Brought down by carb ice?

OneCharlieTango said:
No need to yell. All I know is what I read. I'm just repeating what John Deakin says. It makes good sense.
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Has it happened to you? My airplanes haven't been ice makers but I generally fly with high power at low altitudes. Sometimes in scuzzy weather. No ice. Not once. Go up to higher altitudes and do low a power descent to slip under a cloud layer? Certain ice.
 
Stewartb said:
Vents should be located to prevent icing. Cessna vents hide behind lift struts and the fuel caps are also vented so I have redundancy. I uses the same concept for my Cub. A properly built airplane should have very low risk of fuel vent fouling.
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My Cessna has a blocked vent and the vented caps did not open until I was 5 minutes into a partial engine out due to lack of fuel flow. And this was in a 150 at 5 gph. Maybe a larger engine would have pulled a greater vacuum and popped the vented caps sooner, or perhaps the greater demand for fuel would have made the situation worse.
All I know is that the vented caps are not fool proof and it is good practice to actually check your vents from time to time. I mean actually blowing in them and having someone confirm that it is venting properly. I always looked at my vent tube every preflight, but the blockage was too far to see.
 
kgruber said:
Bad advice, NOT TRUE!!!
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Well, I know that the rules say that idle power is most likely time for carb ice, but the only time I have had it on my O-200 was when I took the 150 out for an altitude record flight (record for me) in the winter and pointed it straight up for a 30 minute climb in 20 degree temps on a clean and a million winter day. I got carb ice at 13,500’ after full power for 30 minutes. Weird, but it happened.
 
Matthew Rogers said:
Well, I know that the rules say that idle power is most likely time for carb ice, but the only time I have had it on my O-200 was when I took the 150 out for an altitude record flight (record for me) in the winter and pointed it straight up for a 30 minute climb in 20 degree temps on a clean and a million winter day. I got carb ice at 13,500’ after full power for 30 minutes. Weird, but it happened.
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"Full" power at 13.5K is maybe, what, 55%. But yes, carb ice is an unknown, to be dealt with.
 
The only time I've gotten serious carb ice was during a climb, about 2000', full power in a C-182.
 
OneCharlieTango said:
The only time I've gotten serious carb ice was during a climb, about 2000', full power in a C-182.
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That makes me always wonder if you were icing on the ground at low power and just iced a bit more. That has happened before
 
kgruber said:
"Full" power at 13.5K is maybe, what, 55%. But yes, carb ice is an unknown, to be dealt with.
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I agree. So what is it about full power that makes icing less likely? Is it the heat from the engine? Or the speed and volume of air the engine is ingesting?
 
Matthew Rogers said:
I agree. So what is it about full power that makes icing less likely? Is it the heat from the engine? Or the speed and volume of air the engine is ingesting?
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PV=nRT, and nearly a nearly adiabatic process.

As you expand air across the throttle plate from ambient to manifold pressure, the temperature drops along with the pressure. More pressure drop (closed throttle), more temperature drop.

At closed throttle, the pressure drop across the throttle far exceeds the pressure drop through the venturi even at high air flows.
 
When I crashed my Luscombe, their first thoughts were carb ice. Turned out to be a fuel system issue, but the NTSB told me they think carb ice is a big factor in airplane crashes. The evidence melts away, leaving no trace, and the engine runs fine when they put it on a stand.
 
benyflyguy said:
That makes me always wonder if you were icing on the ground at low power and just iced a bit more. That has happened before
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Yup. That has caused accidents when airplanes took off and couldn't climb.
 
Lowflynjack said:
When I crashed my Luscombe, their first thoughts were carb ice. Turned out to be a fuel system issue, but the NTSB told me they think carb ice is a big factor in airplane crashes. The evidence melts away, leaving no trace, and the engine runs fine when they put it on a stand.
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Some surveys put carb ice at the top of the list for cuases of engine failures.
 
I made a precautionary landing after my engine started running weird and my JPI showed suddenly low EGTs. This was after an adventure into inadvertent airframe icing, at night. I got a descent to avoid more clouds and to get the ice off and suddenly this was happening, even though I'd put some carb heat in (though not consistently). My plane is not one that is susceptible to carb ice. I made a precautionary landing and had a mechanic look at the plane the next day - no issues. Probably carb ice. Now, if my pitot heat is on in IMC, my carb heat is too.
 
Capt. Geoffrey Thorpe said:
PV=nRT, and nearly a nearly adiabatic process.

As you expand air across the throttle plate from ambient to manifold pressure, the temperature drops along with the pressure. More pressure drop (closed throttle), more temperature drop.

At closed throttle, the pressure drop across the throttle far exceeds the pressure drop through the venturi even at high air flows.
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Pervnert
 
Dan Thomas said:
Yup. That has caused accidents when airplanes took off and couldn't climb.
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Years ago in my Continental O300 172 I was doing my flight review. During my runup prior to departure I pulled CH on and then pushed in back in right away. The CFI admonished me to reapply CH saying "leave it on for a minute, we want to give any ice a chance to melt". We discussed my concerns about unfiltered air and satisfied with his response I incorporated that into my runup henceforth.

I sincerely hope this improves my odds of avoiding your scenario.
 
N1120A said:
My plane is not one that is susceptible to carb ice. I made a precautionary landing and had a mechanic look at the plane the next day - no issues. Probably carb ice.
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I may have mentioned this upthread, but the one time I know I had carb ice, after landing the carb on the Cub had frost all over it, on a relatively warm S FL day. If it happens again, just looking at or feeling the carb after landing may give a big clue as to whether carb ice was the culprit or not.
 
Well, mine won't get carb ice (anymore) since it doesn't have a carb (anymore). Even before when it had the pressure carb, it was thought to be rather immune to ice. Oddly, on a relatively warm day my wife flew it for an extended period at low power. Just about the time we hit the pattern to land the engine started to run very rough. We just put went direct to the numbers rather than trying to diagnose it in the air. It was only on rollout that I thought to check the carb heat. Sure enough, it was ice.
 
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