Carburetor ice ?

[jcomm]

On a humid day, low temps, I can get down at idle, from 6,000', and fear no engine failure even without using carb heat.

Is any form of ice accumulation simulated for the 172, and other accusimed modules with normal aspirated engines ( the 180, the older spits, ...) ?

[Nick - A2A]

Hi jcomm,

The A2A 172R has a Lyco IO-360 engine. The "I" stands for injected so there is no carburettor and therefore no carb heat. However, carb icing is simulated in the A2A Pipers which do have earlier carburetted engines and carb heating systems.

Is any form of ice accumulation simulated for the 172 [...] ?

I don't think there's any simulation of impact icing of the intake screens etc. which I gather can affect even something like a 172R if conditions are bad enough. FSX has a basic simulation of airframe icing by default though, so it might be wrong.

Cheers,
Nick

[jcomm]

Thx Nick,

stupid me not paying attention to that "I" on the 172 Lycoming ...

But, so the 180 can be affected! Great to know

And yes, I am aware of the basic icing modelling in MSFS and derivates, although I still prefer it over what we have in XP10...

[jsbrewster1]

Hi,

Just so you know, they do simulate pitot tube icing, I found to my chagrin in Outer Mongolia, when my airspeed indicator dropped to 0. I wrongly assumed something was wrong with the simulator, but it was PEBYAS (Problem Exists Between Yoke and Seat, to shamelessly steal an IT acronym). Once I turned on pitot heat life was good again.

Regards,

[AKar]

One point worth bringing out, mainly concerning the real world I-rated flyers doing FIKI, is that the Bendix fuel injector used in IO-series Lycomings is not at all immune to icing, though it is relatively rare event in comparison to carburetor icing. The fuel injector is structurally quite similar to carburetor, and uses the exactly same venturi principle - not for fuel suction but for air volume metering. There is a venturi throat and there is a throttle valve, both of which can ice up similarly to the ones in carburetor. The main difference is that the fuel injector unit lacks the cooling effect of the fuel evaporation: in carburetor this takes place in the carburetor itself, while in these fuel injected engines the fuel is injected downstream, to the intake manifold just before the intake valve. Against a common misconception, the venturi pressure drop and associated cooling is not the main cause of carburetor icing phenomenon but the cooling effect from the fuel evaporation is. In case the air getting sucked into the engine is appropriately prone to icing, it will however ice on the fuel injector venturi and throttle restrictions due to that local cooling and presence of suitable impact surface.

Also, as Nick said, the air filter can ice up too. In that case however, typically the alternate air door opens automatically, sucked open by the low pressure created by engine suction. It won't do that in case of injector icing, but needs to be opened manually.

-Esa

[jcomm]

Excellent replies.

Thank you guys!