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  #11  
Old 04-18-2017, 06:23 PM
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N941WR N941WR is offline
 
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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.
You are 100% correct. However, many (most?) airplanes do not have an alternate air path. So, apparently many people, myself included, are willing to take the risk. Although I'm sure it has happened, I am yet to see a plastic bag blowing across any of the airports I have visited or at altitude.

I'm just thankful you didn't not mention having a bird go in the intake. If you are worried about that, then you should cover the canopy with a fence of some type because there is a better chance of taking a bird through the windscreen than in the air intake.
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  #12  
Old 04-18-2017, 06:59 PM
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SMO SMO is offline
 
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Although I'm sure it has happened, I am yet to see a plastic bag blowing across any of the airports I have visited or at altitude.
I bring it up because I believe that was my experience as related in this thread: http://www.vansairforce.com/communit...hlight=plastic
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  #13  
Old 04-18-2017, 07:21 PM
BobTurner BobTurner is online now
 
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You are 100% correct. However, many (most?) airplanes do not have an alternate air path.
Virtually all normally certified planes do have an alternate air path. It's a certification requirement, IIRC.
As an EAB airplane you are of course free to do what you please. But given how relatively easy and inexpensive Vans' alternate air design is, it seems penny wise but pound foolish not to install it.
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  #14  
Old 04-18-2017, 07:36 PM
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N941WR N941WR is offline
 
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Virtually all normally certified planes do have an alternate air path. It's a certification requirement, IIRC.
As an EAB airplane you are of course free to do what you please. But given how relatively easy and inexpensive Vans' alternate air design is, it seems penny wise but pound foolish not to install it.
I do not know what the certification requirements for a new plane are but regarding your "penny wise but pound foolish" comment, I disagree. When I was building a lot of people put in the trap door that was held shut with a magnet. Some of these were suckered into engines. Thus Van's came out with the sliding door. If I remember correctly, there were similar issues with the slider. Thus, rather than risking my engine with a known failure mode, I elected to leave it off.
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  #15  
Old 04-18-2017, 08:03 PM
Robert Anglin Robert Anglin is offline
 
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Default The question.

If I were to be building with the installation of an IO-XXX "take your choice", I would as I have done, install Alt. air for the engine. We have it on our bird for all the good reasons that a Part 23 spam can dose. Just my two cents on the question. Yours, R.E.A. III #80888
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  #16  
Old 04-18-2017, 08:18 PM
rockwoodrv9 rockwoodrv9 is offline
 
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If I were to be building with the installation of an IO-XXX "take your choice", I would as I have done, install Alt. air for the engine. We have it on our bird for all the good reasons that a Part 23 spam can dose. Just my two cents on the question. Yours, R.E.A. III #80888
What about a carb engine with carb heat installed?
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  #17  
Old 04-18-2017, 08:55 PM
BobTurner BobTurner is online now
 
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Originally Posted by rockwoodrv9 View Post
What about a carb engine with carb heat installed?
If you use the stock design where the heated air is introduced before the filter, I'd put in the ALT air. The current pivoting plate door seems pretty robust.
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  #18  
Old 04-18-2017, 08:59 PM
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N941WR N941WR is offline
 
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What about a carb engine with carb heat installed?
I have carb heat and didn't bother with the alt door. I also avoid taking off from shopping center parking lots.

I did replace the almost useless juice can heat muff for this from Wicks and actually see a noticeable RPM drop now.

It really comes down to your risk tolerance. Ask yourself this, "What are the odds of an intake blockage?" If you don't like your answer, install it
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Last edited by N941WR : 04-18-2017 at 09:08 PM.
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  #19  
Old 04-18-2017, 09:23 PM
rockwoodrv9 rockwoodrv9 is offline
 
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This is the exhaust system I have and the heat muff. I do not think it is the best option for exhaust or how the FAB fits to the exhaust. I would not do it this way again.
https://www.vansaircraft.com/pdf/rev...ther/OP-54.pdf

I believe the carb heat I installed is acceptable risk for me and will not be installing the alt air.
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  #20  
Old 04-18-2017, 09:38 PM
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Dbro172 Dbro172 is offline
 
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Default Video

Here is a video of my alt air door in action. This is looking up at the bottom of the filtered air box, controlled from cable in cockpit. https://youtu.be/YhsEx4_Z9v0
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