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Carb Heat with 912ULS

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beachyjeff(at)juno.com
Guest

Posted: Tue Jan 29, 2008 2:49 pm Post subject: Carb Heat with 912ULS

I have a Rotax 912ULS with the Rotax airbox. My cold air is supplied via

a NACA inlet on the cowl then through a filter and on to the airbox. Carb

heat is via a flap in the airbox which pulls unfiltered air from a

muffler cowl to the airbox. I understand that the 912 series is not prone

to icing, but I cannot find anything in the Rotax literature offering

suggested use of carb heat. So, experts, when do I use carb heat with my

912ULS? Only if engine is running rough and icing is suspected? In

landing patterns like a Cub? All those using the Rotax airbox with a 912,

I would appreciate your experience and suggestions. Thanks!



Jeff Beachy

Zenith CH701

jnjkimbell(at)hotmail.com
Guest

Posted: Tue Jan 29, 2008 3:44 pm Post subject: Carb Heat with 912ULS

Jeff, I have the carb heat and having used it close to two hundred times, I did indeed have ice one time.  That happened to be during a time when I was doing stalls and slow flight.  I live in very high humidity Fl.  so on downwind at slightly reduced rpm i pull on Carb heat to see if there are any problems. so far none at that point on final I push in so i will get full rpm if needed.     Joe

  > To: rotaxengines-list(at)matronics.com

[quote] Date: Tue, 29 Jan 2008 17:45:41 -0500

 Subject: Carb Heat with 912ULS

 From: beachyjeff(at)juno.com

 --> RotaxEngines-List message posted by: Jeffrey A Beachy <beachyjeff(at)juno.com>

 I have a Rotax 912ULS with the Rotax airbox. My cold air is supplied via

 a NACA inlet on the cowl then through a filter and on to the airbox. Carb

 heat is via a flap in the airbox which pulls unfiltered air from a

 muffler cowl to the airbox. I understand that the 912 series is not prone

 to icing, but I cannot find anything in the Rotax literature offering

 suggested use of carb heat. So, experts, when do I use carb heat with my

 912ULS? Only if engine is running rough and icing is suspected? In

 landing patterns like a Cub? All those using the Rotax airbox with a 912,

 I would appreciate your experience and suggestions. Thanks!

 Jeff Beachy

 Zenith CH701> 

   	  Quote: 	
		  [b]

gfmjr_20(at)hotmail.com
Guest

Posted: Tue Jan 29, 2008 3:44 pm Post subject: Carb Heat with 912ULS

Jeff--

   I use the carb heat on my Rotax for all landings, slow flight and if I suspect carb icing. 

  

 George May

 601XL 912s



 	  Quote: 	
		   To: rotaxengines-list(at)matronics.com

 Date: Tue, 29 Jan 2008 17:45:41 -0500

 Subject: Carb Heat with 912ULS

 From: beachyjeff(at)juno.com

 

 --> RotaxEngines-List message posted by: Jeffrey A Beachy <beachyjeff(at)juno.com>

 

 I have a Rotax 912ULS with the Rotax airbox. My cold air is supplied via

 a NACA inlet on the cowl then through a filter and on to the airbox. Carb

 heat is via a flap in the airbox which pulls unfiltered air from a

 muffler cowl to the airbox. I understand that the 912 series is not prone

 to icing, but I cannot find anything in the Rotax literature offering

 suggested use of carb heat. So, experts, when do I use carb heat with my

 912ULS? Only if engine is running rough and icing is suspected? In

 landing patterns like a Cub? All those using the Rotax airbox with a 912,

 I would appreciate your experience and suggestions. Thanks!

 

 Jeff Beachy

&g======================
	


 	  Quote: 	
		   ======

 

 

 


	


Helping your favorite cause is as easy as instant messaging. You IM, we give. Learn more.  [quote][b]

chunk(at)xtra.co.nz
Guest

Posted: Tue Jan 29, 2008 5:12 pm Post subject: Carb Heat with 912ULS

Hi Jeff, good question! There is certainly a divergence of opinion about the 

risk of carb icing with the Rotax 912 series. After suffering 3 forced 

landings (2 with the prop stopped!) with carb icing I decided it was time to 

do something about it. I fly an MCR 01 ULC (Ban-Bi) and the many, mainly 

European owners of this marque do not seem to be affected by carb icing. I 

live in New Zealand and it is a well established fact that our particular 

weather conditions do predispose to carb icing. Most 912 installations here 

do have some sort of carb heat provision - particularly if the carb. intake 

air is sourced from a ram air intake outside the engine cowl. Installations 

where the engine intake air temp is the same as the ambient air temp found 

within a tightly cowled engine compartment usually minimises the risk of 

carb icing even here in NZ.

