Return-Path: Sender: (Marvin Kaye) To: lml Date: Tue, 22 Apr 2003 23:42:01 -0400 Message-ID: X-Original-Return-Path: Received: from [32.97.166.34] (HELO prserv.net) by logan.com (CommuniGate Pro SMTP 4.1b4) with ESMTP id 2144017 for lml@lancaironline.net; Tue, 22 Apr 2003 22:13:28 -0400 Received: from b8p5r1 (slip-12-64-228-186.mis.prserv.net[12.64.228.186]) by prserv.net (out4) with SMTP id <2003042302132220403aaadqe>; Wed, 23 Apr 2003 02:13:23 +0000 From: "Larry Henney" X-Original-To: "'Lancair Mailing List'" Subject: RE: [LML] LNC2 Odd Gear Pump Behavior X-Original-Date: Tue, 22 Apr 2003 21:13:54 -0500 X-Original-Message-ID: <000001c3093d$ffa58b00$bae4400c@b8p5r1> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C30914.16CF8300" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.2627 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6600 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C30914.16CF8300 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Lee, I'm not sure that I'm hearing an actual maintenance problem with your hydraulics. Specifically, your nose gear remaining down longer than the mains is potentially normal because of the gas shock strut's added force. The entire system pressure (to raise the gear) remains roughly constant at all times. Therefore, before full gear retraction variable sequencing is probable due to the greater forces holding the nose gear in place. My mains come up non-symetrically with a noticable yaw during gear retraction. However, if further trouble shooting is desired I would consider 4 possible areas of failure. 1) How do I determine if the nose cylinder needs rebuilt or replaced? Assess all 6 cylinders and the free fall vavle for internal leaks (up or down). This is done fastest by owning 12 AN fitting caps. Troubleshooting is a series of elimination of offending components individually. The steady pressure non-chirping pump is a sign of a good internal seals. Internal leaks are noticed by occasional pump chirp (either up or down). Of course with hydraulic pressure gauges this can also be assessed rapidly. The original dump valve supplied in my kit (1996) was rated at 600 psi. The system running up to 1200 psi caused the dump valve's internal failure. This failure does not seem related to your symptoms. 2) Several spool valves have been installed backwards. I would attribute some "quirky" behavior of my system to this. Such behavior included an occasion gear stuck in the down position after takeoff for no apparent reason. The system will however work with the spool valve in backwards but responds better with it in correctly. The fastest way to trouble shoot this is to raise the gear part way. At about 80% raised reverse the gear handle to down. Instantaneous pump reversal denotes a correct installation of the spool valve. A delay of 8-20 seconds would indicate that it is in backwards. 3) The up and down pressure switches have been accused of numerous failures. I don't know that the "new" switches have any adverse track record. These are quickly removed from the electrical circuit with a jumper wire. The switch is nromally closed and should open when adequate pressure is reached, thus turning off the pump. 4) I suppose physical binding or mechanical failure should be your first assessment. If something is indeed hanging up then it'll talk to you. Disconnect the hydraulic cylinders individually and check for smooth free operation of all the gear. Larry Henney LNC2 IO-360 Ft Worth, TX Ok, new symptom today. Upon gear retraction after take-off this morning it took noticeably longer than normal for the nose gear to start retracting (the down light stayed lit 3-4 seconds longer than normal). Am I losing my nose gear actuating cylinder? I don't have the log books handy, but it's my recollection that the nose cylinder was rebuilt about 200 hours ago (by the previous owner). (Reminder: I didn't build my plane). Lee Metcalfe N320WH ------=_NextPart_000_0001_01C30914.16CF8300 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message
Lee,
 
I'm=20 not sure that I'm hearing an actual maintenance problem with your=20 hydraulics.  Specifically, your nose gear remaining down longer = than the=20 mains is potentially normal because of the gas shock strut's added = force. =20 The entire system pressure (to raise the gear) remains roughly constant = at all=20 times.  Therefore, before full gear retraction variable=20 sequencing is probable due to the greater forces holding the nose = gear in=20 place.  My mains come up non-symetrically with a noticable yaw = during gear=20 retraction.  However, if further trouble shooting is desired I = would=20 consider 4 possible areas of failure.
 
1)   How do I determine if = the nose=20 cylinder needs rebuilt or replaced?  Assess all 6 cylinders = and the=20 free fall vavle for internal leaks (up or down).  This is = done=20 fastest by owning 12 AN fitting caps.  Troubleshooting is a series = of=20 elimination of offending components individually.  The steady = pressure=20 non-chirping pump is a sign of a good internal seals.  Internal = leaks are=20 noticed by occasional pump chirp (either up or down).  Of course = with=20 hydraulic pressure gauges this can also be assessed rapidly.  The = original=20 dump valve supplied in my kit (1996) was rated at 600 psi.  The = system=20 running up to 1200 psi caused the dump valve's internal = failure. =20 This failure does not seem related to your symptoms.
 
2)    Several spool = valves have=20 been installed backwards.  I would attribute some "quirky" behavior = of my=20 system to this.  Such behavior included an occasion gear stuck in = the down=20 position after takeoff for no apparent reason.  The system = will=20 however work with the spool valve in backwards but responds better with = it in=20 correctly.  The fastest way to trouble shoot this is to raise the = gear part=20 way.  At about 80% raised reverse the gear handle to down. =20 Instantaneous pump reversal denotes a correct installation of the spool=20 valve.  A delay of 8-20 seconds would indicate that it is in=20 backwards.
 
3)    The up and down pressure switches have = been accused=20 of numerous failures.  I don't know that the "new" switches have = any=20 adverse track record.  These are quickly removed from the = electrical=20 circuit with a jumper wire.  The switch is nromally closed and = should open=20 when adequate pressure is reached, thus turning off the=20 pump.
 
4)     I suppose physical binding or = mechanical=20 failure should be your first assessment.  If something is indeed = hanging up=20 then it'll talk to you.  Disconnect the hydraulic cylinders = individually=20 and check for smooth free operation of all the gear.
 

Larry Henney
LNC2 IO-360
Ft Worth, TX=20


 
Ok, = new symptom=20 today.  Upon gear retraction after take-off this morning it took=20 noticeably longer than normal for the nose gear to start retracting = (the down=20 light stayed lit 3-4 seconds longer than normal).  Am I = losing my=20 nose gear actuating cylinder?  I don't have the log books handy, = but it's=20 my recollection that the nose cylinder was rebuilt about 200 hours ago = (by the=20 previous owner).  (Reminder: I didn't build my=20 plane).
 
Lee=20 Metcalfe
N320WH
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