Carb Ice with the 0-200A

[stroutmail]

This is my second year with the S1 (SN 28). Plane came from Michigan and previous owner claims to never have had carb ice. I have not experienced it either.

Yet, I read so many stories of the 0-200 being an "ice maker" that I am always careful and vigilant. I try not to fly unless ambient and dew point differential is 15F (8C). I always use carb heat while decending in the pattern (turn it off on short final). On days that I suspect risk (see photo) carb-ice-potential-chart.jpg I also test carb heat just before takeoff if I have taxied a long way. (Like when doing pattern practice to a full stop.)

Just did a cross country with ambient of 45F and dewpoint of 28F. At 2500 AGL, outside temp had fallen to 37F. Clouds forming at 4000 AGL. Seemed like high risk (Serious icing while cruising per red chart) for carb ice when crusing at 2250 rpm, so I kept pulling carb heat about every ten minutes or so---and noticed no carb ice. (I run the 52 cartridge on the Sensenich adjustable--so 2250 is my 90-93 mph cruise. If I push the RPM up to 2500, I am way outside of the green arc. Not sure what condiitions are OK outside the green arc---I do know that in central PA below 4000 feet, my little cub moves around a lot--up/down, side to side. ( I dared not let the engine run below 2250. My preferred flying is a little slower 80-85 mph at 2150 RPM. )

Am I being too careful?

Is there an CC approval for a carb temp gauge or the optical sensor type for our cc11-100's?

Appreciate comments and discussion....

[Pete D]

I am not sure if there is a carb ice gauge approved for the Sport Cub. I have seen them in other airplanes but very rarely.

I have quite a bit of time in different Sport Cubs, mostly our Sn 71 which is an S2. I have had carb ice a few times, always in very wet conditions and typically only on the ground. My normal SOP is to taxi at a higher power setting in those conditions, turning the carb heat on to clear it as needed then turn it off. When I line up to take off I will set full power, turn carb heat on as long as needed to clear it up then carb heat off and release the brakes for the takeoff roll. I've never had it ice back up doing that. The conditions I had to do this in were heavy rain over night which soaked the grass so lots of water everywhere (vapor trails off everyone's props) but not actually raining when I was departing so once clear of the ground the moisture level went down significantly.

[stroutmail]

Wow. "vapor trails from props". That would be a sure sign of 100% humidity!

SA_029.pdf

Above is a link to a NTSB Alert that got my attention. The Alert provides links to FAA Advisories.

[stroutmail]

Here is a pretty good video on carb ice..the Cessna 140 he is flying, with a Continental C85 is pretty close comparison to the Sport Cub. Note it is the increase in RPM after using carb heat in cruise that confirms ice was there. It was the small drop in RPM (almost simulating throttle reduction) when throttle was fixed (in conditions where ice is possible) that created suspicion that carb ice was present in cruise.



In my part of the country, that range of temp and humidity where carb ice is possible covers most of the whole calender.

[stroutmail]

https://airfactsjournal.com/2019/11/that-other-ice/

This article showed up in my inbox. This guy was plagued with carb ice.

[stroutmail]

http://https://www.reddit.com/r/flying/comments/du3rvx/i_declared_an_emergency_today/?utm_medium=android_app&utm_source=share

Another article about carb ice with 0-200. Central Texas is not a place you normally think has high humidity.

[Cubdet]

