Carb Ice in a Cherokee/Archer?

RyanB

RyanB

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Has anyone experienced carb ice in a Cherokee/Warrior/Archer? Carb heat seems to generally only be recommended if icing is suspected, whereas the Cessna procedure is to apply when power decreases below the green arc as a preventative measure etc. As far as I can tell, the carburetors are mounted in the same spot on both aircraft and have the same engine type on a few of them as well.

Why is the procedure different?
 
I had carb ice a couple of times in my old Cherokee 140. While it is a rare occurrence, it is something that happens occasionally.

As far as the procedural difference between Cessna and Piper when the engine is effectively the same is concerned, I've heard some claims that the cowling differences between the Cessna and Piper are the cause. Personally, I suspect the guidance Cessna offers on carburetor heat usage is an artifact left over from when the airplanes were Continental powered.
 
Yes, light carb ice twice in two different Cherokees. Both times in cruise, between 3000 and 4500 if I remember correctly, Hudson river valley, high humidity, maybe 60F (guessing). Once daytime just below an overcast layer. Once nighttime with patchy light rain. In both cases applying carb heat cleared it up quickly. We noticed it by a maybe 100-150 drop in RPM during cruise. Here in the NE, I was taught to put in carb heat in the PA-28's downwind in the pattern, or during decent if the dewpoint/temp were close. Never have had any issues doing that.

No idea why Cessna might be different that Cherokees. Maybe because the cowling is different? Just a guess.

When flying cubs, it's always carb heat on downwind at the numbers when pulling power, no exception. It is routine to get carb ice in those during cruise. My technique for that is to apply carb heat until the ice goes away, then take it off again. To track it by RPM. To try not to leave it on as a precaution in cruise, as then you may get stuck w/o a way out if it comes back. I know you didn't ask about other aircraft, just tossing in a random data point that yep, cubs are way icier than Cherokees. Picked up those techniques from guys that have been flying cubs in the Berkshires pretty much forever.
 
mondtster said:
Personally, I suspect the guidance Cessna offers on carburetor heat usage is an artifact left over from when the airplanes were Continental powered.
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I believe this is probably the case (or at least it's partly to blame). Personal experience is that a Lycoming Cessna is not more likely to collect carburetor ice than a Lycoming Piper.

There was no change in the wording in the POH when Cessna went from the 150 to the 152 (Continental to Lycoming). The same is true when Cessna went from Continental to Lycoming for the 172 as well.

However, there was a change from the 1975 C172M to the 1976 C172M, where the checklist went from specifying carburetor heat "as needed to prevent icing" to "apply full heat prior to closing throttle". Maybe Cessna retained new legal counsel that year.
 
geneseib said:
Lycoming engines have carb mounted to oil sump which transfers heat to the carb. Continentals have carb suspended away from engine.
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All of the Piper’s (Cherokee/Warrior/Archer) and the Cessna’s have the same Lyc 320/360, assuming it’s an L thru P model 172.
 
In ~260 hours in carb'd PA-28s, most in an Archer, never even suspected carb ice. In ~20 hours in an o-360 172 I've suspected it twice. Guys with WAYYY more hours than me tell me they've never suspected it in a Piper, and they experience it commonly in the Cessna. I asked the same question to a ~50 year and multiple thousand hour pilot in the Piper club, and he said he's only experienced it once, scud running on a cold day.

The best explanation I ever got was that Piper packaged the engine more tightly, with the exhaust headers and muffler in closer proximity to the carb. I'd love to see them both decoweled side by side to verify this. Perhaps one of our resident A&P's can speak to this theory.
 
geneseib said:
Lycoming engines have carb mounted to oil sump which transfers heat to the carb. Continentals have carb suspended away from engine.
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The 172's Continental O-300 had the carb mounted on the sump just like a Lycoming's.

Right there in the red circle is the carb's mount.

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Installation details matter. The O-320-A2B in the Citabria 7GCBC will ice up in a heartbeat, yet it's no different carb/sump setup than a 172's or a Cherokee's.
 
Dan Thomas said:
Installation details matter. The O-320-A2B in the Citabria 7GCBC will ice up in a heartbeat, yet it's no different carb/sump setup than a 172's or a Cherokee's.
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So what’s the cause for it if their setups are the same?
 
RyanB said:
So what’s the cause for it if their setups are the same?
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Cowling. The Citabria has lots of air moving through a roomy cowling. I could never find any other reason for the difference. The Citabria did have a smaller muffler than the 172, and would maybe radiate less heat. Maybe. The muffler in both the 172 and Citabria are in front of, and close to, the carb; the Cherokee's is well behind it, next to the firewall. You'd think the Cherokee would have more ice problems.
 
