X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 07 Apr 2010 13:41:00 -0400 Message-ID: X-Original-Return-Path: Received: from mta31.charter.net ([216.33.127.82] verified) by logan.com (CommuniGate Pro SMTP 5.3.5) with ESMTP id 4213226 for lml@lancaironline.net; Wed, 07 Apr 2010 13:26:20 -0400 Received-SPF: pass receiver=logan.com; client-ip=216.33.127.82; envelope-from=lhenney@charter.net Received: from imp09 ([10.20.200.9]) by mta31.charter.net (InterMail vM.7.09.02.04 201-2219-117-106-20090629) with ESMTP id <20100407172543.WEPP22217.mta31.charter.net@imp09> for ; Wed, 7 Apr 2010 13:25:43 -0400 Received: from CYBERMAX ([96.39.213.138]) by imp09 with smtp.charter.net id 2hRc1e00R2zjSxc05hRhGQ; Wed, 07 Apr 2010 13:25:42 -0400 X-Authority-Analysis: v=1.0 c=1 a=5YXt1DZx0-0A:10 a=CjxXgO3LAAAA:8 a=Ia-xEzejAAAA:8 a=ZGGhTNpsAAAA:8 a=nUuTZ29dAAAA:8 a=bzRI6E2CCQwLweyRR-QA:9 a=fumcSSDrikeHdLuhFKEA:7 a=_w0XF9D_thzzp3E1WP-WAbsc7WkA:4 a=CjuIK1q_8ugA:10 a=rC2wZJ5BpNYA:10 a=EzXvWhQp4_cA:10 a=ucYnWqgA9Kpy5-HVnxQA:9 a=vr2diW05nWnIwbLMwxUA:7 a=dOse2HfB1wYVEqoRVWJXG8jmaxUA:4 From: "Larry Henney" X-Original-To: "Lancair Mailing List" Subject: FW: [LML] gear retract problems - 320 X-Original-Date: Wed, 7 Apr 2010 12:25:35 -0500 X-Original-Message-ID: <4909E577DB9D43D9A71737937409007B@CYBERMAX> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_007C_01CAD64D.70ACD040" X-Mailer: Microsoft Office Outlook 11 thread-index: AcrWOixr8dgBU3XnQD+KjgxpV/LvOAAPDQ6A X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_007C_01CAD64D.70ACD040 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit John, In 920 hours I've seen this particular hiccup only once. It was exactly as described by Randy (hot day after landing on a cool night). Although a "real" dump valve is a super fix, another get home road alternative is to open the dump valve and short across the down switch momentarily. This pump chirp bumps off the back side pressure (by virtue of engaging the motor). Some folks have little secret switches for bypassing the pressure switches but I've only seen this problem once in 920 hours. Alternatively, dumping the pressure and reclosing the valve upon shut down is 99% affective, too. Larry Henney N360LH Spry Debongers (850 hours trouble free!) _____ From: randy snarr [mailto:randylsnarr@yahoo.com] Sent: Tuesday, April 06, 2010 4:39 PM To: lml@lancaironline.net Subject: Re: [LML] gear retract problems - 320 John, This has gone around several times. 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 the 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! That puts the 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 limit 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 up 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 running. This changes when the pump is running. If you increase the pressure enough 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 the gear will not retract. Sometimes opening the dump valve will help 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 gear 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 flexibity allowing it to balloon a little limiting the heat induce pressure increase. I solved this by replacing the dump valve that does more than connect the high and low pressure 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 dumps 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 to retract the gear by cracking the dump valve and closing it again as you would truely have dumped pressure not just equalized pressure. I have heard of some doing a bypass on the pressure switch to momentarily get the gear 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 system, 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 you 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 My 320 gear did not activate when I selected gear up yesterday - I checked the circuit breaker, opened and closed the dump valve, selected gear down, then up - all to no avail and then landed. I recalled some discussion years ago about this issue and a temporary fix being the "cracking" of the hydraulic pressure to get the system going again - this I did and it worked ! Can someone help me with identifying the actual cause and permanent fix. Thanks John Spry L320 __________ Information from ESET NOD32 Antivirus, version of virus signature database 5002 (20100405) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_007C_01CAD64D.70ACD040 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
John,
 
In 920 hours I've seen this particular = hiccup only=20 once.  It was exactly as described by Randy (hot day after landing = on a=20 cool night).  Although a "real" dump valve is a super fix, another = get=20 home road alternative is to open the dump valve and short across = the down=20 switch momentarily.  This pump chirp bumps off the back side = pressure (by=20 virtue of engaging the motor).
 
