Carb Ice I think

[W.J.Langholz]

I think I experienced carb ice for the first time today. Actually my son John was in the left seat. We were coming back to PQN after a 45 min flight. He did his 5 mile call and I said to him, at the same time he was thinking it, I think we have a bit of a miss, why don't you keep it out from the city and go ahead and pull the carb heat just be ready incase. WHen he pulled the carb heat it did a cough and a studder and then was better but not completely normal so we left the carb heat on did a short finale and a bit of a forward slip to get it down as soon as possible. When we got it on the ground in the run up area we ran up to about 1800-1900 rpm's carb heat on leaned it out and in a few minutes it was running normal. Checked both mags, both the same normal drop. I was a bit surpprised that it took as long as it did to come back around.

When we came in it was 4:45pm we were at -4C and Dew pt -5 alt 2985. By the time we put the plane back in the hanger and had everything buttoned up (aprox 20 mins) it was getting foggy and misty.

Any thoughts? Sticky valve? Fauled plug?

W.

[minton]

WJ,

Think through the senario. High humidity = Carb ice. It slowly creates a richer mixture. Spark plugs don't like overly rich mixtures. Clearing fouled plugs can in most cases be cleared with a high RPM/very lean max power run-up, which you did. It can take awhile to rectify the condition, so just keep an eye on engine temps. In some cases removing the plugs and cleaning is required.

You're lucky to have caught it in time. Good time for a review of procedures.

Also keep an eye on your surroundings when doing run-ups. Aircraft, vehicles, piles of junk, people, dogs, cats, etc can go flying and you are responcible for that prop wash! Even holding the brakes might be problematic. Wet or icy surfaces can ruin your day.

Brings home the risks of winter flying.

[jrenwick]

Hi Willie,

I'm surprised that's your first experience with ice. Do you have a Lycoming conversion? I've found that in our climate, ice is pretty common in the O-300s, even more so in my C90-powered J3. I usually notice it in the warmer weather, with temps in the 70s and haze (high humidity). I flew the J3 a couple of hours today and didn't get any -- but I was looking for it.

John

[W.J.Langholz]

Hey John

I don't have and IFR ticket so I have been very careful on days like yesterday and most of all last week around here anyway. When the temp and dew point get that close you know you will have issues and the closer to dark you get the fog-miss is likely to happen. Most of the time I just don't fly. That time of day you can take off, fly to your destination, and within a half hour after take off end up over the top of a good cloud bank. Yesterday was so nice at noon and I had ordered a new Gill battery so we went in to replace the old one and decided to go up for a bit. We ended up over at BKX and while John was giving his college buddies rides I was hanger gabber jawing with Doc Bailey, he is restoring a V77 Gull WIng, well it ended up a little later than I liked. We called ahead to check the awos b/4 take off and knew we may have and issue with ground fog. Our back-up was to land at home, which is about 300' higher than PQN, or come back to BKX. It was just a little hazy but not bad. Looking back, we may have been better to climb up out of the haze back into the sunshine, but we stayed @ 3000', about 500' under the temp inversion. The other thing that i usually do automaticly when I am in the left seat is to pull the cab heat from time to time. I guess I just do it and don't really think about it.I didn't think of saying anything to John either.
The surprise was how long it took to come back to running normal. We certainly were not in any trouble, and had decided to stay out away from the city keeping as much elevation for glide, if needed, until the last moment for landing. It was more of and uncomfortable feeling than anything else, and had it gotten worse now I would have been nervous. John did good though he had already picked out some alternative landing points and had his check list out ready for the worst
I was glad to be with him and work through something like this, kind of like letting him drive the car for the first time, as time goes on he will just get better and better and then the old man won't worry so much (not)

Ground Fog

IMG_1829.JPG

at my place looking south to PQN

IMG_1829.JPG

same time looking west to BKX

It was also a good day to get some of the snow load off the sheds

IMG_1833.JPG

IMG_1829.JPG

The sun is up and will be a good day to fly again






W.

[Bruce Fenstermacher]

Hey W if I should ever decide to move to Minnesota remind be you gotta snow blow the snow off your roofs there BEFORE I sell my place here PLEASE.

[GAHorn]

You may have had water in your fuel, and you eventually got it out. Try draining your carb bowl. (Small NPT plug. Do NOT overtighten it when reinstalling. It only has to be slightly snug.)

Usually carb ice does not form below freezing and you had -4C. (But flying in freezing conditions with partial carb heat can produce carb ice. Unless you have a carb temp gauge use full carb heat when you need it.

Symptoms of carb ice is not usually a "miss" unless it's extremely far advanced. Long before that occurs, a decrease of engine power will occur. This is indicated by a loss of RPM (fixed pitch) and/or loss of Manifold Pressure.

Pulling full carb heat should give a further loss of RPM and when the ice is removed, an increase/return to a steady RPM slightly below that originally selected. Removing carb heat should return the engine to the selected power setting. (MP will also return to that previously selected. MP gauges are not common in fixed pitch installations. I installed one shortly after I bought my airplane, in accordance with the type depicted by Cessna as an original option. It came in handy the next week as my tach failed on the return from LAS convention. Without a tach it was the only way to reliably monitor steady power settings as a precursor to carb ice.)

