Carb Ice With A C150L

[Aeric]

I went for a flight yesterday afternoon and intended to get at a rather high up for some pictures. I did a constant near Vy climb at full throttle with a couple of partial throttle reductions and pitch to near level to make sure the cylinders stayed happy. As I passed through 8500' (leaning since around 2500') the engine started to run quite rough and I suspected carb ice so I backed off the power a bit and leveled. I applied carb heat, richened the mixture a little and after a few seconds I regained power so I removed the carb heat and then a few seconds later it ran very rough again. I reapplied carb heat, got the power back and after a few seconds removed the heat and it started to run rough again. Carb heat back on, and I left it on for close to a full minute and all was well after removing the heat. Ran fine the rest of the flight.
I realize the first two times I had not left the heat on long enough...lesson learned, this was my first encounter with carb ice.
This happened in absolutely cloudless air and at full or nearly full throttle, and at an altitude that should be rather dry.
I understand that the 0-200 is rather notorious for making ice, but given the conditions, is this unusual?

 

[Tom-D]

I went for a flight yesterday afternoon and intended to get at a rather high up for some pictures. I did a constant near Vy climb at full throttle with a couple of partial throttle reductions and pitch to near level to make sure the cylinders stayed happy. As I passed through 8500' (leaning since around 2500') the engine started to run quite rough and I suspected carb ice so I backed off the power a bit and leveled. I applied carb heat, richened the mixture a little and after a few seconds I regained power so I removed the carb heat and then a few seconds later it ran very rough again. I reapplied carb heat, got the power back and after a few seconds removed the heat and it started to run rough again. Carb heat back on, and I left it on for close to a full minute and all was well after removing the heat. Ran fine the rest of the flight.
I realize the first two times I had not left the heat on long enough...lesson learned, this was my first encounter with carb ice.
This happened in absolutely cloudless air and at full or nearly full throttle, and at an altitude that should be rather dry.
I understand that the 0-200 is rather notorious for making ice, but given the conditions, is this unusual?

The 0-200 is notorious for carb ice, but it can't make it with out water of some kind.

I'd say that you reach DA service ceiling on your 0-200, or you have a induction leak.

 

[Aeric]

The 0-200 is notorious for carb ice, but it can't make it with out water of some kind.

I'd say that you reach DA service ceiling on your 0-200, or you have a induction leak.

That does make sense, however just before I encountered the roughness I was still getting a whopping 300 ft/min climb rate. The outside temp was right around 50F.

 

[denverpilot]

That does make sense, however just before I encountered the roughness I was still getting a whopping 300 ft/min climb rate. The outside temp was right around 50F.

Heh. And now you know why a takeoff in a C-150 up here on a summer day is pretty much an emergency procedure.

Put two people on board, and it gets worse. 300 FPM is good!

Don't know what your altimeter setting was, but if it was 29.92, you were at a DA of 9867.5.

Feel lightheaded at all? Any headache later?

 

[FORANE]

Heh. And now you know why a takeoff in a C-150 up here on a summer day is pretty much an emergency procedure.

Put two people on board, and it gets worse. 300 FPM is good!

Don't know what your altimeter setting was, but if it was 29.92, you were at a DA of 9867.5.

Feel lightheaded at all? Any headache later?

Density altitude is just pressure altitude corrected for non-standard temperature. As the temperature in the lung is a constant, we are not affected by ambient air temperature differences as an airplane motor is. In other words, except for slight variation when our body temperature changes, our density altitude is constant for any given pressure altitude regardless of ambient temperature changes.

 

[flyingron]

Density altitude is just pressure altitude corrected for non-standard temperature.

The above is misleading (and in fact incorrect) in a couple of ways. First, it is not a "correction." A correction would indicate implies you're heading towards some true number. In fact, it is not. Second, it's not just a function of temperature. Humidity plays a smaller factor in DA computation.

Part of the premise is correct, that your lungs are a more constant temperature and humidity so the ambient temperature/humidity are less important. The other issue is that diffusion is driven by PRESSURE not by density.

Engines operate based on the number of atoms and hence are driven by density. Diffusion in the lungs is driven by pressure.

 

[Tom-D]

That does make sense, however just before I encountered the roughness I was still getting a whopping 300 ft/min climb rate. The outside temp was right around 50F.[/QUOTE]

Carb ice.. some days you have water you can't see. There are very few places in this world that have zero humidity.

Some days it will take time to collect enough ice to make the 0-200 quit.

Here in Puget Sound when it is misty rain, and 33 degrees Carb Ice will happen at Idle, before you get enough heat in your mufflers to clear it. that is why we start with carb heat on and leave it on until the take off run.

 

[bnt83]

That does make sense, however just before I encountered the roughness I was still getting a whopping 300 ft/min climb rate. The outside temp was right around 50F.[/QUOTE]

Carb ice.. some days you have water you can't see. There are very few places in this world that have zero humidity.

Some days it will take time to collect enough ice to make the 0-200 quit.

Here in Puget Sound when it is misty rain, and 33 degrees Carb Ice will happen at Idle, before you get enough heat in your mufflers to clear it. that is why we start with carb heat on and leave it on until the take off run.

Was flying around out there out of KTIW, in IMC, watching my brother hard at work focused on the navigation and constantly adding power to an O-300 powered 172 not recognizing the sign before I turned on carb heat

 

[EdLarkin]

Why did you keep turning the carb heat off? If you need it, leave it on - it won't hurt the engine.

 

[Aeric]

Heh. And now you know why a takeoff in a C-150 up here on a summer day is pretty much an emergency procedure.

Put two people on board, and it gets worse. 300 FPM is good!

Don't know what your altimeter setting was, but if it was 29.92, you were at a DA of 9867.5.

Feel lightheaded at all? Any headache later?

If I remember correctly, it was 29.95. Not lightheaded, but I'm sure my pulse rate went up a bit.

 

[Aeric]

That does make sense, however just before I encountered the roughness I was still getting a whopping 300 ft/min climb rate. The outside temp was right around 50F.[/QUOTE]

Carb ice.. some days you have water you can't see. There are very few places in this world that have zero humidity.

Some days it will take time to collect enough ice to make the 0-200 quit.

Here in Puget Sound when it is misty rain, and 33 degrees Carb Ice will happen at Idle, before you get enough heat in your mufflers to clear it. that is why we start with carb heat on and leave it on until the take off run.

Well, I see now that ice can form when it's least expected. And it wasn't just a little roughness, it was a very substantial power loss.

 

[Aeric]

Why did you keep turning the carb heat off? If you need it, leave it on - it won't hurt the engine.

I wanted as much power as possible, if the ice would have melted and stayed away after a short application of carb heat. This didn't happen, so I left it on longer and decided to cancel the climb and the picture session.