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Bugman

407 Heating Systems

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We have operated two Bell 407's at -40 and colder ( with Jet A-1)for the last two winters and had no problem with the heaters keeping up. They are both equipped with Air Comm heaters though and Tanis preheat kits as well. And just for info. when operating in these cold conditions, the smoke that comes out of your exhaust will make you think you blew an oil seal but actually it is normal.

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We have operated two Bell 407's at -40 and colder ( with Jet A-1)for the last two winters and had no problem with the heaters keeping up. They are both equipped with Air Comm heaters though and Tanis preheat kits as well. And just for info. when operating in these cold conditions, the smoke that comes out of your exhaust will make you think you blew an oil seal but actually it is normal.

 

I noticed that blue smoke from about -10 to -15 and colder depending on the 407.But only at idle it seems.

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Yeah the heaters work fine in -30 to -40. You will want to rig up some heater ducting to your bubble window if longlining though.

 

I have always been curious why the Bells limit Jet A-1 to warmer than -32'C. The fuel is good for colder, does anyone know why they limit it?

 

 

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The -32 deg C for Jet A-1 is an engine limitation. It has to do with the fuel viscosity at that temperature according to the fuel specification. In reality the refineries actually produce fuel that is better than the specification so the fuel viscosity, measured in centistokes, at -40 deg C is about what the specification says it should be at -32 deg C. If the fuel viscosity is too high, it can affect the function of the fuel control and limit the engine's ability to restart at cold temperatures.

 

That being said, the critical feature is the fuel temperature and not the ambient air temp. Since most Bell products do not have a fuel temp indicator, ambient air temp is the deciding factor. Hope that sheds some light on the low temp limits.

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The -32 deg C for Jet A-1 is an engine limitation. It has to do with the fuel viscosity at that temperature according to the fuel specification. In reality the refineries actually produce fuel that is better than the specification so the fuel viscosity, measured in centistokes, at -40 deg C is about what the specification says it should be at -32 deg C. If the fuel viscosity is too high, it can affect the function of the fuel control and limit the engine's ability to restart at cold temperatures.

 

That being said, the critical feature is the fuel temperature and not the ambient air temp. Since most Bell products do not have a fuel temp indicator, ambient air temp is the deciding factor. Hope that sheds some light on the low temp limits.

 

 

Thanks for the great info!

 

That has been bugging me for a long time.

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Guest bag swinnger
The -32 deg C for Jet A-1 is an engine limitation. It has to do with the fuel viscosity at that temperature according to the fuel specification. In reality the refineries actually produce fuel that is better than the specification so the fuel viscosity, measured in centistokes, at -40 deg C is about what the specification says it should be at -32 deg C. If the fuel viscosity is too high, it can affect the function of the fuel control and limit the engine's ability to restart at cold temperatures.

 

That being said, the critical feature is the fuel temperature and not the ambient air temp. Since most Bell products do not have a fuel temp indicator, ambient air temp is the deciding factor. Hope that sheds some light on the low temp limits.

 

Hmm, I think I see a new exam question in there...

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