I have fitted a similar carb heat system as you and it works ok. If I was 

building another aircraft I would fit the system that has hot radiator water 

circulating through a jacket around the carb air intake. Fit it and forget 

about when you need to use it as it is on all the time with no significant 

power loss.

To get back to your question though, in my experience with this sort of carb 

heat set up you need to prevent carb ice forming rather than wait till the 

engine starts running rough and then applying carb heat. Similar to GA best 

practise. In my set-up carb heat is not that efficient that I would rely on 

it melting a big ice build up before the engine quits. If the engine starts 

to run rough best to go to full power for a period, apply carb heat and 

leave it on for the rest of your flight.

The best thing I did on my aircraft was to velcro on to my instrument panel 

an inexpensive indoor/outside digital temperature guage. One sensor is poked 

into the carb airbox which gives me OAT and the other sensor is RTVd on to 

the thoat area of the carb body. This probe will tell me when carb ice is 

starting to build. The heat sink effect of the motor temperature on the carb 

body has this sensor showing 22 - 24 degrees Celcius under normal 

conditions. Given carb ice forming this temp reading will gradually fall and 

if it reads 18 degrees C or lower I can expect to experience the effects of 

carb icing. At this point it will take approx 5 min of carb heat to restore 

temps to normal. The temps given here will vary considerably with each 

particular aircraft and are given here as a guide only. Hope this helps!



Evan Gardiner,

MCR 01 ULC

Subject: Carb Heat with 912ULS

 RotaxEngines-List message posted by: Jeffrey A Beachy <beachyjeff(at)juno.com>



 I have a Rotax 912ULS with the Rotax airbox. My cold air is supplied via  a 

NACA inlet on the cowl then through a filter and on to the airbox. Carb heat 

is via a flap in the airbox which pulls unfiltered air from a muffler cowl 

to the airbox. I understand that the 912 series is not prone to icing, but I 

cannot find anything in the Rotax literature offering suggested use of carb 

heat. So, experts, when do I use carb heat with my 912ULS? Only if engine is 

running rough and icing is suspected? In

 landing patterns like a Cub? All those using the Rotax airbox with a 912, I 

would appreciate your experience and suggestions. Thanks!



 Jeff Beachy

 Zenith CH701



--

Gtblu

Joined: 18 Jul 2006
Posts: 37
Location: Australia

Posted: Wed Jan 30, 2008 3:22 am Post subject: Re: Carb Heat with 912ULS

Great post Evan.

RTVd???? What is that? Presume its attached to outside of throat somehow.



regards gtblu

JimT

Joined: 27 Feb 2006
Posts: 22
Location: Auburn, ME

Posted: Wed Jan 30, 2008 2:47 pm Post subject: Carb Heat with 912ULS

I believe this has been mentioned in the distant past.  The concern was it just doesn't draw enough current

 for an appreciable warm generation.

    

   [/url][url=http://www.ulparts.com/SearchResult.aspx?CategoryID=94]http://www.ulparts.com/SearchResult.aspx?CategoryID=94

 

 

 I once spoke to the shop, and they said "no body has complained about it not working.  The leads are a bit fragile however."  Does anybody have any experience?

 

 

 JIm Timoney

 searey 912S-doing the plumbing (plumbing(at)gmail.com)

 

 

 

 

 

 

 

 

 

 

 

   More new features than ever.  Check out the new AOL Mail! 

  [quote][b]

chunk(at)xtra.co.nz
Guest

Posted: Wed Jan 30, 2008 6:16 pm Post subject: Carb Heat with 912ULS

Thanks! RTV is just a generic name for a silicone based sealant. Make sure 

you choose a heat resistant type - usually colored red. There are several 

different brands of exhaust system sealants or oil-pan gasket sealants out 

there that will work.

Locate a part of the carb body close to the intake throat that provides a 

secure position to secure the temp probe. Place the probe against the carb 

body and apply a liberal coating of RTV over the top of the probe and the 

carb body to hold it in place. Leave 24 hrs. to allow the RTV to cure.



Cheers,

Evan Gardiner



---

Gtblu

Joined: 18 Jul 2006
Posts: 37
Location: Australia

Posted: Wed Jan 30, 2008 6:26 pm Post subject: Re: Carb Heat with 912ULS

Good one. I've got some in the hangar. Did you put another probe onto the thermometer or did it already have two "externals". I f so what breed are they.. I have only seen indoor/outdoor with one internal probe and one extended external.

chunk(at)xtra.co.nz
Guest

Posted: Wed Jan 30, 2008 7:46 pm Post subject: Carb Heat with 912ULS

The one I used was made in China and has '2 channels in/out temp' on the 

front panel. Powered by a flat circular battery similar to a watch battery. 

