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I've been flying a PA-18-180 and now I've purchased a PA-18-160....I'm just wondering how critical it the usage of carb heat on the smaller 160 hp engine??? I know the 180 produces enough heat and you basically dont need carb heat......so, how prone is the 160hp to carb icing?? Thanks for any help.
That belief, and 5 gallons of fuel to get you airborne, will get you killed sooner or later.Originally Posted by FlyingY
Anyday the humidity is up a little and the temp is right you can get it in the super cub. I get it all the time, but I fly partial power a lot which helps aggravate the situation
AFNB
Hi FlyingY,
I agree with the above posts. Just treat the possibility of ice like it is a certainty and you will always be ready for it. It doesn't hurt to pull it on if you think you need it.
And welcome to the site. All your supercub questions can be answered here!
ambient temperature and dew point don't care what type or size engine you are using...
had a Chevrolet car that formed carb ice when temp and dew point were conducive.... I would have to stop, shut engine down and let engine/manifold heat melt ice before going again.. Should have seen the look on the GM mechanic's face when I told him... He couldn't comprehend carb ice...
Not a trained pilot obviously...
Treat icing as a probability and not a possibility..
tj.
I like the quote someone said on this forum last year... When you find yourself flying along with nothing to do.... pull carb heat.
I started following this advise last year after encountering severe carb ice during a "nice summer day" north of Anchorage. Going to the cabin with a load of freight. 55 deg day and no visible moisture. Everything was normal (no loss of rpm etc) Started to gently throttle back from level cruse and the engine started to pop/backfire. It got worse as I tried to add throttle back. Luckily I had the lake made as I was loosing altitude fast.
Would be interested to know of experiences of how an engine acts with heavy carb ice when you pull the carb heat.
Ed
On the 160 cub your exhaust and intake filter setup dictates how much ice you build up. I have heard alot of round filter guys say they build it up a lot. My square filter intake hardly builds it at all, but I still use carb heat.
After market exhaust systems do not have as much heat retention in the muffler shroud/ or they have a longer distance to pipe the heat resulting in heat loss (depending on which system you have).
In any case, every engine is a little different in how it builds ice, and it is never fun when you discover you didn't use enough on short final.
Happy New Year! keep the ice in your glass and not in your carburetor.
Ed, that's like the one that they taught us about when to use continuous ignition on the PT6.........
1) In heavy precip,
2) In heavy turbulance, or
3) Whenever it makes you feel better.
Anytime, anyplace is affirmative. We get it a lot going out of dewy wet grass fields on nice autumn mornings. Pull the carb heat on and jeez look at the rpm come back up.....
JP Russell--The Cub Therapist
1947 PA-11 Cub Special
In the J-3 I frequently cycle the carb heat, but the Continental 65 is a notoriously efficient ice maker. The bigger Lycomings mount the carb to ~and route the intake through~ the oil sump (Hotpoint or Hotspot induction, something like that), which warms things up a bit, but not enough to prevent ice accumulation in all scenarios.
Like when you are descending for a long time with the throttle nearly closed, the prop windmilling and acting as a brake. The exhaust cools, and the pistons are sucking lots of air past an almost closed throttle plate. Two old dead guys appear here, named Bernoulli and Charles. Bernoulli says as velocity increases, pressure decreases, and Charles says for a given volume, a decrease in pressure causes a proportional decrease in temperature. Like Bearsnack said, that can make things exciting on short final.
Bearsnack, regarding the round vs. square filters, are you just referring to "impact" ice at the filter, or accumulation in the carb due to Charles law and fuel evaporation cooling? Pulling carb heat will help in the former, but not by melting the ice like it does in the latter. It just allows induction air to be provided form an alternate source, bypassing the clogged filter.
Eddy,
I am referring to ice in the carburetor itself. Its funny that this thread came up because it is just in the last few weeks I have been gathering this information from different cub owners.
It may have something to do with the round filters ability to breathe better, allowing a more favorable condition for icing. Purely speculation on my behalf
Interesting... I'd be interested to know what you find out. It is tickling the back of my brain that the folks on floats were talking about the round vs. square filters awhile back. I can't remember the particulars, whether it is pertinent or not. Gotta go now, but will search tomorrow.
