Hot and lean or rich and cool?

[Htwjr]

On my new to me M20C if I land with carb heat on the engine runs very rough. Should I lean it and use carb heat on landing or leave it rich and not use carb heat?

[Sabremech]

I land with the mixture rich and no carb heat on my C.

David

[Sauduster]

I also land with the mixture rich and no carb heat on my C.

Bob

 

[stevesm20b]

Mixture rich, no carb heat

[Rwsavory]

Carb heat on and about 1/2 inch lean.

[Hank]

Mixture rich, no carb heat

Me, four. And prop forward.

[Oscar Avalle]

mixture rich, no carb heat and prop forward

[Mooneyjet]

Mixture 3/4 of the way in and no carb heat, prop slowly forward. And I use camguard

[SkyBound]

Carb heat off, mixture rich (unless you are landing at higher altitude).  I only use carb heat when there is onset of carb ice.  Use of carb heat in the M20C is infrequent.  I typically have experienced that in visible moisture/rain/clouds. Enjoy!

[Comatose]

No carb heat on landing. You have a carb temperature gauge, why turn it on unless you're gonna get ice?

 

That said, I almost always always have a touch of it on in cruise. I use it to bring my EGT and CHT spreads down, which lets me run leaner 

[Wildhorsesracing]

Add me to the list - mixture rich, no carb heat, prop forward

I have only used carb heat on landing when temps are near freezing and humidity is high

[bumper]

Carb heat off, mixture to idle cut-off  

[lahso]

I only use carb heat when landing in the winter time. Otherwise, it's off. Mixture is rich.

[DS1980]

Good points. For some of these topics, like how rich or lean to run, a graph can do wonders to provide a solution. Doesn't necessarily have to be winter time or the humidity to be high for carb ice to be likely. Remember at low power (when we're landing) the refrigeration effect is greatest. The choice is whether you want to loose about 10% power using carb heat or have the chance to loose 100% power when it ices up. The good news is that in the conditions that require carb heat usually are "better" than standard atmosphere so the performance of the airplane will be better than book. A consideration if hesitating to using carb heat because of the worry of the reduced power for a go around.

 

[pinerunner]

I couldn't believe that there were "conservative" pilots landing with carb heat off. I was raised around flying and was pulling carb heat for landing when I was in the 2nd grade out on the playground.  This article

 

http://flighttraining.aopa.org/students/presolo/skills/carbicing.html

 

"

When you apply carburetor heat to melt ice that has formed in the throat, or venturi, of the carburetor, you may notice that the engine begins to run even rougher. This happens because the fuel mixture, already enriched because the ice is choking off some of the induction air flow, is suddenly made even richer by the addition of hot air.

This triple whammy can make the mixture so fuel-rich it will not ignite in the cylinders. The solution is to lean the mixture (and sometimes it takes some pretty radical leaning) and get a burnable mixture going to the cylinders.

"

explains why its running rough. I guess your planes have the mixture set so rich at full rich that carb heat makes it run rough, something i never heard of before. So it must be set plenty rich enough for take-off, John Deakins would aprove; no need to fight with your mechanic to set it richer.

 

This accident was attributed to carb ice and makes the point that a very likely place for you to run into it is with the power pulled back and on base leg or final. Note that it was summer in Florida.

 

"William Wynne was the passenger in his Corvair powered Pietenpol when it crashed north of Tampa, Florida, on July 14, 2001. The engine cut off at 700' AGL, which gave only 60 seconds to attempt a restart and execute a forced landing."

 

This webpage stars an M20C in a supporting role as an accident caused by carb ice.

 

 

http://www.genebenson.com/newsletter/newsletter_may10.htm

 

Another with Don Maxwell mentions a rash of Mooney carb ice incidents in a given year.

 

Say no more.

[Shadrach]

An engine experiences slight roughness and power loss with carb heat; an engine gets much rougher when you pull carb heat and there's actually ice to melt. It was always my understanding that the roughness was from ice/ moisture ingestion when the carb heat melted the ice.