I have Sport Cub serial no. 15. You had asked earlier in the string about whether or not you are being too careful--I thought all your procedures sounded good. The only thing that got my attention was your personal limit of not flying when the temp/dewpt spread is less than 15 degrees. Seems like that would take out two or three seasons for me in Wisconsin, especially since I do a lot of flying in the morning or evening hours. I do note the spread, especially as it relates to potential fog formation, and heighten my awareness in those conditions. But if you are using appropriate procedures, I don't see the issue with flying in those conditions. I do take special care with full on or full off, never partial carb heat, as stated in the POH. I also take extra care in noting RPM periodically throughout cruise along with a standard scan of engine temp and pressure. In low temp/dewpt spread conditions, I may also periodically just pull the carb heat in cruise and note what happens, as you mentioned--if typical drop that stays steady for a few seconds, with no additional drop or roughness, I presume no ice. If, after applying heat, the drop becomes more severe, or I notice any additional engine roughness over what would normally be expected, I suspect carb ice. I do feel that I have experienced carb ice on a couple of occasions, I would say more prone on dampish cooler days or evenings, but I do think I've experienced it on warm humid evenings as well. Like I say, the spread, or suspicion of carb ice, don't necessarily prevent me from flying, just makes me more aware when conditions seem right. I also may avoid lots of pattern practice in high carb ice conditions--if doing lots of taxiing in between, etc., you need to be really careful of checking for ice and then ensuring that carb heat is off again before take off. Just one of those things that requires extra vigilance, again, as you stated.

I have a fixed prop, and will generally pull carb heat below 2000 RPM, which is usually sometime after midpoint on downwind. I cruise at about 2200 to 2250, same as you, but don't have a problem with 2100 if I need to descend just a bit. I tend to cruise at around 1000 to 1500 AGL which is 2000 to 2500 MSL in my neck of the woods. Density altitude is often 2000' to 2,500' in the summer, though can hit 3,000 on a really warm/humid day--I tend to avoid those anyway a lot of the time since it is pretty uncomfortable.

Leaning has been an ongoing problem for me--I grapple with sort of an 'all or none' response, so I tend to see exhaust soot on the gear more than I'd like, from running richer than I'd like. Any input on leaning on your end?

[stroutmail]

I have Sport Cub serial no. 15. You had asked earlier in the string about whether or not you are being too careful--I thought all your procedures sounded good. The only thing that got my attention was your personal limit of not flying when the temp/dewpt spread is less than 15 degrees. Seems like that would take out two or three seasons for me in Wisconsin, especially since I do a lot of flying in the morning or evening hours. I do note the spread, especially as it relates to potential fog formation, and heighten my awareness in those conditions. But if you are using appropriate procedures, I don't see the issue with flying in those conditions. I do take special care with full on or full off, never partial carb heat, as stated in the POH. I also take extra care in noting RPM periodically throughout cruise along with a standard scan of engine temp and pressure. In low temp/dewpt spread conditions, I may also periodically just pull the carb heat in cruise and note what happens, as you mentioned--if typical drop that stays steady for a few seconds, with no additional drop or roughness, I presume no ice. If, after applying heat, the drop becomes more severe, or I notice any additional engine roughness over what would normally be expected, I suspect carb ice. I do feel that I have experienced carb ice on a couple of occasions, I would say more prone on dampish cooler days or evenings, but I do think I've experienced it on warm humid evenings as well. Like I say, the spread, or suspicion of carb ice, don't necessarily prevent me from flying, just makes me more aware when conditions seem right. I also may avoid lots of pattern practice in high carb ice conditions--if doing lots of taxiing in between, etc., you need to be really careful of checking for ice and then ensuring that carb heat is off again before take off. Just one of those things that requires extra vigilance, again, as you stated.

I have a fixed prop, and will generally pull carb heat below 2000 RPM, which is usually sometime after midpoint on downwind. I cruise at about 2200 to 2250, same as you, but don't have a problem with 2100 if I need to descend just a bit. I tend to cruise at around 1000 to 1500 AGL which is 2000 to 2500 MSL in my neck of the woods. Density altitude is often 2000' to 2,500' in the summer, though can hit 3,000 on a really warm/humid day--I tend to avoid those anyway a lot of the time since it is pretty uncomfortable.

Leaning has been an ongoing problem for me--I grapple with sort of an 'all or none' response, so I tend to see exhaust soot on the gear more than I'd like, from running richer than I'd like. Any input on leaning on your end?

THANK YOU SO MUCH FOR YOUR REPLY !! (I would so much like to be able to share info and ask questions of other Sport Cub owners.)

