Carb Ice?

[Headspace]

I need a reality check. I'm fairly certain what just happened was for real, but to recap:

This happened right before my final approach fix on an LPV approach. I'm in the clouds. Suddenly my engine starts to sporadically "hiccup." I turn on carb heat, and it's on for less than six seconds--immediately I get about 200 RPMs, almost as if I had pushed in the throttle. I kept the heat on.

I was in a PA-28 with a Lycoming O-360. I've been told by a few people that "Lycomings don't ice" (Edit: They meant that figuratively, of course). I've always followed the checklist anyway (because I believe Lycoming's own documentation about their own product), but I usually apply heat after the FAF/FAP. I was about 2 miles from it if I recall correctly.

I'm a fairly low time pilot compared to most here, but does this seem like it was a carb ice or something else? What else could it be?

 

[Rwsavory]

It was carb ice. Occam's razor.

 

[bluerooster]

Sounds like you were in one of the situations where a Cherokee 180 need carb heat on. (visible moisture in the air)
The Lycomings don't require religious use of carb heat as the contis do, but there are times when it's needed.
A carb temp gauge is quite useful.

 

[Headspace]

It was carb ice. Occam's razor.

Yeah. I'll be turning it on earlier in the future if we're in the clouds for sure, Lycoming or no Lycoming.

A carb temp gauge is quite useful.

I'll look into that if I ever decide I want to own my own PA-28. I'm thinking if I do take the ownership route it'll be a Mooney.

 

[poadeleted20]

I don't think anyone ever said "Lycomings don't ice." They are less susceptible to carb icing than the Continental installations in Cessna singles, which is why most Lycoming-powered singles say "as required" rather than "on at all low power settings" like the Continental-powered 150/172/182's, but it can happen in the right conditions, which it sounds like you found.

 

[Headspace]

I don't think anyone ever said "Lycomings don't ice." They are less susceptible to carb icing than the Continental installations in Cessna singles, which is why most Lycoming-powered singles say "as required" rather than "on at all low power settings" like the Continental-powered 150/172/182's, but it can happen in the right conditions, which it sounds like you found.

Thanks for the input, Ron.

It was obviously was meant tongue in cheek when it was said. I doubt any knowledgeable person would actually believe that a carbureted engine cannot experience induction icing--that would violate the laws of physics.

The thing about the PoH is that it seems to not advise using the carb heat unless you actually get it, which runs contrary to what Cessna's PoHs say, even when the same engine is installed. Is there any reason why Piper would differ in their opinion of when to apply it? Cessna seems to favor proactive application and Piper reactive. Is this only because of the continental engines' increased susceptibility and a 'better safe than sorry' policy on the part of Cessna?

 

[flyingron]

Lycomings don't ice.
Pressure carbs don't ice.
You can't get ice on warm days.

BUNK BUNK BUNK BUNK BUNK
(I'd actually use STRONGER words if I didn't fear sanctions here).

My wife was flying from 2W5 back to VKX in the Navion one day. Now they're only 10 miles apart, so she left the throttle at something like 18 inches for the entire flight. On entering the pattern the engine started misfiring. Margy dived for the numbers not knowing what the problem. On roll out, I pulled carb heat and asked her to goose the throttle a bit, and guess what it cleared. Carb Ice:
LYCOMING
PRESSURE CARB (PS-5C)
70 Degrees Ambient on the ground.

Yeah it can happen.

 

[poadeleted20]

The thing about the PoH is that it seems to not advise using the carb heat unless you actually get it, which runs contrary to what Cessna's PoHs say, even when the same engine is installed. Is there any reason why Piper would differ in their opinion of when to apply it?

The induction systems are different.

 

[Headspace]

The induction systems are different.

That explains it, thank you.

 

[greghughes]

The induction systems are different.

Also the way the carb is mounted is different between engines/models. On a Cessna 150 for example there's a collar between the carb and the engine and the air doesn't pass through the oil sump area, so heat doesn't tend to transfer to the cold air too well. On the cherokee it's a different story - pretty much no separating material, and induction air passes by the oil sump, so heat transfers to the carb much more readily. Might not be the best explanation, but point is the physical characteristics of the system and engine can cause heating of the components, reducing likelihood of ice.