I have started to pick up carb ice many times in the PA-18-160 that I used to fly, especially if flying during the humid Memphis summers right after a rain. Carb heat is your friend and pulling it anytime you are not doing something is a good idea.
Earlier this fall while doing some low level river flying in the Maule (O-360) I picked up some carb ice while climbing out of the river over the ridges and forest. This will get your attention in a hurry when you are not equipped with floats and have nothing but trees or water for a few miles.
The outside temp was around 78 degrees and I had been cruising around pretty slowly at 2,500 ft without carb heat and had no trouble. I had throttled way back to slowly cruise the river and enjoying the late afternoon flight. My mistake was that I did not consider the temp /dewpoint spread 10 feet above the water and when I throttles up to climb out my RPM began to drop. I immediately reached for the carb heat and the power returned within a few seconds. Those few seconds seemed like an eternity and I should have known better.
Lesson learned and easily remembered...I won't make that mistake again.
-Chris
delete
Cubpilot2
I think you did good.
Back in the late 70's I was flying a C150 and pulled power and carb heat to do some slow flight and stalls. The temp was 6 degrees F and the engine quit cold after sounding like a snow cone machine. I picked a decent looking field and dove at almost Ne to speed up the fan and got a restart.. Went back up and tried it again, same thing, lost a couple thousand feet each time before it got noisy again. Tried pulling carb heat on the way back to the field with full power and you could hear the ice going through the engine each time so I left it full on. There was no visible moisture and it was very cold.
I believe if you would have pulled carb heat in your situation you would have likely put the fire out.
Heck, I never learned it from the (early) twentysomenting instructor I had when I got my private 18 years ago. He was just building time at my expense. Looking back, several things he did or allowed me to do could have gotten us killed. It wasn't until later, when I transitioned to a plane with the third wheel on the correct end, that I really began learning how to fly. An wise "old" recovering alcoholic in a Citabria taught me what to do, why, and what would happen if I did otherwise.Do the Instructors today teach this?
Speaking of pulling on knobs, WHY did Bellanca tuck the identical looking front vent and parking brake knobs together under the right side of the instrument panel!?!? That was an exciting landing for a brand new taildragger pilot. Pissed off a bunch of folks in the pattern too when I couldn't get the Decathlon off the runway...
AMEN!!!Heck, I never learned it from the (early) twentysomenting instructor I had when I got my private 18 years ago. He was just building time at my expense. Looking back, several things he did or allowed me to do could have gotten us killed. It wasn't until later, when I transitioned to a plane with the third wheel on the correct end, that I really began learning how to fly.Do the Instructors today teach this?
I learned more about flying during my tailwheel instruction from some seasoned tailwheel pilots than I ever learned from a "flight school". My PVT pilot instructor did not know much more about carb ice than it was a knob to pull when entering the clouds or pattern for landing. Carb heat was one of the issues that I learned on my own and from other pilots for the most part. I have spent so much time in recent years flying fuel injected motors that I find myself getting complacent or simply forgetting to pull the carb heat when I fly carbureted...hence the river flight scare. I knew I should be pulling heat ever so often just for good measure, I just got complacent.
-Chris
Didn't the old timers turn their mags off, then on again to blow out the ice with a backfire??
Too chicken to try it...
TJ,
Well said. Seems like a lot of today's pilots act like they are getting charged extra to use carb heat.
I'm with you--pull carb heat on every once in a while, and it'll make your flying a little less exciting at times.
My rule in Kodiak was apply carb heat every time I passed over a bay. That worked out to every five or so minutes in a Cub.
I can't speak for other CFI's, but I sure teach carb heat use.
I doubt that you'll fail the engine with melting ice, but it will certainly sound like it's quitting for a while.
One thing that I emphasize in engine failure drills with students is to get carb heat on RIGHT AWAY, unless you are 50 feet off the ground after takeoff, in which case landing is what should be foremost on your mind.
Switching fuel tanks right away starts getting fuel to a fuel starved engine, so that's an immediate action item, but carb heat is too. Carb heat comes off the muffler shroud. That shroud has cool air moving through it all the time, to prevent overheating.
If the engine fails due to carb ice, and you wait for any substantial period of time (and I don't know what that time period is) you may not have enough residual heat left in that shroud to melt the ice. Note that the manufacturer's certification standard is that the engine has to make adequate carb heat at 75 % power. I have students get out of the plane after a flight and put their hand on the exhaust stack after just a short while. The fact that it's not really hot to the touch reinforces that these systems cool really fast with power back.
