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Carb ice on a 912
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lgold(at)quantum-associat
Guest

Posted: Tue Feb 10, 2009 5:48 pm Post subject: Carb ice on a 912

I had to fly the other day in my Zenith 701 when OAT and dew point were both Zero-degrees. Erring toward caution, I flew high and over landable places since I don’t have carb heat.   

This flight got  gray matter going. I have heard that the 912ULS isn’t very prone to icing but would like a more definitive answer to the carb icing prospects in a 912ULS that is inside a cowling. How important is it to have carb heat if you only fly high mountains in summer months?  

Les  

       [quote][b]

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Tue Feb 10, 2009 6:33 pm Post subject: Re: Carb ice on a 912

The majority of 912ULS's in the world or USA don't have carb heat. Because of the variable throat slide the Bing 64's are not prone to carb ice. Some say they have had it, but there are several well authored articles looking for anyone to actually prove they really had carb ice. I have posted these articles from the aviation world and well known authors on other sites before. There will be people who say they had it and pulled carb heat on and the roughness went away, but other situations can cause engine roughness. The aviation people are still looking for someone to prove carb ice in the 912ULS.

Carb heat in in many planes using the 912 is more of a recent development over the last several years. The 912 has been around since late 1989. They haven't been falling out of the air from carb ice and they fly in every environment in the world. There are after market carb heating units for the carbs. One is electric and another hot coolant. 



Is it impossible well:

"Never say Never"

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

lgold(at)quantum-associat
Guest

Posted: Tue Feb 10, 2009 10:35 pm Post subject: Carb ice on a 912

Thanks Roger,

Les



Do not archive



--

craig(at)craigandjean.com
Guest

Posted: Wed Feb 11, 2009 12:19 am Post subject: Carb ice on a 912

But feeding cool air from outside the cowl gives you more power than the

usual set-up of a filter on each carb drawing warm air from inside the cowl.

How much I can't say. But I'm glad my Skyshop FWF kit for my Zenith 701 came

with the Rotax air box because with my home field at 6300 feet I can use all

the power I can get.



-- Craig



--

ptag.dev(at)tiscali.co.uk
Guest

Posted: Wed Feb 11, 2009 1:07 am Post subject: Carb ice on a 912

Hi! Les.  

I can’t help with the situation on the 912ULS but you say that you usually fly high and over mountains presumably you will at some time of the trips be descending?. If you get a problem it would be descending on a low power setting into humidity at low altitude. You really need to seek out a graph which has been circulating which helps identify the flight envelopes where icing is most likely.  

It is humidity which is the ogre in this problem .  

Unfortunately I can’t point you where to find the graph.  

I have a 914 Turbo which heats the intake charge much more than is healthy for the engine but also have an intercooler which drops the intake temp by 25 deg in the winter and 20 deg in the summer, however I have never seen the throat temp less than 6 deg.  

Regards  

Bob Harrison G-PTAG Europa  

   

--

grahamsingleton(at)btinte
Guest

Posted: Wed Feb 11, 2009 4:46 am Post subject: Carb ice on a 912

Roger Lee wrote:

 	  Quote: 	
		   



 Carb heat in in many planes using the 912 is more of a recent development over the last several years. The 912 has been around since late 1989. They haven't been falling out of the air from carb ice and they fly in every environment in the world. There are after market carb heating units for the carbs. One is electric and another hot coolant. 



 Is it impossible well:

 "Never say Never"

 --------

 Roger Lee

Roger
	


Agree, never say never! The UK Rotax agent has photographs of ice in a 

Bing carb on a 912, (Nigel Beale) He developed the hot coolant carb heat 

which I think makes the engine run better anyway, helps to evaporate the 

fuel drops and give better distribution. Check your EGTs, they swap 

around with different throttle settings due to the bends in the inlet 

manifold

Graham

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Wed Feb 11, 2009 5:01 am Post subject: Re: Carb ice on a 912

Les,



I'm one who knows without a doubt that I've had carb ice in more than one of my 912UL engines. It can't be proven without equipping the engine with a "carb ice detector" because once you've landed and removed the air cleaner and disassembled the carb while the hot engine was melting the ice that was there, it is gone. 



 I've been flying since 1966 long before Rotax was making aircraft engines and have had carb ice on many different aircraft over the years and know how the engine behaves when it has carb ice. I live in a somewhat humid area and have experienced definite carb ice on a cowled 912UL without airbox twice. Catching it early, I've been able to clear the ice by cycling the throttle from full to idle and back a few times. Apparently raising and lowering the slide while opening and closing the throttle valve is sufficient to break it up when caught early enough. The Bing 64 carbs are less likely to encounter carb ice than many other types of carbs but they are not immune to it. It is infrequent enough that I do not consider carb heat a requirement for me. Infrequent is not that same as non-existent. 