Of course, when your engine is still cold that effect is smaller - or non-existant. Last time I experienced carb ince in my Warrior was a couple months ago during the run-up after pulling it from the hangar. Very small amount of visible moisture in the air at the time. The other time I experienced it was while descending in an inversion layer to the traffic pattern, ran rough. A few years ago that happened to me in a C150 where I let it go too long, was almost at idle, added carb heat and it flat out quit until the ice metled and the spinning prop heled it restart. That got my attention.

In the Warrior, the green arc extends all the way to idle, and they say carb heat is to be used as required. Any visible moisture and I use it, and any question in my mind at all and I just use it. I'd much rather have a clear throttle body and ability to feed full power on a go-around.

 

[Rwsavory]

Yeah. I'll be turning it on earlier in the future if we're in the clouds for sure, Lycoming or no Lycoming.

I'll look into that if I ever decide I want to own my own PA-28. I'm thinking if I do take the ownership route it'll be a Mooney.

Come on over to Mooneyspace.com to learn more about Mooney ownership. We have been enjoying our C model, also sporting the O-360.

 

[midlifeflyer]

That explains it, thank you.

BTW, the NTSB is on record as disagreeing that they should be different and has made recommendations that preventive carb heat should be used on all carbureted engines. http://goo.gl/t8ID8 The recommendation was ignored by the FAA and never adopted by any manufacturer AFAIK.

Continuing on the subject of the ability of even a Piper to ice up, I was flying a Comanche 250 at cruise power when it iced up.

 

[redtail]

BTW, the NTSB is on record as disagreeing that they should be different and has made recommendations that preventive carb heat should be used on all carbureted engines. http://goo.gl/t8ID8 The recommendation was ignored by the FAA and never adopted by any manufacturer AFAIK.

Continuing on the subject of the ability of even a Piper to ice up, I was flying a Comanche 250 at cruise power when it iced up.

Having flown a Cherokee for the first time, last week and getting checked out in....now I'm really confused

Do I follow the POH with regard to carb heat or the NTSB

 

[EdFred]

Continuing on the subject of the ability of even a Piper to ice up, I was flying a Comanche 250 at cruise power when it iced up.

Which oddly enough is the only time I've ever had carb ice in Pipers as well. It was 45-50, misty, just the dry side of drizzling, and that's when it started.

Having flown a Cherokee for the first time, last week and getting checked out in....now I'm really confused

Do I follow the POH with regard to carb heat or the NTSB

Your choice. I personally like to run filtered air as much as I can. (no carb heat until there's an issue)

 

[VanDy]

I was always taught that when I reduce power, apply carb heat. If a go around is needed close carb heat after the throttle is all the way in. And when at cruise, if you have any doubt apply carb heat. Granted, I am in a pretty low tech 65hp T-craft, but at the first sign of engine trouble I apply carb heat and do a mag check. Its worked for me so far. I can't see how this would hurt applying it across the board to carb'd engines, but im always open to learning

 

[midlifeflyer]

Having flown a Cherokee for the first time, last week and getting checked out in....now I'm really confused

Do I follow the POH with regard to carb heat or the NTSB

Based on similar discussions in the past, you're likely to get opposite opinions on this one.

I came across this NTSB recommendation during research I did after my carb ice event. My self-analysis was that the lack of automatic mental association between low power and putting on carb heat in a Piper as opposed to a Cessna led to me delaying application of carb heat and I was looking for other similar cases.

In discussions with others, some have alluded to a possible downside to using carb heat as a preventive, although I really haven't heard anything specific that struck me as a real consideration.

Given that, my personal answer is that we're in the area of "technique" rather than requirement. At first, my inclination was toward using it all the time in low rpm flight (I still would not use it in cruise) but I later modified it to adding at least a metal check of "Carb Heat...CONSIDER" when reducing power tor descent and landing as a way of keeping it in mind - it's somewhat similar to what Cirrus pilots are being taught taught about using the chute.

So long as the techniques you use allows you to keep it in mind so that you in fact use it when needed, the techniques itself doesn't matter much IMO.

In the OP, Headspace said:

This happened right before my final approach fix on an LPV approach. I'm in the clouds. Suddenly my engine starts to sporadically "hiccup." I turn on carb heat, and it's on for less than six seconds--immediately I get about 200 RPMs, almost as if I had pushed in the throttle. I kept the heat on.

Sounds like he did it just right.

 

[midlifeflyer]

Which oddly enough is the only time I've ever had carb ice in Pipers as well. It was 45-50, misty, just the dry side of drizzling, and that's when it started.

