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Carb Ice

Started by lbpa18, September 13, 2010, 11:07:47 PM

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Is the PS-5B carb susceptible to carb ice or not? Guidance is conflicting. 

Ken Berger

 No, the PS-5B is not likely to be susceptible to carb ice in the typical conditions that generate it with other planes.  I'm sure it is possible, but not something you will likely encounter.  Just one flight in the increadible heat generating GO480/Helio will dissuade any thought of carb ice.

Ray Dorsey

Iv'e Had an issue , with high humity on the Kusko. were during runup the carb heat
cleaned up the checks,  not sure if it was ice or not hot for the takeoff .this is on floats

Doug Johnson

I found a Graph and this information over at the back country flying site that it shows a tiny area when the Dew Point is between 40 and 50 degrees and Humidity 68 to 70 percent  that carb ice is probable. Really not worth worrying about. seems to me.

In regard to the PS-5C Carburetor.  There is not a thing wrong with them.  They ARE different when compared to float carburetors, however.  They require fuel pressure in order to work.  They will work regardless of the attitude, and do not typically suffer from carburetor ice.  All the Cessna L-19's are equipped with the PS-5C carburetor, and there are several hundred still flying, and flying fine I might add.  It is a rather complicated beast when compared to a float carb, but quite reliable.
WHy did Helio choose the pressure carb?? Seems to be many more float type carb. planes in operation than the pressure carb, must be some reason for that?? I am not knocking the pressure carb just wondering why it is not very popular or if has any advantage over the standard carb on the helio?? Not to mention the cost of rebuild parts.

Actually it was Lycoming that selected pressure carbs (just look in your Lycoming manuals) for use with the GO series engines, not Helio although it would make sense with the design goals of Helio at the the time to be as simple to operate as possible for the pilot... the pressure carb provides automatic altitude mixture control and enhanced cooling with a more efficient power enrichment circuit than most float type carbs for better cylinder cooling at full throttle which was likely Lycoming's main reason for selecting them. These are great carbs both in function and reliability, yes they are more expensive to overhaul and also require a 337 at overhaul as any pressure carb is considered a major repair at overhaul and one should not defer maintenance as one might on a float carbs.
In response to the above post, it will also be interesting to note that the "pressure carbs" were initially designed for use in the Twin Bonanza and Aero Commander. Lycoming developed these for high speed and moderate altitude ops. Most normally aspirated aircraft with geared engine technology brought to you by Lyc. had Bendix design the carb. There are plenty of them, and can be had for reasonable prices as long as they have been "green tagged" and bench tested.
There is a nice little Bendix PS series manual that is available .  When the carb is adj. per conditions. it works better then a float carb ,better mileage per conditions.

See attached Graph


This was my post at back country..

Doug Johnson

Mr. Helio

I apologize for not giving you proper credit. In the future for anything I copy and post I will  Credit the poster and site when posting it.

In my own defense I had copied this for my own information and hadn't intended to repost it. I've been reading old posts here and saw the the post on Carb ice and your post at back country was so well written and informative I thought it belonged over on this site as well. Also I couldn't remember where I found it at back country so I couldn't
go back and find who the original poster was.

There was some more information on Pressure carbs I believe it was posted I think by Louise at the Supercub site I hadn't intended to repost it but in the future in my own notes I'll include who and where the information came from.


I apologize again.



Hi Doug,

No need to apologize, it was meant for public content and discussion, by all means feel free to post way. I got that info from another site anyway, I posted it for everyone's benefit.