Backcountry Pilot • 520 or 470 carb ice

520 or 470 carb ice

Lycoming, Continental, Hartzell, McCauley, or any broad spectrum drive system component used on multiple type.
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Mon Apr 13, 2015 11:13 am

Re: 520 or 470 carb ice

n6zt wrote:I had a PPONK on a C-180 on floats here in Seattle. Many trips up north and never had any more of a problem with Carb Ice than on my0-470. Steve K did do his magic on the carb. when the engine was built. I would certainly discuss with Steve.


Same for me…have flown all over the west both North and South and never had a problem with icing in the Pponk 520. Steve Knopp did the same for my carb as well. Curious about the induction tube size you guys have that are dealing with ice? The old 470 had icing a couple times. Hmmm

AKT
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Mon Apr 13, 2015 2:43 pm

Re: 520 or 470 carb ice

Another thing; Steve does do adjustments to venturi and jets; also, small crossover tube. Large one makes ice.
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Mon Apr 13, 2015 3:02 pm

Re: 520 or 470 carb ice

I got small cross over tube.
I doubt Knopp is doing anything more "magic" with carbs in his shop vs. ones modified per the stc by an authorized Pponk build shop...
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Mon Apr 13, 2015 5:23 pm

Re: 520 or 470 carb ice

Friend had a ponk 520 first carb replaced at 30 hrs also Cyls of same time replaced rod bearings oil pump . Still problems at 90 hrs engine removed sent to another shop oh. Runs good now 3th carb a Ma 5284 470u. Both other where ma 4893 470r carb. Steve would do nothing for warranty problems from day 1. The 5284 tagged but I doubt anthing was don 2 carb
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Mon Apr 13, 2015 7:42 pm

Re: 520 or 470 carb ice

Question as most everything I have flown was either injected, turboed, or round, I know all the round motors have carb temp quages, 985-PZL-jake. they were very accurate as if there was moisture and the temp in the carb was below freezing, you got ice, Seems the easiest cure is a carb temp gauge?
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Tue Apr 14, 2015 4:34 pm

Re: 520 or 470 carb ice

![/quote]


My experience has been the opposite. I've had fewer icing problems with mogas than avgas (lycoming o-540/b4b5), though I didn't realize that until I read your note above. Did the book say about the physics of why avgas is supposed to be worse?[/quote]

My copy of the book isn't convenient, but I did a quick search and came up with this:

Due to its higher volatility, MOGAS is more susceptible to the formation of carburetor icing. In severe cases, ice may form at outside air temperatures up to 20°C higher than with aviation gasoline (AVGAS).
(Source: Transport Canada Aeronautical Information Manual (TC AIM) Section AIR 2.3.)

There is a better explanation here: http://www.tc.gc.ca/media/documents/ca- ... /mogas.pdf but I couldn't copy and paste the relevant segement on page 3
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Tue Apr 14, 2015 5:01 pm

Re: 520 or 470 carb ice

^^ very interesting. I have yet to have any carb ice issues in my 180 with a 0-470R. Ever had any on my 0-320 or 0-200 either. Burning mostly moGas with the odd tank of avgas now and again in all 3. I do live in a fairly drive climate though.
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Tue Apr 14, 2015 5:32 pm

Re: 520 or 470 carb ice

albravo wrote:There is a better explanation here: http://www.tc.gc.ca/media/documents/ca- ... /mogas.pdf but I couldn't copy and paste the relevant segement on page 3


Thanks much. I guess it's just coincidence that I've had better luck with it, I'll have to think about why that might be since the explanation in the manual does indeed make good sense...
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Tue Apr 14, 2015 5:57 pm

Re: 520 or 470 carb ice

I have had lot's of carb ice on other Cessna's I have owned but been flying my PPonk for 4 years all over the country - no ice yet.
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Tue Apr 14, 2015 6:34 pm

Re: 520 or 470 carb ice

albravo wrote:There is a better explanation here: http://www.tc.gc.ca/media/documents/ca- ... /mogas.pdf but I couldn't copy and paste the relevant segement on page 3


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Mon Oct 24, 2016 1:28 pm

Re: 520 or 470 carb ice

Download a copy of this. A couple of the middle chapters get into the O-470's crappy intake design, lack of inherent heat, and why managing partial heat can actually improve the fuel vaporization and reduce fuel flow. This has a ton of other good info on the Skylane as well.
http://www.theskylanepilotscompanion.com/

