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Hank,  Thanks for your comments.  I think the alternate air door I referred
to when I referenced the AD does draw in air from inside the cowl.  I don't
know exactly how it works, but when the air filter ices up,  the vacuum?
builds up enough to where it overpowers the magnetically operated door and
it must open the alternate  air door as a source of air for the engine.  I
had a bonanza that had an alternate air door that must have operated
differently than your Mooney because I did have a situation where the air
filter iced up , MP dropped about 2" and then everything operated normally
again after the alt. air door opened.   I am sure there are subscribers on
this site that can tell us all exactly how it works. The posting that
referenced the iv-p over Montana was true except I thought that it was over
Colorado and  when I heard him telling the story that the first thing he did
was to open the manual alternate air door to avoid loss of air to the engine
as his airplane was immediately covered with small hail stones.  I would be
interested to know if the group on this web site thinks a manual alt. air
door in addition to the magnetically operated one is necessary and/or a good
idea.  John Wright Colorado Springs
-----Original Message-----

 Re: Ice vs. altitude theoretical scenerio


>John:
>I am surprised that the IV-P is not equipped with an automatic bypass door
>that takes air from the engine compartment.
>>Hank - San Mateo, Ca.
>


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