X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from omr-m04.mx.aol.com ([64.12.143.78] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTPS id 6906703 for lml@lancaironline.net; Tue, 27 May 2014 08:31:41 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.143.78; envelope-from=Sky2high@aol.com Received: from mtaomg-mcc02.mx.aol.com (mtaomg-mcc02.mx.aol.com [172.26.253.80]) by omr-m04.mx.aol.com (Outbound Mail Relay) with ESMTP id 7955E701DA4D6 for ; Tue, 27 May 2014 08:31:05 -0400 (EDT) Received: from core-mla005c.r1000.mail.aol.com (core-mla005.r1000.mail.aol.com [172.29.186.83]) by mtaomg-mcc02.mx.aol.com (OMAG/Core Interface) with ESMTP id 44EB238000081 for ; Tue, 27 May 2014 08:31:05 -0400 (EDT) From: Sky2high@aol.com Full-name: Sky2high Message-ID: Date: Tue, 27 May 2014 08:31:05 -0400 (EDT) Subject: Re: [LML] Re: Hydraulic Pressure Spike Video To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_b733c.3ff63529.40b5df90_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [24.14.166.87] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1401193865; bh=sc6tzgmO9wF2qBHurILsdtSGy+r2N3q5ttUKWqabJ24=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=v0p7UB6pMlAhdmelELlWNF3+g6/WuDzfB6Snq0sCXo1clcLf0WZXy4JXDwFJaVG05 Wwt2bn38U3cNe0PkHsiICm7kRteKdcpgl6udIzPhKsID8rDEApG2fjMvts0bFOx9l2 FnvyixKWrLvB3+i0M843yVfqpKVB/zQ+6ywwItF0= x-aol-sid: 3039ac1afd505384858958ec --part1_b733c.3ff63529.40b5df90_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit John, At least for LNC2's the down actuators are to assist gravity and the nose gear gas spring in order to extend the gear. The infamous rat-trap springs on the main gear are to merely lock the over center. Thus, not much hydro pressure is needed to extend the mains and nose even at 122 Kts (max extension speed). When the gear is extended the actuators under pressure are merely used to keep the over center links locked (kinda like a backup system). The actuator down stops must be set to keep hydro pressure off of the links. "Why?" You might ask. Well, examine the geometry - the force triangle is from the pivot to the link to the link-spar attach point and back to the pivot along the spar. If enough hydro force is applied to the actuator, the rod may become bent or the now excessive force present at the link-spar connection can delaminate it from the spar. Hard landings with some side loads have caused failure there and that is why a service bulletin recommends putting a reinforcing plate between the link-spar attach point and the upper spar. Yes, excessive pressure without proper down stop rigging can cause problems. Scott Krueger In a message dated 5/27/2014 7:11:00 A.M. Central Daylight Time, snopercod@comporium.net writes: Chris-- Since the low-side pressure is pushing on the over-center links with the gear down, have you considered whether upping the pressure from 500 to 800 will bend anything down there? Best-- --John On 5/18/2014 6:00 AM, Lancair Mailing List wrote: From: _Chris Zavatson_ (mailto:chris_zavatson@yahoo.com) Sent: Thursday, May 15, 2014 7:33 AM Subject: Hydraulic Pressure Spike Video ... I have my low side pressure switch set to 800 psi which has proven to be high enough to avoid any gear hesitations and/or extension failures. --part1_b733c.3ff63529.40b5df90_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
John,
 
At least for LNC2's the down actuators are to assist gravity and the n= ose=20 gear gas spring in order to extend the gear.  The infamous rat-trap sp= rings=20 on the main gear are to merely lock the over center.  Thus, not=20 much hydro pressure is needed to extend the mains and nose even at 122= Kts=20 (max extension speed).
 
When the gear is extended the actuators under pressure are merely = ;used=20 to keep the over center links locked (kinda like a backup=20 system).  The actuator down stops must be set to keep hydro press= ure=20 off of the links.  "Why?" You might ask.  Well, examine the= =20 geometry - the force triangle is from the pivot to the link to the link-spa= r=20 attach point and back to the pivot along the spar.  If enough=20 hydro force is applied to the actuator, the rod may become bent or the= now=20 excessive force present at the link-spar connection can delaminate it from = the=20 spar.  Hard landings with some side loads have caused failure there an= d=20 that is why a service bulletin recommends putting a reinforcing plate betwe= en=20 the link-spar attach point and the upper spar.
 
Yes, excessive pressure without proper down stop rigging can cause=20 problems.
 
Scott Krueger
 
In a message dated 5/27/2014 7:11:00 A.M. Central Daylight Time,=20 snopercod@comporium.net writes:
=
Chris--

Since the low-side pressure i= s=20 pushing on the over-center links with the gear down, have you considered= =20 whether upping the pressure from 500 to 800 will bend anything down=20 there?

Best--

  --John

On 5/18/2014 6:00 AM, La= ncair=20 Mailing List wrote:
F= rom:=20 Chris= =20 Zavatson
Sent: Thursday, May 15, 2014 7:3= 3=20 AM
Subject: Hydraulic Pressure Spik= e=20 Video

...=20 I have my low side pressure switch set to 800 psi which has proven to b= e=20 high enough to avoid any gear hesitations and/or extension=20 failures.
<= /HTML> --part1_b733c.3ff63529.40b5df90_boundary--