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Dynon heated pitot incident

andrew phillips

Well Known Member
I have the Dynon Heated pitot. I was up in -27 degree celcius weather. The plane is kept in an insulated but unheated hangar. The tube was already frozen on the ground. I only noticed that we had no airspeed on the takeoff roll. The heater did not clear the ice during the flight (30+ minutes). The pitot showed a good current draw in the air so I assumed it was working. Testing on the ground showed that the pitot does get hot. Ice was then cleared with a heat gun on the bottom corner of the tube and one drop of water came out. Why did this not sort itself out during flight?
 
The pitot only is heated in the front portion preventing accumulation of ice. If there is water/ice down steam, the element may do little or nothing to prevent a blockage.

Randy Hooper
 
I hope that no law enforcement people are watching this list. Knowingly taking off and flying with no air speed for 30 min.?
 
I hope that no law enforcement people are watching this list. Knowingly taking off and flying with no air speed for 30 min.?

Actually airspeed isn't required on an experimental airplane. Even if it was, the decision not to abort a takeoff always rests with the PIC

How did the Dynon AHARS handle not having airspeed info?
 
Maybe no AS instrument is required...

Actually airspeed isn't required on an experimental airplane. Even if it was, the decision not to abort a takeoff always rests with the PIC

How did the Dynon AHARS handle not having airspeed info?

...but FAR 91.7 is still in effect for our Experimentals....:)

? 91.7 Civil aircraft airworthiness.

(a) No person may operate a civil aircraft unless it is in an airworthy condition.

(b) The pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight. The pilot in command shall discontinue the flight when unairworthy mechanical, electrical, or structural conditions occur.
 
True but

I guess point I was trying to make was that rejecting a takeoff is not something most people practice. Perhaps it would be better to fly around the pattern and land without the IAS than to botch up a rejected takeoff. Either way it remains the PIC's decision to make, not the FAR's. You have no way of knowing the airspeed isn't working until you start down the runway so the FAR isn't really a factor.
 
I guess the rules that you have in the United States differ quite a bit from those here in Canada. We have to have an Air Speed indicator in any type of plane that we fly in. In an RV I would suggest IMHO that the air speed in indicator would wake up in the first few hundred feet and pulling the power off to abort the take off would not be an issue. If operating out of a very short air field and you elect to take off you certainly would not want to be returning to the same runway without an air speed working, the chance of damage I think would be much greater than aborting in the first place. Accidents very seldom happen with one wrong decision.
 
True for a pattern.... but it...

I guess point I was trying to make was that rejecting a takeoff is not something most people practice. Perhaps it would be better to fly around the pattern and land without the IAS than to botch up a rejected takeoff. Either way it remains the PIC's decision to make, not the FAR's. You have no way of knowing the airspeed isn't working until you start down the runway so the FAR isn't really a factor.

...really was the 30 minute bit that I noticed....:)
 
Does airspeed on a GPS count?...
Well I don't really think it is a safety issue to fly without an airspeed indicator in our planes, after we are familiar with them, but I do have to notice the remark about GPS airspeed. That is something I am not familiar with. What GPS displays airspeed?
 
Well I don't really think it is a safety issue to fly without an airspeed indicator in our planes, after we are familiar with them, but I do have to notice the remark about GPS airspeed. That is something I am not familiar with. What GPS displays airspeed?

Okay, a technicality in my wording. But notice I mentioned the windsock for a brain interpretation of "airspeed".

However, I'm sure my new Garmin 696 must have airspeed somewhere. It does everything else! :D

L.Adamson
 
I wish I was in California

I probably wouldn't get convicted so quickly. I know what I did was wrong but I think my piloting decisions were sound. My mistake was not catching the airspeed condition until rotation. Another pilot was flying from the right seat and I was coaching him through the takeoff. As I told him to target the climb speed I noticed that there was none. This is my mistake and I will learn not to let that happen again. Once airborne I knew we would have to eventually land. The decision was made to fly the plane on MP and RPM. At 25/2500 I knew that I had 160+mph. We went through the problem solving process trying pitot heat and even cabin heat thinking that maybe condensation had frozen inside the cockpit. When we were unable to rectify the problem we returned for landing. The GPS unit provided us with groundspeed and knowing the wind we were able to calculate our rough airspeed. We decided on a straight in approach for final so that there would be no chance of losing too much speed on turns in the pattern. On landing I had the other pilot call out the GPS ground speed and we were able to make a good landing. My flight instructor once had me fly night circuits with all the instruments covered so that I would know how to feel my plane in an emergency. I am grateful for his foresight.