I had the classic "you can get carb ice when its 70°F" situation.

 

[redtail]

Prior to my checkout last week, the last time I flew a carb engine was before my hiatus. It was a 160hp Skyhawk. When I came back two and a half years ago, I started flying the fuel injected Skyhawk SP and Super D.

So last week I was a little surprised to learn that the use of carb heat in the Pipers, is..."as required". I'm going to finish reading and decide if I should include it in my SOP. I'm sort of leaning in that direction right now, based on what I've read so far

 

[redtail]

Based on similar discussions in the past, you're likely to get opposite opinions on this one.

I came across this NTSB recommendation during research I did after my carb ice event. My self-analysis was that the lack of automatic mental association between low power and putting on carb heat in a Piper as opposed to a Cessna led to me delaying application of carb heat and I was looking for other similar cases.

In discussions with others, some have alluded to a possible downside to using carb heat as a preventive, although I really haven't heard anything specific that struck me as a real consideration.

Given that, my personal answer is that we're in the area of "technique" rather than requirement. At first, my inclination was toward using it all the time in low rpm flight (I still would not use it in cruise) but I later modified it to adding at least a metal check of "Carb Heat...CONSIDER" when reducing power tor descent and landing as a way of keeping it in mind - it's somewhat similar to what Cirrus pilots are being taught taught about using the chute.

So long as the techniques you use allows you to keep it in mind so that you in fact use it when needed, the techniques itself doesn't matter much IMO.

In the OP, Headspace said:
Sounds like he did it just right.

Thanks.

I haven't finished the NTSB recommendation that you posted but this part stood out immediately!

"The flight had departed from Richmond, Virginia, and cruised uneventfully at 6,500 feet msl toward Front Royal. On arrival in Front Royal, the pilot reduced power to descend to pattern altitude. The pilot stated after the accident that during the final approach to the runway, the engine did not respond when she attempted to increase power t o maintain the desired glidepath. With the tachometer indicating 1,800 rpm, carburetor heat was applied. The pilot was unable to increase the rpm, and the airplane crashed short of the runway."

 

[Headspace]

Given that, my personal answer is that we're in the area of "technique" rather than requirement. At first, my inclination was toward using it all the time in low rpm flight (I still would not use it in cruise) but I later modified it to adding at least a metal check of "Carb Heat...CONSIDER" when reducing power tor descent and landing as a way of keeping it in mind - it's somewhat similar to what Cirrus pilots are being taught taught about using the chute.

So long as the techniques you use allows you to keep it in mind so that you in fact use it when needed, the techniques itself doesn't matter much IMO.

The problem is that I was at my approach speed when it happened, which is more like lowish cruise RPM (I remember my airspeed so I know I started out around ~2100) and not exactly "low RPM." It was at the high end of low--around 1800--after it developed the ice, though, no question. Being at around 12C in a cloud seems to have been the magic ingredient to produce ice here.

The takeaway from this is that there is a probability distribution for when induction icing can occur. The ideal conditions make it more likely but they don't make it impossible otherwise.

 

[redtail]

"The National Transportation Safety Board determined that the probable cause of the accident was: (1) the pilot's "improper operation of powerplant controls, (2) improper operation of or failure to use anti-icing/de-icing equipment, and (3) carburetor ice."

How/why did the NTSB fault the pilot for following the POH The engine didn't respond so she applied carb heat but it was too late. How was she at fault?

"The pilot stated after the accident that during the final approach to the runway, the engine did not respond when she attempted to increase power t o maintain the desired glidepath. With the tachometer indicating 1,800 rpm, carburetor heat was applied. The pilot was unable to increase the rpm, and the airplane crashed short of the runway."

 

[EdFred]

The NTSB always faults the pilot. Both wings could snap off, and the NTSB would still list the pilot at fault, and the wings falling off as a secondary factory.

 

[VanDy]

The NTSB always faults the pilot. Both wings could snap off, and the NTSB would still list the pilot at fault, and the wings falling off as a secondary factory.

You don't own a Tcraft do you?

But, back to carb ice....

 

[EdFred]

You don't own a Tcraft do you?

But, back to carb ice....

No, I had The World's Ugliest Comanche sitting on the ramp Saturday.

 

[VanDy]

No, I had The World's Ugliest Comanche sitting on the ramp Saturday.

