Cessna 152 carb heat question
- Thread starter Texguy
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USMCmech
Well-Known Member
Once about every 20 minutes should be ok when opperating at cruise power. Anytime you are below the green arc on the tach you should ad carb heat as well.
The really important thing to watch is the realitive humidity. 80% or better and 50 deg F is the worst conditions for carb iceing.
I was reading about Beech 18s recently and they recomended running carb heat at all times after take off.
The really important thing to watch is the realitive humidity. 80% or better and 50 deg F is the worst conditions for carb iceing.
I was reading about Beech 18s recently and they recomended running carb heat at all times after take off.
Alchemy
Well-Known Member
Don't do it too much in Alliance's 152's, especially 4951A....it likes to foul spark plugs.
If you use carb heat for extended periods, lean the mixture to compensate. Realistically, unless they're operating below the green arc (which if I recall correctly is about 1500rpm or less) I taught my students only to use carb heat if they suspected carb ice (engine not making full rpm) or encountered structural icing. I also had them pull the carb heat abeam the numbers on downwind as a precaution.
So to answer your question, in 60 degree weather I would not use carb heat during cruise at all, unless you notice your engine isn't make full power.
If you use carb heat for extended periods, lean the mixture to compensate. Realistically, unless they're operating below the green arc (which if I recall correctly is about 1500rpm or less) I taught my students only to use carb heat if they suspected carb ice (engine not making full rpm) or encountered structural icing. I also had them pull the carb heat abeam the numbers on downwind as a precaution.
So to answer your question, in 60 degree weather I would not use carb heat during cruise at all, unless you notice your engine isn't make full power.
DE727UPS
Well-Known Member
Well. I own one and never use the carb heat in cruise unless I have a reason too, which would be at the first perception of an RPM drop, for any reason. My understanding in that the butterfly valve, or plate, or whatever it's called, is parallel with the airflow inside the carburator at full throttle (I always cruise at full throttle since 152's are so slow). Because of this, there isn't much surface area for any ice to stick to.
Anyways, if you were flying with me and pulled the heat on in cruise every 20 minutes, I'd wonder what you were doing. Then I'd mention that I don't think it's really necessary. Then, if you still wanted to do it, I could care less.
I've heard Lycomings are less likey to get carb ice than Continentals. So, a 150 would be more of a problem than a 152.
Also, humidity plays a big role. I fly in low humidity, almost arid, Eastern Washington. Other parts of the country you may need to pay more attention to carb ice.
Anyways, if you were flying with me and pulled the heat on in cruise every 20 minutes, I'd wonder what you were doing. Then I'd mention that I don't think it's really necessary. Then, if you still wanted to do it, I could care less.
I've heard Lycomings are less likey to get carb ice than Continentals. So, a 150 would be more of a problem than a 152.
Also, humidity plays a big role. I fly in low humidity, almost arid, Eastern Washington. Other parts of the country you may need to pay more attention to carb ice.
USMCmech
Well-Known Member
[ QUOTE ]
Anyways, if you were flying with me and pulled the heat on in cruise every 20 minutes, I'd wonder what you were doing. Then I'd mention that I don't think it's really necessary. Then, if you still wanted to do it, I could care less.
Also, humidity plays a big role. I fly in low humidity, almost arid, Eastern Washington. Other parts of the country you may need to pay more attention to carb ice.
[/ QUOTE ]
I did most of my C-150 time on the Texas gulf coast. One of the planes at the FBO was notorious for carb ice, especially in the fall or spring.
In a drier climate like yours twice an hour would definately be overkill.
Anyways, if you were flying with me and pulled the heat on in cruise every 20 minutes, I'd wonder what you were doing. Then I'd mention that I don't think it's really necessary. Then, if you still wanted to do it, I could care less.
Also, humidity plays a big role. I fly in low humidity, almost arid, Eastern Washington. Other parts of the country you may need to pay more attention to carb ice.
[/ QUOTE ]
I did most of my C-150 time on the Texas gulf coast. One of the planes at the FBO was notorious for carb ice, especially in the fall or spring.
In a drier climate like yours twice an hour would definately be overkill.
Kloader
New Member
Yeah, some good posts here. I pretty much consider everything posted thus far when I fly, but this is what I end up doing with my own C150. I never pull the carb heat unless I hear or feel roughness. Of course, on an O-200, this could be anytime, even during run-up. But the only time I do a 'prescribed' carb heat cycle is during the down wind, then off again before base leg. Here's my rational: The engine is turning too slow considering the magneto's only cruise ignition timing of 25 degrees BTDC. As the rpm's drop below 2000 all the way to 700 for landing, the engine is running cruddier and cruddier with unburned fuel everywhere muddying up the plugs. The ignition timing in the flare is still 25 degrees. Realistically, the timing should adjust like an old VW down to 7 degrees BTDC at idle in order to allow more time for the fuel to burn, but not so for us. So I don't add insult to injury and enrichen the cylinder when I am already risking an engine stall from surplus fuel. I've rented other planes whose engine's would stall if not for the prop windmilling the engine. So, for what its worth, that's how I keep my engine happy in case I need it for a go around.
(And I think all of this applies to the C152's lycoming, even though the word on the street that its carb updraft through the oil sump keeps the air a little toastier....)
My rambling 2 cents. Cheers.
(And I think all of this applies to the C152's lycoming, even though the word on the street that its carb updraft through the oil sump keeps the air a little toastier....)
My rambling 2 cents. Cheers.