One other thing...back on topic. Does it not seem strange that a heated pitot tube will not deal with a little bit of water that freezes inside? If you flew through rain before encountering icing or through some climactic condition that caused condensation inside the tube would it not be reasonable to expect that a heated tube could deal with this? The blockage was at the back of the tube where the horizontal becomes vertical as it goes up into the wing and it was literally 1 drop of water
 
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I dont think you did anything wrong,you used sound judjment for the problem at hand ,the airplane wouldnt fly any different if it was 30 min or 90 mins,you had a good instructor to teach you to fly by attitude and visual references.If nothing else all the flames from here should have melted all of the ice and you wont have any further problems!Enjoy your airplane and have fun.Bob
 
That is a common problem with some heated pitot tubes. There is usually a drain hole at the back of them to allow the water to flow out. Yes the water does freeze there and the heat won't typically get rid of it. That is why if freezing conditions exist and rain or snow or other high moisture levels are present the heat should be turned on in advance of an ice build up, to prevent this from happening. Not after the fact. Most of the all metal pitot tubes will get hot enough to melt the ice and also discolor the paint on the mast. The molded plastic ones don't seem to get that hot over the entire body.
 
I understand your decision to fly, and to continue flying to see if the blockage would clear. I also understand that not everyone looks at the ASI early into the takeoff run; I don't. On my first departure from OSH after the big show I picked up a bug on takeoff and had 0 AS for about 30 minutes. I didn't even think of an abort with a C-180 right behind me.

This looks like good reason to learn the partial panel may include loss of airspeed. There are still some advanced instructors out there that teach that. It's not that hard to master.

Bob Kelly
 
I probably wouldn't get convicted so quickly. I know what I did was wrong but I think my piloting decisions were sound. My mistake was not catching the airspeed condition until rotation.
You're still here, right?:D I had a blocked pitot on one of my solo flights with under 20 hours. I didn't notice the lack of airspeed until about 1/3 of the way down a 2500' runway, so I just took off, flew the pattern and landed. One thing that I think is a good idea is to either not touch the elevator trim, or at least know the trim settings well enough that you can get it right for landing and have the same feel for the airspeed that you have on the rest of your flights.

As far as the pitot ingesting water and then freezing in flight, shouldn't the water pretty much blow out of the drain hole almost as soon it enters the pitot?
 
As far as the pitot ingesting water and then freezing in flight, shouldn't the water pretty much blow out of the drain hole almost as soon it enters the pitot?[/QUOTE]

Yes it should only if the pitot is above the freezing temperature, hence the need to turn it on before hand.
 
Be Careful

There's very few posts on this website that give me a shiver, and this is one of them.

"Airspeed off the peg" should be part of every take-off roll cross check. You should also always have an abort plan if things don't look right. For me, if I don't see the anticipated RPM, MP, airspeed, oil temp, and oil pressure with at least 2,000 feet remaining, it's Throttle - IDLE, Brakes - Apply.

If we were talking about heavy aircraft, there would be a specific point after which you have no choice but to take the plane into the air and figure it out on downwind. But our airplanes don't have V1 and S1 speeds, so if you have enough runway left to bring the airplane to a stop, you ought to be aborting.

And whether or not your Operating Limitations requires a functioning airspeed indicator, I can think of all kinds of scenarios where you could be high power, low airspeed. That's why we practice power-on stalls. And GPS ground speed is no substitute. If you have any kind of tailwind and are trying to figure out your airspeed, your GPS is lying.

I certainly don't mean to call anyone on the carpet, but the casual attitude of this conversation has made me nervous. Please, please, please, have a plan for what's going to happen when you push up the throttle and things don't go as you expect. Decide ahead of time when you're going to abort and how. Have a plan for when the engine fails on takeoff. At what point will you land straight ahead and at what point will to attempt to turn back? Run through the steps in your mind each and every time you're about to take the active runway. Expect something to go wrong. Be surprised when it doesn't.

Having a plan and being proficient at it is free, and it might save your bacon.

-Martin
402BD
 
There's very few posts on this website that give me a shiver, and this is one of them.

I think some are overdoing this.......a bit. I didn't get a shiver, because I can think of many situations that are far worse. How about smoke pouring over the canopy; or perhaps a wheel that just fell off..

It's not all that hard to judge a bit of extra airspeed to allow for a safety margin, and then keep it off the runway while reducing power to land. As to the "tail wind" & GPS groundspeed; this was most likely taken into account when choosing the runway for departure.

However, I'd make it a point to find out what's wrong before the next takeoff, or at least abort if the airspeed doesn't rise on the takeoff roll.

L.Adamson --- RV6A
 
"Airspeed off the peg" should be part of every take-off roll cross check.

I did a rental checkout a couple weeks ago in a C-172, and on the takeoff roll I called out "airspeed active" as it came up around 40 knots or so, and the instructor immediately, quick as a flash, put a cover over the ASI just as I was rotating. Once around and down, non-issue.

