Carb Heat on landing?

Saintroad

Saintroad

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Saintroad
I am located in Tampa, FL. I have been in training and have about 50 hours total. Mostly in Luscombes, J-3, Champs and other TW aircraft at first, until I decided to specialize over the last 6 months in low-wing PA-28 Pipers for my PPL. In the J-3, I would always be told to reduce power at end of numbers, perform the final orientation, add carb heat and bring her in.

In the newer Pipers, not so much.

In fact, my CFI has never been told me to touch it in a PA-28 plane. I have been training in an Archer II and the only time we have ever touched the Carb Heat was at run-up. Plan on getting a Cherokee 160C or 180D perhaps and want to know your opinions on this...

Does sunny FL not have the proper conditions for ice building during descent? I thought I was told that ice could form almost anywhere, anytime even above 70F which some like to down-play, especially during a reduced power throttle setting.

Just trying to be safe and conscientious with my carb heat practices and rules of usage.
Thanks for the insight and knowledge.
 
Best do what the aircraft manual says. I have Lycoming 320 in a pusher and haven't touched carb heat in 11 years. . .and you can see from the map below where it has been.
 
I have a carb temp gauge. If it's not below 50 or so I don't add carb heat. No reason to enrichen things to that point if I don't have to. W/O a carb temp gauge...yeah, I used it every time.

I fly a Cessna though, It's my understanding the Pipers' carbs are warmer.
 
Saintroad said:
I am located in Tampa, FL. I have been in training and have about 50 hours total. Mostly in Luscombes, J-3, Champs and other TW aircraft at first, until I decided to specialize over the last 6 months in low-wing PA-28 Pipers for my PPL. In the J-3, I would always be told to reduce power at end of numbers, perform the final orientation, add carb heat and bring her in.

In the newer Pipers, not so much.

In fact, my CFI has never been told me to touch it in a PA-28 plane. I have been training in an Archer II and the only time we have ever touched the Carb Heat was at run-up. Plan on getting a Cherokee 160C or 180D perhaps and want to know your opinions on this...

Does sunny FL not have the proper conditions for ice building during descent? I thought I was told that ice could form almost anywhere, anytime even above 70F which some like to down-play, especially during a reduced power throttle setting.

Just trying to be safe and conscientious with my carb heat practices and rules of usage.
Thanks for the insight and knowledge.
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what does the POH say?
 
I've always applied the heat anytime the power comes out of the green arc. Flying in 70deg+ Wx has a slim to nil chance of carb ice occuring. Best to check the POH as others have said.
 
I fly a 1969 Cherokee and I don't touch the carb heat except for the run up checklist and flying into precipitation in temps below 70 degrees.
 
Small Continentals are ice makers. Lycoming design causes much less ice with intake manifold running through oil pan.


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Iirc, the small PA28s have their carb intake running through the oil sump. They are not as susceptible to carb icing as other designs.
 
Some thoughts here.

When you are using Carb Heat, are you doing it based on location in the pattern or by the markings on your tach? The latter is probably what is called out in the planes literature.

Turning to the Cherokees - That green marking on the tach goes all the way down to idle. Not too surprising that you're not taught to worry about it.

I've had three CFI's 'discuss' carb heat on a PA28-180 with me. Each time I told them that their boss trained me, so ask him! And on the next lesson they'd be like "Spoke to so-and-so and you are correct"
 
The Piper manuals almost always say to not mess with carb heat unless you suspect icing. Cessnas usually have it on prophylactically primarily because the manual was written back in the days the 172 was equipped with an O-300 which was much more susceptible to icing than the Lycomings were.
 
In my opinion carburetor icing can happen from 20 degrees F to 90 degrees F.
Please read your POH and follow their recommendations for the aircraft you are flying.
 
Found it in Section III: (Approach and Landing)
Carburetor heat should not be applied unless there is an indication of icing, since the use of this heat causes a reduction in power which may be critical in case of a go-around.
 
Like weilke said, it's not just the type of engine, it's also the way heat is distributed in the specific engine-airframe installation. In almost 1,000 hours in Cherokees, I suspected carb ice maybe twice. But the Lycoming O-360 in my 172 is no stranger to carb ice below 2200 rpm, and in cool, moist air.
 
N3368K said:
Small Continentals are ice makers. Lycoming design causes much less ice with intake manifold running through oil pan.


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More correctly, Lycoming's carb is mounted to the bottom of the oil sump. But unless the oil is hot, it can still ice up, and quickly. Saw it many times in the flight school on pleasant summer mornings at 70+°F.

