X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 30 Jan 2013 12:30:59 -0500 Message-ID: X-Original-Return-Path: Received: from blu0-omc3-s24.blu0.hotmail.com ([65.55.116.99] verified) by logan.com (CommuniGate Pro SMTP 6.0.1) with ESMTP id 6037038 for lml@lancaironline.net; Wed, 30 Jan 2013 11:25:32 -0500 Received-SPF: pass receiver=logan.com; client-ip=65.55.116.99; envelope-from=gary21sn@hotmail.com Received: from BLU172-DS8 ([65.55.116.74]) by blu0-omc3-s24.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675); Wed, 30 Jan 2013 08:24:57 -0800 X-EIP: [SkJi4R/ctkemhGaRO2/+89fmQepNgl/N] X-Originating-Email: [gary21sn@hotmail.com] X-Original-Message-ID: X-Original-Return-Path: gary21sn@hotmail.com From: "Gary Edwards" X-Original-To: "Lancair Mailing List" References: Subject: Re: Thermal influence on Hydraulic Pressure In-Reply-To: X-Original-Date: Wed, 30 Jan 2013 08:24:56 -0800 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_03A9_01CDFEC3.492D3630" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V10.50.0008.2100 Seal-Send-Time: Wed, 30 Jan 2013 08:24:56 -0800 X-OriginalArrivalTime: 30 Jan 2013 16:24:57.0035 (UTC) FILETIME=[57BAA9B0:01CDFF06] This is a multi-part message in MIME format. ------=_NextPart_000_03A9_01CDFEC3.492D3630 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Rob, Most likely the original VEP switches will be internally corroided and = not usuable if they have never been put into service. I went thru that = situation years ago (1990's) during the extended build time. It cost a = fortune to have the VEP company even just test them them, more than a = new set from Lancair would cost for the new style. And the new style is = install and fly, whereas the VEP's require adjustments during new flight = hours, a big inconvenience. Gary Edwards LNC2=20 From: Chris Zavatson=20 To: lml@lancaironline.net=20 Sent: Wednesday, January 30, 2013 5:28 AM Subject: [LML] Re: Thermal influence on Hydraulic Pressure Rob, Lancair carries a new type that is much more reliable. I forget the = brand name. Chris Zavatson N91CZ 360std 1,400 hrs http://www.n91cz.net/ =20 From: Stevens Family = > To: lml@lancaironline.net=20 Sent: Tuesday, January 29, 2013 6:40 PM Subject: [LML] Re: Thermal influence on Hydraulic Pressure Chris, I am interested in your comment about the =E2=80=9COld VEP pressure = switches=E2=80=9D. The 360 kit I am building comes with those pressure = switches. What do you recommend we should use in place of them? Thanks again. Rob Stevens Perth, Western Australia. From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Chris Zavatson Sent: Tuesday, 29 January 2013 11:56 PM To: lml@lancaironline.net Subject: [LML] Re: Thermal influence on Hydraulic Pressure Scott, Yep, the failure modes are completely unrelated to each other. There is a second failure-to-retract mode. In fact, it is the only = one I experienced in my plane. It was with the old VEP pressure = switches. They would stick open on occassion. Then the problem is not = too much pressure, it is not having any.=20 Failure to retract can be a bit more serious if in IMC or taking off = at high density altitude. The failure to extend can be fixed by simply raising the operating = pressure of the low side circuit. I have looked at pumps spanning the 95 to 2011 manufacturing time = frame. The only one that would lock up on the ground had spool return = springs. Since the 70g rattle-your-spool controversy appeared, I have = also been measuring the spool resistance in every pump I get my hands = on. -haven't found an outliers yet, but I will keep looking. Chris Zavatson N91CZ 360std 1,400hrs http://www.n91cz.net/ From: "Sky2high@aol.com" = > To: lml@lancaironline.net=20 Sent: Tuesday, January 29, 2013 5:27 AM Subject: [LML] Re: Thermal influence on Hydraulic Pressure 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.=20 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.=20 <> <<..........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/ From: Wolfgang > To: lml@lancaironline.net=20 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 -----=20 From: Charles Brown=20 To: lml@lancaironline.net=20 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 =20 -- For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html ------=_NextPart_000_03A9_01CDFEC3.492D3630 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
Rob,
 
Most likely the original VEP switches will be internally corroided = and not=20 usuable if they have never been put into service.  I went thru = that=20 situation years ago (1990's) during the extended build time.  It = cost a=20 fortune to have the VEP company even just test them them, more than a = new set=20 from Lancair would cost for the new style.  And the new style is = install=20 and fly, whereas the VEP's require adjustments during new flight hours, = a big=20 inconvenience.
 
Gary Edwards
LNC2 
 
From: Chris Zavatson
Sent: Wednesday, January 30, = 2013 5:28=20 AM
Subject: [LML] Re: Thermal = influence on=20 Hydraulic Pressure

Rob,
Lancair carries a new type that is much more = reliable.  I=20 forget the brand name.
 