Following is a link to a probability chart for atmospheric conditions that are conducive to carb ice. 



http://www.ez.org/carb_ice.htm



If you live in Arizona or other part of the SW or other arid desert areas, you will probably never encounter carb ice because the atmospheric conditions that are conducive to carb ice are unusual events, compared to other areas. In the eastern part of the US and other humid areas of the world a 912 engine can have carb ice. 



Notice on the chart that really cold temps are less prone to carb ice than moderate temps.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

grahamsingleton(at)btinte
Guest

Posted: Wed Feb 11, 2009 5:45 am Post subject: Carb ice on a 912

Thom Riddle wrote:

 	  Quote: 	
		   



 Les,



 I'm one who knows without a doubt that I've had carb ice in more than one of my 912UL engines. I

 If you live in Arizona or other part of the SW or other arid desert areas, you will probably never encounter carb ice because the atmospheric conditions that are conducive to carb ice are unusual events, compared to other areas. In the eastern part of the US and other humid areas of the world a 912 engine can have carb ice. 



 Notice on the chart that really cold temps are less prone to carb ice than moderate temps.



 --------

 Thom Riddle



   

Les
	


Spot on! You won't get ice with dry air. Humidity is the problem. 

Nigel's hot water heater works well

Graham

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Wed Feb 11, 2009 6:15 am Post subject: Carb ice on a 912

 	  Quote: 	
		  From what I've read about the Bing carbs, the possibility of carb icing

increases with the use of an airbox.  Fortunately most of the engines with
	


the airbox also have carb heat.  Past posts have described icing but always

with the airbox...  Go figure!



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Wed Feb 11, 2009 7:04 am Post subject: Carb ice on a 912

I think there is one of those graphs in the Cessna 172 POH.   

   

Noel  

       

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of Robert C Harrison

 Sent: Wednesday, February 11, 2009 5:36 AM

 To: rotaxengines-list(at)matronics.com

 Subject: RE: Carb ice on a 912  

  

  

   

Hi! Les.  

I can’t help with the situation on the 912ULS but you say that you usually fly high and over mountains presumably you will at some time of the trips be descending?. If you get a problem it would be descending on a low power setting into humidity at low altitude. You really need to seek out a graph which has been circulating which helps identify the flight envelopes where icing is most likely.  

It is humidity which is the ogre in this problem .  

Unfortunately I can’t point you where to find the graph.  

I have a 914 Turbo which heats the intake charge much more than is healthy for the engine but also have an intercooler which drops the intake temp by 25 deg in the winter and 20 deg in the summer, however I have never seen the throat temp less than 6 deg.  

Regards  

Bob Harrison G-PTAG Europa  

   

--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Feb 11, 2009 7:49 am Post subject: Re: Carb ice on a 912

I have Nigel's carb heater system instead in my humid area of the

NE USA.  Unlike Cessna carb heat, it does not heat the inlet air, only the

metal carb body, so there is little to no performance hit.  It also

weighs very little.  I would certainly install it again if I were starting

over.



From my week in Kingman, Az last summer, I can see how it would

be hard to find icing condx in the summer (9) months of the year in Az.

_________________
Ira N224XS

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Wed Feb 11, 2009 8:00 am Post subject: Re: Carb ice on a 912

You can't apply standard icing issues to a 912ULS with the [b]variable throat[/b] carb because those studies are done with a fixed throat carb. If any of you have a picture or any proof please post it. There are several aviation authorities that would like to see this. I will try to dig back up those articles. I know what the conditions are that cause the problem, but we still don't see any 912ULS engines quitting because of carb ice. I haven't read any FAA investigations laying the blame on carb ice. These engines have been flying in all parts of the humid world (hot and cold) for decades with no carb ice heater.



The variable throat is still the key help.

If you have some proof please post it so I can send it on to the aviation authorities.

I don't believe it is impossible, just so highly unlikely no to ever worry about.



