Carb temperature enroute: Any icing concerns?

[AggieMike88]

This weekend, I flew our club's 1975 C182P to Sugar Land and back. The airplane is equipped with one of EI's carb temp probe and display (http://buy-ei.com/portfolio/ca-1-carb/). This is the unit that also has the "Ice Zone" indicator when the temp is low enough that carb ice might form.

While enroute from KDTO to KSGR at 5500, I glanced at the temp display and noted it was showing about 34°F. And the Ice Zone light was lit.

I did experiment a bit by pulling partial carb heat until the temp got to 40° and the light went out. Then pushing the carb heat back in to the firewall. Both times listening to the engine noise and watching the RPM gauge. I didn't notice any significant changes to engine performance.

When landing, I have carb heat deployed (especially beginning this time of year). But while in cruise, should I be paying attention to this "Ice Zone" and temp indication and doing something about it?

 

[kgruber]

With a carb temperature gauge, yes. You should pull partial carb heat to extinguish the light and leave it there.

 

[Capt. Geoffrey Thorpe]

I've picked up what I believe to be carb ice during cruise (fixed with carb heat)

 

[poadeleted20]

With a carb temperature gauge, yes. You should pull partial carb heat to extinguish the light and leave it there.

Concur.

 

[N747JB]

With a carb temperature gauge, yes. You should pull partial carb heat to extinguish the light and leave it there.

What about without a gauge? Seriously, our old 182 had an old style carb temp gauge and the one I have now doesn't have one. I've never used carb heat at cruise without some indication of carb icing, but I usually run fairly high power settings.

 

[denverpilot]

Just because the temperature is in the range, doesn't mean carb ice WILL form, but it's generally considered good form to just put the carb heat on and make the little light go out, if you have the temp gauge.

Carb ice in the C-182/O-470 combo usually exhibits itself as a really slow power loss in cruise that isn't always all the noticeable at first. I've had it once, with no gauge... airspeed slowly creeping down in cruise and a feeling something wasn't quite right... pulled the carb heat on and *COUGH*... chunk of ice melts and goes through the engine... and 'lo and behold... airspeed is back to normal and airplane isn't wanting to slow down anymore.

 

[ChitDisturber]

When landing, I have carb heat deployed (especially beginning this time of year). But while in cruise, should I be paying attention to this "Ice Zone" and temp indication and doing something about it?

I perfer to turn carb heat off on short final, I want all available power, also I like filtered air on touch down, esp on dirt strips.

 

[bobmrg]

This weekend, I flew our club's 1975 C182P to Sugar Land and back. The airplane is equipped with one of EI's carb temp probe and display (http://buy-ei.com/portfolio/ca-1-carb/). This is the unit that also has the "Ice Zone" indicator when the temp is low enough that carb ice might form.

While enroute from KDTO to KSGR at 5500, I glanced at the temp display and noted it was showing about 34°F. And the Ice Zone light was lit.

I did experiment a bit by pulling partial carb heat until the temp got to 40° and the light went out. Then pushing the carb heat back in to the firewall. Both times listening to the engine noise and watching the RPM gauge. I didn't notice any significant changes to engine performance.

When landing, I have carb heat deployed (especially beginning this time of year). But while in cruise, should I be paying attention to this "Ice Zone" and temp indication and doing something about it?

The only time you should use partial heat is when you have a carb heat temperature gauge or equivalent...page 46 in Key Reprints from the Lycoming Flyer. Without it, the rule is full heat or none. You are fortunate to have one in the club plane.

You took the appropriate action.

Bob Gardner

 

[yakdriver]

Bob, what's wrong with running partial carb heat without a gauge? I do it all the time when the OAT and humidity is in the icing zone. Tell me how that is going to hurt an engine. Don

 

[rbridges]

Bob, what's wrong with running partial carb heat without a gauge? I do it all the time when the OAT and humidity is in the icing zone. Tell me how that is going to hurt an engine. Don

I'm curious, too.

 

[BiffJ]

I agree that just having the temp in the freezing range isn't really grounds to run partial heat. I've got a guage in the 175/lycoming and while it sometimes registers low temps it doesn't mean there will be ice unless enough moisture is present. I don't think running partial heat will hurt anything other than allowing unfiltered air into the engine. This time of year in the midwest that is a bad thing with all the harvesters filling the air with dust. I watched leaves from cornstalks falling from higher up when I was cruising at 3500ft last friday. Took a bit to figure out what the slowly spiralling leaves were. Thermals carry stuff a long way up and spread it out for our engines to ingest. My filter is pretty dusty and has lots of bugs splattered on it as well. I do occasionally pull the carb heat and check for ice by watching the MP. Checking RPM in a plane that has a constant speed prop won't tell you anything so watch to see if the manifold pressure climbs over time while the heat is on. I have sometimes seen evidence of ice when checking but primarily when humidity is up. When its cold outside humidity will be lower so if you're cruising along with OAT at 35F and carb temps of 30F or so I don't think there is much likelyhood of carb ice .....

