Just a friendly reminder that icing season is upon us. I had a little scare on Friday night. Departed 30 min before sunset for a short 50 min flight home, temp was around 65F on the ground and 75F at 3000ft. Dew point was 57F. Humidity near 70%. As I reached 3000ft and leveled off for cruise the engine started to stumble. I was over no mans land, about 15-20 miles from the airport I just departed. Did an immediate 180 and limped back to the airport, just made it with the limited power and altitude I had.

Never in the process did I think it could have been icing. I guess I'm used to thinking it's a descent issue only, but with the right conditions and a temperature inversion, it can happen on climb out.

The next day I pulled all the plugs, did an extended run-up and circled over the field at 3000ft for 10 minutes before I departed. The engine purred like a kitten. My only explanation is that it had to be icing. Per this chart conditions were perfect for icing. I will never forget to try carb heat in that situation again!

I've been in conditions with an O-200 where I had to run carb heat at nearly full throttle.

Yea I’ve heard O200s and O300s can have major icing issues. I imagine that’s a scary situation to be in.

My 0-300 makes carb ice under the right conditions in the dead heat of Summer.

That's really scary, my first thought was that I too would not have thought it would be icing. All the more reason to have the loss of power checklist memorized, my CFI worked with me on it a lot and I rehearse it in my mind before I go flying. Just like I always rehearse PARE before doing stalls.

Here’s my view:

I recommend a carburetor inlet temperature gauge. The price is negligible considering the cost of most aircraft.

Reason a derated (manifold pressure) engine is required to have a carburetor temperature gauge operational before flight (and a full throttle [WOT] warning light) is...

The R44 engine is derated by limiting the MAP. RPMS are constant at 102%. Only once has the “WIDE OPEN THROTTLE” light illuminated during my flights. DA was about 7,000’. It is a serious condition because there is no more extra power to turn the rotors at 102%. The overwhelming majority of flights use partially opened throttle. Which is where carburetor ice is more likely to occur.

Note: The engine RPM governor easily hide carburetor ice, hence the “FULL THROTTLE” warning light:

Note2: 24.9” Redline on MAP gauge

Maybe I'm a bit to old school but I was always taught too, on regular intervals run a bit of carb heat through out a flight due to the incidous nature of carb icing.

Mapleflt wrote:Maybe I'm a bit to old school but I was always taught too, on regular intervals run a bit of carb heat through out a flight due to the incidous nature of carb icing.

That's not a bad idea, but depending on OAT that can actually cause freezing, from what I've read. If OAT is below 20F applying carb heat will warm the air back up near the dew point causing it to freeze.

I think after this looking into a carb temp probe isn't a bad idea as 8GCBC mentioned.

In the event of an engine failure after lowering the nose and flying the airplane the first thing that should be accomplished is carb heat then run thru the remaining checks and procedures. If you pull carb heat later in the emergency then you will have less heat to melt any carb ice that may have caused the engine failure in the first place. Pulling carb heat first uses the residual heat before its gone.

Kurt

I have had a carb temp sensor since I bought my C180. The O-470 has a reputation for carb icing. I upgraded to the O-520 shortly thereafter and I am not sure if there less risk with this engine. The graph you posted is awesome. I am proactive with the carb heat when I feel there is increased risk for development. The combination of the sensor and being mindful of the high risk conditions where it can occur has made me fortunate never to have encountered it in my C180. When I do apply carb heat - it is on full. The carb heat is really only available for prevention of icing. The only time I run partial carb heat is for more even EGT running LOP. I think I am going to add flying over rough terrain as another potential location for application of carb heat in high risk conditions. Sounds like time moved very slowly for those moments limping back home - very scary.



Josh

The manifold pressure gauge indicates carb ice before the rpm starts falling on my O-300-A. I have a carb inlet temp gauge too, and if you wait too long you won't have enough heat left in the engine to melt it and keep it running.

Hopefully you have enough altitude to let it melt on its own if you get to that tipping point.

With the 41 degrees temps this morning (snow on the mountain, a skiff, behind my place) my climb performance was greatly enhanced over last weeks near 100 degree temps, and when I got to my destination 30 miles away, I had to burn off a lot of altitude, having climbed without really trying to 9K and needing to get down to 6. I have learned (the hard way) that with my Rotax, I can use the oil temp as a carb ice predictor. Anything below 140 for very long, and I will clear the throttle now and then. And yes, Rotax's can suffer from the affliction, though it seems somewhat more mildly then a legacy engine, at least in my case there has always been enough power to easily maintain level flight. But, if I am careless and have let it cool down too far, and suddenly pull the power back, it has died on me, though 5 seconds later (a long 5 seconds) a re-start gives full power.

Carb heat should be the first thing you apply when the engine gets rough. I had that beat into my head when I was learning to fly. Along with when you pull the carb heat and the engine starts to run rougher you shouldn’t turn the carb heat back off. It is likely that the hot air is melting ice and the engine is ingesting water. Leave the heat on for a while and give it time to melt the ice.

