X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 15 Oct 2013 16:28:55 -0400 Message-ID: X-Original-Return-Path: Received: from qmta01.westchester.pa.mail.comcast.net ([76.96.62.16] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6541994 for lml@lancaironline.net; Tue, 15 Oct 2013 15:26:28 -0400 Received-SPF: pass receiver=logan.com; client-ip=76.96.62.16; envelope-from=jmorgan1023@comcast.net Received: from omta08.westchester.pa.mail.comcast.net ([76.96.62.12]) by qmta01.westchester.pa.mail.comcast.net with comcast id dPgn1m0080Fqzac51XRwmb; Tue, 15 Oct 2013 19:25:56 +0000 Received: from [192.168.1.102] ([24.11.157.196]) by omta08.westchester.pa.mail.comcast.net with comcast id dXRv1m00L4EXR5U3UXRv6Q; Tue, 15 Oct 2013 19:25:56 +0000 From: Jack Morgan Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: multipart/alternative; boundary="Apple-Mail=_C6376D23-F160-4445-A886-9756CC1C39DD" Subject: Dukes pressure contoler vacuum pump function X-Original-Date: Tue, 15 Oct 2013 15:25:54 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <7DEAA3FC-6006-41FD-9809-D2A2DEFD19D3@comcast.net> X-Mailer: Apple Mail (2.1283) --Apple-Mail=_C6376D23-F160-4445-A886-9756CC1C39DD Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=iso-8859-1 Hi Paul, The rate control on the cabin panel controller just changes the speed of = the electric motor in the outflow valve. There is no vacuum connection = to the cabin panel controller. The electric motor in the outflow valve = has a very large gear reduction which slowly changes the set point = altitude for the onset of cabin pressurization based on the panel = controller setting. The "vaccum source for differential control" is still in place in the = form of a tube from the controller to the atmosphere located in the tub = that holds the outflow valve. A second vacuum connection is provided by = Dukes which provides enough force to fully open the outflow valve when = rapid venting of the cabin is desired. Activating the dump valve = solenoid in the outflow valve admits the vaccum to the outflow bellows = fully opening the valve. Without the vacuum applied and the dump valve = activated, the outflow valve only partially opens when below the set = altitude. Many of the Pressurized Lancairs weather new or upgraded no longer need = vaccum for the instruments which raises the issue of providing a vacuum = source to the controller. Since releasing the door seal is a very = effective way to depressurize the cabin, most owners have elected to = tolerate the minor pressure bump on take off with a rapidly advanced = throttle caused by the partially opened valve. Per Dukes there is no = other undesirable side effect from not providing the vacuum.=20 Hope this helps, Jack Morgan On Oct 15, 2013, at 6:01 AM, Lancair Mailing List wrote: > From: Paul Miller > Subject: Re: [LML] Re: Removing vacuum pump? (LIVP) > Date: October 14, 2013 8:14:11 AM EDT > To: lml@lancaironline.net >=20 >=20 > If the pressure controller on the panel has rate of climb and cabin = altitude settings (like a Garrett), it likely uses the vacuum line to = modulate the outflow valves (pull them open). That modulation is what = provides the signal to allow the cabin to climb or descend. I don't = know what controller is in place but the vacuum is for cabin = differential control. The squat switch is for ground use or emergency = and simple opens the outflow to a maximum. In a typical situation, the = outflow closes with wheels up then the vacuum signal starts to open the = valves to provide the differential required to either climb or hold the = cabin as set by the controller. >=20 > If the vacuum is disconnected, I suspect you simply are running with a = fully closed outflow valve and the cabin pressure is an open loop with = whatever pressure is supplied from the firewall. Does that sound about = right? >=20 > What I am missing is if there is no vacuum line then why install the = controller? How does it control anything? Those controllers can't be = cheap. >=20 --Apple-Mail=_C6376D23-F160-4445-A886-9756CC1C39DD Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=iso-8859-1 Hi = Paul,

The rate control on the cabin panel controller = just changes the speed of the electric motor in the outflow valve. There = is no vacuum connection to the cabin panel controller. The electric = motor in the outflow valve has a very large gear reduction which slowly = changes the set point altitude for the onset of cabin pressurization = based on the panel controller setting.

The = "vaccum source for differential control" is still in place in the form = of a tube from the controller to the atmosphere located in the tub that = holds the outflow valve. A second vacuum connection is provided by Dukes = which provides enough force to fully open the outflow valve when rapid = venting of the cabin is desired. Activating the dump valve solenoid in = the outflow valve admits the vaccum to the outflow bellows fully opening = the valve. Without the vacuum applied and the dump valve activated, the = outflow valve only partially opens when below the set = altitude.

Many of the Pressurized Lancairs = weather new or upgraded no longer need vaccum for the instruments which = raises the issue of providing a vacuum source to the controller. Since = releasing the door seal is a very effective way to depressurize the = cabin, most owners have elected to tolerate the minor pressure bump on = take off with a rapidly advanced throttle caused by the partially opened = valve. Per Dukes there is no other undesirable side effect from not = providing the vacuum. 

Hope this = helps,

Jack Morgan

On = Oct 15, 2013, at 6:01 AM, Lancair Mailing List wrote:

To: If = the pressure controller on the panel has rate of climb and cabin = altitude settings (like a Garrett), it likely uses the vacuum line to = modulate the outflow valves (pull them open).  That modulation is = what provides the signal to allow the cabin to climb or descend.   = I don't know what controller is in place but the vacuum is for cabin = differential control.  The squat switch is for ground use or = emergency and simple opens the outflow to a maximum.  In a typical = situation, the outflow closes with wheels up then the vacuum signal = starts to open the valves to provide the differential required to either = climb or hold the cabin as set by the controller.

If = the vacuum is disconnected, I suspect you simply are running with a = fully closed outflow valve and the cabin pressure is an open loop with = whatever pressure is supplied from the firewall.  Does that sound = about right?

What I am missing is if there is = no vacuum line then why install the controller?  How does it = control anything?  Those controllers can't be cheap.

=
= --Apple-Mail=_C6376D23-F160-4445-A886-9756CC1C39DD--