Carb Heat on Lycomings?

airdale

airdale

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airdale
I trained mostly in Pipers/Lycoming engines, where the POH does not recommend carb heat on landing. More recently, I am also flying various CAP Cessnas -- many of which also have Lycoming engines.

The Cessna POHs tend to want carb heat on landing, which I believe is an artifact of their traditional procedures for Continental engines.

It seems to me that routine use of carb heat on Lycomings is unnecessary because of the intake manifold design and that the Piper approach is better. One less thing to deal with on a go-around.

Please spare me the " ... (thump chest) I say: Follow The POH! ... " recommendations. I will not bore you with the whole engineer joke, but the punch line is "You guys never take anyone's word for anything." I am looking for some real-world comments and practices.

TIA
 
Well, I flew the Socata TB9 and TB10s with Lycs too, and their procedures called for checking carb heat as part of the prelanding checklist.

Looking through my one checklist for a carb'ed 172, it also calls for checking the carb heat, but not leaving it on for the whole approach and landing.
 
The question came up because I was looking at the 182RG POH landing checklist, which does call for the O-540 Lyc to have full carb heat for landing.

I have a 172P/Continental POH here and it calls for full carb heat as well. But ... the CAP 172Ps have been converted to Lyc O-360 (Airplains STC) and the STC supplement does not address carb heat yea or nay.

My 182R/Continental POH calls for full carb heat on landing too. I do it on that one.

When you say "checking" do you just mean pulling it to see if there is an RPM drop? I have this as part of the runup sequence on all my carburated engine checklists but have not heard of it before on a prelanding checklist.
 
The carburetor on the Continentals is generally located under the engine, while Lycoming puts it above. That, combined with differences in induction system design, makes the Cont much more prone to carb ice than the Lyc.

In a carbureted Lycoming, I would not use carb heat ON as a routine item on the prelanding checklist. In a carbureted Cont, I would.
 
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Well in my experience (320, 360, 540), the Lyc carburetors are updraft, located below the engine, with the intake manifolding integral to/routed through the oil sump (where a slow-moving air flow will be warmed by the oil).

Another thing, I just found a Lycoming O-540 Operator's Manual: " ... In making an approach for a landing, carburetor air heat should generally be in the 'Full Cold' position. [unless] icing conditions are suspected ... "
 
airdale said:
When you say "checking" do you just mean pulling it to see if there is an RPM drop? I have this as part of the runup sequence on all my carburated engine checklists but have not heard of it before on a prelanding checklist.
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Yes, I have that check on the pre-landing checklist, usually done on downwind - since there's been a power reduction, and you may need full power for a balked landing, you check and make sure that you get a drop with carb heat and that the engine doesn't improve shortly thereafter - the same way you'd check carb heat while flying in potential carb ice conditions.
 
While Lycoming O-235/320/360's are relatively resistant to carb ice compared to others such as the O-200/300-powered Cessnas, they are not immune, especially during a power-off approach in cool, moist air (another reason to make partial-power approaches?). The carb ice chart attached gives you an idea of where the heart of the carb ice envelope is, and if you’re in it, you should consider preemptive carb ice application at low power settings.

Also, if you are using carb heat during a touch-and-go, apply full power before you push the carb heat off – the engine doesn’t create a lot of heat at low-to-idle power, and ice can form even with the carb heat selected on. If you push the carb heat off before applying full power, you won’t have the proper de-icing effect that you get if you add power and then select carb heat off. Just remember that the use of carb heat during takeoff saps power, so don’t leave it on beyond the initial application of power.

One point on takeoff which I’ve noticed while flying with other pilots is that many folks hurry the carb heat check. They pull the knob, look for a drop, and quickly shove it back in. Always stop for a few seconds with the carb heat on after the initial drop and see if the RPM rises by itself. If it does, that means there was ice in the carb which the heat melted out. When you push the heat back in (off), you’ll see the RPM rise to a level higher than when you pulled it out (on). This will confirm that there was ice present. If that happens, you might want to leave the carb heat on until you add power for takeoff on the runway, and at the very least, when you take the runway, run up to about 1800, apply carb heat, apply full power to assure max heat to the carb for a few seconds, and then turn the carb heat off.