The thing is that this unit (and probably most other similar products) have 

only one external lead so the outside temp can be read and transfered to the 

unit. The indoor temp is read from the units internal sensor. You need to 

solder a lead long enough to glue the other end of the lead to the carb 

body. It is a few years ago since I did this and I do not remember it being 

a difficult task or needing a thermocouple lead or anything fancy. But that 

may depend on the unit you choose.



Good luck,

Evan Gardiner



MCR 01 ULC 413 hrs.

Sent: Thursday, January 31, 2008 3:26 PM

Subject: Re: Carb Heat with 912ULS

 	  Quote: 	
		   



 Good one. I've got some in the hangar. Did you put another probe onto the 

 thermometer or did it already have two "externals". I f so what breed are 

 they.. I have only seen indoor/outdoor with one internal probe and one 

 extended external.



 --------

 Slepcev Storch

 912 uls 731 hours




	




--

ami(at)MCFADYEAN.FREESERV
Guest

Posted: Thu Jan 31, 2008 3:37 am Post subject: Carb Heat with 912ULS

With some makes of digital thermometer it is possible to buy additional 

probes.

I have these (3 in total) wired through a selector switch. Problem then is 

that the switch has its own resistance and reduces the reading by (in my 

case) 6 deg; but at least this reduction is consistent.



I don't generally see carb body temps less than 20C (Europa Classic, cold 

air supply to carbs., no formal carb heat), unless OAT is well below 

freezing, whilst under-cowl temps in the proximity of the carbs  are about 

10C greater than this.



Elsewhere (Skydrive?) it has been mentioned that a carb body temp of 

anything less than 2C is cause for worry; so not sure who is right on the 

issue of limiting temperatures, and not willing to find out!



Duncan McF.



---

chunk(at)xtra.co.nz
Guest

Posted: Thu Jan 31, 2008 5:16 pm Post subject: Carb Heat with 912ULS

Your point is very valid, it is not so important what the actual normal 

tempereture reading of your carb body is - what the temp guage gives you is 

the ability to recognise that the carb body has, over a short period of 

time, cooled by 4-6 degrees. Under these circumstances the only thing that 

could have caused the carb body to cool that much, that quickly, must be 

that a build up of ice has formed on the carb throat. Time to deal to the 

problem!



Evan Gardiner



MCR 01 ULC



 	  Quote: 	
		   

 <ami(at)mcfadyean.freeserve.co.uk>



 With some makes of digital thermometer it is possible to buy additional 

 probes.

 I have these (3 in total) wired through a selector switch. Problem then is 

 that the switch has its own resistance and reduces the reading by (in my 

 case) 6 deg; but at least this reduction is consistent.



 I don't generally see carb body temps less than 20C (Europa Classic, cold 

 air supply to carbs., no formal carb heat), unless OAT is well below 

 freezing, whilst under-cowl temps in the proximity of the carbs  are about 

 10C greater than this.



 Elsewhere (Skydrive?) it has been mentioned that a carb body temp of 

 anything less than 2C is cause for worry; so not sure who is right on the 

 issue of limiting temperatures, and not willing to find out!



 Duncan McF.


	




--

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

Posted: Thu Jan 31, 2008 11:51 pm Post subject: Carb Heat with 912ULS

Hi! All

I have been passed a Rotax CD which seems to recommend some form of carb

heat when a 914 is fitted with an intercooler (yes, you've guessed it I

have such a combination!)  Whilst I do appreciate that the presence of

moisture and ambient humidity provide a huge range of Carb icing

probabilities I had understood that on a straight turbo combination the

final intake temps are in the 40deg to 60 deg. Fitting the intercooler

does drop the intake temps to approx 16 deg at 10,000ft with ground

ambient 4 deg (all celcius)and the inside of the screen freezing over!

With the air filter directly turbo intake mounted it will be a humongous

task to re-route hot air to the system.

ST Aviation have a metal carb heat electric element (obviously two

needed on the Rotax which "pull" 10 amps when switched on )has anyone

tried these guismos on a Rotax? Alternatively does anyone have

suggestions concerning collection of engine compartment air to provide

carb heat in an icing emergency?

Regards (here we go again!)

Bob Harrison G-PTAG 



--

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