If you are flying I wouldn't lose any sleep over it. I have flown all over the country with a 912 ULS from sea level to 16K, from 0F-115F and 

7%-95% humidity, rain and snow and have never had a problem.If you really think about so do all of you fly in these conditions because you live all over the world and we fly and don't have any issues. You shouldn't always think because your engine had a rough moment that it was carb ice.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Wed Feb 11, 2009 8:29 am Post subject: Re: Carb ice on a 912

Roger,

No one is arguing that carb ice is unlikely with the variable venturi type carbs.  I stated that myself in my posts on this subject both today and in previous posts. I've also stated that without a carb ice detector installed in the carb there can be no scientific proof that ice actually formed in the carb. This statement applies to all carburetors, not just Bing 64. The closest thing to proof one can get without an ice detector is with a manually controllable carb heat device, like those on virtually all GA aircraft engines. When the engine behaves as if the carb is icing, apply this manual carb heat and see the results which are described in virtually every GA aircraft POH built in the last 40 years or so. To my knowledge, no one has "proven" that carb ice existed in these GA aircraft engines without a carb ice detector but by the same token nobody disputes it is happening without said proof.



Absence of proof (carb ice detector) is not absence of evidence, regardless of whether you are talking about a conventional GA aircraft engine carburetor or a variable venturi carburetor.



Your travels all over the country including humid conditions without experiencing carb ice is not proof that sometimes some Bing 64s do ice up. As I've stated multiple times. I rarely (not the same as never) get carb ice in my Bing 64 carbs but it does happen occasionally; in my case twice in the last eight years of flying 912 engines. This is based on the distinctive symptoms that accompany carb ice and the elimination of those symptoms by the method I already described. BTW, are you aware that the Diamond Katana, type certificated airplane with Rotax 912 certificated engine is equipped with manual carb heat? 



If you insist on proof that a Bing 64 carb has actually iced up, I must ask for similar proof from you that it CANNOT ice up. Works both ways.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

Gilles.Thesee(at)ac-greno
Guest

Posted: Wed Feb 11, 2009 9:17 am Post subject: Carb ice on a 912

Thom Riddle a écrit :

 	  Quote: 	
		   BTW, are you aware that the Diamond Katana, type certificated airplane with Rotax 912 certificated engine is equipped with manual carb heat? 

Thom and all,
	




Diamond and some others have chosen the easiest way : implement the carb 

heat systems specified in the FAR/JAR 23.

No problem with red tape, no problem with the majority of pilots who 

have only heard of Lyco/Conti engines.



Now the question might be,  is this carb heat efficient or not, do 

others way to prevent carb ice exist ?

To my knowledge, no one has a clear idea as to when, how, under what 

conditions the Bing carburetors do ice up and deice.



The only thing I know for sure, is that ice cannot possibly build up in 

a warm carb body, and our own carbs do run warm. Are our carb throats, 

needles, jets etc. warm enough, I don't know.

Are the off-the-shelf electric or water heating devices efficient, I 

don't know either.



Bottom line, if one builds with the inspector's approval on mind, do put 

a carb heat devised for a Marvel carb, he'll be happy.

If one builds for maximum safety, the question is still open.

Best regards,

-- 

Gilles

http://contrails.free.fr

pjeffers(at)talktalk.net
Guest

Posted: Wed Feb 11, 2009 9:55 am Post subject: Carb ice on a 912

In the UK we probably fly in more potentially icing conditions than in most

other locations.

I fly my Europa with a 912ul engine with plenum chamber fitted and no carb

heater of any kind.  I now have some 1200 hours on the aircraft and can

definitely affirm that we do experience what we take to be carb icing. Yes

probably carb icing because it always and only occurs in high humidity

conditions.  I have found it to be fairly predictable, to the extent that I

can warn my passengers in advance when I expect it to occur and it usually

does. The symptoms are not the same as those experienced on

Continentals/Lycomings where a slow almost imperceptible loss of power with

constant throttle is observed.

On the 912 the clue is a short period (1 or 2 seconds) of rough running

which then clears to normal running followed a few moments later by the same

symptoms presumably the other carb.

The whole sequence will then be repeated several minutes later (assuming you

do nothing about it).  I find that warming the engine by making it work ie

climbing or accelerating for a few minutes will delay a further event by

some considerable length of time if not the rest of the flight.

The other solution is a carb heater. The best is that which uses engine

coolant to warm the carb body.



Pete Jeffers



--Original Message-----

From: owner-rotaxengines-list-server(at)matronics.com

[mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of Thom

Riddle

Sent: 11 February 2009 16:29

To: rotaxengines-list(at)matronics.com

Subject: Re: Carb ice on a 912






Roger,

No one is arguing that carb ice is unlikely with the variable venturi type

carbs.  I stated that myself in my posts on this subject both today and in

previous posts. I've also stated that without a carb ice detector installed

in the carb there can be no scientific proof that ice actually formed in the

carb. This statement applies to all carburetors, not just Bing 64. The

closest thing to proof one can get without an ice detector is with a

manually controllable carb heat device, like those on virtually all GA

aircraft engines. When the engine behaves as if the carb is icing, apply

this manual carb heat and see the results which are described in virtually

every GA aircraft POH built in the last 40 years or so. To my knowledge, no

one has "proven" that carb ice existed in these GA aircraft engines without

a carb ice detector but by the same token nobody disputes it is happening

without said proof.