With all due respect, and exceptions for Phase I, but if you can't fly (and land) your airplane without an operating ASI, you need more stick time.
 
I think you SHOULD fly a few CCTs without the ASI......... but as pointed out above, you should always have a pre takeoff brief, even in your head, and as you roll do the scans and be ready.

There is no substitute for being prepared for anything! :eek:

DB:cool:
 
With all due respect, and exceptions for Phase I, but if you can't fly (and land) your airplane without an operating ASI, you need more stick time.

AMEN!!!!! These planes land EASILY in 1000 feet and most of us have something over 3000 feet to work with at our airports (I've got >8000!!). If you can't manage without an ASI please quit flying. Cut the guy some slack and lets get back on topic.

I'd be extremely disapointed if my heated pitot couldn't clear the drain hole. It seems to me the heat eliment should've been carried back further rather than just at the ram inlet/front.

When did you turn on the pitot heat, if you said it I missed it. Did you turn it on before taxi or after realising the ASI was inop? Please ignore the sniping by the Tuesday morning quarter backs, you did fine.
 
Been there done that myself.

Just a quick point of reference. Most glass doesn't start "off the peg" until 40 "ish" and some lightly loaded Rv's with light fuel on a cold day and a strong engine with c/s prop will be airborne in the 50's. Not much time between 40 and 50's to check instruments when the total takeoff roll might be 300' or so.

My 2 cents as usual.

Cheers,
Stein
 
...The heater did not clear the ice during the flight (30+ minutes)....

This is all quite disturbing. I am about to select a heated pitot tube for my 9A. Has anyone ever seen any test results showing how effective any uncertified heated pitot is at preventing, or clearing ice? Has anyone ever had an operating heated pitot ice up in flight?
 
I have the Dynon Heated pitot. I was up in -27 degree celcius weather. The plane is kept in an insulated but unheated hangar. The tube was already frozen on the ground. I only noticed that we had no airspeed on the takeoff roll. The heater did not clear the ice during the flight (30+ minutes). The pitot showed a good current draw in the air so I assumed it was working. Testing on the ground showed that the pitot does get hot. Ice was then cleared with a heat gun on the bottom corner of the tube and one drop of water came out. Why did this not sort itself out during flight?


Did anyone notice that the ambient temperature was -27 C? That's pretty cold in most people's books. Perhaps, with it that cold out, the heat conduction (my new scrabble word) from the front of the pitot to the rear was just not adequate to keep up with the OAT and/or with the added windchill from relative airspeed.

Of course, why anyone would want to go out and subject themselves to that kind of frigid misery is another story....:eek:
 
As to taking off/landing without a functioning A/S indicator - I wouldn't personally do it. Like a prior poster, if I don't see "off the peg" I abort. It may not be technically against the rules, but I would ask myself "what peacetime mission is so important you can't stop for a few minutes and find out why your airspeed indicator isn't working?" Once assured that it was simply ice (which you would then no doubt fix) and not that something had ripped off your pitot tube half way to leave it flapping against the lower wing skin, you could then certainly make an INFORMED decision to conduct a Ferry flight - but without knowing why one thing is suddenly broken how do you know what else might be?

What would concern me is not the fact that the pilot chose to fly, but the appearance that the thought-process was one that says that "this flight is too important to let anything slow me down even for a few minutes to check it out." "Get Home-itis" is perhaps the single leading cause of accidents. I've lost too many of my friends over the years, and I don't want to lose any more - even if I don't know you personally. To the original poster, and to everyone else here who said, "Sure - press on!" - Please think about the reasons you chose / might choose to do this and then make an abort plan for the future.

As for the Dynon heated pitot, I wouldn't be concerned that it didn't clear the ice after airborne considering the temperature. Had the pilot landed and left it on for a bit without the engine running, my guess is that it would probably then have gotten warm enough to melt the accumulated ice - but then again, it is only a 100 Watt heater. Oh, and I wouldn't recommend sticking your tongue on the pitot to help thaw it at those temps!!!

:D
 
Don't let em get you down

I thought we were talking pitots here, not procedure. Shiver me timbers. C'mon these are lightplanes, not Concordes.
 
Pitot Heat, Anti-ice not De-ice

Pitot heat is designed for anti-ice. It is designed to keep ice from forming and impairing the pitot static system. It is not designed to de-ice the pitot system. It must be turned on before entering icing conditions. If the pitot system has already been subjected to ice before it is turned on than there are no guarantees the pitot heat will protect the pitot system.

I am sure the pitot heat system worked as designed, as an anti-ice system, not as a de-ice system.

Fly safe, Justin
RV-8, waiting for the fuselage.
 
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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