And some Lycomings appear to have the carb on the sump, but the sump is actually above that. The lower cavity is an intake plenum, with the intake runners open inside it, and the oil is above a "ceiling" above that plenum. Some 360s, at least, are like that, and they have little or no benefit from oil heat on the carb body. Some of the 540s have the carb on a plenum at the rear of the sump and similarly gets no oil heat into the carb.

Those who say it's nearly impossible at or above 70 are fooling themselves. The accident stats are full of accidents for which there was no defect found for the engine's failure, yet the atmospheric conditions were conducive to carb icing. This phenomenon is one of those aspects of flight training that is poorly understood or misunderstood by too many instructors, who pass on that ignorance to students, who then mishandle an icing situation and end up hurt or dead. A carburetor on ANY engine is an icemaker, and its operating environment determines whether it will be prone to icing. Piper's Cherokee series have a tightly cowled Lycoming with exhaust pipes radiating lots of heat all around it. Cessnas--Lycomings in roomier cowlings, less exhaust plumbing. Small Continentals--carbs mounted to intake spiders that induct very little heat off the crankcase and will ice up readily.

Know your airplane. Study carb icing; there's no lack of professional info on the 'net about it.

http://www.ntsb.gov/safety/safety-alerts/Documents/SA_029.pdf

https://www.aopa.org/-/media/files/aopa/home/pilot-resources/asi/safety-briefs/sb09.pdf?la=en
 
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Why on earth did you downgrade to a PA28?

Ether way, to your question, I'd follow the POH, only diffrence with how I fly carbs is that I turn carb heat off on short final, reason is I want immediate access to 100% power with the least engine configuration changes possible, I also don't want to have unfiltered air that close to, and on, the ground.
 
Dan Thomas said:
And some Lycomings appear to have the carb on the sump, but the sump is actually above that. The lower cavity is an intake plenum, with the intake runners open inside it, and the oil is above a "ceiling" above that plenum.
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And I wish I had a nickle for every Navajo with a sump heater glued to the bottom of the plenum. :loco: I think I've seen two in the last five years installed correctly.
 
Do exactly as your flight manual says. Do NOT listen to anyone here. If you have some sort of incident, "well so & so on POA said to do that" will not be a defense. The aircraft manual is God like in these situations.
 
Kritchlow said:
Do exactly as your flight manual says. Do NOT listen to anyone here. If you have some sort of incident, "well so & so on POA said to do that" will not be a defense. The aircraft manual is God like in these situations.
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So, if you have modern day instrumentation that provides you with real-time information that wasn't provided when the plane was built and the POH written (i.e. a digital carb temp gauge on a '57 C172) then you should ignore that information and rotely do exactly as the POH/checklist states even if that action could be detrimental (i.e. cause severe engine stumbling at high density altitudes, plug fouling, etc.).

i.e. never use your ability to reason and think.

Got it!

:rolleyes:
 
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timwinters said:
So, if you have modern day instrumentation that provides you with real-time information that wasn't provided when the plane was built and the POH written (i.e. a digital carb temp gauge on a '57 C172) then you should ignore that information and rotely do exactly as the POH/checklist states even if that action could be detrimental (i.e. cause severe engine stumbling at high density altitudes, plug fouling, etc.).

i.e. never use your ability to reason and think.

Got it!

:rolleyes:
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I am curious. As part of the stc do they amend the poh operating procedures?
 
PPC1052 said:
I am curious. As part of the stc do they amend the poh operating procedures?
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More rote.

Am I going to pull carb heat in a O470 powered 182 coming into Flagstaff on a 85dF day just because the POH tells me to?

Ummmm...no!

Especially when it's my airplane and I have a very good feel for when it ices and when it doesn't.
 
timwinters said:
More rote.

Am I going to pull carb heat in a O470 powered 182 coming into Flagstaff on a 85dF day just because the POH tells me to?

Ummmm...no!

Especially when it's my airplane and I have a very good feel for when it ices and when it doesn't.
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Yup, paint by numbers isn't good

I recall something a few years ago about a pitts or some such going into Vegas that gupped out when the guy went rote mixture rich, carb heat on, for landing.
 
timwinters said:
More rote.

Am I going to pull carb heat in a O470 powered 182 coming into Flagstaff on a 85dF day just because the POH tells me to?

Ummmm...no!

Especially when it's my airplane and I have a very good feel for when it ices and when it doesn't.
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Actually, my question was meant to be generalized. I wasn't trying to argue about whether to apply carb heat in your plane. Do they amend the POH when they issue an STC that might affect normal or emergency operating procedures? I have all stock equipment, so I don't have personal knowledge on this.
 
