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SchulerJL
12-14-2012, 02:31 PM
I have a 1954 PA18 L21B with a Lycoming 0-320 A2B with 900 hours on it. I have been getting lots of carb ice lately under atmospheric conditions that I would not have encounterd carb ice in the past. Here's my question - would a carb overhaul help the problem? If so who would you reccommend? If the carb runs rich - is there a greater chance of carb ice? It is starting to drive me crazy, I must have spent 5 minutes clearing ice that formed from takeoff to 500' AGL this morning.

spinner2
12-14-2012, 02:35 PM
I have a 1954 PA18 L21B with a Lycoming 0-320 A2B with 900 hours on it. I have been getting lots of carb ice lately under atmospheric conditions that I would not have encounterd carb ice in the past. Here's my question - would a carb overhaul help the problem? If so who would you reccommend? If the carb runs rich - is there a greater chance of carb ice? It is starting to drive me crazy, I must have spent 5 minutes clearing ice that formed from takeoff to 500' AGL this morning.

A vernatherm valve helps once the oil is up to temperature.

8GCBC
12-14-2012, 02:44 PM
What are the indicators? RPM, MP, EGT, CHT, CARB TEMP? What are weather conditions?

jgerard
12-14-2012, 02:56 PM
How many years since overhaul on that carb and do you run car gas sometimes? Also do you have slick mags and how long ago where they gone through? Regardless of slick or bendix mags you're coming up on a recommended inspection interval.


Jason

SchulerJL
12-14-2012, 02:59 PM
What are the indicators? RPM, MP, EGT, CHT, CARB TEMP? What are weather conditions?

It was 34F this morning with a dew point of 29 as I recall. Seems to happen any time there is a less than 6 degree difference between temp and dew point. 70 degrees 50 degrees, it does not matter. I get a very slight roughness after takeoff - slowly add heat and it runs very rough, black smoke comes out of the exhaust, 500 rpm drop. I work the carb heat fully out and leave it for a few minutes, close it and all runs well. Generally when it heats up, it does not do it again on multiple takeoff and landings. I do not have a MP, CHT or Carb temp.

8GCBC
12-14-2012, 03:13 PM
Thank you. The temperature / dew point spread makes sense to me. But, I know little on the subject....

SteveE
12-14-2012, 03:13 PM
Might run carb heat right before takeoff, mine would get ice on the ground in moist conditions, but wouldn't get it once up. 0360

bgriffel
12-14-2012, 03:14 PM
500 RPM is pretty noticeable. Out of the 2 cubs I've owned never had that bad of an ice issue. In a PA-22 I would get ice regularly but only had it that bad once and I'm positive I had a large amount accumulated just prior to take off due to a high speed taxi over wet snow to pack it down followed by a takeoff with out clearing the ice.

Couple of questions,

Whats your oil temp?

Where is cooler mounted?

Any autogas?

Do you lean while applying carb heat?

SchulerJL
12-14-2012, 03:22 PM
The engine was manufactured in May of 1988 and was STC'd to my plane in 2007. Log states that the carb, Marvel Schebler, was removed for inspection and repair in July of 94 at 248hrs, replaced venturi pin. Mags serviced in 2001 at 738 hours. How would the mags affect carb ice? And, I never run car gas - 100LL

SchulerJL
12-14-2012, 03:28 PM
500 RPM is pretty noticeable. Out of the 2 cubs I've owned never had that bad of an ice issue. In a PA-22 I would get ice regularly but only had it that bad once and I'm positive I had a large amount accumulated just prior to take off due to a high speed taxi over wet snow to pack it down followed by a takeoff with out clearing the ice.

Couple of questions,

Whats your oil temp?

Where is cooler mounted?

Any autogas?

Do you lean while applying carb heat?

Oil temp is low, when this happens 110 or so. I do preheat the engine with a Tannis. The oil cooler is old style cowling, square air filter. I have a plate with holes cut in it for between 30 and 40f. I use a solid plate to block the oil cooler when below 30f, from Atlee I think. No autogas. I did lean today as I worked the ice out - seemed to help.

8GCBC
12-14-2012, 03:29 PM
If you have bursting black smoke intermittently, it seems to indicated carburetor running way to rich. Just a thought to point to an overhaul?

SchulerJL
12-14-2012, 03:32 PM
Might run carb heat right before takeoff, mine would get ice on the ground in moist conditions, but wouldn't get it once up. 0360

When I did my mag check this am I had a normal 100 or so RPM drop - no indication of ice during run up. No long taxi or anything that would have allow a lot of ice to build

SchulerJL
12-14-2012, 03:34 PM
If you have bursting black smoke intermittently, it seems to indicated carburetor running way to rich. Just a thought to point to an overhaul?

Definitely black smoke - saw it on my GoPro. But only when I had the carb heat on and was clearing the ice.

bgriffel
12-14-2012, 03:46 PM
I would second the overly rich condition. I would say maybe overhaul the carb, lean during run up aggressively to help warm the engine and keep plugs clean.

I would bet the square filters contribute to more ice than round dome style.

cubflier
12-14-2012, 03:47 PM
Look at the joint of your carburetor halves for fuel staining. If you have a round air cleaner give it a shake to see if their is any play in it. These halves will loosen over time and fool you into thinking it's running rich and is making ice. It will be running rich but no ice. It just makes it seem that way when you pull carb heat. Another symptom (of loose carb halves)will be excessive rpm drop when you pull carb heat.

Jerry

SchulerJL
12-14-2012, 04:02 PM
Look at the joint of your carburetor halves for fuel staining. If you have a round air cleaner give it a shake to see if their is any play in it. These halves will loosen over time and fool you into thinking it's running rich and is making ice. It will be running rich but no ice. It just makes it seem that way when you pull carb heat. Another symptom (of loose carb halves)will be excessive rpm drop when you pull carb heat.

Jerry

I will give it a shake and check. It is a square filter. Funny thing about it is that once the ice is cleared after initial takeoff - it's cleared. Once the engine is warm I can do multiple TO's and LDG's and not have the problem reoccur. Occasionally it will occur on subsequent climb-outs but rarely.

If the engine is overly rich - would carb ice be more likely to form?

sierra bravo
12-14-2012, 04:10 PM
The comment that got my attention is that it takes 5 minutes of carb heat to clear ice. That doesn't make sense to me. My carb heat will clear ice in a few seconds. I'd question whether it's ice.

Related question for all. What temps, time, or other factors do you use to consider the engine "warmed" enough to apply taxi or take-off power? Oil temp? CHT? 2 minutes? What's your "go" threshold?

jgerard
12-14-2012, 04:12 PM
tired mags leads to weak spark leads to poor burning of the fuel leads to fowled plugs leads to black smoke leads to possible poor combustion that is compounded by the carb ice. I always ground lean all times of the year hot or cold engine regardless of altitude. I never cut the power, go to full rich, full carb heat, when landing which loads up the engine and can cause black smoke on the go-arround/take off. What kind of rise do you get when you pull the mix back to kill the engine? Square vs round filter should have no issue on richness. I bet that the carb needs to be gone through "July of 94" was a long time ago. If your carb is not quite as it should be and your spark is kinda week then you're going to have the problems you are describing. Make sure the resistance in your spark plugs in less than 2500 ohms. Good plugs test about 750-1500 ohms



Jason

SchulerJL
12-14-2012, 04:41 PM
The comment that got my attention is that it takes 5 minutes of carb heat to clear ice. That doesn't make sense to me. My carb heat will clear ice in a few seconds. I'd question whether it's ice.

