X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 06 Apr 2010 17:39:16 -0400 Message-ID: X-Original-Return-Path: Received: from web111405.mail.gq1.yahoo.com ([67.195.15.156] verified) by logan.com (CommuniGate Pro SMTP 5.3.5) with SMTP id 4211706 for lml@lancaironline.net; Tue, 06 Apr 2010 11:26:44 -0400 Received-SPF: none receiver=logan.com; client-ip=67.195.15.156; envelope-from=randylsnarr@yahoo.com Received: (qmail 14970 invoked by uid 60001); 6 Apr 2010 15:26:07 -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:In-Reply-To:MIME-Version:Content-Type; b=jIi4f/8OB66sa7BjrQfaw/VOA3Ng2wtfE7mujDLi00mdbzxZMbzip6MxyM32z8lqRHIYdA9aZY38uGaEWeQUs+YkBVic8LlbCJbAH9HeBam2DlyYva4TI3vl4sJn9KIen7QS2g0jZyo267G0KzGT9fcXl7unjVhfuJNe5kox8mI=; X-Original-Message-ID: <731416.14704.qm@web111405.mail.gq1.yahoo.com> X-YMail-OSG: PjvIiW8VM1mwzzY3ZKFywqVRtYbmsCmhHyqP5i46fthFj7v HChps4pX3PbYEn8ritNIkSHMKw1Lf2OSHE83GqTPznskgEtTe8OBvYH5QFuu gqWtBuR4L4U8K1OP6jMIXVyofkDgT_6q.NAyGCh.rqPAethhctcTcPqmEh8b dXXX2t8VLdQuDmpH.JZsEUyagtq4YuENqmiq790eFMfQ1AW4XTO4ns2dSeh6 nAXBG.m26F_eM9okrFAWgeBqfNxldqFDz8pLb91g6zv0o2f7AfWf7d9du9KT _Ec4dz.RQX95Kp_QGVWk3caxh7wpDkj2VmPRrjYmrxdwsLQ9zock6XQhUs2J EtgUbaz1BGGprdI8aSAHk59Klug-- Received: from [76.8.220.18] by web111405.mail.gq1.yahoo.com via HTTP; Tue, 06 Apr 2010 08:26:07 PDT X-Mailer: YahooMailClassic/10.0.8 YahooMailWebService/0.8.100.260964 X-Original-Date: Tue, 6 Apr 2010 08:26:07 -0700 (PDT) From: randy snarr Subject: Re: [LML] gear retract problems - 320 X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-831655267-1270567567=:14704" --0-831655267-1270567567=:14704 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable John, This has gone around several times.=20 The dump valve you have is really a pressure equalization valve. A true dump valve will dump the pressure to 0. I will explain. This has happened to me as well. I installed hydraulic gauges which tells t= he story. When you pull the airplane out of a cool hangar into the warm sun= , the system heats up and pressure on both the high and low sides increase = pretty much equally. Example: my high pressure (gear up) side may start at = 0 and the low side ( gear down) at 500 when in the cool hangar.Pull it into= the sun for 30 minutes and both will increase say 700 psi. No kidding! Tha= t puts the high at 700 and the low at 1200. If the increase of the system h= its 900 or so ( low now at 1400 high at 900)=A0=A0 you have hit the gear up= limit pressure switch which tells the system (if it were in transit) to st= op raising the gear. In your case, when you try to retract the gear the upp= er limit just keeps the pump from starting as it thinks the gear is already= up because the upper limit has already been hit. In our systems, both side= s are closed meaning neither vents to the resevoir when the pump is not running. This changes when the pump is running. If you increase the pr= essure enough on both sides (again with heat) while on the ground the the p= ressure on the high side will eventually open the upper limit pressure swit= ch. and the gear will not retract. Sometimes opening the dump valve will he= lp as it equalizes the pressure on both sides. If this equalization results= in the high side dropping below the high side limit (appx. 900 psi), the g= ear will retract. It the equalization does not result in this it will not, = thus you have to climb out and crack a fitting somewhere releasing the heat= induced pressure increase in the system. This happened a few times for me and I think I am more suseptable to it as = I used small hot rod stainless braid hydraulic lines instead of the factory= rubber stuff. I think the factory stuff although much heaver has some flex= ibity allowing it to balloon a little limiting the heat induce pressure inc= rease. I solved this by replacing the dump valve that does more than=A0 con= nect the high and low pressure sides. Mine does that but it has an extra li= ne that not only connects the high and low pressure sides equalizing pressu= re on each side, it also dumps the pressure to 0 with a low pressure return= line to the resevoir. If you had my dump valve and low pressure return lin= e, you would have been able to retract the gear by cracking the dump valve = and closing it again as you would truely have dumped pressure not just equa= lized pressure. I have heard of some doing a bypass on the pressure switch to momentarily g= et the gear pump to move, for me I like my set up which is similar to the L= egacy. I like the idea of being able to release all pressure from the syste= m, not only to solve the issue describe here but to ensure I can always get= the wheels down without power as there is no way to keep the gear up if yo= u vent the pressure to 0. FWIW... Randy Snarr N694RS 235/320 --- On Tue, 4/6/10, John Spry wrote: From: John Spry Subject: [LML] gear retract problems - 320 To: lml@lancaironline.net Date: Tuesday, April 6, 2010, 5:59 AM =0A=0A =0A =0A=0AMy 320 gear did not activate when I selected gear =0Aup ye= sterday - I checked the circuit breaker, opened and closed the dump valve, = =0Aselected gear down, then up - all to no avail and then landed.=0A=A0=0AI= recalled some discussion years ago about this =0Aissue and a temporary fix= being the "cracking" of the hydraulic pressure to get =0Athe system going = again - this I did and it worked !=0A=A0=0ACan someone help me with identif= ying the actual =0Acause and permanent fix.=0A=A0=0AThanks=0A=A0=0AJohn Spr= y=0A=A0=0AL320 =0A =0A__________ Information from ESET NOD32 Antivirus, version of virus signa= ture database 5002 (20100405) __________ =0A =0AThe message was checked by ESET NOD32 Antivirus. =0A =0Ahttp://www.eset.com =0A=0A=0A=0A=0A=0A --0-831655267-1270567567=:14704 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
John,
This has gone around several times. =
The dump valve you have is really a pressure equalization valve.
A t= rue dump valve will dump the pressure to 0. I will explain.

