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Tiger6k

Carb heat destroys engines even when off.

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I just started a flight in Las Vegas where I live IRL.  Temp outside is 39 degrees Celsius.  I loaded the plane in a cold and dark state, and immediately I get a message saying "Warning! Carb temp causing engine damage!"

 

After a minute or two (in cold & dark) the engines go black in the maintenance window.

 

If I reset the damage, I can start them and the carb temperate goes down and the engines don't die, but... is this working properly?

 

Thanks,

 

KrisWhMiLxQ.jpg

 

As you can see above, engine 1 & 2 were never started, and you can see the carb heat way up.  I reset 3 & 4 engines and started them immediately, and the damage was minimized. You can see the carb heat cooled down after start.

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I had the same thing happen to me also in Vegas today. The outside air temperature at the time was 37C. It happened with the aircraft powered off after landing, and after a replay  so I initially attributed it to some systems not re-initializing correctly after the replay. The cowl flaps were fully open at the time

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What's interesting also is after the engines are started, the carburetor air drops to around 12 degrees Celsius. (as you can see in the picture) How is that possible?  Wouldn't the carb air still be fairly hot?  Or at least not almost 30 degrees cooler than outside air temp?  I would think idling on the ground for an extended amount of time in this heat could damage the engines, but not when the engines are off.  Seems a little backwards to me.

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Wouldn't the carb air still be fairly hot?

 

No. Research how a carb works.

 

Drop in pressure = drop in temperature. This is why carb ice is a higher risk in Florida in spring/fall than Minnesota in winter: high humidity and right temps for the carb temp drop into freezing.

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Hm, so I just tried closing the cowl flaps fully while idling on the ground @ 39 degrees Celsius.  No temperature issues at all after 15+ minutes.  Turning the carb heat on obviously gets the carb air all the way back up to almost 40 degrees Celsius.  But should the engines stay that cool with the cowl flaps closed?


No. Research how a carb works.

Drop in pressure = drop in temperature. This is why carb ice is a higher risk in Florida in spring/fall than Minnesota in winter: high humidity and right temps for the carb temp drop into freezing.

 

Fair enough.  So should I report the bug about the engines frying while they're off then at least?

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So should I report the bug about the engines frying while they're off then at least?

 

Already passed it on.

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Before carb heat can operate, the engine must be warmed up as the engine itself provides the heat source (either exhaust or oil heat exchanger), so until the engine has warmed up, there is no carb heat available.

 

Rob Smith.

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