Related question for all. What temps, time, or other factors do you use to consider the engine "warmed" enough to apply taxi or take-off power? Oil temp? CHT? 2 minutes? What's your "go" threshold?

I just rewatched the video - I may have over estimated the 5 minute time - it was more like two minutes - seemed like 5. I'll try to post the video as soon as I cut it in IMovie

SchulerJL
12-14-2012, 04:44 PM
tired mags leads to weak spark leads to poor burning of the fuel leads to fowled plugs leads to black smoke leads to possible poor combustion that is compounded by the carb ice. I always ground lean all times of the year hot or cold engine regardless of altitude. I never cut the power, go to full rich, full carb heat, when landing which loads up the engine and can cause black smoke on the go-arround/take off. What kind of rise do you get when you pull the mix back to kill the engine? Square vs round filter should have no issue on richness. I bet that the carb needs to be gone through "July of 94" was a long time ago. If your carb is not quite as it should be and your spark is kinda week then you're going to have the problems you are describing. Make sure the resistance in your spark plugs in less than 2500 ohms. Good plugs test about 750-1500 ohms



Jason

Makes sense - thanks. Seems like it would be a good idea to have both the carb and mags closely looked at.

SchulerJL
12-14-2012, 09:51 PM
Ok, so here is the video - what's the opinion? does this happen to everyone anytime the temp/dew point gets close? do I need to have my carb rebuilt or is this just normal?


http://youtu.be/YPtHyXZ41_g

8GCBC
12-14-2012, 09:59 PM
No visible moisture. Dew point spread appears wide? I see black smoke, a rich mixture maybe, or worse....

I would do a 100 hour inspection on engine only and switch the carb... But, I m not paying so that's easy to say.

SchulerJL
12-14-2012, 10:20 PM
Just had an annual, #4 cylinder new rings exhaust valve. Was the same before annual as after -same ice problem. Had exhaust replaced about 4 months ago with Atlee dodge hot rod - that seemed to make it slightly worse.


Sent from my iPad using Tapatalk HD

Nathan K. Hammond
12-14-2012, 10:39 PM
Have you looked at the exhaust under the muff? If it was cracked, adding carb heat could make it run rough and rich. A stumble from carb ice could be throwing off the true cause. Might be a stretch on a new exhaust, but it doesn't cost anything to check.

nkh

8GCBC
12-14-2012, 10:44 PM
Just curious...what are compression readings? Oil consumption (approx )?

N86250
12-14-2012, 11:34 PM
Obviously rich with too much smoke. The stack looks really sooty black even in the video. Has fuel consumption gone high? All good calls on possible problem areas above. Is your primer locked in? If it was a small Continental engine I would insist on checking the primer for internal leaking before I spent any big money. jrh

DesperadoPilot
12-14-2012, 11:58 PM
An intake leak could cause the same symptoms.

8GCBC
12-15-2012, 12:03 AM
Intake leak = lean? Not normally for that type of smoke?

SchulerJL
12-15-2012, 04:53 AM
Just curious...what are compression readings? Oil consumption (approx )?

Compressions good, just had annual and cylinder reworked. Oil consumpion, quart every 8 or 10 hours.

SchulerJL
12-15-2012, 04:54 AM
Have you looked at the exhaust under the muff? If it was cracked, adding carb heat could make it run rough and rich. A stumble from carb ice could be throwing off the true cause. Might be a stretch on a new exhaust, but it doesn't cost anything to check.

nkh

Just replaced exhaust and crossover stacks. Atlee hod rod muffler.

RAC cubs
12-15-2012, 09:16 AM
I live in Racine Wi. have three cubs this is normal have operated,for 25 years banner towing. we have same condtions lately.

Very Funny Story
Lasty sunday one pilot is returning from 3 hour tow low 70 miles under tow to chicago,he is 10 miles out so I ask him how its runing whats oil temp? he said there something wrong the carb heat cable it pushing the throttle foward every time he pushs the carb heat foward the rpm increases 400 rpm,I said its carb ice no no carb ice makes it run rough,and its runing smoth. he wanted me to test fly I told him this was induction ice not on the throttle plate that makes it run rough ,and this ice melts out smoother. he can't beleive it.

call me I will explain

Ted 414 791 9872

this nomal see it on climb I teach pull carb heat on takeoff only thing you can try is climb flat higher speed,theaching in c 180 old one yesterday and was getting alot of ice


you waited way to long to clear start at 300 feet on takeoff



e

SchulerJL
12-15-2012, 02:42 PM
I live in Racine Wi. have three cubs this is normal have operated,for 25 years banner towing. we have same condtions lately.

Very Funny Story
Lasty sunday one pilot is returning from 3 hour tow low 70 miles under tow to chicago,he is 10 miles out so I ask him how its runing whats oil temp? he said there something wrong the carb heat cable it pushing the throttle foward every time he pushs the carb heat foward the rpm increases 400 rpm,I said its carb ice no no carb ice makes it run rough,and its runing smoth. he wanted me to test fly I told him this was induction ice not on the throttle plate that makes it run rough ,and this ice melts out smoother. he can't beleive it.

call me I will explain

Ted 414 791 9872

this nomal see it on climb I teach pull carb heat on takeoff only thing you can try is climb flat higher speed,theaching in c 180 old one yesterday and was getting alot of ice


you waited way to long to clear start at 300 feet on takeoff



e

That's very intersting - thanks for the information. I have not heard that as usual procedure. So you clear the carb at about 300' ? I will give you a call to discuss further

Scooter7779h
12-15-2012, 10:11 PM
Carburetor ice in part lead to the demise of 79H. That -12, which I had for 34 years and 3900 hours was always very very prone to carb ice, visible moisture or not. I learned to mitigate it by liberal application of carb heat. After putting in a digital tachometer in the plane at the last re-engine (700 some hours prior to accident), you could watch it closely, when it would drop 20-30 rpm, pull heat, it would clear and go right back to the RPM you had been running at. It had the original small airbox with square filter. In post accident discussion with NTSB, I got forwarded to a person who was doing a study on the carb ice issues with small single engine pipers. After I described in length all of my experience with 79H, he told me that my experience was aligning with his preliminary hunch that the small airbox, when put in 150/160 O-320's seems to have this propensity The problem with the data is that it is only some, not all. After that insight, and purchasing Sierra Bravo's PA-12 which has the big airbox with round filter, I have seen no indication at all of carb ice even in perfect conditions for it (visible moisture and even temp/dew point). I always heard that some people said they never use carb heat unless they are in those conditions which I though risky based on my decades of experience with my 12. So, this is all empirical information, but it might useful to some. Knowing now what I do, I would have loved to convert to the different airbox and filter on 79H and see if the situation changed.

