X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-ma05.mx.aol.com ([64.12.100.31] verified) by logan.com (CommuniGate Pro SMTP 6.0.1) with ESMTP id 6034651 for lml@lancaironline.net; Tue, 29 Jan 2013 08:27:44 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.100.31; envelope-from=Sky2high@aol.com Received: from mtaomg-ma02.r1000.mx.aol.com (mtaomg-ma02.r1000.mx.aol.com [172.29.41.9]) by imr-ma05.mx.aol.com (Outbound Mail Relay) with ESMTP id BF85C1C0000F9 for ; Tue, 29 Jan 2013 08:27:09 -0500 (EST) Received: from core-mte004c.r1000.mail.aol.com (core-mte004.r1000.mail.aol.com [172.29.236.77]) by mtaomg-ma02.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 81B37E000082 for ; Tue, 29 Jan 2013 08:27:09 -0500 (EST) From: Sky2high@aol.com Full-name: Sky2high Message-ID: <2956c.f968d4f.3e39282c@aol.com> Date: Tue, 29 Jan 2013 08:27:09 -0500 (EST) Subject: Re: [LML] Re: Thermal influence on Hydraulic Pressure To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_2956c.f968d4f.3e39282c_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [67.175.156.123] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1359466029; bh=Ig0BnTa5fco0uHtnMHeYtz3LT93l8b+6Mgi05FCg6rE=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=LZhIF0KzFlovPiGHds0Lo0/0ieGOCOdOktb4ozojy8I4L6yeF1vkWGfqqmzLCEpcU yyLhajAlfB7QZja20Z3IbYpD8mKcvmmgXg1ujoBiJ5VK3l0NJxzdyHQ45/X9ikqGAP fvZxbzI2SesnIBR694uhg7NUOENnFJPbdwinml3U= X-AOL-SCOLL-SCORE: 0:2:461392064:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d29095107ce2d0a0c --part1_2956c.f968d4f.3e39282c_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Chris, While waiting for Wolfgang's answer, some 200/300 series pilots are becoming concerned that they can't get the gear down when needed. First, Lorn's secondary problem is that he didn't look for the "gear down and locked" lights before landing. While the gear down pressure switch saw enough pressure to not allow the pump to start, the failure to recognize that the gear was not down contributed to the belly in landing. To allow people to be more comfortable about the hydro-electric system they should be reminded of this 1. The failure to RETRACT the gear because of high pressure on both sides is a problem because of the safe design. Opening the dump valve doesn't resolve the problem because the system is in a static state with the gear down and locked. There are no physical forces able to change the system condition - no G-maneuvers, no slips or skids, nada. 2. The failure to EXTEND the gear because of high pressure on both sides is different. Opening the dump valve (allowing down side fluid to flow to the upside) will allow the gear to "emergency" extend because of gravity on the mains and the nose gear gas spring. OK, maybe the nose gear might not extend all the way at 120 KIAS (max gear extension speed), but the pressure lock has been broken and the pump will start if the switch is down and the pump breaker is closed. Close the dump valve to complete the process. As a matter of fact, assuming everything is normal and the gear down switch is selected but nothing happens, it may merely require momentarily cracking the dump valve to relieve the hydraulic constipation. Failing to retract is a nuisance. Failing to extend is, uh, more serious, but resolvable. Scott Krueger AKA Grayhawk In a message dated 1/29/2013 6:54:27 A.M. Central Standard Time, chris_zavatson@yahoo.com writes: Wolfgang, I seem to recall you dismissed the idea of a three-way valve previously. <> <<..........Automatic action by my module can prevent these problems for both up and down gear operation. Wolfgang>> Could you please explain how your module will prevent the gear extension lock-up failures. Recall Lorn's photo after his extension failure and gear up landing. Both pressure gauges showed around 500 psi. The system is hydraulically locked with one switch open and one closed. Chris Zavatson N91CZ 360std, 1,400 hrs _http://www.n91cz.net/_ (http://www.n91cz.net/) From: Wolfgang To: lml@lancaironline.net Sent: Saturday, January 26, 2013 11:24 AM Subject: [LML] Re: Thermal influence on Hydraulic Pressure This has been covered at great length before. Some take the position that "real pilots" don't need anything but the dump valve. I have proposed two answers, 1) replace the dump valve that only opens a port between the HI and LO sides with a dump valve that dumps back to the pump reservoir. 2) install a small electric module I make across the pressure switches that runs the pump to relieve the over pressure in the "wrong" line automatically. Wolfgang ----- Original Message ----- From: _Charles Brown_ (mailto:browncc1@verizon.net) To: _lml@lancaironline.net_ (mailto:lml@lancaironline.net) Sent: Saturday, January 26, 2013 2:07 AM Subject: Re: [LML] Re: Thermal influence on Hydraulic Pressure This has happened to me even at the beginning of a flight, if the temps in the hangar have gone from cold on a previous day, to warm on flight day. I guess cold temps shrink the fluid and suck more from the reservoir into the lines, and when it warms, the pressure builds on both sides of the system, so that the "up" and "down" pressure switches are both open and the gear won't move until I pop the bleed valve. Nasty when the gear won't retract just after blasting off into a low overcast. Charley Brown Legacy #299 200 hr On Jan 25, 2013, at 7:23 AM, randy snarr wrote: . I dont like having to open the dump valve but it is necessary once in a while especially when it is cold. The pressures on both sides of the system climb due to the engine heat and the gear sometimes will not move without dumping the pressure. -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html --part1_2956c.f968d4f.3e39282c_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Chris,
 