The C85 in my Luscombe was an ice maker. That thing would make ice all year long it seemed. On one occasion, early in my flying, I was flying across central Idaho and kept having to push the throttle in to keep the cruise rpm I wanted but I assumed that the friction lock was loose and the throttle kept backing out. The last time I went to push the throttle it wouldn’t go in anymore, it was already WOT. I got spooked for a second, then pulled the carb heat and that’s when the engine started running rough, real rough. I left in it and after a few minutes the roughness went away, the rpm came up to what it should have been and I continued on my way. After that I paid more attention and would notice carb ice pretty quick so I’d apply carb heat for a while. On really bad days when the ice kept forming I just leave the heat on all the time.

Dog is my Copilot wrote:I have had a carb temp sensor since I bought my C180. The O-470 has a reputation for carb icing. I upgraded to the O-520 shortly thereafter and I am not sure if there less risk with this engine. The graph you posted is awesome. I am proactive with the carb heat when I feel there is increased risk for development. The combination of the sensor and being mindful of the high risk conditions where it can occur has made me fortunate never to have encountered it in my C180. When I do apply carb heat - it is on full. The carb heat is really only available for prevention of icing. The only time I run partial carb heat is for more even EGT running LOP. I think I am going to add flying over rough terrain as another potential location for application of carb heat in high risk conditions. Sounds like time moved very slowly for those moments limping back home - very scary.
Josh

My 180 likes to make ice like other O-470s, it can develop quite aggressively. I do have a carb temp gauge which I monitor religiously. Carb heat is always applied fully when ice is suspected, and then I will go with a partial setting using enough to keep the temps out of the yellow arc on the temp gauge.

Just awaiting my approval to convert my engine to fuel injection....hopefully this winter.

Flying out of Fairbanks, the perfect storm, opening day of moose hunting and the first snow fall of the season. I was in a cub circling over a high point and retarded the throttle before I pulled carb heat.The engine quit right now. Without the extra gliding space off that high point I would have been walking or worse. That same day there were 6 crashes and 3 people killed. Lesson to my young self: never-ever retard throttle till carb heat is on full.
Flying in a Stinson to Homer with wife and kids. Out in the middle of a large lake the engine stumbled and quit. Pulled carb heat even while my wife had the circulation cut off in my right arm. Got way too close to the water before got power back. Note to self, pull carb heat every 10-15 min to check for ice.

Makes me want to check carb heat before I turn off the cruise control.

I have had carb ice a few times in my 180. Once on downwind where I kept pushing throttle in with no response. And a few times on takeoff, I know, it’s not supposed to happen then, but it has. I know others with -50’s that have had it happen to as well.
I live in a very dry climate, so it’s rare, but on a humid morning I keep a close eye on the carb temp. If it’s in the 28 to 34 range I pull carb heat until I get low 40’s. On a dry day I still keep an eye on it, and will pull a little bit of heat to “check” for ice.

Last week I was flying through Lake Clark Pass. Nice warm day with some low lying clouds and a bit of precip. Engine ran smooth but kept dropping RPM a few at a time. Pulled on carb heat as soon as I noticed it and cleared it up. Most days I pull it on every 15 minutes or so just for the hell of it. The pacer seems to make carb ice easier than the 12 did.

I am not sure any plane will make ice faster than a 172. Initial instructor was adamant about pulling carb heat before pulling power and it was hammered into me many years ago. It is something I always do even when its 80+ out in the summer.

Not being a part of your routine makes things get forgotten.

As others have pointed out, there is no such thing as "Icing Season" when it comes to carb ice. Spent 8 years flying on Kodiak, where carb ice is a constant companion.

In other parts of the world, not so much, which can allow an episode of carb icing "sneak up" on the unwary pilot. Continentals tend to be a bit worse in this regard than small Lycomings, due to the design of the induction, but both will make ice.

A couple years ago, I was getting ready to take off from a backcountry strip, elevation 5000, and after taxiing to the departure end of the strip, I made a point of doing a brief runup and apply carb heat. Engine quit. I cranked it and it ran fine, with carb heat. I ran it with heat on for a bit to verify, but the bottom line is, I'd built up quite a bit of carb ice just taxiing to takeoff. Weather was cool, and sort of damp morning. Duh.

You MUST have an "Immediate Items" mental checklist for your airplane that you immediately go through after an engine failure or partial loss of power. This is not a "drag it out of the side pocket" kind of thing, it is committed to memory, and it's a flow. Number one on that list, as others have noted, should be apply carburetor heat. That muffler shroud has a lot of air flowing through it, so it cools quickly. Get carb heat on quick, then go through the rest of your flow. Then, of course, FLY the plane. If you have time, drag out the checklist.

But, engine stumble, loss of MP, etc.....Carb heat to HOT.

MTV

My SOP is a carb heat function check along with mags during every runup be it on wheels or float, regardless of season or current atmospheric conditions

Well all this talk has made me decide to add a carb temp gauge to the top of my to do list, as well as learning to pulling carb heat BEFORE reducing throttle. I’m not sure why carb temp gauges aren’t more popular? The cost to add one to my EI UA-8a is around $90 if I remember correctly. Getting that done ASAP!