BTW, my bite came from 20 minutes prior to landing "loafing" at 1800 rpm spotting fish, then finding and examining landing area. Perfect conditions for carb ice, rain/fog temp/dew point close if not the same. During this time I applied carb heat very frequently, and was clearing ice. However, in hindsight now, the low RPM may have not created enough heat to fully clear it, in fact it may have induced more ice. I made a perfect approach to a short but land-able sandbar, took a little hop across a swale and could not brake on the hop, and with 300' left thought I was doing the safe thing and decided to go around. The engine RPM increased, but I only had 1/2 power. This lead to a go off the end, waterski get in the air but would not climb then had a bank I could not clear in the way. With impact certain, I maneuvered to drop a wing in the water to scrub speed, pulled stick in lap and did a three point on two mains and the belly pod against a 10' bank on the river outside bend (20' deep and 5,000cfs current). It was only after the accident was over later in the day that I came to realize I had a partial power situation because looking at the scene I knew that my Cub should have been long gone out of there on a go-around. Try a go around with 1/2 power fully loaded out of 300 feet, just was not going to work. There is much more to the story of what happened after we successfully "planted" with no injuries, for a future "lessons learned" thread. But this part of the story is: a go around is not always the most safe thing, there is a liability if you cannot make full power due to carb ice.

BTW, as SB will tell you, I am still smiling in my new -12, the brainchild and years of his hard work and brilliant insight on how to make a wonderful PA-12 as the project lead of 53M. Since August I have 80 hours on it, and grin ear to ear each time I fly it. Like today.

skywagon8a
12-16-2012, 05:18 AM
Just as a reminder, maximum carburetor heat is only available at full power during a climb. All other times there is some degree of less heat.

SchulerJL
12-16-2012, 05:51 AM
Carburetor ice in part lead to the demise of 79H. That -12, which I had for 34 years and 3900 hours was always very very prone to carb ice, visible moisture or not. I learned to mitigate it by liberal application of carb heat. After putting in a digital tachometer in the plane at the last re-engine (700 some hours prior to accident), you could watch it closely, when it would drop 20-30 rpm, pull heat, it would clear and go right back to the RPM you had been running at. It had the original small airbox with square filter. In post accident discussion with NTSB, I got forwarded to a person who was doing a study on the carb ice issues with small single engine pipers. After I described in length all of my experience with 79H, he told me that my experience was aligning with his preliminary hunch that the small airbox, when put in 150/160 O-320's seems to have this propensity The problem with the data is that it is only some, not all. After that insight, and purchasing Sierra Bravo's PA-12 which has the big airbox with round filter, I have seen no indication at all of carb ice even in perfect conditions for it (visible moisture and even temp/dew point). I always heard that some people said they never use carb heat unless they are in those conditions which I though risky based on my decades of experience with my 12. So, this is all empirical information, but it might useful to some. Knowing now what I do, I would have loved to convert to the different airbox and filter on 79H and see if the situation changed.

BTW, my bite came from 20 minutes prior to landing "loafing" at 1800 rpm spotting fish, then finding and examining landing area. Perfect conditions for carb ice, rain/fog temp/dew point close if not the same. During this time I applied carb heat very frequently, and was clearing ice. However, in hindsight now, the low RPM may have not created enough heat to fully clear it, in fact it may have induced more ice. I made a perfect approach to a short but land-able sandbar, took a little hop across a swale and could not brake on the hop, and with 300' left thought I was doing the safe thing and decided to go around. The engine RPM increased, but I only had 1/2 power. This lead to a go off the end, waterski get in the air but would not climb then had a bank I could not clear in the way. With impact certain, I maneuvered to drop a wing in the water to scrub speed, pulled stick in lap and did a three point on two mains and the belly pod against a 10' bank on the river outside bend (20' deep and 5,000cfs current). It was only after the accident was over later in the day that I came to realize I had a partial power situation because looking at the scene I knew that my Cub should have been long gone out of there on a go-around. Try a go around with 1/2 power fully loaded out of 300 feet, just was not going to work. There is much more to the story of what happened after we successfully "planted" with no injuries, for a future "lessons learned" thread. But this part of the story is: a go around is not always the most safe thing, there is a liability if you cannot make full power due to carb ice.

BTW, as SB will tell you, I am still smiling in my new -12, the brainchild and years of his hard work and brilliant insight on how to make a wonderful PA-12 as the project lead of 53M. Since August I have 80 hours on it, and grin ear to ear each time I fly it. Like today.


I think it would be great to have the "Round airbox vs. square airbox discussion" Since I have a square airbox I can attest to frequent carb ice in conditions that you would not think by observation. I reallly go by this chart and it seems to work - however it seems like I am in the serious icing zone everytime I fly.

The website for this is: http://www.atsb.gov.au/media/56519/carb_icing.pdf9574

SchulerJL
12-16-2012, 06:36 AM
As a second item - how difficult is it to change to the round airbox? My lower cowl does have some cracks and dents.

tempdoug
12-16-2012, 08:09 AM
http://www.supercub.org/forum/showthread.php?43292-Carb-Ice&highlight=carb+heat+boxthis link is to addition for whats going.

tempdoug
12-16-2012, 08:19 AM
Some of the carb heat boxes have a baffle in them like a cross and some dont right before the air enters the carb. Jason would know. Would this make any difference to carb icing? I have a cowling sitting on my table where the square filter was switched to a round one using the square carb heat box. Guy gave it to me yesterday. I will get a picture on here. He was going to give me the carb heat box also and i noticed it had the cross fins in it.

RAC cubs
12-16-2012, 08:58 AM
I have round air fillters on all three one has no cowl one is 160hp the ice maker two are 180 hp they all fly same time same weather

WHEN ONE GETS ICE THEY ALL GET ICE! the 160 is the worse its were you fly me Lake Michigan fly here LOW 1000agl or less here alot of ice. most people c 172 ect fly at 2000ft plus that will take you out of the ice most of the time.

SchulerJL
12-16-2012, 09:16 AM
I have round air fillters on all three one has no cowl one is 160hp the ice maker two are 180 hp they all fly same time same weather

WHEN ONE GETS ICE THEY ALL GET ICE! the 160 is the worse its were you fly me Lake Michigan fly here LOW 1000agl or less here alot of ice. most people c 172 ect fly at 2000ft plus that will take you out of the ice most of the time.

Thanks for the round Vs square clarification. I'm sure I've seen your banners over Chicago before - I never read the banner - just looked at the plane, hahaha

sierra bravo
12-16-2012, 09:31 AM
For under $200 you can buy a TSO'd carb temp gauge. For a little more you can buy digital and even optical instruments. For many years I had a Mid Continent carb temp gauge in my 180. It ran in the yellow zone all the time and I never encountered ice. When I added a JPI EDM700 I opted for a carb temp probe. I rarely view that display option. In your case, being that you're convinced you're experiencing significant carb icing? I'd recommend an instrument to assist you in managing the problem.