Yes, the 15 degree F Dew Point Spread that I use as "go-no go" is certainly more conservative than necessary. The red section of the chart for "Serious Icing (Cruise Power)" kind of concerned me. So, like many of my personal minimums-it is subject to change. (My max crosswind component is 8mph, but I am getting more comfortable with crosswinds, so I will probably up that to 10 mph soon, for example.) I would like to fly more during mornings and evenings--less wind and turbulence. Most of my flying in the Cub has been in afternoon on sunny days and my oh my does the little Cub rock and roll around a lot.

What concerned me is that ambient temps get lower with altitude. (I use rule of thumb of about 3 degrees F for eavh 1000 feet AGL.) Like you, I often fly at 1500 AGL, but often fly at 3000 AGL when flying over forested areas with no place to land or over Class D space. So at 3000 AGL, I figure the ambient is usually 10 deg lower than at ground. So a 15 degree F spread on the ground, I figure is really only 5 degree spread at my cruise altitude as the dewpoint supposedly does not change much with altitude.

I am getting comfortable with the periodic use of carb heat to prevent issues. I watch RPM and EGT very carefully and if I see them declining, it is really not a problem to put on carb heat for 10-15 seconds to check and/or prevent any problems. As a matter of habit, if there is ANY risk of carb ice, I always check for carb ice just before entering the runway before takeoff.

As far as leaning---I have the same issue. Nothing much seems to happen for the first 1/2-1 inch---one to one and one half fingers, and then there is a dramatic change. (At not much more than one inch, the engine will either stall or seriously threaten shutdown with severe miss.) Would like to have a vernier control cable to be more precise in that area where small movements matter. I am very careful to not pull the knob out too far in flight. (I do pull it out 3/4 inch when applying carb heat during cruise power, but not during pattern descent.)

I am sure that my engine is too rich on a hot day--I get soot on gear "wings" also, and my exhaust seems to have more soot than I would like. Seems less of an issue on colder days. (I asked my A&P if changing carb jets in the summer made sense and he shrugged his shoulders with the "I don't think it is needed" comment.) I always run full rich on takeoff and on approach. Before shutting engine down though, I will run it up to 1700 RPM and lean (pull until it misses and then rich just a little) and run for maybe 30 seconds (watching the EGT rise) to clean the plugs. My engine always starts on first or second blade.

AGAIN, THANK YOU FOR YOUR COMMENTS--VERY HELPFUL!!

[stroutmail]

One aspect of flying is gaining insight regarding weather. I am no expert, but I try to keep learning.

Managing risk regarding carb ice seems to benefit from an understanding of what is called the condensation level..LCL and CCL..altitudes at 100% relative humidity.. This can be the cloud base, but in many circumstances the moisture above becomes supercooled and clouds form higher. Water can be in a supercooled liquid state below 32 deg F (O Deg C)

As I mentioned, the dewpoint spread gets smaller with altitude..at rates that can differ..ranging fro 3 deg F per 1000 feet to 5 deg F per 1000 feet. (2 to 3 degrees C) So, it the dewpoint spread, if any aloft at your cruising altitude may be much lower than what is listed in METAR.

In the fall, I sometimes see a haze level at around 3000 AGL..this is saturated air with a high risk of carb ice. I try to fly below that in most cases or considerably higher than that level. Since the Cub does not have a great heater, going really high and "cold" is not my idea of fun tho.

https://schaeferflight.com/index.php...12/haze-layer/

[stroutmail]

Here is discussion from another thread.


http://forum.cubcrafters.com/showthr...5-Carb-Ice-yes
http://forum.cubcrafters.com/showthr...5-Carb-Ice-yes
I particularly liked Ralph's comment
Centmont's
Jan 2010
Winifred, Montana Re: Carb Ice, yes
With my 0-200 if I run too rich, I need carb heat. If I reduce throttle after a climb...need heat. If one of my tires is too low....need heat. If the stock market goes down...need, well, you get the picture. Ice has always been part of the picture with small Continentals... R