X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 18 Apr 2012 11:00:39 -0400 Message-ID: X-Original-Return-Path: Received: from nm2-vm0.bullet.mail.bf1.yahoo.com ([98.139.213.127] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with SMTP id 5486292 for lml@lancaironline.net; Wed, 18 Apr 2012 01:29:36 -0400 Received-SPF: none receiver=logan.com; client-ip=98.139.213.127; envelope-from=chris_zavatson@yahoo.com Received: from [98.139.212.151] by nm2.bullet.mail.bf1.yahoo.com with NNFMP; 18 Apr 2012 05:29:00 -0000 Received: from [98.139.212.250] by tm8.bullet.mail.bf1.yahoo.com with NNFMP; 18 Apr 2012 05:29:00 -0000 Received: from [127.0.0.1] by omp1059.mail.bf1.yahoo.com with NNFMP; 18 Apr 2012 05:29:00 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 853150.69606.bm@omp1059.mail.bf1.yahoo.com Received: (qmail 56263 invoked by uid 60001); 18 Apr 2012 05:29:00 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=rqI2Km0lDOWZ1+B4V74YVCKumczrQE2+AEu1FGl6xIEzGfa8gdRCV0QWf/slYspkVKOxMOekTDm40kCU5oe1+fmnqrc554KlBQoZ4y8xRbjbLGFSm3tQ9rFCPxcUo9Dnp0nQffM/RA5aEDCfaj7aiW3ojtO6roH6CXLzDzL9m1s=; X-YMail-OSG: RwB2dw0VM1kFjseiqp.owjkf3OIVXdCVs9GVch7wMUD7.UA woaGXngw_OfScIEPpoDcLur8myAR6Oq2MzbxzQZprwMxS_9u2MVLn2sij.sm .G92vKPUqeOGcn4uSa.lEXFNrR8ZiN7i68x7elAUW2PT2TVckLmBrAtOjM_4 LB5bgMWJ2uy1w_z4LiZmajLrlG7M.NX02K3sq7drLi6vrCQOiCXw55znZur7 BRk0n3y4.okHMbvi9NSVsUDb.qwALPnoD86k01Qv7qMvRtihCeBRXpdtnYMt S.LINo9Cw.M4fXm0m8oOeLwwwFn2JABirE2NQ4J8MG3KIvGO8Raddb8cmvRa A43h8vkplBL67AaJsWQYhyF9NLyfXGQ1SsB65GU1rvt.UHX0..qhrnaJBeih OdB9oeqO8BbfmWJW5f11HCrMX4d11sdX7ei2yEbB6j8oXaLtoZg7pUKavayF 04KsMKYiHO3EBfsS65n7pxwJWvRtVrVIjbor5iWpvSjkVY876s5VK8XIqxPQ NzxqP4dog38AOBQCSz6bQd0WPwUSdoLNocVqCPKaJVcsu3KsIJWdPuKUONMU bvbt77pgtk0djhsYtzihNpVYmeNh6CTtap.KObgu3bWWYAWgalnxoUGJFsl8 YDlX3Sc2xAbD36s1bwFf_3Euy9HQZHTDWfqiqoM1rA_ACSKGDQj0J5oj.7B0 YrnRy4lhGo75ylT_ZvA5_oDESLYbCqQuKGg-- Received: from [99.140.63.246] by web160406.mail.bf1.yahoo.com via HTTP; Tue, 17 Apr 2012 22:29:00 PDT X-Mailer: YahooMailWebService/0.8.117.340979 References: X-Original-Message-ID: <1334726940.56079.YahooMailNeo@web160406.mail.bf1.yahoo.com> X-Original-Date: Tue, 17 Apr 2012 22:29:00 -0700 (PDT) From: Chris Zavatson Reply-To: Chris Zavatson Subject: Re: [LML] Excessive down hydraulic pressure X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="1741458154-980315594-1334726940=:56079" --1741458154-980315594-1334726940=:56079 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable =A0=0AAdam,=0ANow that is very interesting.=A0 Observing pressure in the=A0= low=A0circuit while charging the high side looks very much like the 320/360= system sees when the spool is reversed.=A0 Excess return flow is forced to= exit the loop via the low side pressure relief valve.=A0 Now being that yo= u have a Legacy, the system should be replenishing fluid from the reservoir= during retraction.=A0 Most like Figure 10 in the following document. (Cyli= nders extending) =0Ahttp://www.n91cz.com/Hydraulics/Lancair%20Hydraulics.pd= f=0AYour pump is behaving as though the internal return line to the gear pu= mp is blocked thus forcing the fluid past the relief valve.=A0 Concerning i= s that the pressurized low circuit isn't readily bleeding down.=A0 In fact,= it starts following the high pressure in the lower plot.=A0 This could be = the result of spool return springs.=A0 =0ANoteworthy is that the first retr= action looks normal.=0ACan you pull the manufacturing date and part number = off the pump?=0A=A0=0AChris Zavatson=0AN91CZ=0A360std=0Awww.N91CZ.net=0A=0A= =0AFrom: Adam Molny =0ATo: lml@lancaironline.n= et =0ASent: Monday, April 16, 2012 5:14 AM=0ASubject: [LML] Excessive down = hydraulic pressure=0A=0A=0AOn my fourth test flight I tested the normal and= emergency gear extension/retraction and everything worked fine. My first l= anding attempt resulted in a go-around due to gusty winds. When I extended = the gear again on downwind nothing happened. After a few seconds of head-sc= ratching I momentarily cracked the dump valve. That fixed the problem and t= he landing was uneventful (if a bit firm).=A0http://www.youtube.com/watch?v= =3Dfo1qnhBuqS8=0AThe attached JPG file shows the up and down hydraulic pres= sure readings throughout the flight. The x-axis is time, with the flight be= ginning at 20:32Z and ending at 21:12Z. You can see the gear retraction tes= ts beginning around 20:43 and 3500' altitude. Notice that after the last te= st the down pressure remains around 500psi for about 90 seconds even though= the gear is retracted. The up pressure fluctuates a bit then the down pres= sure drops to near zero.=A0=0AThe bottom graph is a closer view of the land= ing sequence. The go-around occurs at 21:05Z. When I retracted the gear the= up pressure went to 950psi as expected, but the down pressure fluctuated a= round 500psi. This kept the down pressure switch open, preventing gear exte= nsion.=0ADoes anyone have an idea as to what's causing the pressure buildup= on the down side?=A0=0AThanks,=0AAdam Molny=0AN181AM 6.1hrs hobbs time=0A-= -=0AFor archives and unsub http://mail.lancaironline.net:81/lists/lml/List.= html --1741458154-980315594-1334726940=:56079 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
 
