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Regarding the discussion on monitoring carb temp.
I got out my Thorp's Lycoming 0-320 manual.
The manual has a full page on the use of carb heat but the part that got my attention was:
"WHEN ICE HAS BEEN MELTED FROM THE INDUCTION SYSTEM, HEAT SHOULD BE USED AS LONG AS KNOWN OR SUSPECTED ICING EXIST.
"ONLY THOSE AIRCRAFT EQUIPPED WITH A CARBURETOR AIR TEMPERATURE GAGE MAY PARTIAL HEAT BE USED TO KEEP THE MIXTURE TEMPERATURE ABOVE FREEZING POINT (32F)"
So without a temp gage we are best guessing until something noticeable occures.
Ordered one from Spruce a few minutes ago.
Thanks to all for the great lesson on carb ice and especially Mr. Allen, Thank you sir.
---------- Original Message ----------
From: "Jerry Marstall" <jnmarstall@...>
Subject: Re: [Q-List] Your Opinion
Date: Thu, 07 Jan 2021 08:19:42 -0500
GREAT article Mike. Thks. Jerry
-------- Original message --------
From: Mike Dwyer <q200pilot@...>
Date: 1/7/21 7:56 AM (GMT-05:00)
Subject: Re: [Q-List] Your Opinion
Mike.. what temp gauge are you using.. do you remember the supplier? My O-200 Cessna did not have a carb temp gauge but
to me that was one instrument it should have had added. I will be adding to both my Experimentals.
Had carb ice in my 1962 150 once. I made a habit of pulling the heat on every 5 or so minutes in cruise after then. Not a serious
problem but it did get my attention VFR over Eastern Oklahoma between cloud!
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.