Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Tue, 08 Feb 2005 11:53:57 -0500 Message-ID: X-Original-Return-Path: Received: from imo-d05.mx.aol.com ([205.188.157.37] verified) by logan.com (CommuniGate Pro SMTP 4.3c1) with ESMTP id 720268 for lml@lancaironline.net; Tue, 08 Feb 2005 09:56:26 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.157.37; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-d05.mx.aol.com (mail_out_v37_r3.8.) id q.1dc.3637bf1a (17377) for ; Tue, 8 Feb 2005 09:54:54 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <1dc.3637bf1a.2f3a2cbe@aol.com> X-Original-Date: Tue, 8 Feb 2005 09:54:54 EST Subject: Re: [LML] Hydraulic pressure:LNC2 X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1107874494" X-Mailer: 9.0 Security Edition for Windows sub 5000 -------------------------------1107874494 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 2/8/2005 5:01:27 A.M. Central Standard Time, goconnell@dodo.com.au writes: Instead of the usual 1350 psi I noticed it had shot up to 1700psi. There has been no external interference since the previous flights. Has anyone else had this happen? I imagine its' a problem with the internal relief valve? Is sustained operation at this pressure likely to cause problems i.e can I just ignore it for the time being? Gerard, I don't have a pressure gauge plumbed in my system, but I have observed the operation (on the ground) of several that did. Generally, the gear can be moved towards full retraction with about 500-600 psi. The final tuck-up seems to require about 1100-1200 psi. The dead band of the pressure switches is several hundred psi (i.e. the pressure switch remains open over a drop of a few hundred psi). Oildyne claims that the pump internal relief valves should be set approximately 400 psi greater than the controlling pressure switches. Note that the relief valve will not stop the pump from running. Did the pump continue to run? With the above information and assuming the pump stopped running, it may be that a sluggish (slow to act) pressure switch that took too long to act allowed the system hit the relief valve pressure for a moment. Side note: Over the years there has been 3 or 4 versions of the pressure switch - earlier versions had problems - I know because I have had them all installed over time. If you suspect a faulty one, consider replacing it. Further note: The latest iterations install differently than the earliest ones - if I remember correctly. The system should be able to handle pressures as great as the relief valve pressures if the actuator stops are properly adjusted since the stops and actuators will bear the brunt of the additional pressure instead of the linkages and bendable actuator push rods. Of course, it would be better that the system regularly operate in the designed pressure range so as to keep the component wear and tear down as well as your nerves when the pressure spikes show up in the middle a cross country night flight. Perhaps someone with pressure gauges will respond with their experiences. Scott Krueger AKA Grayhawk Lancair N92EX IO320 SB 89/96 Aurora, IL (KARR) Fair and Balanced Opinions at No Charge! There is an oxymoron in that, somewhere... -------------------------------1107874494 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 2/8/2005 5:01:27 A.M. Central Standard Time,=20 goconnell@dodo.com.au writes:

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>Instead=20 of the usual 1350 psi I noticed it had shot up to 1700psi. There has been=20= no=20 external interference since the previous flights. Has anyone else had this= =20 happen? I imagine its' a problem with the internal relief valve?

Is= =20 sustained operation at this pressure likely to cause problems i.e can= I=20 just ignore it for the time being?

Gerard,

I don't have a pressure gauge plumbed in my system, but I have observed= the=20 operation (on the ground) of several that did. Generally, the gear can= be=20 moved towards full retraction with about 500-600 psi. The final tuck-u= p=20 seems to require about 1100-1200 psi. The dead band of the pressure=20 switches is several hundred psi (i.e. the pressure switch remains open over=20= a=20 drop of a few hundred psi). Oildyne claims that the pump internal= =20 relief valves should be set approximately 400 psi greater than the=20 controlling pressure switches. Note that the relief valve will not sto= p=20 the pump from running.

Did the pump continue to run?

With the above information and assuming the pump stopped running, = it=20 may be that a sluggish (slow to act) pressure switch that took too= =20 long to act allowed the system hit the relief valve pressure for a=20 moment. Side note: Over the years there has been 3 or 4 versions of th= e=20 pressure switch - earlier versions had problems - I know because I have= had=20 them all installed over time. If you suspect a faulty one, consider replacin= g=20 it. Further note: The latest iterations install differently than the=20 earliest ones - if I remember correctly.

The system should be able to handle pressures as great as the reli= ef=20 valve pressures if the actuator stops are properly adjusted since the s= tops=20 and actuators will bear the brunt of the additional pressure instead of the=20 linkages and bendable actuator push rods. Of course, it would be=20 better that the system regularly operate in the designed pressure range so a= s to=20 keep the component wear and tear down as well as your nerves when the=20 pressure spikes show up in the middle a cross country night flight.

Perhaps someone with pressure gauges will respond with their=20 experiences.

Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)

Fai= r=20 and Balanced Opinions at No Charge!
There is an oxymoron in that,=20 somewhere...

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