I've experienced carb ice many times in O-200 engines and perhaps once or twice in O-300's...but never in my O-300. It was never in below freezing conditions. It was always in fairly temperate wx with cumulus clouds in the area. (Not an axiom...only an observation.)

[pdb]

W:

We need to know a bit more. Your symptoms are not inconsistent with carb ice, especially at the temp you indicated. Carb ice can indeed occur at that temp in high humidity conditions. Just adding carb heat may, in some cases make it worse when you are at a low power setting.

What can happen at lower power settings is that the application of heat raises the carb air temp just above freezing but not high enough to melt the accumulating ice. It makes things worse because now you have created idea conditions in the carb for carb ice formation, temps just above freezing in the presence of high humidity.

The solution is to apply carb heat while you still have power and hence heat, and then reduce power as required to land.

In Alaska, especially in the spring and fall, we spend a lot of time flying in ideal carb icing conditions, ie., 40-50 degree air and high humidity. O-300s ice readily in those conditions but the problem is easy to deal with the proper use of carb heat.

[W.J.Langholz]

I was up for about and hour yesterday and wanted to see if I could recreate the same issue but could not. The weather conditions were almost identicle. I did clean out the plugs as much as pos during run-up and leaning out to get any clinkers out. I did some touch and goes, watched my cylinder temp go from 310-380 during the process.
George, I never thought about the carb bowl, I will check that out. I did have a bit of water mid summer in the one wing sump but haven't seen any since.

pdb, it is interesting in watching the air temps, yesterday it was a -4c on the ground and a +6 at about 3,000 ft.

What was still interesting was the day before we had both noticed a slight miss before we pulled in the carb heat. We definately had a cough and a studder then, more than just a decrease in power,the power came back with in seconds but not 100% normal until we were on the ground and did a run up test.
At any rate it gave us both and oppertunity to run though our emergency land check list.......and above all keep your wits about you and FLY the airplane.


W.

[jrenwick]

We've been having very strong temperature inversions in the upper Midwest lately. Saturday mid-day I was out Cubbing on skis, and pilots were reporting +13C at 3500', while on the ground it was -4C or so. There was a wind shear at about 2200' MSL. Above that, we had a 40 knot tailwind component flying east. Below, 20 knots. It was a very sharply defined layer that you could see clearly from the air. We've also been having dense fog warnings for the last couple of mornings, so clearly (or hazily?) the inversion is trapping a lot of humidity close to the ground.

With all that, Saturday was a beautiful flying day. We landed on Balsam Lake in NW Wisconsin, and had a hamburger at Paradise Landing (which I can recommend as a great $100 hamburger spot if you're on floats or skis). We talked about going over to Lake Calhoun, but we all agreed the landing fee is too much. (I used to live a block from Lake Calhoun, and always daydreamed about landing the Cub there. I knew it wasn't legal.)

There's a little discussion of the Lake Calhoun incident here: http://www.skiplane.org/cgi-bin/yabb2/Y ... 1263248467. Scroll down to where the restaurant is doing a fundraiser to help the pilots with their fees and fines!

I don't know exactly where they landed and took off on the lake, but half of it is in Class B airspace:

Calhoun.jpg

(Lake Calhoun is labeled. It's the nearly-round lake near the middle of the snapshot.)

[GAHorn]

It's virtually impossible to have (significantly) below-freezing temperatures combined with high-humidity. Any moisture in the air is already frozen and has fallen out and cannot re-freeze upon contacting a cold surface such as a carburetor-throat.

What CAN occur however, is a surprise when the aircraft climbs into a temperature inversion where warmer air exists above cooler air. A pilot can find oneself in carb-icing conditions when least expected.

I'm about to leave warm TX off for 5 days in cold Burlington, VT. brrrrrr.

[jrenwick]

Saint Paul right now has a temperature of -5C, dewpoint -7, with a forecast of patchy ground fog. These temps aren't significantly below freezing, and there's visible moisture in the air. We've been having this kind of weather for a few days now. Your point about getting into warmer air above is very well taken. In the Twin Cities on Saturday, the inversion layer was barely 1000' AGL.

John

[GAHorn]

Do you have any Saint Pauli GIRLS?

[jrenwick]

Heh. Yeah, lots of 'em! Eat yer heart out! (Or drink?)

[W.J.Langholz]

George
I got to go with John on this one. i think it was carb ice. I visited some of the local boys today, 1 had a simular issue.


W.

[Brad Brady]

Ice is a funky thing...I have run into carb ice at 70 F and 20 F. As George mentioned, the atmosphere has to be right, or you create an atmosphere that is conducive to Ice. Until you have encountered it, there is no way to tell someone what to expect. When instructing students you can only tell them where the problems will be. If your lucky, like I have been several times (Depending your take of lucky) You can show a student what Ice is all about. And from my stand point it's just management. How much or how little heat to make things work. After all you can create more problems by slugging the carb with water.......Brad