Frank

 

[bobmrg]

Bob, what's wrong with running partial carb heat without a gauge? I do it all the time when the OAT and humidity is in the icing zone. Tell me how that is going to hurt an engine. Don

I don't know as much about engines as Lycoming does, so let's see what they have to say on the subject:

"In conditions where carburetor ice is likely to form, the pilot may use heat during cruise to prevent the formation of ice in the carburetor. It is also appropriate to use full carburetor heat, if needed, to prevent icing when operating at low power for instrument approaches, or for flight in the traffic pattern. Unless the aircraft is equipped with a carburetor air temperature (CAT) gauge, and a very few general aviation aircraft are, use of full carburetor us recommended. An unknown amount of partial heat can actually cause induction ice in the float type carburetor. This may occur when moisture in crystal form in the incoming air that would ordinarily pass through the induction system without any problem is melted by the partial heat. This moisture then freezes when it comes in contact with the cold metal of the throttle plate."

Bob

 

[charheep]

I don't know as much about engines as Lycoming does, so let's see what they have to say on the subject:

"In conditions where carburetor ice is likely to form, the pilot may use heat during cruise to prevent the formation of ice in the carburetor. It is also appropriate to use full carburetor heat, if needed, to prevent icing when operating at low power for instrument approaches, or for flight in the traffic pattern. Unless the aircraft is equipped with a carburetor air temperature (CAT) gauge, and a very few general aviation aircraft are, use of full carburetor us recommended. An unknown amount of partial heat can actually cause induction ice in the float type carburetor. This may occur when moisture in crystal form in the incoming air that would ordinarily pass through the induction system without any problem is melted by the partial heat. This moisture then freezes when it comes in contact with the cold metal of the throttle plate."

Bob

And again I learned something new. Thanks Bob!

 

[yakdriver]

I don't know as much about engines as Lycoming does, so let's see what they have to say on the subject:

"In conditions where carburetor ice is likely to form, the pilot may use heat during cruise to prevent the formation of ice in the carburetor. It is also appropriate to use full carburetor heat, if needed, to prevent icing when operating at low power for instrument approaches, or for flight in the traffic pattern. Unless the aircraft is equipped with a carburetor air temperature (CAT) gauge, and a very few general aviation aircraft are, use of full carburetor us recommended. An unknown amount of partial heat can actually cause induction ice in the float type carburetor. This may occur when moisture in crystal form in the incoming air that would ordinarily pass through the induction system without any problem is melted by the partial heat. This moisture then freezes when it comes in contact with the cold metal of the throttle plate."

Bob

Makes sense to me. So I will use full heat when conditions warrant. Also remember to lean the mixture when using carb heat. Thanks Bob. Don

 

[Dan Thomas]

When its cold outside humidity will be lower so if you're cruising along with OAT at 35F and carb temps of 30F or so I don't think there is much likelyhood of carb ice .....

Frank

It can happen down to -20°C (-4°F) since moisture can exist as liquid in microscopic droplets down to that point. Below that it's pretty much ice crystals that can melt if carb heat is used, and freeze farther up in the induction system.

It's the temp/dewpoint spread that's important. When they're close, watch out.

Dan

 

[jasont]

This weekend, I flew our club's 1975 C182P to Sugar Land and back. The airplane is equipped with one of EI's carb temp probe and display (http://buy-ei.com/portfolio/ca-1-carb/). This is the unit that also has the "Ice Zone" indicator when the temp is low enough that carb ice might form.

While enroute from KDTO to KSGR at 5500, I glanced at the temp display and noted it was showing about 34°F. And the Ice Zone light was lit.

I did experiment a bit by pulling partial carb heat until the temp got to 40° and the light went out. Then pushing the carb heat back in to the firewall. Both times listening to the engine noise and watching the RPM gauge. I didn't notice any significant changes to engine performance.

When landing, I have carb heat deployed (especially beginning this time of year). But while in cruise, should I be paying attention to this "Ice Zone" and temp indication and doing something about it?

Mike, I was at Sugarland last weekend too. What were you doing there? I'll have to meet up with you one of these days.

 

[coma24]

I've had two engine failures, both in IMC, both attributed to carb ice. Was running wide open throttle at the time.

One was at 10,000ft and was a non-event, got it started again at around 7000ft.

The other was at 3000ft and was less relaxing.

Even since then I watch my IAT like a hawk. If there's any precip and it's close to zero degs C, then ram air off, carb heat on.

 

[Jeff Oslick]

What about without a gauge? Seriously, our old 182 had an old style carb temp gauge and the one I have now doesn't have one. I've never used carb heat at cruise without some indication of carb icing, but I usually run fairly high power settings.

O-470's are ice machines...highly recommend getting a carb temp gauge. They are about the cheapest insurance you can have, and easy to install. I've experienced carb ice in 182s during initial climb out (<1,000' AGL) and in cruise flight. A high power setting doesn't protect you. With the carb temp gauge, I just always keep the temp set in the low 40's (F).

Jeff

 

[Morne]

I have a 182 and have only ever experienced carb ice twice. Both times were at cruise, above 8,000' and over Texas in October/November VMC. I do not have a carb temp gauge.