This has= happened to me as well. I installed hydraulic gauges which tells the story= . When you pull the airplane out of a cool hangar into the warm sun, the sy= stem heats up and pressure on both the high and low sides increase pretty m= uch equally. Example: my high pressure (gear up) side may start at 0 and th= e low side ( gear down) at 500 when in the cool hangar.Pull it into the sun= for 30 minutes and both will increase say 700 psi. No kidding! That puts t= he high at 700 and the low at 1200. If the increase of the system hits 900 = or so ( low now at 1400 high at 900)   you have hit the gear up l= imit pressure switch which tells the system (if it were in transit) to stop raising the gear. In your case, when you try to retract the gear the upper= limit just keeps the pump from starting as it thinks the gear is already u= p because the upper limit has already been hit. In our systems, both sides = are closed meaning neither vents to the resevoir when the pump is not runni= ng. This changes when the pump is running. If you increase the pressure eno= ugh on both sides (again with heat) while on the ground the the pressure on= the high side will eventually open the upper limit pressure switch. and th= e gear will not retract. Sometimes opening the dump valve will help as it e= qualizes the pressure on both sides. If this equalization results in the hi= gh side dropping below the high side limit (appx. 900 psi), the gear will r= etract. It the equalization does not result in this it will not, thus you h= ave to climb out and crack a fitting somewhere releasing the heat induced p= ressure increase in the system.
This happened a few times for me and I think I am more suseptable to it as I used small hot rod stainless b= raid hydraulic lines instead of the factory rubber stuff. I think the facto= ry stuff although much heaver has some flexibity allowing it to balloon a l= ittle limiting the heat induce pressure increase. I solved this by replacin= g the dump valve that does more than  connect the high and low pressur= e sides. Mine does that but it has an extra line that not only connects the= high and low pressure sides equalizing pressure on each side, it also dump= s the pressure to 0 with a low pressure return line to the resevoir. If you= had my dump valve and low pressure return line, you would have been able t= o retract the gear by cracking the dump valve and closing it again as you w= ould truely have dumped pressure not just equalized pressure.
I have hea= rd of some doing a bypass on the pressure switch to momentarily get the gea= r pump to move, for me I like my set up which is similar to the Legacy. I like the idea of being able to release all pressure from the sys= tem, not only to solve the issue describe here but to ensure I can always get th= e wheels down without power as there is no way to keep the gear up if you v= ent the pressure to 0.

FWIW...
Randy Snarr
N694RS
235/320--- On Tue, 4/6/10, John Spry <spry@paradise.net.nz> = wrote:

From: John Spry <spry@paradise.ne= t.nz>
Subject: [LML] gear retract problems - 320
To: lml@lancairon= line.net
Date: Tuesday, April 6, 2010, 5:59 AM

=0A=0A =0A =0A=0A
My 320 gear did not activate when I selected gear =0Aup yesterday - I che= cked the circuit breaker, opened and closed the dump valve, =0Aselected gea= r down, then up - all to no avail and then landed.
=0A
 
=0A
I recalled some discussion years ago about this =0Aissue and a = temporary fix being the "cracking" of the hydraulic pressure to get =0Athe = system going again - this I did and it worked !
=0A
 
=0A
Can someone help me with identifying the actual =0Acause and perma= nent fix.
=0A
 =
=0A
Thanks
=0A
 
=0A
John Spry
=0A
 
=0A
L320
=0A
=0A__________ Information from ESET NOD32 Antivirus, version o= f virus signature database 5002 (20100405) __________
=0A
=0AThe mess= age was checked by ESET NOD32 Antivirus.
=0A
=0Ahttp://www.eset.com
= =0A=0A=0A

=0A=0A --0-831655267-1270567567=:14704--