Simviation Forums

I am so ahamed but what does carb heat do.  I fly the DC-3 so much that Ive mastered Cowl Flaps, RPM, Manifold Pressure, and overall engine management, but I have no idea what carb heat is or what it does.  Please help!  Fozzer?

Carb heat is the de-ice for a carburetor. All it does is keep the carburetor warm so ice doesnt form inside and screw up the air fuel mixture you have set.

Papa has got it sorted, Jake...!

I use it on all my piston props, (including radials), fitted with carburetored engines, every time I close the throttle, (reducing speed for a landing, etc).
That is the most dangerous time for ice to appear in your carburettor and block off the air flow, due to the rapid stream of air being forced through the small aperture in the carburettor, (closed),which causes the carburettor body to cool rapidly and any water contained in the air to freeze on the carb'...!
It's always used in the little Cessna 152's for example...

Operating the Heater knob re-routes incoming air past the exhaust pipe, heated, en-route to the carburettor.

Unfortunately engine failure due to carb icing isn't simulated in the Sim...
...maybe in the next version....I hope!

Cheers, Jake... ...!

Paul...(being sensible...for a change... ...!

...just remember, carb heat reduces the power in the engine....so cancel carb heat just before you land...in case you have to perform a go-around when you will need maximum power again....!!!

Sometimes called De-ice and you can hear the engine slur and drop a note if you like, as Paul said. Remember to cancel it or you'll be flying inefficiently.

Sometimes called De-ice and you can hear the engine slur and drop a note if you like, as Paul said. Remember to cancel it or you'll be flying inefficiently.

I dunno, Ben....
Doesn't "De-ice" refer to inflating bladders fitted in the front of aircraft wings to break up any ice forming on them....?...mainly high altitude commercial jets...?
...also heaters on the leading edge of propellers to prevent the formation of ice leading to in-efficiency...?

I think "Carburettor Heat" does just that....heats the carburettor body by inducing hot air... ...!

Paul ...A biker, with a bike fitted with carburettors... ...!
LOL...!

Actually Fozzer, I dont think high altitude jets need them because they fly fast enough that heat is generated on on the leading edge, thus preventing ice buildup.  Thats not to say that a commercial jet cant have ice buildup if they continuously fly through saturated air at slower speeds in temps below freezing, such as a holding pattern. Turboprops on the other hand, that still fly fairly high but not as fast, require them, as do many smaller prop planes.  Todd

Fozzer,

You are thinking of the structural de-ice boots on the leading edges.  Unfortunately structural icing is not modeled in the sim.... so there would be no need for them.  

But I THOUGHT that the carb heat and potential carb icing WERE modeled juast like pitot heat and pitot icing?

best,

...............john

Well, I maybe wrong - (quite likely ) but I assumed that they were all basically one and the same thing. To stop the build up of ice in the engine which could cause the engine to cut. I thouhgt they were just different names. Of course they work slightly differently in different planes (a jet engine is different to a piston one of course), but I thought the principle was the same and that it had the same effect.

Fozzer,

 ......But I THOUGHT that the carb heat and potential carb icing WERE modeled just like pitot heat and pitot icing?

best,

...............john

Hi John....!
I don't fink so......!

It's always been one of my pet peeves, that engine failure due to carb icing is not realistically simulated...!
Having a hand close to the Carb Heat knob on a real Cessna 152 is part of flying them......!

Engine, etc,  failures can be selected in the Sim, but they always fail at pre-selected times... ...!

I hope that the next version of the sim incorporates realistic Carb Heat effects...!

I've spent years flying various sim Cessna 152's, etc,  in atrocious weather conditions and never yet experienced an engine failure due to Carb icing*...!

Cheers...!

Paul...warming his carburettor... ...!

*It's one of the commonest causes of unexplained light aeroplane fatal crashes... ...!
By the time the aircraft has been recovered, the ice has melted...!

Another good reason to turn off the carb heat as soon as you land is that the heated air doesn't pass through a filter, so you could be sucking it bugs, dirt and all kinds of stuff... of course, the sim doesn't do that either. But just to clarify, I'm still happy with the current version.

...just remember, carb heat reduces the power in the engine....so cancel carb heat just before you land...in case you have to perform a go-around when you will need maximum power again....!!!

My flight instructor has taught me (It's also on the aircraft checklists) to apply the carb heat as you enter the pattern or preparing to land, and shut it off after landing

Okay!  Thanks!  Now I know, thanks to Foz and everyone, that on approach and landing, Ive been doing everything wrong!  Okay, mental note: close cowls, carb heat on, throttle idle (on final), DONT FORGET GEAR.  I think me an duggy will be just fine

Fortunately for me, I learned about carb icing on the ground, in an older UK made car. After driving a short distance the engine would quit (which wasn't unusual for older UK cars)I would try the usual things, wipe the HT lead and check the choke. Then try again and it would go for another mile and quit. Then I decided to remove the air filter and look down the carb throat and BINGO, there was all this rime ice plugging the throat, and while I watched, it melted away so I could go another mile. I guess thats why car makers routed the air intake over the exhaust manifold.
Icing conditions occur under Murphy's law, if you forget one day to use the carb heat, engine will quit!

AND ... carbureator icing can  and does occur even when the ambient temp (Farenheit) is as high as in the fifties ...
papa-metro usaf 1953-57

My flight instructor has taught me (It's also on the aircraft checklists) to apply the carb heat as you enter the pattern or preparing to land, and shut it off after landing

Hi Andrew... ...!

I'm still not convinced by your instructors recommendation to shut off Carburettor Heat AFTER landing... ...!
I reckon that Carb heat should be shut off just PRIOR to landing, because when carb heat is applied a lot of engine power is lost, and if the landing is considered to be too dangerous, and a go-around is necessary, you will need all the power your engine can produce, on full throttle, to be able to safely climb out again...!!!
It's a procedure which I always apply for safety.......!

Cheers Andrew...!

Paul The Carburettor Man.......!
LOL...!