What they are saying is, use carb heat per the POH, but understand what it does, how it works, when it helps and when it hurts, now use the POH and also use common sense and logic.
 
James331 said:
What they are saying is, use carb heat per the POH, but understand what it does, how it works, when it helps and when it hurts, now use the POH and also use common sense and logic.
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Was that addressed to my post? I can't tell for sure.

My question (which is admittedly a little off topic) is: Do they amend the POH when they issue an STC that might affect normal or emergency operating procedures?
 
No, no instrumentation that I know of amends the POH recommendation. Carb temp instruments are primarily used to manage cruise temps, not to nullify carb ice procedures during low power ops.

My 180 doesn't make ice. I know an identical airplane that makes ice regularly. I rarely use carb heat. If I flew another 180 that I was unfamiliar with I'd follow the standard precautionary practices until I had enough familiarity with that plane to deviate from them. Common sense 101.

One of the problems with POH carb heat recommendations is that guys don't understand what it may do. On downwind over hostile terrain if you have carb ice and pull heat you may get a real close-up of the hostile terrain. Use carb heat before you get into a position where you'd least like the engine to quit, don't wait until that moment and pull carb heat. Maximizing/maintaining your engine performance is what carb heat is for. POH procedures fail in that respect.
 
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I have experienced carb ice before on a PA28 140, on a day that wasn't that cold.
 
ircphoenix said:
I haz a 140. Give me the circs so I know what to look for.
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So there I was...

I was approaching a mountain airport on a coolish day, no visible precipitation (maybe a slight spotty mist in places), in a decent under low power, still aways from the pattern, and the engine started running rough. I applied carb heat, and it cleared it up.
 
OK, so interesting topic for me. Just last week did my first "small xc" (25mile) from our big class C to our small practice airport. 1974 PA-28-140 (160 conversion) Flew at 3000', temp was about 55-60F, and there was a notable inversion right at 3000'. Was not particularly humid, but there was no wind and earlier in the morning there had been noticeable valley fog all over. Very sunny, about 9:30am.

My descent from 3000 to TPA at 1300 took probably 5 minutes at aprox 1900RPM.

When I entered the pattern and powered back up to 2300RPM on downwind it seemed fine. Reduce power abeam the numbers and it seemed to be running very slightly rough. Like when I have a slightly fouled plug on runup. I was not particularly concerned, but I did notice it, and thought I'd land and check things out, do a full runup again, etc.

Because we don't train carb heat on in descent in the PA-28, I didn't think of it until after the flight. Have never had this happen before, and when I spoke to my instructor after, he said "carb heat, you probably had a little ice". I was mad at myself for not thinking that and flipping carb heat on. OTOH, I was also thinking "engine is running fine, I'm able to make the runway from here if I have to, let's just not mess with it [the engine] and land"

Seems like carb heat on in descent wouldn't be a bad SOP for all carburated engines. POH recommendation or not.
 
I hit carb ice during pilot training (C-152) on a mild early summer day. Descending out of 3000, all I needed to hear was the engine starting to run rough. On came the carb heat and within seconds was running smooth again. I believe the POH for the 152 says carb as required, but no mention of it on approach.

I think the POH is the guide you should follow, but @timwinters makes a valid point that it can't be without pilot judgement. If I don't have the fancy gauges, I'll keep with the manual until then :)
 
PPC1052 said:
My question (which is admittedly a little off topic) is: Do they amend the POH when they issue an STC that might affect normal or emergency operating procedures?
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Oh, a genuine question! So unusual around here. ;)

As Stewart said, no.

Sac Arrow said:
I have experienced carb ice before on a PA28 140, on a day that wasn't that cold.
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Air temp drops going thru the carb. That's why it doesn't have to be a freezing day to get carb ice. IIRC, my temps are approximately 15dF below ambient at cruise power settings. At idle when coming in to land, the carb temp rises to very close to ambient. (but it's been a while since I really analyzed this so that may be off a bit).

The stock carb temp gauge that I took out of my 182 when I installed the engine monitor had a yellow arc from -15dC to +5dC. And was labelled with something like "stay out of yellow arc during possible icing conditions." So, even before getting the digital gauge, if the needle was at 10dC or higher when coming in to land, I never used carb heat. That gave me a 5dC safety margin allowing for gauge inaccuracy.