The first time it took a minute to figure out why I kept having to trim nose-up. Finally looked at my engine gauges and saw CHT and EGT were higher than normal. Finally the RPM needle started oscillating and I could feel cylinders skipping. Turned towards nearest airport before trouble-shooting (nervous, with a solid undercast layer). Finally pulled the carb heat knob and the engine shuddered like a Floridian in snow before coming back to full RPM.

The second time I was better at keeping an eye on it and caught the EGT climbing before any other symptoms displayed. I put on full carb heat until the EGT dropped, then applied partial to keep the EGT steady where it belonged. If the EGT started climbing again I increased carb heat until it dropped again. Advised ATC and kept going on my merry way, took maybe 20 minutes to get out of the conditions.

Cruise settings, even WOT above 8,000', are NOT impervious to carb ice. That goes double for the Continental O-470. It is a great engine one a great plane, but just like anything it has its quirks.

 

[AggieMike88]

Mike, I was at Sugarland last weekend too. What were you doing there? I'll have to meet up with you one of these days.

Attending ScottD's most excellent weather workshop held at Anson aviation.

 

[hindsight2020]

Cruise settings, even WOT above 8,000', are NOT impervious to carb ice. That goes double for the Continental O-470. It is a great engine one a great plane, but just like anything it has its quirks.

That's a hell of a quirk. That would cure me from flying behind a carb honestly. Most of the carb setups I've flown or owned tend to be warmer than that, so not as much of a problem, but I'm surprised there's no STC to slap a fuel injection assembly on the O-470 as installed on 182s. Either that or make the carb setup warmer somehow.

 

[Morne]

That's a hell of a quirk. That would cure me from flying behind a carb honestly. Most of the carb setups I've flown or owned tend to be warmer than that, so not as much of a problem, but I'm surprised there's no STC to slap a fuel injection assembly on the O-470 as installed on 182s. Either that or make the carb setup warmer somehow.

Two instances, over about 300 hours of flying, and you'd stop flying??? Especially since neither resulted in engine stoppage and both with tons of altitude to play with? As "bad stuff" goes in aviation I think my experience is pretty darn minor.

Now would I prefer a fuel injected engine? Sure. But carb was what I could afford and heck, I learned on a carb engine. I would also prefer a twin. A turbine would be ideal. Make it a King Air and I'd be in heaven. But hey, you have to draw the line somewhere. Our family does OK financially, but we ain't made out of money, either.

The Continental O-470R in my 182 has a 2000 hour TBO. It is very reliable and produces enough thrust that even with all 4 seats loaded and bags packed I get good climb rates. Even when it gets a little carb ice it is easily rectified by applying heat. Best of all, it has a MoGas STC.

Lycomings have their own quirks, like the cam/lifter corrosion issue. So if your position is based on Lycoming-fanboyism be warned.

I don't have the safety stats on Cessna 182s with the O-470 Continental engine but I'll wager they are pretty darn good for a high performance fixed gear plane. But if you would prefer to fly a Lycoming powered Glasair instead that's cool.

 

[denverpilot]

The Continental O-470R in my 182 has a 2000 hour TBO.

You sure about that? I think 2000 hours started at the O-470U. Everything prior was 1500.

 

[Jeff Oslick]

That's a hell of a quirk. That would cure me from flying behind a carb honestly.

If you have a simple carb temp gauge it is really not an issue at all. I fly with partial carb heat most of the time. We have carb temp wired into our EI-UBG-16
with an alarm set at 35F for carb temp, warning light right in front of the pilot.

Jeff

 

[Morne]

You sure about that? I think 2000 hours started at the O-470U. Everything prior was 1500.

With an oil filter it is extended to 2000 hours. My bird has a filter.

 

[N747JB]

It's funny, I didn't know any 182's DIDN'T have carb temp gauges until I bought this one! This thread got me thinking, which is a little dangerous, but I will have one installed on the next major maintenance or at the annual, which ever comes first!

O-470's are ice machines...highly recommend getting a carb temp gauge. They are about the cheapest insurance you can have, and easy to install. I've experienced carb ice in 182s during initial climb out (<1,000' AGL) and in cruise flight. A high power setting doesn't protect you. With the carb temp gauge, I just always keep the temp set in the low 40's (F).

Jeff

 

[N747JB]

With an oil filter it is extended to 2000 hours. My bird has a filter.

Most 182's have filters by now, my old one did, it was a 1973 P model and it had a 1500 hour TBO. Not saying you're wrong, I just never heard of the pre-Q models having the 2000 hour TBO's, and Q's turn slower and can't use Mogas.

 

[denverpilot]

Most 182's have filters by now, my old one did, it was a 1973 P model and it had a 1500 hour TBO. Not saying you're wrong, I just never heard of the pre-Q models having the 2000 hour TBO's, and Q's turn slower and can't use Mogas.

I also haven't seen anything that indicates our O-470S gets a TBO bump for her filter. Not that we won't see if she will go to 2000, anyway. But I'd check that. If you're not using it commercially I guess it won't matter anyway.