If the engine dies on you, switch fuel tanks and pull on carb heat, while you're looking for a place to park.
MTV
TJ,
Excellent advice.... never thought of doing that but always wondered.
I am a little disappointed though.... Weren't you looking for just a little fight??
Happy New Year!!!!
Steve
Steve:
Na...Its Christmas time and I'm in the Christmas spirit!
If you have carb heat and a mixture control, lean the mixture and the engine will continue to run even with a big load of carb ice. Carb ice makes the mixture too rich and the engine quits. Lean the mixture and the engine will run. The stacks will be hot so there will be plenty of carb heat. When the ice melts the engine may want to quit again because the mixture is too lean, so push the knob in!
Archie
TJ,
In, or into the Christmas spirits??
Happy New Year!
MTV
seaplane, good info....
So, has anyone tried backfiring the engine??
fobjob
Back when I was learning to fly, the prewar Military Pilots Training Handbook said exactly that. As a last resort leaning the mixture may cause a backfore that may blow the ice out of the carburetor. Never did figure that one out.
Leaning the mixture will keep an iced up carburetor from killing the engine. Tried it myself many times. Needless to say, over a safe landing area. Never did need it though!
Archie
Anyone notice we lost the original poster!!??
Not what we intended...don't be scared off...we just like to keep the few that join the great world of flight alive.... to share their tales with us!
I suppose you could try flipping your mags on and off, if you needed something to keep you entertained. Wouldn't do much for carb ice though as it doesn't produce a backfire at all. The bang you get when you turn your mags on and off isn't a backfire (although it's often erroneously called that) it's properly called an afterfire, it's an explosion that happens after or downstream of the combustion chamber. Makes a big bang, and it might even blow the stacks off your engine, but it won't do a thing to your intake system, ice or not. A true backfire is air/fuel mixture igniting in your in your induction system, ie: fire shoots out your intake. It results from letting the mixture lean out too much on starting (or sticking intake valves). It's the primary cause of DC-6 FEs buying beer for the captain and FO. And yes, it will blow a big ball of fire out the intake scoop under the right conditions.
I think that this "cure carb ice by making it backfire" probably can be traced back to a chapter in Ernest Gann's "Fate is the Hunter" in which he was in severe icing in a DC-2 and losing power because the air scoops were icing shut. His captain blew the ice off the scoops by leaning the mixture until the engines backfired. Did it actually happen? I don't know, maybe. But maybe Gann took some poetic license and turned some crew-room speculation into a good story.
Will it cure Carb ice to lean an engine out and make it backfire ? I don't know, perhaps, but in Gann's story, apocryphal or not, it was induction icing that was the problem, not carb icing. I think you'd have a pretty tough time producing a backfire of any strength in a GA engine. I've leaned GA engines out a little too far probably dozens of times and they've just quitetly lost power. You get a much better backfire in a big radial bacause there a much larger volume of fuel/air mixture contained in the Carb throat, blower tnat intake tubes. For sure, turning your mags on and off won't do anything but perhaps damage your exhaust system.
When I had the "carb ice incident" the popping would have been an "after-fire" condition due to the excessively rich mixture. It was the same reaction you get when pulling the throttle back too quickly at higher altitudes along with a rich mixture, only continuous, and many times more aggressive.
In my situation I didn't think fast enough to consider the mixture leaning idea, (which should work) as things were happening fast, coupled with a rapid "puker factor" increase.
I think that now having experienced this first hand; I will react much more appropriately. It is not something you can forget easily!
Ed
...I know the 180 produces enough heat and you basically dont need carb heat......
On a beautiful cloudless day this last August, in my PA 14 180, I had just past Port Allsworth when I noticed that the distance between the knob on the throttle and the panel seemed a less than normal for my typical cruise at 2300 rpm (my fingers on the throttle felt a little more crouded than usual). I pulled carb heat and after a short delay, the engine revved up past 2500 rpm. Whew. That got my attention! "Anywhere any time!"
I'm upgrading to an EI UBG-16 this year and I get an additional free temperature gauge as a promotion. It will be a carb temp.
Reviving a 17 year old thread! Wohooo!
I was always taught to pull carb heat on landing prior to pulling back the power. I keep it on until touchdown. Thats the only time I use it. Maybe I should use it more often?
