I got Carb Ice

[Kyle Boatright]

This morning, I was attempting an early departure and there was fog in the vicinity of the airfield (the field is adjacent to a river). Some parts of the runway were fogged in, others were not. I was in the runup area waiting for temps to come up and the RPM began sagging. They probably dropped from 1500 to 1300 before I figured out the cause - carb ice.

In hindsight, it isn't surprising at all - very high relative humidity and a low power setting are two of the common causes.

So, to sort it out (before I realized it was carb ice) I checked both ignitions, then had the aha moment and pulled the carb heat knob. I have the standard Van's carb heat and it cleared the ice within a very few seconds. I was impressed with the performance because I've always wondered about the effectiveness of the system.

Anyway, I thought it was interesting and that I'd share..

[arffguy]

That is interesting because I was led to believe that the RV's had a somewhat weak carb heat system. The one I have flown in the most seems to have almost no drop at all during the run-up. Thanks for the info.

[terrykohler]

..and it certainly isn?t an anti-ice device. On the ground when you?re not ramming air into the front end is nothing like you might encounter while flying, so it was a good lesson/heads up.
In icing conditions and especially in visible moisture (IMC) pull carb heat and turn on pitot heat beforehand. While most pitot heaters will melt ice when loaded, don?t count on your carb heater doing the same.
You should also be aware that the biggest danger area is usually near the cloud tops. When climbing with the heater on,you?re going to have less H.P. available when you need it most. If you?re flying, think about possible exit strategies and the possible risk in each course. It might be better to deal with turbulence down low where the temps are higher then looking for a smooth ride where ice is likely.
Terry, CFI
RV9A N323TP

[mbauer]

Here in Alaska need to watch for carb ice all the time.

Found a couple of charts that help, great to use before heading out for the pre-flight:

Temp in deg F:


Temp In Deg C:


Reading the probable cause section, noticed a few carb ice induced accidents. The charts above provide a good visualization of what to expect for certain flights.

Had an interesting experience with carb icing in the summer once in my old Piper Cherokee 140. By the time heat was applied the RPM was below 2000. Lots of sputtering before finally ran smooth again.

Best regards,
Mike Bauer

[Sam Buchanan]

Originally Posted by Kyle Boatright

This morning, I was attempting an early departure and there was fog in the vicinity of the airfield (the field is adjacent to a river). Some parts of the runway were fogged in, others were not. I was in the runup area waiting for temps to come up and the RPM began sagging. They probably dropped from 1500 to 1300 before I figured out the cause - carb ice.

In hindsight, it isn't surprising at all - very high relative humidity and a low power setting are two of the common causes.

So, to sort it out (before I realized it was carb ice) I checked both ignitions, then had the aha moment and pulled the carb heat knob. I have the standard Van's carb heat and it cleared the ice within a very few seconds. I was impressed with the performance because I've always wondered about the effectiveness of the system.

Anyway, I thought it was interesting and that I'd share..

I've had carb ice in the RV-6 (O-320) under the same conditions a couple of times and the standard carb heat cleared it quickly. I'm thankful I don't have to deal with it like I do with the O-200 in the Fokker replica...that thing is a bona-fide ice maker. Initial taxi has to be conducted with full carb heat or it will choke on ice.

[catmandu]

While we're all here, has anyone experienced carb ice in the landing pattern in their Lycoming powered RV?

[Infidel]

Nope, not yet. But when the temp & dew point are close together I'll use carb heat & avoid the chances.

[Vlad]

Originally Posted by catmandu

While we're all here, has anyone experienced carb ice in the landing pattern in their Lycoming powered RV?

Once. On purpose some years ago staying in close pattern and accumulating. It progressively became rougher and application of carb heat followed by landing didn?t improve much. I suspect the air filter got finally packed with frozen sleet. Not enough time to melt it at low rpm. Pitot tube still had a 1/8 passage, leading edges got 1/8 but prop was surprisingly clear.

[David Paule]

My Cessna 180 had an ARP carburetor ice detector. That thing really works!

It gives reliable warnings of ice at the very onset.

It works by having a light and probe in the carb throat to see actual ice. Ice isn't all or nothing, it starts small and grows.

I like the device so much that I bought one for my RV-3B project, too.

https://www.aircraftspruce.com/catal...s/icedetect2.p
hp?clickkey=5526900

My only connection is as a very satisfied customer.

Dave

[Dbro172]

Originally Posted by catmandu

While we're all here, has anyone experienced carb ice in the landing pattern in their Lycoming powered RV?

Yes, after touch n go. Definite cough on departure, swallowing the ice buildup on low power decent.

On the other hand, carb heat improves my mixture distribution and has very little effect on power. Really no differenece if i fly around with half carbs heat on at all times, actually better fuel/air mixture.