RAC cubs
12-16-2012, 09:36 AM
Its hard to teach but there is a way to find a spot to place carb heat . First in the climb the engine is warming up, so all this are in flux ie the first takeoff at same place will be differant than second because the core of engine has warmed up . but up at level flight I would teach climb but in your case and mine we chose to stay low me for work you for fun. now pull full carb heat clear then return to 3/4 carb heat then pull again if no ice then keep at 3/4 if ice then 1/2 for 3 min try again most of the time you will find a place that will keep it free of ice but not always I think has to do with ram pressure not rpm in climb slow air speed full power alot of heat the most ice altough the economizer value is open above 75% throtle rich but normal takeoff power for us no banner is 2000rpm and get alot ice that way too. this is a big problem when you need hp to pull big sign. I would like fuel injection

SchulerJL
12-16-2012, 09:51 AM
http://www.supercub.org/forum/showthread.php?43292-Carb-Ice&highlight=carb+heat+boxthis link is to addition for whats going.

I probably should have added to the existing thread and not started a new one. Possibly our moderator could link the two?

SchulerJL
12-16-2012, 10:02 AM
For under $200 you can buy a TSO'd carb temp gauge. For a little more you can buy digital and even optical instruments. For many years I had a Mid Continent carb temp gauge in my 180. It ran in the yellow zone all the time and I never encountered ice. When I added a JPI EDM700 I opted for a carb temp probe. I rarely view that display option. In your case, being that you're convinced you're experiencing significant carb icing? I'd recommend an instrument to assist you in managing the problem.


It's definitely on my list of things to buy - I have a spot picked out in the panel.

SchulerJL
12-16-2012, 10:13 AM
Seems like it would be good to know if it is ice or the carb. If it is ice, a detector would be good, could not hurt to have one anyway. Aircraft spruce has three listed:

http://www.aircraftspruce.com/search/search.php?s=carb%20ice

This one was suggested in a previous post:

http://www.aircraftspruce.com/catalog/inpages/icedetect.php?clickkey=26499

Anyone have any experiance with it?

sierra bravo
12-16-2012, 10:21 AM
If it was me? I'd prefer a dial with a yellow arc. Perhaps because that's what I've been used to but it does the job inexpensively.
http://www.aircraftspruce.com/pages/in/carburetorgauges/carburetorairtemp2.php

Here's the one I had for most of my 180's life. I can't say it's worth 5x more than the Westach but I wasn't the one who orignally installed it.
http://www.aircraftspruce.com/catalog/inpages/carbtempkit.php

skywagon8a
12-16-2012, 10:38 AM
Just remember that the yellow arc only means that there could be a possibility of carb ice. That you are in the temperature range which is the most likely that ice could form. Maybe yes, maybe no.

sierra bravo
12-16-2012, 10:44 AM
Point being that a dial instrument is a temperature management instrument. An optical instrument is an ice presence indicator. A guy needs to decide what's important to him.

Tom Jones
12-16-2012, 10:52 AM
I had an O-290-11 in my 1951 L-21A with a square Bracket foam air filter. I made the big mistake of cleaning it and applying some K&N filter oil to it (I know ..). That turned out to be a really, really bad idea. It was summer when I did it, and as the weather cooled off, the filter oil had a tendency to congeal under low throttle conditions and did a wonderful job of imitating really bad carb ice. Lots of heat and full throttle usually cleared it up nicely, and it stayed cleared until the next time I was at or near idle throttle and cool. It took me a couple of weeks of head scratching before I remembered the cleaned filter. I swapped out the oiled one, put in a new one, and the problem instantly went away. If you haven't already, I'd pull the filter and see if there is some kind of air flow restriction causing it to run too rich.

By the way, I run a K&N filter now and the oil works as advertised on their filter. Just don't put it on anything else!

Tom

tempdoug
12-16-2012, 11:06 AM
http://www.supercub.org/forum/attachment.php?attachmentid=8400&d=1345947512&thumb=1 (http://www.supercub.org/forum/attachment.php?attachmentid=8400&d=1345947512)would these crosshair baffles have any effect on carb ice developing or not?

skywagon8a
12-16-2012, 11:56 AM
http://www.supercub.org/forum/attachment.php?attachmentid=8400&d=1345947512&thumb=1 (http://www.supercub.org/forum/attachment.php?attachmentid=8400&d=1345947512)would these crosshair baffles have any effect on carb ice developing or not?

They should not. The ice is formed downstream of the fuel nozzle.

captainron55746
12-16-2012, 12:08 PM
I haven't had much ice trouble with the 12 but the 180 has scared me a few times over the years. When you are picking up carb ice, the ice restricts the airflow, not the fuel, so your mixture becomes richer and richer. If you don't notice the power loss until engine roughness, then adding carb heat, which expands the air and makes the mixture richer yet, can kill the engine from over richness. You should always expect to lean when adding carb heat, it may restore engine power even if only half power which would buy time to let the ice clear while still producing heat. I was taught that partial heat was not effective at all in removing ice, maybe in prevention, but I don't like partial heat for long periods because you bypass the airfilter and bring in unfiltered air. In my wilderness bush flying courses I was taught a couple of things that I hadn't learned before and I have to say that I have't had scarey issues with carb ice since. The first one is that in winter flying or anytime it is conducive to carb ice, apply carb heat a minute before take off and leave it on until you are in the air. That full power full heat run of 30 seconds or so cleans the carb out good and you should be fine till you get to altitude. The second point is that if your engine quits, you realistically have 30 seconds of heat maybe, before the exhaust muff cools off and is ineffective. Apply carb heat first, pull the mixture all the way out - don't use any of the heat to vaporize gas, let it melt the ice and 10 seconds or so later start coming in with mixture and see if it catches. While you were waiting you would check tanks and any other things that are in your emergency procedure, keep nose up, trim for glide, troubleshoot, etc. Obviously your proximity to the ground will color whether you can wait 10 seconds, but use the heat for ice not vaporizing fuel. The black smoke just confirms you are running rich when you add carb heat and you should now know that already. I don't know that I would overhaul the carb because of the black smoke, it may need it for other reasons but not because of the soot during carb heat and ice incident.
Ron

SchulerJL
12-16-2012, 12:11 PM
I had an O-290-11 in my 1951 L-21A with a square Bracket foam air filter. I made the big mistake of cleaning it and applying some K&N filter oil to it (I know ..). That turned out to be a really, really bad idea. It was summer when I did it, and as the weather cooled off, the filter oil had a tendency to congeal under low throttle conditions and did a wonderful job of imitating really bad carb ice. Lots of heat and full throttle usually cleared it up nicely, and it stayed cleared until the next time I was at or near idle throttle and cool. It took me a couple of weeks of head scratching before I remembered the cleaned filter. I swapped out the oiled one, put in a new one, and the problem instantly went away. If you haven't already, I'd pull the filter and see if there is some kind of air flow restriction causing it to run too rich.