My sarcasm font didnt come through, and I forgot the smiley

Tcraft lost a lift strut in '07, sea plane on salt. Thats why.

 

[bobmrg]

Having flown a Cherokee for the first time, last week and getting checked out in....now I'm really confused

Do I follow the POH with regard to carb heat or the NTSB

The NTSB. They made that recommendation because the various POHs created uncertainty of the type you illustrate.

Bob Gardner

 

[Shepherd]

I was always taught that when I reduce power, apply carb heat. If a go around is needed close carb heat after the throttle is all the way in. And when at cruise, if you have any doubt apply carb heat.

I was taught the same thing, except a little more extreme. When the engine RPM drops below the "green" zone, apply carb heat.

 

[Headspace]

Having flown a Cherokee for the first time, last week and getting checked out in....now I'm really confused

Do I follow the POH with regard to carb heat or the NTSB

I would suggest putting it on at low RPM like the Cessna manual recommends. I've always done it that way, and I turn it off when I'm on the ground (make sure not to leave it on during a touch and go). Now that this happened, I'll be turning it on when making power changes in the downward direction if I'm in the clouds on an approach like I was here, even if the RPMs aren't leaving the green zone.

Either way make sure to watch your engine. Watch oil pressure, watch manifold pressure, RPMs, and temps. Induction icing is only one thing that can go wrong.

 

[redtail]

The NTSB. They made that recommendation because the various POHs created uncertainty of the type you illustrate.

Bob Gardner

I would suggest putting it on at low RPM like the Cessna manual recommends. I've always done it that way, and I turn it off when I'm on the ground (make sure not to leave it on during a touch and go). Now that this happened, I'll be turning it on when making power changes in the downward direction if I'm in the clouds on an approach like I was here, even if the RPMs aren't leaving the green zone.

Either way make sure to watch your engine. Watch oil pressure, watch manifold pressure, RPMs, and temps. Induction icing is only one thing that can go wrong.

Thanks.

 

[poadeleted20]

Your choice. I personally like to run filtered air as much as I can. (no carb heat until there's an issue)

Where the POH says "as required," I'm with Ed.

 

[poadeleted20]

The NTSB. They made that recommendation because the various POHs created uncertainty of the type you illustrate.

Bob Gardner

It's called "negative training transfer," and that's what you get when people try to apply something they learned in one airplane to different airplane. That's how the original AA-1 Yankee got its original bad rep -- folks who'd never flown anything but a Cessna 150 (and back then you could go all the way through CFI-ASEL-IA that way) tried to fly it like a Cessna 150, with predictably* bad results. IOW, it's poor training, not the POH's, which created that uncertainty.

* if you knew anything about aerodynamics and the designs of the two planes.

If you fly each plane per its manual, you can expect to get good results. The issue here is that poorly trained pilots are doing things not because the manual for that plane says to do them, or because they understand the need (or lack thereof) to do them, but because some poorly trained CFI told them "this is how you do it" without explaining either a) why we do it that way in this plane, or b) that it's done because of the way this plane is designed, not because it is supposed to be done that way in all planes. The NTSB seems to be trying to reduce it to the least common denominator rather than encouraging proper training in type. I don't like that concept, since it encourages mindless training without understanding.

 

[Headspace]

Ron:

You make a good argument and I can't fault your logic. But I'm curious how the following factors into it.

An overwhelming number of aircraft in the "fleet," as it were, are of 60s, 70s, and early 80s vintage. They've experienced multiple overhauls and repairs over the past several decades. How, if at all, does that factor into the procedures aspect?

 

[poadeleted20]

Ron:

You make a good argument and I can't fault your logic. But I'm curious how the following factors into it.

An overwhelming number of aircraft in the "fleet," as it were, are of 60s, 70s, and early 80s vintage. They've experienced multiple overhauls and repairs over the past several decades. How, if at all, does that factor into the procedures aspect?

If they've been properly maintained, I see no reason why that should be a factor. If not, and that improper maintenance has altered their characteristics to the point that procedures other than the manual with which they came are required, then they I'd say they are no longer airworthy (i.e., no longer in compliance with their type certificate) and shouldn't be flown at all.

 

[redtail]

So the pros with thousands of hours, can't agree on a standard procedure! Follow the POH or the NTSB recommendation!
Great, that leaves us low time pilots scratching our heads even more

I mean no disrespect but this is crazy!

