X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 16 Apr 2009 22:20:21 -0400 Message-ID: X-Original-Return-Path: Received: from web36908.mail.mud.yahoo.com ([209.191.85.76] verified) by logan.com (CommuniGate Pro SMTP 5.2.13) with SMTP id 3584164 for lml@lancaironline.net; Thu, 16 Apr 2009 22:19:56 -0400 Received-SPF: none receiver=logan.com; client-ip=209.191.85.76; envelope-from=chris_zavatson@yahoo.com Received: (qmail 85199 invoked by uid 60001); 17 Apr 2009 02:19:20 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type; b=pNPbxyRDu4oeGxU4Vc4ZUepPmPLaFgWGgU8DCDJszj56q7tR7yqhkr3T2PlqnvY/gV1rzcBDinIoRunOB49JUvleR0Jyou7FlFFrL41Pnpj+NyuP6dQmt8Jj4tOL4i5uTfTcokPHJ+RZvap+8yw7Cd9JYeonI3ONo9iPWb2Q5rI=; X-Original-Message-ID: <336386.83521.qm@web36908.mail.mud.yahoo.com> X-YMail-OSG: 5PNyKEQVM1mo3VDNsxeGgGr5KHS.ryoH61Z.u3aVvDdnd5uWqUfX8I4m1Fgl9b3RxMIws5Rc.KndoM.mwO2eOx3cKUCWmgQeSikuyRwPlpeudyihj8wlidF1FCbs.sqe_JdxO677ILec2hhPR0zHRLKzJDQEP_Oo.o5RMMfXjGqyEPrClROMpTuCi02AkPe6rXW10EphMu.b38uLn5PKhW8xWr_Sn18KBd76HQ3cb6g2OTG9KJPDQJc.FroargsBSeXy7BABng12RrnTnl2iuS2E5ru2ioYDqjoWyNnIhXRJeCpF4YaWDXsv_UVQAC1xr5W62OZ5CaFsEAlrFF9jSMlX8VESXamAvS0- Received: from [149.32.224.34] by web36908.mail.mud.yahoo.com via HTTP; Thu, 16 Apr 2009 19:19:20 PDT X-Mailer: YahooMailRC/1277.35 YahooMailWebService/0.7.289.1 X-Original-Date: Thu, 16 Apr 2009 19:19:20 -0700 (PDT) From: Chris Zavatson Subject: Re: [LML] AW: Gear Free Fall X-Original-To: Lancair Mailing List MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1840269612-1239934760=:83521" --0-1840269612-1239934760=:83521 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable =A0=0AThis is the source of many of our behavioral differences between plan= es of different vintages.=0A=A0=0A<<- when hydraulic pump is off it shut of= f the high and low pressure lines too>>=0A=A0=0AThe most recent 320/360 pum= ps do not shut off both high and low sides when shut down.=A0 The most comm= on spool valve has an o-ring with a=A0pretty tight fit.=A0=A0With the pump = shut down, the only force acting on it is=A0a tiny little=A0return spring= =A0for the poppet valve.=A0 The spool valve thus stays put in its last comm= anded position and holds open one circuit - the opposite of the one last se= lected or pressurized.=A0 =0AThere are, however, spool valves without o-rin= gs.=A0 These can more easily slide back to center and lock both up and down= circuits (see Lorn's post about having pressure in both the high and low s= ides at the same time).=0ASo, if you need to push the gear up by hand, you = need to first unlock the down-side poppet valve to allow the excess fluid t= o return back to the tank.=A0 Even with the dump valve open, a quick burst = by the pump in the retract direction will slide the spool valve over to the= retract position=A0eliminating the hydraulic lock condition.=A0 Some time = ago I made a video showing this hydraulic lock and how bumping the pump to = slide the spool valve into the up position opened a path for the excess flu= id to escape.=0A=A0http://www.n91cz.com/VideoClips/Push_Gear_Up_Hydr_Lock.W= MV=0A=A0=0AChris Zavatson=0AN91CZ=0A360std=0Awww.N91CZ.com=0A=0A=0A=0A = --0-1840269612-1239934760=:83521 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable

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This is the source of man= y of our behavioral differences between planes of different vintages.

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<<- w= hen hydraulic pump is off it shut off the high and low pressure lines too&g= t;>

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The most recent 320/360 pumps do not shut off bo= th high and low sides when shut down. The most common spool valve has= an o-ring with a pretty tight fit. With the pump shut down= , the only force acting on it is a tiny little return spring = ;for the poppet valve. The spool valve thus stays put in its last com= manded position and holds open one circuit - the opposite of the one last s= elected or pressurized.

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There are, however, spool valves without = o-rings. These can more easily slide back to center and lock both up = and down circuits (see Lorn's post about having pressure in both the high a= nd low sides at the same time).

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So, if you need to push the gear up by h= and, you need to first unlock the down-side poppet valve to allow the exces= s fluid to return back to the tank. Even with the dump valve open, a = quick burst by the pump in the retract direction will slide the spool valve= over to the retract position eliminating the hydraulic lock condition= . Some time ago I made a video showing this hydraulic lock and how bu= mping the pump to slide the spool valve into the up position opened a path = for the excess fluid to escape.

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http://www.n91cz.com/Vid= eoClips/Push_Gear_Up_Hydr_Lock.WMV

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Chris Zavatson

=0AN91CZ=

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360std

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= www.N91CZ.= com

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=0A=0A --0-1840269612-1239934760=:83521--