Some folks have little secret switches for = bypassing=20 the pressure switches but I've only seen this problem once in 920 = hours. =20 Alternatively, dumping the pressure and reclosing the valve upon shut = down is=20 99% affective, too.
 
Larry Henney
N360LH
Spry Debongers (850 hours trouble=20 free!)

From: randy snarr = [mailto:randylsnarr@yahoo.com]=20
Sent: Tuesday, April 06, 2010 4:39 PM
To:=20 lml@lancaironline.net
Subject: Re: [LML] gear retract problems = - 320=20

John,
This has gone around several times. =
The dump=20 valve you have is really a pressure equalization valve.
A true = dump=20 valve will dump the pressure to 0. I will explain.

This has = happened to me as well. I installed hydraulic gauges which tells = the=20 story. When you pull the airplane out of a cool hangar into the = warm sun,=20 the system heats up and pressure on both the high and low sides = increase=20 pretty much equally. Example: my high pressure (gear up) side may = start at=20 0 and the low side ( gear down) at 500 when in the cool = hangar.Pull it=20 into the sun for 30 minutes and both will increase say 700 psi. No = kidding! That puts the high at 700 and the low at 1200. If the = increase of=20 the system hits 900 or so ( low now at 1400 high at = 900)   you=20 have hit the gear up limit pressure switch which tells the system = (if it=20 were in transit) to stop raising the gear. In your case, when you = try to=20 retract the gear the upper limit just keeps the pump from starting = as it=20 thinks the gear is already up because the upper limit has already = been=20 hit. In our systems, both sides are closed meaning neither vents = to the=20 resevoir when the pump is not running. This changes when the pump = is=20 running. If you increase the pressure enough on both sides (again = with=20 heat) while on the ground the the pressure on the high side will=20 eventually open the upper limit pressure switch. and the gear will = not=20 retract. Sometimes opening the dump valve will help as it = equalizes the=20 pressure on both sides. If this equalization results in the high = side=20 dropping below the high side limit (appx. 900 psi), the gear will = retract.=20 It the equalization does not result in this it will not, thus you = have to=20 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=20 think I am more suseptable to it as I used small hot rod stainless = braid=20 hydraulic lines instead of the factory rubber stuff. I think the = factory=20 stuff although much heaver has some flexibity allowing it to = balloon a=20 little limiting the heat induce pressure increase. I solved this = by=20 replacing the dump valve that does more than  connect the = high and=20 low pressure sides. Mine does that but it has an extra line that = not only=20 connects the high and low pressure sides equalizing pressure on = each side,=20 it also dumps the pressure to 0 with a low pressure return line to = the=20 resevoir. If you had my dump valve and low pressure return line, = you would=20 have been able to retract the gear by cracking the dump valve and = closing=20 it again as you would truely have dumped pressure not just = equalized=20 pressure.
I have heard of some doing a bypass on the pressure = switch to=20 momentarily get the gear pump to move, for me I like my set up = which is=20 similar to the Legacy. I like the idea of being able to release = all=20 pressure from the system, not only to solve the issue describe = here but to=20 ensure I can always get=20 the wheels down without power as there is no way to keep the gear = up if=20 you vent the pressure to 0.

FWIW...
Randy=20 Snarr
N694RS
235/320
--- On Tue, 4/6/10, John Spry=20 <spry@paradise.net.nz> wrote:

From:=20 John Spry <spry@paradise.net.nz>
Subject: [LML] gear = retract=20 problems - 320
To: lml@lancaironline.net
Date: Tuesday, = April 6,=20 2010, 5:59 AM

My 320 gear did not activate = when I=20 selected gear up yesterday - I checked the circuit breaker, = opened and=20 closed the dump valve, selected gear down, then up - all to no = avail and=20 then landed.
 
I recalled some discussion = years ago about=20 this issue and a temporary fix being the "cracking" of the = hydraulic=20 pressure to get the system going again - this I did and it = worked=20 !
 
Can someone help me with = identifying the=20 actual cause and permanent fix.
 
Thanks
 
John Spry
 
L320


__________=20 Information from ESET NOD32 Antivirus, version of virus = signature=20 database 5002 (20100405) __________

The message was = checked by=20 ESET NOD32 Antivirus.

http://www.eset.com

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