And, like Stewart, my O470 is not an ice making machine like many are. I only experienced ice once; on a PnP trip that was a very humid 50dF (or so) day, staying low below the clouds. That's the only time I've ever had to fly with carb heat on for an entire trip. If I would shut it off then the engine would start stumbling again in just a few minutes. Definitely an attention getter!
 
timwinters said:
Oh, a genuine question! So unusual around here. ;)

As Stewart said, no.
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No worries. In all candor, I am not above Socratic method argument. So, it's not unreasonable to interpret my question as such.
 
+1 for following the POH. I flew a Lycoming 0-360 Scout for decades, in Alaska, and experienced carb ice many dozens of times, often quite severe, at pretty much every power setting below 60%, at temps from 30 to 80 degF. You definitely wanted to use carb heat on power reductions as specified in the manual. I am now flying an 0-360 powered Tiger in the Southwest US. I have not noticed any carb ice symptoms in my flying, and the typical humidity is much lower. Still, it is an 0-360, and the manual says carb heat at power reduction. So, I do it.
 
timwinters said:
Air temp drops going thru the carb. That's why it doesn't have to be a freezing day to get carb ice. IIRC, my temps are approximately 15dF below ambient at cruise power settings. At idle when coming in to land, the carb temp rises to very close to ambient. (but it's been a while since I really analyzed this so that may be off a bit).
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Some of those gauges are pretty inaccurate, and the probe is located above (downstream of) the throttle plate. One of the phenomena involved here is the big temperature drop right at the edge of that throttle plate, caused by the huge increase in air velocity as it squeezes past the plate when the plate is closed at idle. That creates a very small, localized place where ice can build, yet the temperature probe is in normal velocity (and therefore normal temperature) air just beyond it and doesn't think anything is wrong. This is the thing that causes carbs to ice up at idle soon after startup on nice, warm but relatively humid mornings, and the engine wants to quit if the pilot pulls the throttle to idle, so he just pushes it in a bit without realizing that ice is building and he'd better watch out.

Temperature and dewpoint. What's the spread? That's what makes the difference. A carb at Phoenix on an 80°F day is unlikely to make ice. A carb on an 80°F day in New York will be a different animal altogether.

carb_ice.gif


This chart give an idea of the increasing risk as dewpoint rises to meet temperature. It's not specific to any engine installation and so wide variations in ice susceptibility can be expected between models and engines.

Note the increased risk at lower throttle settings. This is why so many are simply taught by rote to pull the carb heat on approach. No real understanding of what's going on and what the immediate risks might be.
 
I've flown a lot of smaller Cessnas plus champs etc. most have cont. engines. Always use carb. Ice . If I have to go round I simply push in the carb. Heat knob and go round. If your familiar with the aircraft, you know immed. Upon applying power that you left it on. Not a big deal.
 
weilke said:
Iirc, the small PA28s have their carb intake running through the oil sump. They are not as susceptible to carb icing as other designs.
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:yeahthat:

Vance Breese said:
Please read your POH and follow their recommendations for the aircraft you are flying.
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The POH on my ol' Cherokee used to say "carb heat as needed". Not much help to rule followers since one has to make an informed decision based on current conditions and circumstances.

Sac Arrow said:
So there I was...

I was approaching a mountain airport on a coolish day, no visible precipitation (maybe a slight spotty mist in places), in a decent under low power, still aways from the pattern, and the engine started running rough. I applied carb heat, and it cleared it up.
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Is this a pop quiz?
If so, my answer is "if you forgot to enrichen the mixture in the "decent descent", the engine became rough (overly lean) and by adding carb heat, you enrichened the mixture, thus fixing the symptom".
Now what did I win? :D
 
Lycomings have their induction tubes routed through the sump. Carb ice happens in the carb. Lots of Supercubs make ice. Some don't. They all use Lycomings. Don't dismiss carb ice because you fly a Lycoming.
 
The original question was if conditions existed in sunny Florida for carburetor ice on landing?

I feel the answer is yes.

I fly out of Santa Maria, California and have had experience with carburetor ice with a Lycoming O-290.

In my experience waiting to notice carburetor ice before pulling carburetor heat is not a good plan.

I have had more than one simulated engine landing out turn into a real engine out landing due to carburetor ice.

In my experience there is not time on short final to restart the engine during a carburetor ice event.

Once the engine has stopped; pulling carburetor heat didn’t have much effect.

It is all good practice; I would rather not create a real emergency to practice for an emergency.

Carburetor ice is one of the reasons we installed a Lycoming IO-320 in my aircraft.

I don’t miss carburetor ice a bit and I am happy every time I don’t have to pull carburetor heat when I reduce power.

I recommend following the directions in the POH for the use of carburetor heat.
 
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