By the way, I run a K&N filter now and the oil works as advertised on their filter. Just don't put it on anything else!

Tom


Thanks Tom - I will check that.

tempdoug
12-16-2012, 12:17 PM
Also if you have a screwdriver down around the carb halves sometime maybe check the screws?

RAC cubs
12-16-2012, 12:48 PM
The other thing that is most important is where the door is . is it bent some have it open little in the off stop

talk to Randy Rupert maker of carb boxs some don,t close all the way or are bent letting heat though in the off posision.that will sometimes in duce ice.induction ice is up in the tubes thats why j3s have covers or warmers for the tubes

SchulerJL
12-16-2012, 12:51 PM
The other thing that is most important is where the door is . is it bent some have it open little in the off stop

talk to Randy Rupert maker of carb boxs some don,t close all the way or are bent letting heat though in the off posision.that will sometimes in duce ice.induction ice is up in the tubes thats why j3s have covers or warmers for the tubes

Do you know how I can get in touch with Randy Rupert? I have heard his name before. Mechanic mentioned that there was some play in my system at last annual.

tempdoug
12-16-2012, 01:34 PM
7018473008

SchulerJL
12-16-2012, 01:36 PM
7018473008

Got it - thanks I was just reading pervious posts and it is Randy Rubbert

DENNY
12-16-2012, 03:00 PM
Just to repeat what a few others have said. Before you spend a lot of money check the 4 carb bool screws!!! if they are loose it will run rich and act like carb ice. You may even see gas staining down the side if you look close.
DENNY

SchulerJL
12-16-2012, 03:41 PM
Thanks to RAC cubs for spending the time to talk to me on the phone. This is a great organization! I keep learning more and more

DesperadoPilot
12-16-2012, 04:00 PM
Just to repeat what a few others have said. Before you spend a lot of money check the 4 carb bool screws!!! if they are loose it will run rich and act like carb ice. You may even see gas staining down the side if you look close.
DENNY


That is basically what I was trying to say in Post #27 when I said an intake leak could cause the same symptoms. Maybe I just worded it wrong. Been there, done that.

jgerard
12-17-2012, 03:56 AM
Carb Ice is not worse square or round filter. There are examples of aircraft either loosing or gaining carb ice problems after an engine change using the same air box and not just cubs or small Lycomings. You're carb has been un opened for 18 years and is only getting an average of 36 hrs a year since it was last inspected. I'm guessing it probably had some long periods of inactivity over those 18 years as well. Air and fuel passages in the casting wear and or plug up over time. I would exchange it for a fresh overhauled one. That is cheaper than switching bottom cowlings and air boxes. You should also check to see how big of a lip you have between the sump and the top of the carburetor. Ice builds on sharp or rough edges. You need to pull the carb to inspect that area. I have cleaned up a few sumps now to remove excess metal and smooth airflow. Have also smoothed out rough edges on the Venturi in the carburetor. I am not saying that's the issue but might be worth looking at. Also I remember there is a difference between tapered riser and straight riser sumps and I'm thinking there was an adapter or you were supposed to match the carb to the sump or something like that.

Jason

SchulerJL
12-17-2012, 07:01 AM
Carb Ice is not worse square or round filter. There are examples of aircraft either loosing or gaining carb ice problems after an engine change using the same air box and not just cubs or small Lycomings. You're carb has been un opened for 18 years and is only getting an average of 36 hrs a year since it was last inspected. I'm guessing it probably had some long periods of inactivity over those 18 years as well. Air and fuel passages in the casting wear and or plug up over time. I would exchange it for a fresh overhauled one. That is cheaper than switching bottom cowlings and air boxes. You should also check to see how big of a lip you have between the sump and the top of the carburetor. Ice builds on sharp or rough edges. You need to pull the carb to inspect that area. I have cleaned up a few sumps now to remove excess metal and smooth airflow. Have also smoothed out rough edges on the Venturi in the carburetor. I am not saying that's the issue but might be worth looking at. Also I remember there is a difference between tapered riser and straight riser sumps and I'm thinking there was an adapter or you were supposed to match the carb to the sump or something like that.

Jason


That's great advice - just from the point of view that it has not been looked at in many years, I think it is due irregardless. If it helps, great, if not at least I have that item checked off. From what I am hearing from the group, with the exception of RAC cubs - who is in a similar environment to me - that not everyone has carb ice of the type in the video on almost every flight. I find it hard to beleive that Central Illinois would be more ice prone than Washington, Oregon and Alaska.

Bill Rusk
12-17-2012, 07:05 AM
Interesting thought. I was flying formation to Alaska with DW. I had a square box and carb ice issues, DW has a round box, and in the same atmospheric conditions 100' apart, he had no carb ice issues. The only time I have ever had carb ice has been with the square box.

Coincidence?

Bill

SchulerJL
12-17-2012, 08:12 AM
Interesting thought. I was flying formation to Alaska with DW. I had a square box and carb ice issues, DW has a round box, and in the same atmospheric conditions 100' apart, he had no carb ice issues. The only time I have ever had carb ice has been with the square box.

Coincidence?

Bill

I don't think there is a big climate difference between Peoria and Poplar Grove. What percent are square boxes - probably a pretty small number. RAC cubs seems to get a lot in Racine with a round box, however banner towing could change the equation.

SchulerJL
12-17-2012, 10:22 AM
Ok - just talked to the mechanic at Poplar Grove Airmotive - says he gets them to ice up on the test stand, should not fly it - I should just put my plane away for the winter, hmmmm not what I had in mind.

skywagon8a
12-17-2012, 10:29 AM
Square vs Round Ice vs No Ice?

Just thinking out loud: Are there any other differences in the installation? Does one have the outside ram air blocked around the air box towards the carburetor and the other not? Is the air flow around the oil cooler scoop different in the two installations? Is there more outside cold air blowing on the outside of the carburetor in one than in the other? If there is more outside air blowing on the outside of one of the carburetors it could cool down the housing enough to reduce it's resistance to ice. If the carb housing were warmer it could help reduce the propensity to ice up. There is supposed to be a baffle blocking free flow of air around the air box in one of these installations if not both, thus keeping the carb area warmer. Maybe SchulerJL does not have this baffle?

If the oil temperature is higher, then the sump would be warmer thus reducing the icing possibility.

cubdriver2
12-17-2012, 10:57 AM
Mount your gopro down there next time your flying and see whats going on.

Glenn

SuperCub MD
12-17-2012, 12:23 PM
I fly around Peoria a lot when working, the river valley is a prime spot for ice, lots of juice holds in the air. Have a Cub up here with the same engine as yours and round filter, makes ice all the time. Would like to try a different carb but its a lot cheaper to just clear it. The old -12 carb taper riser 320s seem to be a lot less prone to ice than the new -32 straight risers, don't really know why other than they run leaner. Figure out your fuel burn and monitor it, maybe have the carb checked or exchanged if it is excessive. If you are not doing it, put a heavy blanket over the cowl when the tannis is plugged in. This will help the whole engine to warm up (including the carb/intake), not just make hot and cold spots.