Absence of proof (carb ice detector) is not absence of evidence, regardless

of whether you are talking about a conventional GA aircraft engine

carburetor or a variable venturi carburetor.



Your travels all over the country including humid conditions without

experiencing carb ice is not proof that sometimes some Bing 64s do ice up.

As I've stated multiple times. I rarely (not the same as never) get carb ice

in my Bing 64 carbs but it does happen occasionally; in my case twice in the

last eight years of flying 912 engines. This is based on the distinctive

symptoms that accompany carb ice and the elimination of those symptoms by

the method I already described. BTW, are you aware that the Diamond Katana,

type certificated airplane with Rotax 912 certificated engine is equipped

with manual carb heat? 



If you insist on proof that a Bing 64 carb has actually iced up, I must ask

for similar proof from you that it CANNOT ice up. Works both ways.



--------

Thom Riddle

Buffalo, NY

http://riddletr.googlepages.com/sportpilot-cfi

http://riddletr.googlepages.com/a%26pmechanix





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p 29764#229764





Checked by AVG - www.avg.com 

17:44:00

craig(at)craigandjean.com
Guest

Posted: Wed Feb 11, 2009 10:14 am Post subject: Carb ice on a 912

But the same Bing carb (at least style) is fitted on Jabirus and their FWF

kits routinely include carb heat.



-- Craig



--

grahamsingleton(at)btinte
Guest

Posted: Wed Feb 11, 2009 10:15 am Post subject: Carb ice on a 912

Thom Riddle wrote:

 	  Quote: 	
		   



 Roger,

 No one is arguing that carb ice is unlikely with the variable venturi type carbs.   This is based on the distinctive symptoms that accompany carb ice and the elimination of those symptoms by the method I already described. BTW, are you aware that the Diamond Katana, type certificated airplane with Rotax 912 certificated engine is equipped with manual carb heat? 



 If you insist on proof that a Bing 64 carb has actually iced up, I must ask for similar proof from you that it CANNOT ice up. Works both ways.



 --------

 Thom Riddle

   

Thom
	


You are right. I have seen photographs showing carb ice, taken by Nigel 

Beale, <http://www.skydrive.co.uk> at least ten years ago. It does happen.

He used them to help market his carb heater.



What more proof do you want Roger?



Graham

Gilles.Thesee(at)ac-greno
Guest

Posted: Wed Feb 11, 2009 10:21 am Post subject: Carb ice on a 912

Craig Payne a écrit :

 	  Quote: 	
		   But the same Bing carb (at least style) is fitted on Jabirus and their FWF

 kits routinely include carb heat.

   


	


What is not sure is, did they do their homework and conducted a thorough 

icing study, or did they do like others and install a Lyco carb heat ?

Now a Jabiru quitting in flight due to carb ice is something unheard of  



Best regards,

-- 

Gilles

http://contrails.free.fr

craig(at)craigandjean.com
Guest

Posted: Wed Feb 11, 2009 11:05 am Post subject: Carb ice on a 912

Doesn't that make sense? Engines with air boxes are drawing cool air from

outside the cowl. Engines without are drawing warm air from under the cowl.

Without an air box carb heat is essentially always on.



-- Craig



--

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Wed Feb 11, 2009 12:03 pm Post subject: Carb ice on a 912

As I have been reading the mail on this thread something came to mind...  

As a Kid I owned a 69 Rover SC 2000 car complete with the side draft SU

carb...  I eventually swapped out a few parts and turned it into  a TC (

Twin carb )  Today I can't remember ever seeing a heat stove hooked up to

that carb.  I also don't remember a heat stove on any of the Jags, minis or

even the couple of RR that I had the chance to peek under the bonnet.  If

those cars can work for decades without carb heat I guess the 912 will too

with the similar bing carb..



Later I had a Pontiac Safari Station wagon with a 305 (terrible engine) for

some reason the scat tube form the heat stove to the air cleaner had been

removed.  Almost every time it rained I would have carb ice but at that time

I didn't know what it was... until the day the throttle froze open.  As was

mentioned about taking apart the air cleaner and having a look down the

throat of the carb by that time a lot of the ice had melted.  I wasn't long

hooking up the heat stove again.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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