While waiting for Wolfgang's answer, some 200/300 series pilots are=20 becoming concerned that they can't get the gear down when needed.  Fir= st,=20 Lorn's secondary problem is that he didn't look for the "gear down and lock= ed"=20 lights before landing.  While the gear down pressure switch saw e= nough=20 pressure to not allow the pump to start, the failure to recognize that= the=20 gear was not down contributed to the belly in landing.
 
To allow people to be more comfortable about the hydro-electric system= they=20 should be reminded of this
 
1. The failure to RETRACT the gear because of high pressure on bo= th=20 sides is a problem because of the safe design.  Opening the dump = valve=20 doesn't resolve the problem because the system is in a static state wi= th=20 the gear down and locked.  There are no physical forces able to c= hange=20 the system condition - no G-maneuvers, no slips or skids, nada.
 
2. The failure to EXTEND the gear because of high pressure on both sid= es is=20 different.  Opening the dump valve (allowing down side fluid to flow t= o the=20 upside) will allow the gear to "emergency" extend because of gravity on the= =20 mains and the nose gear gas spring.  OK, maybe the nose gear migh= t not=20 extend all the way at 120 KIAS (max gear extension speed), but the pressure= lock=20 has been broken and the pump will start if the switch is down and the pump= =20 breaker is closed.  Close the dump valve to complete the process. = ; As=20 a matter of fact, assuming everything is normal and the gear down switch is= =20 selected but nothing happens, it may merely require momentarily cracking th= e=20 dump valve to relieve the hydraulic constipation.
 
Failing to retract is a nuisance.  Failing to extend is, uh, more= =20 serious, but resolvable.
 
Scott Krueger AKA Grayhawk
 
In a message dated 1/29/2013 6:54:27 A.M. Central Standard Time,=20 chris_zavatson@yahoo.com writes:
=
Wolfgang,
I seem to recall you dismissed the = idea of=20 a three-way valve previously.= =20
<<That's a sound and= =20 positive fix.
- - However it requires ch= anging=20 the dump valve, running a return line and pump modification (replace the= =20 reservoir).
..........................= .........
Wolfgang>>
<<..........Autom= atic=20 action by my module can prevent these problems for both up and down gear= =20 operation.
Wolfgang>>
 
Could you please explain how your m= odule=20 will prevent the gear extension lock-up failures.  Recall Lorn's pho= to=20 after his extension failure and gear up landing.  Both pressure gaug= es=20 showed around 500 psi.  The system is hydraulically locked with one= =20 switch open and one closed.
 
Chris Zavatson
N91CZ
360std, 1,400 hrs
 
<= B>From: Wolfgang=20 <Wolfgang@MiCom.net>
To: lml@lancaironline.net
<= SPAN=20 style=3D"FONT-WEIGHT: bold">Sent: Saturday, January 26, 2013 1= 1:24=20 AM
Subject: [LML] Re: = Thermal=20 influence on Hydraulic Pressure

This has been covered at great length be= fore.=20 Some take the position that "real pilots" don't need anything but th= e=20 dump valve.
I have proposed two answers,
1) replace the dump valve that only open= s a port=20 between the HI and LO sides with a dum= p valve=20 that dumps back to the pump reservoir.
2) install a small electric module I mak= e across=20 the pressure switches that runs the pump to relieve the over=20 pressure in the "wrong" line automatically.
 
Wolfgang
----- Original Message -----
From: = Charles=20 Brown
To: lml@lancaironline.net
Sent: Saturday, January 26, 2013= 2:07=20 AM
Subject: Re: [LML] Re: Thermal= =20 influence on Hydraulic Pressure

This has happened to me even at the beginning of a flight, if the = temps=20 in the hangar have gone from cold on a previous day, to warm on flight = day.=20  I guess cold temps shrink the fluid and suck more from the reserv= oir=20 into the lines, and when it warms, the pressure builds on both sides of= the=20 system, so that the "up" and "down" pressure switches are both open and= the=20 gear won't move until I pop the bleed valve.

Nasty when the gear won't retract just after blasting off into a l= ow=20 overcast.

Charley Brown
Legacy #299  200 hr

On Jan 25, 2013, at 7:23 AM, randy snarr wrote:

. I dont like having to open the dump v= alve=20 but it is necessary once in a while especially when it is cold. The=20 pressures on both sides of the system climb due to the engine heat and = the=20 gear sometimes will not move without dumping the pressure.





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