RyanB said:
Has anyone experienced carb ice in a Cherokee/Warrior/Archer?
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I suspect I had it once in a Challenger, partial power descent on a warm humid day.
 
400 hours in a Challenger (73 Archer 1) and never had any icing. The one additional explanation that I have heard is that the intake air goes through tubes cast into the sump, providing some heating for the intake air. I do test for icing after long descents, particularly in IMC.
 
Yup....had it in the Six. 0-540. Was doing some maneuvers doing a BFR and engine almost quit when making a power change. Applied heat and got the cough and sputter....then clearing.
 
I had the carb ice up on a Cherokee 140 on my approach to landing on my long XC for PPL. Not fun.
Glad to be fuel injected :yesnod:
 
I've got over 1k hours in a Warrior and never an ice issue. In training I asked my CFI about it, since he said not to use it, and his reply was that he had thousands of hours Warriors and never experienced carb ice.
 
I have experienced a slight drop in RPM in the clouds in my Archer a couple of times. Applied carb heat and it went back to normal. Probably don’t need to, but it is part of my pre landing check list.
 
I had a PA-28-160 try to kill me on takeoff during my initial checkout in a Cherokee. At 300' AGL the engine lost at least 50% power. My hand got to the carb heat before the owner's hand. Problem solved. Clearly not the first time for this plane, because the owner had a carb ice detector (yes, detector, not a temp gauge) install already in the plane.

This was on a day with temps prob in the 60's, and not particularly humid.
 
I had suspected carb ice in the Cherokee once in cruise. Humid day, flew just below the cloud deck and OAT on the ground was 65. I add carb heat in the pattern despite what the POH says.
 
Hang 4 said:
400 hours in a Challenger (73 Archer 1) and never had any icing. The one additional explanation that I have heard is that the intake air goes through tubes cast into the sump, providing some heating for the intake air. I do test for icing after long descents, particularly in IMC.
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Heating the intake air downstream of the carb doesn't prevent carb icing. The only thing the sump's heat does for the carb is to heat its body somewhat, but there is so much air going through that carb that it is not a cure-all for carb ice.

Many times pilots have ice but they don't know it. Icing is worse at partial throttle, due to the pressure drop as the air squeezes around the partly-closed throttle plate, accelerating while it does so. Ice can start to build on the plate and adjacent carb bore, and if the RPM falls a bit the pilot is inclined to just open the throttle further. That opens the throttle plate, reducing the restriction, which reduces the acceleration and therefore the pressure and temperature drop, and the ice, if the conditions are right on the edge, will disappear, and the pilot never had any idea he had ice. So we get guys saying that they've never had ice in a thousand hours of flying a Cherokee. That's impossible unless all that flying was on very warm, dry days in the American Southwest.

When pilots are unaware, they can get hurt. I often heard students firing up a 172 on the ramp on a nice, sunny summer morning. The engine ran fine for a minute, and then the RPM would fall off and the engine would almost die, but the student (and often the instructor as well) would just open the throttle to get the RPM back. I'd go out, bang on the pilot's door, and tell him to pull the carb heat and touch nothing else. Their eyes would get real big as the RPM climbed 200 or 300 RPM. All by itself. A stark lesson about how you can take off with ice in the carb, and crash.

They learn about it in groundschool, but it's entirely academic--and often forgotten---until it actually happens.
 
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Very true. I have under 100 hours in a Cherokee and I know I had ice on at least one occasion, probably more often than that in cruise though without really knowing. I pull carb heat no matter what every 15 -30 minutes in cruise and leave it on for a few seconds, which I think, gets rid of some ice that is forming without me even knowing. Also, in order to prevent takeoff with ice in the carbs, I usually pull the carb heat while holding short before entering the runway just to be sure there is no ice. It's part of my hold-short checklist and comes from the days when I was flying the Ercoupe with the C-85 engine which is an ice machine. The Cherokee is much better but I still kept that part on the checklist just to be sure.
 
Way back when, I was landing at KBDR in an Archer. The day was very humid, dew point in the mid-70’s. Landed normally, and then the engine stopped. I strongly suspected Carb Ice was the culprit. The engine restarted promptly, pulled the carb heat lever down, and taxied to parking.
 