What is the reasoning behind leaving CH on all the way to touchdown? It's been years since I've flown a carbed engine, so take it easy on me!

Seems that pulling it in the descent and closing it when the gear gets dropped or first notch of flaps (IFR approaches would have to be modded to the user's SOP).

Seems like there's no good reason to be coming down the hill to land with your engine unhappy...

Best yet, just get a carb temp gauge..

[Sabremech]

I have Carb temp on my Insight G1 engine monitor and applying carb heat is not on my landing checklist. I haven't encountered any flying yet where I felt I needed it in my Mooney. Seems not to be stressed in my transition training like it was when I flew a Cherokee and a Cessna.

David

[Hank]

Carb heat isn't emphasized for two reasons: 1) air intake is through the oil pan, preheating the air; 2) tight cowling retains engine heat.

I have a Carb Temp gauge and rarely use carb heat except on the After Start checklist.

[pinerunner]

An engine experiences slight roughness and power loss with carb heat; an engine gets much rougher when you pull carb heat and there's actually ice to melt. It was always my understanding that the roughness was from ice/ moisture ingestion when the carb heat melted the ice.

What is the reasoning behind leaving CH on all the way to touchdown? It's been years since I've flown a carbed engine, so take it easy on me!

Seems that pulling it in the descent and closing it when the gear gets dropped or first notch of flaps (IFR approaches would have to be modded to the user's SOP).

Seems like there's no good reason to be coming down the hill to land with your engine unhappy...

Best yet, just get a carb temp gauge..

The reasoning behind carb heat on throughout landing is that it is both the worst possible place for carb ice to bite you and the most likely with the power pulled way back and the engine developing minimum heat. Since I have an E I don't know what the POH says for a C. Maybe the M20C's don't really need carb heat for the reasons Hank mentioned but if so I'm surprised. If you guys are skating on thin ice the place where you finally find out will be most inconvenient. Not a small issue and it must have come up in the past either in accidents or in heated discussions.

 

Dave 

[Sabremech]

The reasoning behind carb heat on throughout landing is that it both the worst possible place for carb ice to bite you and the most likely with the power pulled way back and the engine developing minimum heat. Since I have an E I don't know what the POH says for a C. Maybe the M20C's don't really need carb heat for the reasons Hank mentioned but if so I'm surprised. If you guys are skating on thin ice the place where you finally find out will be most inconvenient. Not a small issue and it must have come up in the past either in accidents or in heated discussions.

 

Dave 

 Hi Dave,

 We're all pretty clear on the reasoning behind carb heat as it's drilled into us during our training in the brand X airplanes. That doesn't make it necessary in other makes and models of aircraft. My C model POH has it listed to apply during landing, but my checklist does not. I have not used the carb heat yet in My C model for landing in any time of the year flying that I've done. Each one of us have developed what's comfortable and normal to us as far as our own SOP's. There's nothing wrong with that and we probably won't change our ways until or unless we encounter a problem.

 We're not automatically going to become a statistic or an accident waiting to happen just because we don't use carb heat.

 David

[Seanhoya]

 Hi Dave,

 We're all pretty clear on the reasoning behind carb heat as it's drilled into us during our training in the brand X airplanes. That doesn't make it necessary in other makes and models of aircraft. My C model POH has it listed to apply during landing, but my checklist does not. I have not used the carb heat yet in My C model for landing in any time of the year flying that I've done. Each one of us have developed what's comfortable and normal to us as far as our own SOP's. There's nothing wrong with that and we probably won't change our ways until or unless we encounter a problem.

 We're not automatically going to become a statistic or an accident waiting to happen just because we don't use carb heat.

 David

David -   Is your checklist a Mooney product?  According the the FARs, we are required to follow the POH - not aftermarket checklists, unless we make a conscious decision to deviate, and then must be prepared to justify it.  Unfortunately, my POH (from 1968) is really lacking - the only emergency procedure that it lists is emergency gear extension - which is a moot point in my 1968 M20G with manually retractable gear.  But as a matter of good practice, I am loathe to deviate from my POH.

