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04-18-2017, 03:29 PM
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Join Date: Mar 2017
Location: Birmingham, Alabama
Posts: 1,643
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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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RV-14A #140376
N196 (Flying)
2019 Bronze Lindy
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04-18-2017, 03:41 PM
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Join Date: May 2009
Location: Wahpeton, ND
Posts: 167
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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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Brian Steeves
#40955 RV-10 - N413BS - Sold
It is Airworthy and Flying. But are they ever done?
First Flight 9/28/2013
#41714 RV-10 - N272BS
Phase 1 Finished, Getting Painted
#120849 RV-12 - N112AB
Flying. First flight Nov 26, 2017
Challenger II - N272MP - Sold
First Flight in 2011
www.briansrv10.com
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04-18-2017, 03:46 PM
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Join Date: Mar 2017
Location: Birmingham, Alabama
Posts: 1,643
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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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RV-14A #140376
N196 (Flying)
2019 Bronze Lindy
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04-18-2017, 03:49 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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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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04-18-2017, 03:50 PM
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Join Date: Mar 2017
Location: Birmingham, Alabama
Posts: 1,643
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Bob, that brings it home, perfect, thank you.
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RV-14A #140376
N196 (Flying)
2019 Bronze Lindy
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04-18-2017, 03:54 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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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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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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04-18-2017, 05:35 PM
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Join Date: Oct 2007
Location: Salmon Arm, BC
Posts: 933
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Quote:
Originally Posted by N941WR
It depends on how you fly........
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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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Mark Olson
1987 RV-4 Sold
2003 Super Decathlon - Sold
F1 EVO Rocket, first flight May 31/14
First in line for the Sonex JSX-2T kit
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04-18-2017, 05:41 PM
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Join Date: Oct 2012
Location: Clearwater, FL KCLW
Posts: 1,281
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Quote:
Originally Posted by BobTurner
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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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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Chris Johnson
RV-9A - Done(ish) 4/5/16! Flying 4/7/16
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04-18-2017, 05:48 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Quote:
Originally Posted by YellowJacket RV9
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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You are correct. I should have said "You have most likely been flying CERTIFIED carbureted...."
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04-18-2017, 06:12 PM
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Join Date: Dec 2011
Location: Meridian ID, Aspen CO, Okemos MI
Posts: 2,645
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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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rockwoodrv9a
Williamston MI
O-320 D2A
Awaiting DAR Inspection
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