Mailing List lml@lancaironline.net Message #46697
From: Jeffrey Liegner, MD <liegner@embarqmail.com>
Sender: <marv@lancaironline.net>
Subject: Re: IVP flapping/banging noise
Date: Sat, 29 Mar 2008 23:25:10 -0400
To: <lml@lancaironline.net>
Re: IVP flapping/banging noise
I found a noise like you described came from the flapper door in the back, on the aft bulkhead, behind the fan, for incoming air off the naca scoop (located on the tail).  As the power is pulled back, the turbo air pressure lessens, but your airspeed on downwind is still high, and the naca scoop pressure feeding cabin air opens and flaps that little door...bang, bang, bang.  You can not tell where it's coming from except it's behind you somewhere.  It's a bit nerve racking, but nothing seemed broke, and it remained an auditory mystery for sometime.  It's only heard at certain times, when power is pulled, and the cabin air flow is shifting from the pressurized airbox input to the rear naca scoop incoming air.

Hope this helps.

Jeff L
LIVP


I have a problem that developed at about 60 hours.
It's a flapping banging noise that sounds about like a main gear door when it snaps closed.   It happens with the gear down or up.  I don't hear it on take off or climbout but I do hear it, e.g. on downwind.   Originally it had a metallic ring to it but now it's more muffled.   I can't tell for sure what part of the plane it's coming from.   I've scoured the engine compartment but don't find anything.   If it is gear doors, I don't know what would have changed.
 
Any ideas?
 
Colyn
 

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