Adam,
Now that is very = interesting.  Observing pressure in the low circuit while ch= arging the high side looks very much like the 320/360 system sees when the = spool is reversed.  Excess return flow is forced to exit the loop via = the low side pressure relief valve.  Now being that you have a Legacy,= the system should be replenishing fluid from the reservoir during retracti= on.  Most like Figure 10 in the following document. (Cylinders extendi= ng)
Your pump is behaving as though the internal return line to the = gear pump is blocked thus forcing the fluid past the relief valve.  Co= ncerning is that the pressurized low circuit isn't readily bleeding down.&n= bsp; In fact, it starts following the high pressure in the lower plot. = ; This could be the result of spool return springs. 
Noteworthy is that the first retraction looks normal.
Can you pull the manufacturing date and part number off the pump= ?
 
Chris Zavatson
N91CZ
360std

=

From:= Adam Molny <adam@validationpartners.com>
To: lml@lancaironline.net
Sent: Monday, April 16, 2012 5:14 AM<= BR>Subject: [LML] Excessive= down hydraulic pressure

On my fourth test flight I tested the normal and emergency gear extens= ion/retraction and everything worked fine. My first landing attempt resulte= d in a go-around due to gusty winds. When I extended the gear again on down= wind nothing happened. After a few seconds of head-scratching I momentarily= cracked the dump valve. That fixed the problem and the landing was unevent= ful (if a bit firm). http://www.youtube.com/watch?v=3Dfo1qnhBuqS8
The attached JPG file shows the up and down hydraulic pressure reading= s throughout the flight. The x-axis is time, with the flight beginning at 2= 0:32Z and ending at 21:12Z. You can see the gear retraction tests beginning= around 20:43 and 3500' altitude. Notice that after the last test the down = pressure remains around 500psi for about 90 seconds even though the gear is= retracted. The up pressure fluctuates a bit then the down pressure drops t= o near zero. 
The bottom graph is a closer view of the landing sequence. The go-arou= nd occurs at 21:05Z. When I retracted the gear the up pressure went to 950p= si as expected, but the down pressure fluctuated around 500psi. This kept t= he down pressure switch open, preventing gear extension.
Does anyone have an idea as to what's causing the pressure buildup on = the down side? 
Thanks,
Adam Molny
N181AM 6.1hrs hobbs time

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