I got a pretty thorough checkout in the Cherokee and I'm looking forward to flying it but I'm really unsure what method I should adopt when reducing power below 2000 RPM. On the checkout flights (2), we followed the POH and only touched carb heat during the runup.

Edit: according to the pilot in the NTSB report, she followed the POH

"the engine did not respond when she attempted to increase power t o maintain the desired glidepath. With the tachometer indicating 1,800 rpm, carburetor heat was applied"

 

[Fearless Tower]

How/why did the NTSB fault the pilot for following the POH The engine didn't respond so she applied carb heat but it was too late. How was she at fault?

When the NTSB has a particular agenda, they have been known to use specific cases to further that agenda in an effort to drive the change they seek.

 

[Cap'n Jack]

Ron:

You make a good argument and I can't fault your logic. But I'm curious how the following factors into it.

An overwhelming number of aircraft in the "fleet," as it were, are of 60s, 70s, and early 80s vintage. They've experienced multiple overhauls and repairs over the past several decades. How, if at all, does that factor into the procedures aspect?

I'm assuming you don't mean upgrades and STCs and stuff like that? I _think_ the STCS or upgrades would have a supplement to the POH or the type certificate or whatever documents are needed to make the plane airworthy, so Ron's comment should still be valid.

 

[Headspace]

I'm assuming you don't mean upgrades and STCs and stuff like that? I _think_ the STCS or upgrades would have a supplement to the POH or the type certificate or whatever documents are needed to make the plane airworthy, so Ron's comment should still be valid.

No, not STC's. Nothing that would end up manifesting itself as an addendum to the POH or what needs to be carried along in the plane.

 

[midlifeflyer]

So the pros with thousands of hours, can't agree on a standard procedure! Follow the POH or the NTSB recommendation!
Great, that leaves us low time pilots scratching our heads even more

I mean no disrespect but this is crazy!

It is. Now you see what I meant about diametrically opposed opinions, much of with is based on a "belief" structure.

Ron, for example, tries to scare you away from doing it, not because it harms the aircraft or engine in any way, but rather because he equates putting on carb heat at low power settings in a Cherokee as the equivalent of landing a Yankee with too much airspeed because you (incorrectly) expect it to slow down the way a 152 would. IOW, if you decide to use carb heat in a Cherokee, you will someday crash something.

If you can see a difference between the two, you're doing great and can probably make your own good decision.

OTHO, if someone comes up with a reason that makes the results of use of carb heat at low power settings in a Cherokee any different than in a Cessna 172 in terms of engine health and safety, that would be something to seriously consider.

Besides, don't worry. If you choose to apply carb head as a preventive, you are following the POH. The Warrior POH, for example calls for carb heat to be "ON if required" for descent. "Required" doesn't mean you have to wait for the furst signs of carb heat. As the POH goes on tot say in the expanded tasks,

==============================
If a prolonged power off descent is to be made, apply full carburetor heat prior to power reduction if icing conditions are suspected.
==============================

There it is in a Piper POH - use of carb heat as a preventive. Starting a descent on a humid day with the temperature in the 70°F and below range is a scenario in which icing conditions should be expected.

 

[poadeleted20]

Ron, for example, tries to scare you away from doing it, not because it harms the aircraft or engine in any way, but rather because he equates putting on carb heat at low power settings in a Cherokee as the equivalent of landing a Yankee with too much airspeed because you (incorrectly) expect it to slow down the way a 152 would. IOW, if you decide to use carb heat in a Cherokee, you will someday crash something.

That is a serious distortion of what I said. My only point was that doing something in a
one type because you were taught to do it that way in a different type and for no other reason is "negative training transfer." And as Ed pointed out, there are valid reasons for not using carb heat when it isn't needed.

BTW, the use of excess airspeed during landing with the Yankees was not the problem back when they were introduced.

 

[midlifeflyer]

That is a serious distortion of what I said. My only point was that doing something in a
one type because you were taught to do it that way in a different type and for no other reason is "negative training transfer." And as Ed pointed out, there are valid reasons for not using carb heat when it isn't needed.

What were they. I mustve missed them.

So, you disagree with the use of carb heat as a preventive in a Piper. What about the POH language I quoted above? Are you now saying don't follow the POH?

Not one person on this thread supporting the use of carb heat as a preventive suggested doing something "for no other reason."