OLDCROWE
12-17-2012, 12:29 PM
Ok - just talked to the mechanic at Poplar Grove Airmotive - says he gets them to ice up on the test stand, should not fly it - I should just put my plane away for the winter, hmmmm not what I had in mind.Or you could give it to an Okie for winter "keeping"

SchulerJL
12-17-2012, 01:43 PM
I fly around Peoria a lot when working, the river valley is a prime spot for ice, lots of juice holds in the air. Have a Cub up here with the same engine as yours and round filter, makes ice all the time. Would like to try a different carb but its a lot cheaper to just clear it. The old -12 carb taper riser 320s seem to be a lot less prone to ice than the new -32 straight risers, don't really know why other than they run leaner. Figure out your fuel burn and monitor it, maybe have the carb checked or exchanged if it is excessive. If you are not doing it, put a heavy blanket over the cowl when the tannis is plugged in. This will help the whole engine to warm up (including the carb/intake), not just make hot and cold spots.


Just spent some time on the phone with Randy Rubbert in North Dakota. He said that my ice seems excessive, really great welth of information. I have the 3678-32 and the opinion seems to be just to switch it out with another and see if it makes a difference. He has a lower cowl and air box that I think I will switch to - just cause I want a round air box. I doubt that is the problem. I believe Randy also said the -32's are cooler and richer. I have a Bruce's custom cover for the cowling - another great company - they adjusted it at no charge when I changed to the Atlee muffler.

SuperCub MD
12-17-2012, 02:50 PM
Randy is the guy to deal with on the round airbox/cowl, and the carb swap is a good idea. I think you are on the right track, good luck.

kevin
12-17-2012, 04:54 PM
I have been following this thread. I'm quickly getting ready to purchase my bottom cowl for me -12 restoration...from Clyde Smith. It is a PA-12 with O320-A2B Kenmore STC. Is it better to have a square airbox over a round airbox? I would think that the square airbox will be faster than the round due to less drag but the round seems to me to give more air to the motor. Is this true? Does anyone have any hard data that the square airbox would be more prone to carb ice over the round? Also, how hard is it to get a round airbox approved on this plane. The Kenmore STC calls out for a square filter.

8GCBC
12-17-2012, 05:01 PM
GoPro on strut and some streamers on the cowl may show some hidden issues?

RAC cubs
12-17-2012, 05:08 PM
The pa 18 is a perfect dream machine only weak link is carb ice I can't believe some one did not get a good injection mod for cheap , but they think TV screens on the panel are more important

8GCBC
12-17-2012, 05:11 PM
Have you used lycoming IO -xxx ? It ain't that great in my book. But, never say never for me.

SchulerJL
12-17-2012, 05:43 PM
GoPro on strut and some streamers on the cowl may show some hidden issues?

Tell me more - I'm always looking for new camera angles

8GCBC
12-17-2012, 05:50 PM
Use telltales on areas of the airframe where you think airflow could be modified. Use GoPro to film area at different airspeed and AOA. Record modify and/or repeat until happy.



en.wikipedia.org/wiki/Tell-tale
Jump to Sailing‎: In a nautical or sailing context a tell-tale, sometimes known as a tell-tail, is a piece of cloth or fabric that is tied or attached to a stay, any of ...

tempdoug
12-17-2012, 10:23 PM
heres some pictures of a cowl that a round filter was adapted to a square airbox. The square carb heat box had a plate with a round tube that attached to the scat hose. i dont know why it was done like this. or maybe this is the way it was first done when some wanted a round filter. This cowling has been laying in a shed for a lot of years. I still cant see where anything is gained because it all necks down to the size where the heat box fastens to the carb.

jgerard
12-18-2012, 12:56 AM
I have been following this thread. I'm quickly getting ready to purchase my bottom cowl for me -12 restoration...from Clyde Smith. It is a PA-12 with O320-A2B Kenmore STC. Is it better to have a square airbox over a round airbox? I would think that the square airbox will be faster than the round due to less drag but the round seems to me to give more air to the motor. Is this true? Does anyone have any hard data that the square airbox would be more prone to carb ice over the round? Also, how hard is it to get a round airbox approved on this plane. The Kenmore STC calls out for a square filter.


Stick with the square filter, not worth the time money or energy required to get the approval. I would put money on the table that the square vs' round filter debate on carb Ice is pointless. And speed...you will loose more speed to having the plane out of rig than you would ever see changing from a square to round filter.

Sometimes just changing how you operate the engine will have a noticeable effect on things like fowled plugs, carb ice, sticky valves, and fuel/oil consumption. I think everyone needs to read the Skyranch engineering manual. There are many great tips that every pilot should know and understand in that book.

Jason

skywagon8a
12-18-2012, 05:14 AM
The pa 18 is a perfect dream machine only weak link is carb ice I can't believe some one did not get a good injection mod for cheap , but they think TV screens on the panel are more important


Have you used lycoming IO -xxx ? It ain't that great in my book. But, never say never for me.

I have a IO-360 in my experimental Cub. It runs great, burns less fuel and never gets carburetor ice. Don't even have a heat muff installed. Alternate air yes, but no heat. Once you learn the proper cold and hot starting methods all the rest is gravy. I have operated Lycoming IO-s from the 320 to the 720 and they are all the same. Just mount an auxiliary fuel pump between the fuel shut off valve and the firewall. I think that misunderstanding the hot start procedure has soured a lot of folks on the IOs.

RAC cubs
12-18-2012, 07:51 AM
If I could use experimental aircraft I would do the same tomorrow,But we have rules

skywagon8a
12-18-2012, 08:01 AM
If I could use experimental aircraft I would do the same tomorrow,But we have rules

Without going into a long discussion, in my opinion based on past experience, it would be relatively easy to get an STC to install a fuel injected engine on a certified Cub. I did not say to increase the HP. Do it with a 150.

SchulerJL
12-18-2012, 08:20 AM
Without going into a long discussion, in my opinion based on past experience, it would be relatively easy to get an STC to install a fuel injected engine on a certified Cub. I did not say to increase the HP. Do it with a 150.

What is the weight penalty? I often wondered why CubCrafters did not have a fuel injected 180 on the Carbon Cub. I asked that question at Oshkosh and the sales guy told me it was too heavy - of course that was LSA rules

8GCBC
12-18-2012, 10:37 AM
I have a IO-360 in my experimental Cub. It runs great, burns less fuel and never gets carburetor ice. Don't even have a heat muff installed. Alternate air yes, but no heat. Once you learn the proper cold and hot starting methods all the rest is gravy. I have operated Lycoming IO-s from the 320 to the 720 and they are all the same. Just mount an auxiliary fuel pump between the fuel shut off valve and the firewall. I think that misunderstanding the hot start procedure has soured a lot of folks on the IOs.

