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  #1  
Old 04-18-2017, 03:29 PM
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bkervaski bkervaski is offline
 
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Default Alt Air?

Guys --

What's the purpose of the Alt Air control I see on some of the panels .. it's not alt static but something to do with the carb .. trying to figure out why some have it and others don't and is this something that would be needed on the IO-390.

Thanks!

-- Bill
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  #2  
Old 04-18-2017, 03:41 PM
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These are two separate things. The alternate air is a backup for the air intake into the engine, in the case that the filter gets plugged and engine cant get enough air for some reason.

There is also the alternate static in the case that the static ports get blocked.

Both should be incorporated into the build.

Hope this helps.
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  #3  
Old 04-18-2017, 03:46 PM
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bkervaski bkervaski is offline
 
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Ahh, okay, that, and a bit of searching, it makes way more sense now. I've never seen an "Alt Air" port in any of the stuff I've been flying.

(thanks)

So much to learn and loving every minute!
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  #4  
Old 04-18-2017, 03:49 PM
BobTurner BobTurner is offline
 
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You most likely have been flying airplanes with 'carb heat'. Carb heat not only supplies warm air to the carb, it also bypasses the air filter in case it's clogged.
Most fuel injected engines do not have a heated air option, just a filter bypass called alternate air.
If you choose to install a carbureted engine you'll want carb heat instead of ALT air.
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  #5  
Old 04-18-2017, 03:50 PM
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bkervaski bkervaski is offline
 
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Bob, that brings it home, perfect, thank you.
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  #6  
Old 04-18-2017, 03:54 PM
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It depends on how you fly. In my VFR plane I have neither Alt Air or Alt Static Air.

If I were to add IFR capability to my plane, you can bet I would add both.
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  #7  
Old 04-18-2017, 05:35 PM
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Quote:
Originally Posted by N941WR View Post
It depends on how you fly........
And the level of risk you are willing to accept. A plastic bag blocking the air intake can stop your engine, an alternate air source can keep it running.
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  #8  
Old 04-18-2017, 05:41 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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Quote:
Originally Posted by BobTurner View Post
You most likely have been flying airplanes with 'carb heat'. Carb heat not only supplies warm air to the carb, it also bypasses the air filter in case it's clogged.
Most fuel injected engines do not have a heated air option, just a filter bypass called alternate air.
If you choose to install a carbureted engine you'll want carb heat instead of ALT air.
On the RVs (at least those that I know of) carb heat does not bypass the filter, so alternate air is still often recommended. It is introduced by means of a trap door in the base of the filtered air box.

Chris
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  #9  
Old 04-18-2017, 05:48 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by YellowJacket RV9 View Post
On the RVs (at least those that I know of) carb heat does not bypass the filter, so alternate air is still often recommended. It is introduced by means of a trap door in the base of the filtered air box.

Chris
You are correct. I should have said "You have most likely been flying CERTIFIED carbureted...."
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  #10  
Old 04-18-2017, 06:12 PM
rockwoodrv9 rockwoodrv9 is offline
 
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Is it opinion to have the alt air intake in addition to carb heat or recommendation? My understanding was it was a choice and not really needed if carb heat is installed. It isn't a difficult thing to add, not nearly as tricky as the carb heat.

I did not plan to have the alt air. Should I?
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