The only time I ever picked up carb ice was night flying off the coast of Southern California. Recognized it quicky- pulled heat and up went my RPM’s.
perhaps less of an issue in the high desert where I fly now.
do most pull carb heat for landing?
First you need to under stand why carb ice forms, a search will lead you to some good threads. It is not just cold weather as some would think and several factors come into play carb heat can actually bring about carb ice if used incorrectly. Like on previous threads you will want to develop a flow for everything you do. You can change the flow depending on the situation, but checking/applying carb heat should be a habit. As others have said just make it part of your normal instrument scan to occasionally pull carb heat, even when you know you won't have a problem your hand should just move to the knob as reflex not just because you remembered you should check it. I like to check it any time I change flight conditions, before going over water/into mountains/low and slow flight/anytime I will be districted by the flight. Also as I approach a runway I do a carb heat check before I do my first power reduction or change altitude. Then apply carb heat on downwind. I take it off on short final. Remember that is unfiltered air and kicking up a lot of dust and dirt into the carb is not a good thing. Some of the small motor carbs do not have an accelerator pump and if you quickly push the throttle in from idle for a go around they will die. This has been passed on as the gossip that carb heat has to be left on until the plane has landed. Not needed in a carb with an accelerator pump!! Another great way to build carb ice is go to idle on downwind and take forever to get the plane on the ground. Power on landing helps generate carb heat something to consider. Do not do partial carb heat without a carb temp gauge or carb ice indicator, you can create a condition that causes carb ice. Without proper instruments check it if it is good push it back in. Wash/rinse/do again as needed. Carb heat is useful at -30 degrees to help with atomization of the fuel, you will get a 200 rpm boost on a good day. Every plane/engine is different so no one plan works for all. Do some google stuff and look at the temps/humidity that carb ice occurs and how the throttle plate effects carb ice. Know your carb. Build your flow off of that.
DENNY
That is a safe habit to maintain.
NX1PA
I agree, but recommend removing carb heat just prior to landing, but not for the reason Denny noted. Rather, if I need to go around, I want full power ASAP, and that’s not a great time to have to remember to remove carb heat.
MTV
If I use card heat I do so on downwind. Part of my routine on final is to push carb heat in, push the prop pitch in, and push the mixture in.
Last edited by stewartb; 02-05-2023 at 11:37 AM.
I pull carb heat well back from my landing zone and leave it on until short final, then it goes to "off". I want full power if I have to go around to avoid a moose swimming across the lake.
When in cruise carb heat goes on every twenty minutes or so, and anytime I descend.
Its interesting- I trained with probably 10 instructors for primary. Probably 80 hrs of dual (long story) and I only recall 3 instructions for carb heat:
1. When landing
2. When RPM drops in flight unexpectedly
3. When operating below normal operating RPM limits (maybe 2000 RPM on most the planes I was flying)
Wonder if some of it was because of where I was training: Southern CA for most and high desert for some.
I never was told to just throw it on occasionally. I also was never told to turn it off on short final. For go around it was full power followed immediately by carb hear off. Never heard anything about sucking dust into carb on touchdown as Denny mentioned (but all initial training in socal was pavement)
The “apply carb heat every twenty minutes” that Nunavut mentioned is something you learn when flying in very damp, cool climates. When I started flying in Kodiak, I had a few “deeply moving religious experiences” with carb ice before I adopted Nunavut’s technique.
Also, Lycoming engines tend to be somewhat less susceptible to carb ice than Continentals, due to the design of the inductions.
MTV
Most Cub pilots I know and observe work the throttle on final. That practice doesn’t favor carb heat and odds are your primary instructors didn’t teach that technique.
The PPL is only a license to continue learning!! Instructors only have so much time to teach so often you get the simple get you up and down training. Also many don't really understand why they teach what they do it is only a matter of teaching how they were taught. For example is going to full power at the start of a go around always the right answer?? So much to learn grasshopper, keep reading and always question what you already know!
DENNY
skywagon8a liked this post
Try that quick power go around first at altitude. Try it with and without carb heat applied. Convince yourself what's best for power recovery at 10' and how much altitude is lost before a climb begins. Also make sure the idle mixture is adjusted and the accelerator pump is set not too rich or lean for the air temps.
Gary
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