It's the nozzles clogging that is dangerous and costly from our experiences here. Hot starts are easy after some practice for me.

skywagon8a
12-18-2012, 10:40 AM
From the TC data sheets the basic weight for a 0-320-A1A is 244 lbs and the IO-320-A1A is 252 lbs. So, it is 8 lbs plus the weight of the aux fuel pump. In my view a small price to pay. Switch from a metal prop to a wood prop and you will gain back the weight sacrifice. Wood Vs metal props is another separate discussion.

skywagon8a
12-18-2012, 10:46 AM
It's the nozzles clogging that is dangerous and costly from our experiences here. Hot starts are easy after some practice for me.

I've been operating fuel injected airplanes for 50 years and have never had a nozzle clog. Yes periodically I do take them out to clean them.

8GCBC
12-18-2012, 10:57 AM
What part of the country? We thought maybe bad fuel here in the Pacific region?

Make sure to have Hoppies Gun Clearner in the tool box!

skywagon8a
12-18-2012, 01:47 PM
What part of the country? We thought maybe bad fuel here in the Pacific region?

Make sure to have Hoppies Gun Clearner in the tool box!

New England

8GCBC
12-18-2012, 05:27 PM
New England

Better maintenance there!

SchulerJL
12-19-2012, 01:05 PM
Talked to my mechanic about swapping carbs - the question came up - where is the best place to get an overhauled carb to swap out? Any suggestions? It is an 10-3678-32

tempdoug
12-19-2012, 01:13 PM
starting point anyway.http://www.aircraftspruce.com/catalog/eppages/tempestvolarerebuildoverhaul.php

8GCBC
12-19-2012, 01:14 PM
Spruce treats me right. They are good folks.

tempdoug
12-19-2012, 01:17 PM
and another, aeroinstock,





http://www.supercub.org/products/buttons/nopic_thumb.gif

]Item #: 10-3678-32-O-V-E (http://www.supercub.org/products/10-3678-32-O-V-E/6519/53339/product_detail/index.html)
CARB ASSY MA-4SPA
Retail Price: $1260.00

Your Price: $718.20

SchulerJL
12-20-2012, 03:08 PM
Ok - I just ordered a rebuilt carb and from Randy Rubbert a lower cowl, round air box and carb heat box. If it does noting, at least I have piece of mind. Anyway, I always liked the round air box better than the square one. I'll let everyone know if it works or not. Thanks for everyone's help on this.

8GCBC
12-20-2012, 03:20 PM
I like your attitude! Peace of mind takes work and money sometimes 8)

OLDCROWE
12-20-2012, 04:41 PM
For future reference

http://www.aircraftaccessoriesofok.com/index.php

Aircraft Accessories of Oklahoma is a class act!

SchulerJL
12-20-2012, 04:41 PM
I better spend it before it goes over the fiscal cliff. Isn't it the end of the word tomorrow- 11:12 Zulu? Hmmmm what else can I buy???

jgerard
12-20-2012, 05:17 PM
Better to get a factory rebuilt carb than have your old carb overhauled because a factory rebuilt carb almost always has new top and bottom body castings. They are basically new carburetors but they charge you for a core because they want to get the old worn out ones off the market. The old stuff quite often gets destroyed. Even a new off the shelf carb can benefit from some massaging of the internals and set up on a flow bench by a knowledgeable mechanic.


Jason

SchulerJL
12-20-2012, 05:42 PM
Better to get a factory rebuilt carb than have your old carb overhauled because a factory rebuilt carb almost always has new top and bottom body castings. They are basically new carburetors but they charge you for a core because they want to get the old worn out ones off the market. The old stuff quite often gets destroyed. Even a new off the shelf carb can benefit from some massaging of the internals and set up on a flow bench by a knowledgeable mechanic. I think FobJob had some good info on improving carburetor performance and efficiency and evening out EGT's

Jason

That's exactly what I did. Easier to change out rather than send mine back, wait and have it sent back. I want a completely new carburetor start

Gordon Misch
12-20-2012, 06:45 PM
Interesting thread, thanks to all for sharing ideas.

For whatever it's worth, I have the square filter airbox and a -32 carb on the O-320-A2B in my 12. I have not had any significant carb ice issues. I lean aggressively, pull carb heat fairly frequently, and watch the carb temp gauge. Fortunately I haven't had to fight ice even when temp and humidity are "just right" for icing. Just my personal experience - - -

SchulerJL
12-20-2012, 07:17 PM
Interesting thread, thanks to all for sharing ideas.

For whatever it's worth, I have the square filter airbox and a -32 carb on the O-320-A2B in my 12. I have not had any significant carb ice issues. I lean aggressively, pull carb heat fairly frequently, and watch the carb temp gauge. Fortunately I haven't had to fight ice even when temp and humidity are "just right" for icing. Just my personal experience - - -



I doubt there is a difference between square and round air boxes. However there may be a difference between a good carb heat box and a bad one. Or a good carb and a bad carb. The fact that a new Rubbert carb heat box is attached to a really cool looking round air filter is good enough for me. I was alerted to the carb heat box on my plane at my last annual when my mechanic said "That's the cheapest looking carb heat box I have ever seen" I have been looking for an excuse to dump it.

What does perpelx me about this whole thing is that some people have a lot of problems with ice and others do not - even operating in the same environment.

Gordon Misch
12-20-2012, 07:36 PM
Yep - BTW, my carb heat box is from Randy Rubbert. He rebuilt it and it looks like new - -

And maybe, ice isn't the root of the problem you're experiencing. Watching the video, I noticed that the black exhaust smoke is somewhat intermittent. Puffs, then lapses. Dunno what that might mean, but makes one wonder. Seems to me that the carb would certainly be a suspect in this mystery!

SchulerJL
12-20-2012, 09:24 PM
Yep - BTW, my carb heat box is from Randy Rubbert. He rebuilt it and it looks like new - -

And maybe, ice isn't the root of the problem you're experiencing. Watching the video, I noticed that the black exhaust smoke is somewhat intermittent. Puffs, then lapses. Dunno what that might mean, but makes one wonder. Seems to me that the carb would certainly be a suspect in this mystery!

Although I am far from an expert, I could not agree more. It seems like ice, but there seems to be more to it. Can't wait to report back!

jgerard
12-20-2012, 09:44 PM
before you box up the carb to return as a core I would open it up and take a look inside. Work with a knowledgeable mechanic and check the float level, check the air passageways for obstructions. Also look at the condition of the fuel nozzle and look for oval wear/erosion on holes in the jets. Check the throttle shaft for play. Check the accelerator pump operation and make sure the pump is set on the proper hole in the cam ( 3 options ) Check the Venturi for looseness. Check the accelerator pump nozzle for looseness. And look for signs of staining where fuel might have been leaking along with signs of dirt/sludge/and water in the bowl and other fuel passages. Also now is a good time to clean the screen in your gaskolator and maybe replace the fuel hose to the carb.


