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Mike, I have a carb temp sensor as well and agree with what you said. I think the cowl being so tight to the engine helps. Like I said, I’ve only experienced decent carb ice in my Q a couple times in 20 years and it’s been in 21
states under many weather conditions. I do use carb heat occasionally. You just have stay aware of the temps and dew point.
From: main@Q-List.groups.io <main@Q-List.groups.io> on behalf of One Sky Dog via groups.io <Oneskydog@...>
Sent: Tuesday, January 5, 2021 7:17:16 AM
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Subject: Re: [Q-List] Your Opinion
Good observations. The big gorilla is the latent heat of evaporation cooling of 40 to 50 degrees F. The higher the fuel vaporization rate the more cooling takes place. In dry west there is usually not enough moisture to condense. That is also why cloud
base is at 15,000 ft and above with little moisture it has to be really cold to make a cloud. It is really cold hanging out between 15 - 19 K MSL you have to dress for it. Even if it is 100 F on launch, hope for a quick thermal climb out to traveling altitude.
I have had ice twice both times in humid air partial throttle. Once with an Ellison and VW on touch and go that turned into a land back. Once in my old C-172 coming home from Beatrice FOD descending into Hugoton KS with partial power and low clouds. Carb
heat quickly fixed it. You should adjust the mixture for the heated air.
I think at full throttle air flow the ice point is past the carb. At idle not enough fuel is being vaporized to maintain freezing temps. Low to mid throttle is the sweet spot.
Exception idling for 5 minutes before take off in humid air. Snowflake warning Graphic accident ice, stall spin on takeoff https://youtu.be/IEikGJJhanA
Carb heat on during takeoff is also not good if waiting a long time do a quick carb heat check before crossing hold short.
Fly safe things to check,
On Jan 5, 2021, at 6:24 AM, Mike Dwyer <q200pilot@...> wrote:
I have a carb temp gauge and have observed the temp at different conditions.
At idle the carb runs quite hot. Probably from engine hearing and no airflow around it.
At full power, same thing. More engine heat and more airflow.
At low power cruise it gets quite cold in the carb, 40F to 50F lower than the ambient air.
Strangely at no power glide the carb actually gets warmer. Probably the fuel flow is way down and not cooling the carb.
So my observation is that carb ice takes a really humid day or flying through visable moisture (a cloud) and it takes some time for the ice to build up at low power cruise. Here in Florida we are known for humidity and clouds. I seldom use
carb heat. The way I use it now is after a long slow flight with the carb at or near freezing I get within glide distance of an airport and before reducing power I pull the carb heat. After the carb is up to 40 or more degrees F the carb heat gets returned
to off and I throttle back for landing.
I'd encourage everyone running a carb to get a carb throttle plate temp sensor. It's eye opening. The MA3SPA carb has a pre drilled hole ready to install a sensor.
Did you note how long he stayed on the taxiway before departing......
Naah. Wasn't carb ice. Doesn't form at full power and doesn't form that fast.
Bad Carb heat again;
Uh-oh! If it’s a Certified engine in a certified airframe, it should be able to idle with carb heat without stopping. That’s just bad maintenance.
A Lycoming with the Marvel Schebler carb is straightforward to set up - 1930’s tech. :^)
On Mon, 4 Jan 2021 at 17:06, Richard Thomson <richard@...
It wasn't on my 0200, it was a club Cherokee with a Lycoming, but it taught me a lesson that sticks in the mind for the future reference. :-Br
On 04/01/2021 10:47, Bill Allen wrote:
Hi Rich - what engine do you have? If it rich-cuts at idle, it should be possible to alter the setup so that it doesn’t....
On Mon, 4 Jan 2021 at 11:35, Richard Thomson <richard@...
Thanks Bill, that is some interesting information to consider.
The reason I select carb heat cold on late final is not damage to the engine but Rich Cut, and even then that is not a problem if you are landing, but on T&G's and on short fields can be a decider if you end up in the hedge ( or at Henstridge in the
fence or girders), so I my norm is Carb Heat Cold on late final and a gentle cycle of the throttle to check its still there.
On 04/01/2021 08:13, Bill Allen wrote:
You wrote: << I was hoping for some info regarding the use of Prist. >>r
Joel Ventura did quite a detailed article on Prist etc here:
Note: Prist wont stop carb ice, which comes out of the atmosphere. Prist deals with water already in suspension within the fuel.
On Mon, 4 Jan 2021 at 03:58, Keith Welsh <klw544@...
All your comments, experiences and knowledge no doubt turned out to be a real education. I don’t know about y’all but icing is normally not a discussion item. I’m glad I took the chance to post the article. Learned more than I thought I would. And
thank you all for “Your Opinions”
I must admit I was hoping for some info regarding the use of Prist. I did actually use it in the Quickie for a time. Reckon it did ok..that was several years ago. My Q does not have carb heat nor does the carb have access to outside air, only hot air
off the engine and is why the interest in the Teflon coating. The carb on the newer Onan sets higher so to accommodate a new heat box I would need to make a new cowl bump....like that was gonna happen! Not surprised no one had much to say about it.
Like Jay I’m sure ice will form Teflon or not but I’ve never used a Teflon coated anything that anything would stick to it. I once froze water in both a steel pan and a Teflon one. Guess which one the ice slid out of. The steel pan had ice remnants
sticking to it after most was chipped out. Yeah, pretty unscientific but.... Think about your plastic ice server bucket when guest come over, the ice sticks to everything even fingers. At least modern technology has provided us with some options.