X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 31 Jan 2010 08:09:25 -0500 Message-ID: X-Original-Return-Path: Received: from smtp-auth-04.mx.pitdc1.expedient.net ([206.210.66.137] verified) by logan.com (CommuniGate Pro SMTP 5.3.2) with ESMTPS id 4105176 for lml@lancaironline.net; Sat, 30 Jan 2010 18:06:38 -0500 Received-SPF: none receiver=logan.com; client-ip=206.210.66.137; envelope-from=rpastusek@htii.com Received: from HTBOB001 (static-72-66-86-7.washdc.fios.verizon.net [72.66.86.7]) by smtp-auth-04.mx.pitdc1.expedient.net (Postfix) with ESMTPSA id B0A25E455C for ; Sat, 30 Jan 2010 18:06:02 -0500 (EST) From: "Robert Pastusek" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: RE: [LML] Re: Airspeed sensing switch: Pressurization X-Original-Date: Sat, 30 Jan 2010 18:06:02 -0500 X-Original-Message-ID: <049a01caa200$cb4559e0$61d00da0$@com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_049B_01CAA1D6.E26F51E0" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Acqh5FJeFunWS0FPSTqI+nLr53+j7gAGpqtQ Content-Language: en-us This is a multi-part message in MIME format. ------=_NextPart_000_049B_01CAA1D6.E26F51E0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Jeff, At 5.5 PSI differential, I start to lose cabin pressurization between 27-28" of manifold pressure. Testing done between 16,000 and 17,000'. I can maintain some pressurization down to about 24" but below that the cabin is at ambient. I've actually pulled the power up high and verified that the cabin air back-flows through the firewall mounted controller into the intake system. Bob PS: I don't have a cabin dump switch on my instrument panel for the reasons you lay out below. Bob Pastusek Upper deck has to be higher than the indicated MAP, at least by 10" if we want to siphon off 10" for the 5 psi cabin differential (assuming a perfectly sealed cabin). The TBM has a back flow valve that limits the venting of cabin pressure, something the LIVP does not have. Also, the outside attendant can not open the cabin no matter what until we drop the door seal. I can't even throw the door cleats back over center (from inside) when the door seal is inflated. The ultimate cabin dump switch is the door seal; it takes less than a second to normalize cabin-to-ambient pressure. Throw that anytime and everything vents out the door. If I had smoke in the cabin, would I throw the Cabin Dump switch (on the panel) and open the Duke's Valve, inviting all that smoke to travel past me towards the rear sear, or should I deflate the door seal (switch by my elbow on the door)? In my mind (and my POH), the door seal does the trick. So why even have a "Cabin Dump" switch on the panel? I've asked myself this, but still I have one. I would love for every LIVP to fly level at 16000', cabin differential 5psi (fully pressurized), 31" MAP, and start pulling MAP off and observe when the cabin (and Duke's Valve) begins to lose pressurization. I think mine is 28" MAP, but I'm working that currently with the annual. If other's hold cabin 5 psi differential down to 18", wow...that's a huge difference. You'd have bragging rights. Post your numbers for the community. Jeff LIVP ------=_NextPart_000_049B_01CAA1D6.E26F51E0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Re: Airspeed sensing switch: Pressurization

Jeff,

 

At 5.5 PSI differential, I start to lose cabin = pressurization between 27-28” of manifold pressure. Testing done between 16,000 = and 17,000’.  I can maintain some pressurization down to about 24” but below that = the cabin is at ambient. I’ve actually pulled the power up high and verified = that the cabin air back-flows through the firewall mounted controller into the intake = system.

 

Bob

 

PS: I don’t have a cabin dump switch on my = instrument panel for the reasons you lay out below.

 

Bob Pastusek

 <= /o:p>

 

 

Upper deck has to be higher than the indicated MAP, = at least by 10" if we want to siphon off 10" for the 5 psi cabin = differential (assuming a perfectly sealed cabin).

 

The TBM has a back flow valve that limits the = venting of cabin pressure, something the LIVP does not have.  Also, the = outside attendant can not open the cabin no matter what until we drop the door seal.  I can't even throw the door cleats back over center (from = inside) when the door seal is inflated.

 

The ultimate cabin dump switch is the door seal; it = takes less than a second to normalize cabin-to-ambient pressure.  Throw = that anytime and everything vents out the door.  If I had smoke in the = cabin, would I throw the Cabin Dump switch (on the panel) and open the Duke's = Valve, inviting all that smoke to travel past me towards the rear sear, or = should I deflate the door seal (switch by my elbow on the door)?  In my mind = (and my POH), the door seal does the trick.  So why even have a = "Cabin Dump" switch on the panel?  I've asked myself this, but still = I have one.

 

I would love for every LIVP to fly level at 16000', = cabin differential 5psi (fully pressurized), 31" MAP, and start pulling = MAP off and observe when the cabin (and Duke's Valve) begins to lose pressurization.  I think mine is 28" MAP, but I'm working that currently with the annual.  If other's hold cabin 5 psi = differential down to 18", wow...that's a huge difference.  You'd have bragging rights.  Post your numbers for the community.

 

Jeff

LIVP

 

 

 

 

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