Jason

SchulerJL
12-21-2012, 07:32 AM
before you box up the carb to return as a core I would open it up and take a look inside. Work with a knowledgeable mechanic and check the float level, check the air passageways for obstructions. Also look at the condition of the fuel nozzle and look for oval wear/erosion on holes in the jets. Check the throttle shaft for play. Check the accelerator pump operation and make sure the pump is set on the proper hole in the cam ( 3 options ) Check the Venturi for looseness. Check the accelerator pump nozzle for looseness. And look for signs of staining where fuel might have been leaking along with signs of dirt/sludge/and water in the bowl and other fuel passages. Also now is a good time to clean the screen in your gaskolator and maybe replace the fuel hose to the carb.


Jason

I will do just that - kind of like a carburator autopsy. I'll let you know what I find.

mvivion
12-21-2012, 09:59 AM
As to differences in carb ice accumulation, I've seen this first hand. I flew a Cub in Kodiak (home of carburetor icing, year round) for a number of years and a thousand hours or so. It made some carb ice, but nothing scary.

Came time for an engine overhaul. I don't know what all was done, and wasn't smart enough at the time to find out if carb was changed, air box was rebuilt or???? BUT, the bottom line was, that airplane made carb ice like no machine I've ever been around, and I owned a Cessna 180 for a number of years.....

Why did that same airplane suddenly make carb ice more frequently than before? No idea. Obviously something changed, whether it was air box, carburetor or something else. Point is, different airplanes are going to make carb ice at different rates.

I try to teach students to always be on guard for carb ice, because it can be a sneaky bastard, creeping up on you slowly and quietly, right up till the loud noise up front ceases....

MTV

spinner2
12-21-2012, 10:20 AM
I try to teach students to always be on guard for carb ice, because it can be a sneaky bastard, creeping up on you slowly and quietly, right up till the loud noise up front ceases....

MTV

I decided to do a little night flying last night. I'd pulled off my 31's and switched over to 8's in anticipation of installing my wheel-penetration skis. There was some moonlight after changing the tires and I thought, why not go for a night flight and get three landings in. With the little tires I land on the runway and could use the runway lights. With the 31's I always land on a parallel section I keep mowed.

This was my first night flight in this Cub. I was making a much bigger pattern than my usual keep-it-in-close pattern landing in the grass. I'd turned final and was headed down towards the inviting runway lights and decided to pull carb heat. This plane doesn't usually make much ice and often I don't use carb heat but decided to now. But instead of pulling carb heat in the dark I pulled the mixture control. That made things quiet. Power was quickly restored when I pushed it back in. My two knobs are side by side and in the dark I didn't notice my error until things went quiet.

SteveE
12-21-2012, 10:39 AM
Got your attention didnt it? :lol:

SchulerJL
12-21-2012, 11:17 AM
I decided to do a little night flying last night. I'd pulled off my 31's and switched over to 8's in anticipation of installing my wheel-penetration skis. There was some moonlight after changing the tires and I thought, why not go for a night flight and get three landings in. With the little tires I land on the runway and could use the runway lights. With the 31's I always land on a parallel section I keep mowed.

This was my first night flight in this Cub. I was making a much bigger pattern than my usual keep-it-in-close pattern landing in the grass. I'd turned final and was headed down towards the inviting runway lights and decided to pull carb heat. This plane doesn't usually make much ice and often I don't use carb heat but decided to now. But instead of pulling carb heat in the dark I pulled the mixture control. That made things quiet. Power was quickly restored when I pushed it back in. My two knobs are side by side and in the dark I didn't notice my error until things went quiet.


My carb heat and my mixture were right next to each other when I bought my plane, same size knob -one was red the other black. Changed it out first thing to a big bumpy red knob for the mixture

spinner2
12-21-2012, 07:27 PM
Got your attention didnt it? :lol:
Hi Steve. Ya kind of like the time I took off to the north from Polson in the Cessna and blew an injector line over the lake. I made a quick 180 and landed down wind.

Gordon Misch
12-21-2012, 08:56 PM
With my Sutton exhaust, if I'm parked outside in windy rain, water can collect in the carb heat shroud and I think probably in the aeroduct. Then it can freeze, and then unfreeze and drown out the engine when carb heat is pulled after the engine has been running for a bit. Discovered that when I pulled carb heat shortly after takeoff from my hayfield over rugged and forested terrain, and the engine quit cold. Didn't sputter, just plain quit. It restarted promptly when I pushed the carb heat back in. But it took awhile for my heart to re-start, cuz I didn't know for sure what was going on! Now that I know that, I pull carb heat good and long with lots of power during runup, then V E R Y gradually the first time in flight, in case water in the heat duct was frozen and is melting slowly. And oh yeah, carb heat and mixture are on opposite sides of the panel!

NimpoCub
12-21-2012, 10:33 PM
I (almost) never pull carb heat or change fuel tanks over inhospitable ground. Over cautious, chicken? I also fill 'er up every time I come down to prevent excessive condensation. I certainly do carb heat once in awhile but never had any ice indication, guess I got a good carb system. :)

Gordon Misch
12-21-2012, 11:36 PM
I (almost) never pull carb heat or change fuel tanks over inhospitable ground. Over cautious, chicken? I also fill 'er up every time I come down to prevent excessive condensation. I certainly do carb heat once in awhile but never had any ice indication, guess I got a good carb system. :)
But you see, jolly St Nimp, down here in this corner of Washington, it's MOSTLY inhospitable ground. No choice. (Waiting for Torch now - 8):lol:) But actually it's true in the vicinity of my farm, and it was prime atmospheric conditions for carb icing.

To be a little more serious though, deferring carb heat ain't always such a hot (haha, get it?) idea either. I came close to losing my engine to carb ice over the Juneau Ice Field one time - Beautiful day, CAVU - who would suspect carb ice? Just keep adjusting mixture due to the altitude, right? Wrong. After finally pulling carb heat, had to nurse the carb heat and mixture back and forth together for a little bit to keep her going. REALLY got my attention, and ever since then I pull carb heat frequently even if I don't really suspect ice, just to be on the cautious side.

NimpoCub
12-21-2012, 11:45 PM
Mebbe I should have reiterated that I fly floats, & I meant I always look for a wet spot before I "change" anything. You may well know it's somewhat "bumpy" up here too! :) Yep, the Torch will be all over that :)

aktango58
12-22-2012, 08:07 AM
Dan,

The exact reason that I will put the carb heat and mixture apart from each other...

Geezer: yes, I get the ice up here all the time... and I know of one plane that almost crashed because the freeze thaw weather had allowed water to get into the scat hose between the heat muff and the air box. He pulled heat and sent warm moist air into the carb and puff, no power.

a good preflight check for all there.

Logan: as long as it is not a wet spot on the seat:wink:

but as much ice as we get here you don't have that option of waiting, you pull the heat on every little while.

S2D
12-22-2012, 04:35 PM
My two knobs are side by side and in the dark I didn't notice my error until things went quiet.

Something I'd change right away.