If the carb icing is so severe that carb ice forms on the ground while full power is applied, you should consider waiting until conditions improve before taking off. If you choose to take off with carb heat applied, consider yourself at a density altitude about 3000 feet higher than you are and recompute your takeoff distances accordingly.
 

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We never used carb heat on the R182 I used to fly. The A&P showed me where it was located and how it was so well blanketed in heat, it had very little chance of ice until some extremely low temperatures, Michigan style.
 
While Lycoming O-235/320/360's are relatively resistant to carb ice ...<snip>
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Thanks, Ron. I did not mean to imply that I think Lycs are immune. Of course not. But I am even more inclined, after reading these posts, to think it is unnecessary and probably unwise to routinely use carb heat when landing. Your thoughts?


 
The NTSB put out a paper in the 70's saying that having different procedures for different airplanes was a recipe for disaster, and suggested that pilots use FULL heat whenever the power was reduced below cruise. I have tracked this document down to an archives in Washington that wants $27 for providing a copy, so I can't reproduce it for you. Suffice it to say that if you treat all carbureted engines alike you won't go wrong.

Bob Gardner
 
bobmrg said:
The NTSB put out a paper in the 70's saying that having different procedures for different airplanes was a recipe for disaster, and suggested that pilots use FULL heat whenever the power was reduced below cruise. I have tracked this document down to an archives in Washington that wants $27 for providing a copy, so I can't reproduce it for you. Suffice it to say that if you treat all carbureted engines alike you won't go wrong.

Bob Gardner
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Bob, PM the data to me. I may be inclined to buy it.
 
its really not that hard to just push both handles forward on a go around.
 
tonycondon said:
its really not that hard to just push both handles forward on a go around.
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Gotta agree with this opinion. At low power settings carb heat sure isn't going to hurt anything. So when you boil everything down to bare bones and look at the risk/reward picture it's clear that using carb heat is the correct choice.

You do remember to do an idle check with carb heat on after the run-up, don't you? If you don't remember then put it on your personnal checklist now.
 
airdale said:
But I am even more inclined, after reading these posts, to think it is unnecessary and probably unwise to routinely use carb heat when landing. Your thoughts?
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See post #9, know the characteristics of the plane you're flying, and act accordingly.
 
airdale said:
Thanks, Ron. I did not mean to imply that I think Lycs are immune. Of course not. But I am even more inclined, after reading these posts, to think it is unnecessary and probably unwise to routinely use carb heat when landing. Your thoughts?
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Read the NTSB reports. Search "loss of power" and Cessna 182. You will find a very large number of carb ice accidents in C-182s. As Ron says, know your airplane.
 
airdale said:
Thanks, Ron. I did not mean to imply that I think Lycs are immune. Of course not. But I am even more inclined, after reading these posts, to think it is unnecessary and probably unwise to routinely use carb heat when landing. Your thoughts?
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Lycoming doesn't agree. Go to www.lycoming.textron.com/support/publications/index.html and read the article on induction icing. The paragraph you want to commit to memory is this:

"Because flight instructors and other experienced pilots fly various models of manufacturer's airplanes and engines, it would be helpful to standardize the instruction on the use of heat in the landing configuration on aircraft using the float-type carburetor. Avco Lycoming has no objection to the consistent use of carburetor heat in the landing configuration."


...but read the whole thing.

Bob Gardner
 
> its really not that hard to just push both handles forward on a go around.

It's a bit awkward on my cherokee 140. The throttle gets pushed forward and,
reaching around the mixture, the carb heat lever gets pulled up.
 
Read the NTSB reports. Search "loss of power" and Cessna 182
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Thanks, Ken. That is a fun place to play around. I have not done that before. I ran exactly the query you suggested, spanning 20 years. Only one hit was determined by NTSB to be carb ice. IMHO in two others it was a possibility and in two more it was a long shot possibility. All involved Continental engines.