Dan Thomas said:
Heating the intake air downstream of the carb doesn't prevent carb icing. The only thing the sump's heat does for the carb is to heat its body somewhat, but there is so much air going through that carb that it is not a cure-all for carb ice.
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To quote Homer Simpson "Duh!". Can't tell you how many times I've heard this and looked at the engine and it just slipped by me the tubes were downstream of the carb. Thanks
 
Dan, thanks for posting that. I'd suspected the same. When I had ice the first time I had a CFI beside me. I'd been watching the tach. I told him I thought we had some carb ice. He looked at me like I had 2 heads, and I just said "humor me". So we applied CH, rpm dropped, rough a little, and no kidding the RPM then came up a bit after a little bit. We get back to the airport and now have the crazy story of "hey we had carb ice in a Cherokee!"

I can't imagine anyone flying in this area that hasn't picked up carb ice unless they only fly beautiful days. But where the humidity is always low? Sure, absolutely. Albany isn't Phoenix, though, or even Texas. It's wet here.
 
Never and owned a couple of them…but still make sure it’s working on run up…
 
I find a lot of pilots do a pretty poor job of actually checking the Carb heat during the runup. I see a lot of them pull the carb heat, see an RPM drop and turn it back off.
What I teach is to note the RPM, pull the carb heat, let the RPM stabilize and hold for 3-5 seconds. see that the RPM drops and what RPM it stabilizes at, if ice is present you often can watch it drop 200-300 rpm and then gain 100 or more RPM.
Turn the Carb heat off, compare the RPM to the RPM prior to the check. If Ice was present the RPM will be higher after checking the Carb heat.

On a humid 50 degree morning it is almost a guarantee quite a few (carbureted) planes will build up ice just taxiing to the runup area.

If you detect ice during the runup, you might want to consider leaving the carb heat on until take off power, or re-checking just prior to going to take-off power.

Brian
CFIIG/ASEL
 
Albany Tom said:
Dan, thanks for posting that. I'd suspected the same. When I had ice the first time I had a CFI beside me. I'd been watching the tach. I told him I thought we had some carb ice. He looked at me like I had 2 heads, and I just said "humor me". So we applied CH, rpm dropped, rough a little, and no kidding the RPM then came up a bit after a little bit. We get back to the airport and now have the crazy story of "hey we had carb ice in a Cherokee!"

I can't imagine anyone flying in this area that hasn't picked up carb ice unless they only fly beautiful days. But where the humidity is always low? Sure, absolutely. Albany isn't Phoenix, though, or even Texas. It's wet here.
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That is pretty much how I have detected Ice in Cherokees. Hey its seems like it is running a bit rough, did it lose some RPM? Pull the carb heat a its get worse and then better, turn the carb heat off and I have gained back the RPM I suspected I had lost.

Had a C-150 lose 300 RPM at about 400feet on take off, pulled the Carb heat and lost another 200rpm and just enough power to maintain altitude. Turned back to the runway, but once I knew I had the runway made I decided to continue downwind for a normal landing. About midfield 20-30 seconds after pulling the carb heat the RPM's came up and all was right with the world again. Lesson. don't give up on the carb heat it may take some time.

Brian
CFIIG/ASEL
 
brcase said:
I find a lot of pilots do a pretty poor job of actually checking the Carb heat during the runup. I see a lot of them pull the carb heat, see an RPM drop and turn it back off.
What I teach is to note the RPM, pull the carb heat, let the RPM stabilize and hold for 3-5 seconds. see that the RPM drops and what RPM it stabilizes at, if ice is present you often can watch it drop 200-300 rpm and then gain 100 or more RPM.
Turn the Carb heat off, compare the RPM to the RPM prior to the check. If Ice was present the RPM will be higher after checking the Carb heat.

On a humid 50 degree morning it is almost a guarantee quite a few (carbureted) planes will build up ice just taxiing to the runup area.

If you detect ice during the runup, you might want to consider leaving the carb heat on until take off power, or re-checking just prior to going to take-off power.

Brian
CFIIG/ASEL
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I think the poor carb heat check during runup is due to a lack of understanding of why it is being checked. In my opinion, the carb heat check is less about seeing if the carb heat is functional and more about making one last attempt at melting any ice that may have formed between engine start and takeoff. I always try and make sure any student I fly with understands that and does a thorough carb heat check.

A few years back a friend of mine destroyed a very nice airplane during takeoff due to carb ice that formed during the taxi out. He is a high time pilot and should have known better, but apparently it didn't occur to him that ice was a possibility.
 
POA discussions are almost always entertaining, and sometimes also informative. This is a good one.
 
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