that there is not a software select to use GPS assist.
 
Interesting Stephen. Personally, it's the first time I've read about consistent reocurrences and the general conditions it's happened in. I know there's been talk about the weep holes being too small, or the heater element not heating all the way back. Most of them were connected in the thread last year (Dec. 2012) when Jon last posted about this phenomenon.

Not to switch sides, but I honestly wonder how Garmin's heat-regulated probe is designed, and how it's any better. It's got an AOA port, it's regulated heat, it's the same two-piece construction. Wonder if we can get g3xpert Steve to chime in on how Garmin's design is different from Dynon's... lest they run into the same problems eventually also.
 
[email protected]; said:
There has been some suggestion that there might be accumulated moisture within the pitot lines in the wing well away from the pitot that freeze... but that does not match my observations of extended flight in below freezing conditions prior to having a pitot failure .
Click to expand...

It seems to me your data supports the problem being inside the wing, not the pitot. The pitot, stuck in the 100 mph wind, will come to thermal equilibrium very quickly, while there will be a significant delay for tubing deep inside the wing.
 
could be...

I don't know Bob, could be... twice I would say that conditions supported the potential of a slowly cooling wing at a close temp... one other time I blew out the lines afterwards and found no moisture... the other two times I was in very cold air for hours and the wing was most certainly well below freezing at a steady state before the incident.
 
BobTurner said:
It seems to me your data supports the problem being inside the wing, not the pitot. The pitot, stuck in the 100 mph wind, will come to thermal equilibrium very quickly, while there will be a significant delay for tubing deep inside the wing.
Click to expand...

Even if one could decide that the blockage was in the wing, I'm not at all sure you could point the finger away from the Dynon probe. Why aren't we reading about other probes having the same issue? The pitot line routing in the wing is pretty much identical in most RVs.

Weep hole size perhaps? Not letting so much moisture into the line? I don't know, but this Dynon problem has been there for years and they keep saying "working on it". Point being, this is a pretty simple probe. Having spent years in R&D chasing production issues and safety hazards in the auto industry I can say without question that nothing takes this long to figure out if you have even a single engineer working on it.

These systems are expensive, we as a group should not allow such long delays on safety issues.
 
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I have done about 950 hours and a significant portion IFR in IMC. I have never seen this. Even in mild icing, because with a system not approved or designed for FIKI we have rarely been in icing conditions.

We have been in ICE, and never had a problem. Maybe we could have been and some of you have been more so. All of this is subjective.

I have seen water build up from flying in rain cause some odddities below 30 knots, usually in the hangar afterwards, but never in flight.

Curiously interested.................

DB
 
David, what temps are you seeing? My understanding is that this isn't an issue in the southern states and warmer climates where icing is just below freezing. It's an issue of true and significant COLD weather flying.
 
Bill,

I guess you can tell that we tropical species have no concept of what you call cold :eek:

But I do wonder about the tiny drain holes.

So it seems that the heat is on but there are insufficient watts to keep it warm enough when you are in well below zero C.

By the way FIKI is not for RV's....but we all knew that. But I do wonder if we are expecting more of the probe than anyone designed it for.

Question would be how does it compare to say the probe on a Bonanza for example?
 
This is great visibility to the issue, I have heard about this for some time now and has always worried me flying in potential icing conditions.

Glad that the message is coming clear and is being reported by far to many credible sources to not be considered a real problem.

Glad Dynon is looking into this with highest priority.

Looking forward to hearing about potential solutions for existing Dynon Pitot Tube owners as well as future owners.

Thanks
 
Since this thread is primarily about our Heated AOA/Pitot Probe, I wanted to let you guys know that we have a big update on this issue, including a replacement program for any of you that currently have our Heated AOA/Pitot Probe. See this thread for more details.

Michael Schofield
Marketing Manager
Dynon Avionics
 
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