I then ran an all airplanes/all dates query for "carburetor ice" and got 71 hits. I only looked at the most recent half of them before getting bored but the results were kind of interesting: 10 for Lycoming, 13 for Continental. So the folklore about Lycs being significantly more resistant to icing may not be valid.

Re Bob's and other comments about standardizing checklists, I am a huge believer in this. In fact I have some software to generate checklists for the airplanes I regularly fly; it guarantees standardization of format, wording and sequence across all of them. But that said, injected engines inevitably have different checklists than carbureted ones. So I can "standardize" Lyc engines with the injected engines for Pre-Landing as easily as I can "standardize" them with Continental-engines. No difference, again IMHO. I'm not saying I'm going to do this, especially after the query results above; I'm just saying that I don't think the logic is sound -- whether the NTSB says it or not.
 
Bob Noel said:
> its really not that hard to just push both handles forward on a go around.

It's a bit awkward on my cherokee 140. The throttle gets pushed forward and,
reaching around the mixture, the carb heat lever gets pulled up.
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The discussion was mostly geared towards carb heat use in Cessnas. But either way, it still isnt prohibitive in the Pipers, and unless you are right on the edge weight and Density Altitude wise the airplane should climb with full power and carb heat on. Quick action is typically not required.
 
I'm not a big fan of standardizing procedures across different aircraft types -- too many opportunities for negative transfer. I'd rather have folks know the plane they're flying and do what's right for that type. So having "carb heat" in the checklist is fine, but not blindly doing the same thing with the carb heat in all aircraft/situations.
 
I'm not a big fan of standardizing procedures across different aircraft types
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Yes. If you were referring to my post, I'll clarify: Each checklist's items are exactly tailored to the airplane (usually by tail number) but the syntax, the format, and the sequence of items is standard. Conceptually/oversimplified, think of a spreadsheet where the leftmost column has all possible checklist items, then each aircraft's column has an "x" in each row where the aircraft checklist is to include that item from the master list. In some case a row may have only one "x" -- i.e., that item from the master list is only used on one airplane. The software then assembles and formats the checklists as the x's indicate.
 
bobmrg said:
The NTSB put out a paper in the 70's saying that having different procedures for different airplanes was a recipe for disaster, and suggested that pilots use FULL heat whenever the power was reduced below cruise. I have tracked this document down to an archives in Washington that wants $27 for providing a copy, so I can't reproduce it for you. Suffice it to say that if you treat all carbureted engines alike you won't go wrong.

Bob Gardner
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Exactly -- this goes into the "Why add risk for no (or little) added benefit?" file.
 
Ron Levy said:
I'm not a big fan of standardizing procedures across different aircraft types -- too many opportunities for negative transfer. I'd rather have folks know the plane they're flying and do what's right for that type.
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I'd take this a step farther, and say that if you're flying so many airplanes that you have trouble keeping these things straight, you're flying too many airplanes. I've refused to fly certain airplanes that I've been qualified in at various times for exactly that reason.

While standardization is a good thing in general, fuel pump operation, fuel tank selection, flap settings, brake systems, and any number of other straight-forward items can become killers when "standardized" across different types, particularly as you broaden the range of airplanes you fly.

Fly safe!

David
 
tonycondon said:
The discussion was mostly geared towards carb heat use in Cessnas. But either way, it still isnt prohibitive in the Pipers, and unless you are right on the edge weight and Density Altitude wise the airplane should climb with full power and carb heat on. Quick action is typically not required.
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Hmmm...

I watched my Dad just barely clear the warehouse roof at the end of the runway in a PA-28(140) -- problem?

Carb heat on during t/o after a touch and go. He learned that lesson, but good.

I think the only time we need to do a quick reconfigure is a go-around, and typically (typically) we're not doing a go-around while holding it off for touchdown.

So we teach a particular sequence, which follows some generalized script, such as "add full power, hold the yoke against the nose up trim, start cleaning up -- carb heat, flaps, (gear, cowl flaps -- whatever for this a/c....)"

I think the "carb heat off because I might go-around" is similar to the "No flaps on a approach because I might go missed" reasoning.