 

Frankly, I don't remember whether my POH says to use carb heat (It's not in front of me - my sense is that it does), but I always do.  As a CFI, I am required to teach its proper use, and don't ignore my own training as a matter of habit.  As a matter of technique, I apply carb heat during approach, and then push it in on short final (technique only, if conditions allow).

 

Htwjr

 

Easy answer - if the POH says use carb heat - THEN USE IT!  If you experience slight engine roughness - ADJUST MIXTURE!  If it gets real rough, SEE A MECHANIC!

 

Be careful as a new Mooney owner - your aircraft, its engine, and the weather in your local area should all dictate whether you use carb heat, to include your POH.  Just because a bunch of other Mooney pilots don't use carb heat means nothing when it comes to you and your airplane - their conditions will necessarily be different from yours. I have had carb icing in clear air at full power (In California in the Winter).  I fly a normally aspirated Mooney with O-360, but I fly all over the US and abroad - such varying conditions greatly affect the performance of the aircraft, and render "rules of thumb" less universal.  

 

And any deviation from the POH needs to be justifiable - a little engine roughness, in my opinion, is not sufficient reason to justify deviating from the POH - I just tell everyone in the aircraft that the engine is going to get rough for the next thirty seconds, and not to worry.  If it is too rough, see a mechanic - it sounds like your mixture might be too rich.  And keep following your training and POH - it will keep you alive.

[Sabremech]

Hi Seanhoya,

I have the checklist laminated from my POH. As pilot in command, I can make decisions to deviate from the POH if I feel it necessary. Who do I need to justify that to? What do you do when you encounter something that isn't in the POH? Who are you going to call to find out? Do you call the FAA and report yourself?

We offered our techniques to the original poster in an effort to answer their question. If it doesn't agree with your SOP, that's fine, but I'd appreciate not being lectured in how to follow the FAR's.

[Seanhoya]

Sabremech,

 

Point well taken.  I am just concerned that we don't give advice to a new Mooney owner which may get him or her in trouble because their situation is different than ours.

 

I think that you put it well - "The reasoning behind carb heat on throughout landing is that it both the worst possible place for carb ice to bite you."  Given the consequences, I think that it is better to error on over-application than the opposite.

 

If his engine is running too rough, it is probably because the fuel mixture is too rich.  The correction for this is to have a mechanic adjust the engine, not to rule out the use of Carb Heat entirely.  I think that we probably are in agreement on this point.

 

Sorry for the lecture.

[Marauder]

Also keep in mind that a POH is different than an AFM or a OM. In my OM, only two sections in the OM are designated as FAA approved (have an FAA signature page). The section with the checklist procedures is not designated as FAA approved. You also need to keep common sense in mind when you look at a 30 to 50 year checklist in your manual. I have added or remove items that clearly are not there because the technology didn't exist at that point in time or I removed the equipment.

[Shadrach]

David - Is your checklist a Mooney product? According the the FARs, we are required to follow the POH - not aftermarket checklists, unless we make a conscious decision to deviate, and then must be prepared to justify it. Unfortunately, my POH (from 1968) is really lacking - the only emergency procedure that it lists is emergency gear extension - which is a moot point in my 1968 M20G with manually retractable gear. But as a matter of good practice, I am loathe to deviate from my POH...

Show me the FAR that requires a factory checklist...or any check list for that matter?

I understand the thinking behind carb heat. But I think it's sub optimal.

I think it far better to pull CH in the descent. This would ensure the carb was clear at a time when you're not going to need power. Close the CH abeam the numbers or on short final. If you forget to close it, big deal, so the engine runs a bit rich if you need to go around (you have a many more chances to close it if you need power).

The thing is with a CS prop, you really won't see symptoms of carb ice like you would with a fixed pitch prop (gradual reduction in RPM).

IMHO, CH causes a loss in power, but should not cause significant roughness; significant roughness with the application of CH typically comes from ingesting melting ice. Why wait to pull CH at a time when your low and slow? If you do have ice in the throttle body, is that a good time to be sucking water and an overly rich mixture through a throttle body that's reduced in size by ice?