I haven't had an icing problem with a stock 470 here in CO, however have been flying a rental 182R with a Texas Skyways 280HP conversion lately and have encountered carb ice on multiple occasions with that bird (always interesting when you're trying to claw your way over Rawlins Pass in a bit of a downdraft). I have not attempted the carb heat-for-vaporization thing mentioned in that book yet, but certainly will give it a go.
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Mon Oct 24, 2016 7:07 pm

Re: 520 or 470 carb ice

Some make ice and some don't, for seemingly no rime nor reason. 30 years in a 180J with an O-470S with virtually no icing, nearly 10 years with a TX Skyways O-520 in the same airframe and still no icing.
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Tue Oct 25, 2016 10:22 am

Re: 520 or 470 carb ice

This may be an asinine question, but...

Is there any sort of a bench test that can be done by an engine shop to test for carb icing tendencies? Not necessarily an exact diagnostic, but just to get a handle on things?

It's almost 2017, so is there any modern software for Continental venturi simulations, etc. that shops / builders can use?

I know it's all part of a complex chain of different factors, but still ...

Just curious,,,,

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Tue Oct 25, 2016 12:17 pm

Re: 520 or 470 carb ice

Denali wrote:This may be an asinine question, but...

Is there any sort of a bench test that can be done by an engine shop to test for carb icing tendencies? Not necessarily an exact diagnostic, but just to get a handle on things?

It's almost 2017, so is there any modern software for Continental venturi simulations, etc. that shops / builders can use?

I know it's all part of a complex chain of different factors, but still ...

Just curious,,,,

Image


Good question...don't know if one exists...but one could be devised. Not sure if would be a manageable solution due to the fact that you'd have to build a precise model with ANSYS CFD (like you have pictured) or with something like Solidworks fluid (I have no experience with SW).

My take is that its geometry, velocity, humidity and thermally driven....a lot of variables. Maybe a simple test would be to build it in SW based on two o470's on a bench. One engine a known "icer" and the other one not. Maybe set those two as the upper and lower limits. Seems reasonable that a small matrix of relative humidity's, temps and power settings (velocity) could yield a set of bench guide lines in predicting it. Short of CFD modeling....I bet some guys back in the 30's with slide rules came up with a similar test and resulting matrix for our POH. Interesting stuff.

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Tue Oct 25, 2016 4:32 pm

Re: 520 or 470 carb ice

I threw this out once before in a discussion like this.

I like these. Let you know positively when ice is building, easy to cure.

http://www.aircraftspruce.com/catalog/i ... etect2.php

They have been very reliable for me. I have put one in any 470/520 that I have had.

Gary
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Thu Oct 27, 2016 3:34 pm

Re: 520 or 470 carb ice

I haven't had much trouble with carb ice in the 100 hours I've flown my C180B since it was P-Ponk'd; I think the reason is this:

Image

I took this picture this AM 48 deg F at 3000 ft; 92% humidity on the ground. Small crossover tube.
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Fri Oct 28, 2016 7:42 am

Re: 520 or 470 carb ice

168 deg F carb temp? I'd like to put a sensor in mine, too.


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Fri Oct 28, 2016 2:42 pm

Re: 520 or 470 carb ice

Wow! I've never had carb temp that high without the carb heat pulled. I'm not even sure that it'll go that high with it pulled. When I get to flying again any day now (FAA called for more info, which I faxed to them 2 days ago), I'll have to check it out. I regularly look at the carb temp in flight, but once I've pulled it for descending to land, I don't typically look at it again.

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Sat Oct 29, 2016 6:56 am

Re: 520 or 470 carb ice

I wonder if there is a test that would prove my theory that running E10(10% ethanol blend) prevents the formation of ice. It is like having de-icing fluid mixed in the fuel.
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Sat Oct 29, 2016 4:32 pm

Re: 520 or 470 carb ice

180Marty wrote:I wonder if there is a test that would prove my theory that running E10(10% ethanol blend) prevents the formation of ice. It is like having de-icing fluid mixed in the fuel.


Probably better to try it with Prist for 100LL. I used that last winter, but I couldn't tell whether it made any difference, because although I've had a few carb icing experiences with this airplane, it's been very seldom--none last winter, though. It's kind of a pain to use, because invariably the wind is blowing, the temp is pretty cold, and balancing the fuel nozzle in one hand and the Prist can in the other is a bit of a juggle--it has to be sprayed in at the same time that the refueling is taking place.

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