In both cases I have (somewhat reluctantly, as it went against my primary training) concluded that argues for the optimum configuration for the intended task, with the brain on standby to reconfigure as needed when needed for the subsequent task.

I'm sure there are reasonable counter-arguments, but, there it is.
 
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Dan, your thinking on the flaps/carb heat business is 100% aligned with mine.

BTW, for the g/a, I teach "power UP, pitch UP, flaps UP" as the initial "go" procedure, adding "positive rate - gear UP" for retractables. And moving all levers (including carb heat and props) forward is part of "power UP."
 
Thanks for asking this question. I had never heard there might be any other way to land. In fact, every CFI I ever had gave me grief whenever I forgot to pull carb heat on landing. And in fact, I never had any problem whenever I forgot (which is often).
 
i agree with you don and ron. a lot of people forget that carb heat IS power.
 
AuntPeggy said:
Thanks for asking this question. I had never heard there might be any other way to land. In fact, every CFI I ever had gave me grief whenever I forgot to pull carb heat on landing. And in fact, I never had any problem whenever I forgot (which is often).
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It sounds like all your CFIs were helping to inculcate some measure of attention to the pre-landing/pre-takeoff check.

While carb heat off on final may not be a big deal 99% of the time in a simple fixed pitch trainer, when you move up to complex, retractable, high performance airplanes you'll be glad you were forced to think through and double-check before touching down.

I teach GUMPS -- even in fixed gear airplanes. Why not? Some even say G stands for Gear in a fixed gear, and that requires a check for brake pressure ...

Anyway, good habits help prevent that screeching sound heard when landing gear up -- it's the sound of money.
:hairraise:
 
dmccormack said:
It sounds like all your CFIs were helping to inculcate some measure of attention to the pre-landing/pre-takeoff check.

While carb heat off on final may not be a big deal 99% of the time in a simple fixed pitch trainer, when you move up to complex, retractable, high performance airplanes you'll be glad you were forced to think through and double-check before touching down.

I teach GUMPS -- even in fixed gear airplanes. Why not? Some even say G stands for Gear in a fixed gear, and that requires a check for brake pressure ...

Anyway, good habits help prevent that screeching sound heard when landing gear up -- it's the sound of money.
:hairraise:
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and on the flip side if the student gets used to saying "gear" and having absolutely nothing about the airplane change, they could be more likely to have a gear up landing in the future.
 
tonycondon said:
and on the flip side if the student gets used to saying "gear" and having absolutely nothing about the airplane change, they could be more likely to have a gear up landing in the future.
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Agree :yes:
 
I would consider it an example of negative transfer of learning, associated with the Law of Exercise.
 
tonycondon said:
and on the flip side if the student gets used to saying "gear" and having absolutely nothing about the airplane change, they could be more likely to have a gear up landing in the future.
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Maybe, but we always make a point to look out the window and say "down and welded." That way we're taking action on the item.
 
Ken Ibold said:
Read the NTSB reports. Search "loss of power" and Cessna 182. You will find a very large number of carb ice accidents in C-182s. As Ron says, know your airplane.
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Hmmm. I was gonna ask about the O-470 Continentals - In 200+ hours in the 182 behind one, I forget carb heat most of the time and I don't ever remember a carb ice encounter. In under 20 hours in a Dakota behind a Lyc, I did have some (in IMC). :dunno:
 
airdale said:
I then ran an all airplanes/all dates query for "carburetor ice" and got 71 hits. I only looked at the most recent half of them before getting bored but the results were kind of interesting: 10 for Lycoming, 13 for Continental. So the folklore about Lycs being significantly more resistant to icing may not be valid.
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Of course, that may be partially due to the pilots with the Continentals being more primed for carb ice - Was there any indication on the Lyc ones that the pilots had even pulled carb heat? It's easy to get complacent on that sort of thing if you don't worry about it most of the time...
 
gprellwitz said:
Maybe, but we always make a point to look out the window and say "down and welded." That way we're taking action on the item.
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I was also taught to actually look out the windows and make sure the tires still appeared to be inflated properly and not blown (on a C172). More action.
 
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