Chris Zavatson
N91CZ
360std 1,400 hrs

 
From:=20 Stevens Family <stevens5@swiftdsl.com.au>=
To: lml@lancaironline.net =
Sent: Tuesday, January 29, 2013 = 6:40=20 PM
Subject: [LML] = Re: Thermal=20 influence on Hydraulic Pressure

Chris,
 
I=20 am interested in your comment about the =E2=80=9COld VEP pressure = switches=E2=80=9D. The 360=20 kit I am building comes with those pressure switches. What do you = recommend we=20 should use in place of them?
 
Thanks=20 again.
 
Rob=20 Stevens
Perth,
Western=20 Australia.
 
 
From:=20 Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Chris=20 Zavatson
Sent: Tuesday, 29 January 2013 11:56 = PM
To:=20 lml@lancaironline.net
Subject: [LML] Re: Thermal influence = on=20 Hydraulic Pressure
 
Scott,
Yep, the = failure=20 modes are completely unrelated to each other.
There is a = second=20 failure-to-retract mode.  In fact, it is the only one I = experienced in my=20 plane.  It was with the old VEP pressure switches.  They = would stick=20 open on occassion.  Then the problem is not too much pressure, it = is not=20 having any. 
Failure to = retract=20 can be a bit more serious if in IMC or taking off at high density=20 altitude.
 
The failure = to extend=20 can be fixed by simply raising the operating pressure of the low side=20 circuit.
I have = looked at=20 pumps spanning the 95 to 2011 manufacturing time frame.  The only = one=20 that would lock up on the ground had spool return springs.  Since = the 70g=20 rattle-your-spool controversy appeared, I have also been measuring the = spool=20 resistance in every pump I get my hands on.  -haven't found = an=20 outliers yet, but I will keep looking.
 
Chris=20 Zavatson
N91CZ
360std=20 1,400hrs
http://www.n91cz.net/
 
From: "Sky2high@aol.com" <Sky2high@aol.com>
To: lml@lancaironline.net=20
Sent: Tuesday, January 29, 2013 5:27 AM
Subject: = [LML]=20 Re: Thermal influence on Hydraulic Pressure
 
Chris,
 
While=20 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=20 secondary problem is that he didn't look for the "gear down and = locked" lights=20 before landing.  While the gear down pressure switch saw = enough=20 pressure to not allow the pump to start, the failure to recognize = that=20 the gear was not down contributed to the belly in = landing.
 
To=20 allow people to be more comfortable about the hydro-electric system = they=20 should be reminded of this
 
1.=20 The failure to RETRACT the gear because of high pressure on both = sides is=20 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 with=20 the gear down and locked.  There are no physical forces able = to=20 change the system condition - no G-maneuvers, no slips or skids,=20 nada.
 
2.=20 The failure to EXTEND the gear because of high pressure on both sides = is=20 different.  Opening the dump valve (allowing down side fluid to = flow to=20 the upside) will allow the gear to "emergency" extend because of = gravity on=20 the mains and the nose gear gas spring.  OK, maybe the nose = gear=20 might not extend all the way at 120 KIAS (max gear extension speed), = but the=20 pressure lock has been broken and the pump will start if the switch is = down=20 and the pump breaker is closed.  Close the dump valve to complete = the=20 process.  As a matter of fact, assuming everything is normal and = the gear=20 down switch is selected but nothing happens, it may merely require = momentarily=20 cracking the dump valve to relieve the hydraulic=20 constipation.
 
Failing=20 to retract is a nuisance.  Failing to extend is, uh, more = serious, but=20 resolvable.
 
Scott=20 Krueger AKA Grayhawk
 
In a=20 message dated 1/29/2013 6:54:27 A.M. Central Standard Time, chris_zavatson@yahoo.com = writes:
Wolfgang,
I seem to = recall=20 you dismissed the idea of a three-way valve previously.
<<That's a sound and positive fix. =
- - However it requires changing the dump = valve,=20 running a return line and pump modification (replace the=20 reservoir).
...................................
Wolfgang>>
<<..........Automatic = action by=20 my module can prevent these problems for both up and down gear=20 operation.
Wolfgang>>
 
Could you = please=20 explain how your module will prevent the gear extension lock-up=20 failures.  Recall Lorn's photo after his extension failure and = gear up=20 landing.  Both pressure gauges showed around 500 psi.  The = system=20 is hydraulically locked with one switch open and one=20 closed.
 
Chris Zavatson
N91CZ
360std, 1,400 hrs
 
From:=20 Wolfgang <Wolfgang@MiCom.net>
To= :=20 lml@lancaironline.net=20
Sent: Saturday, January 26, 2013 11:24 = AM
Subject:=20 [LML] Re: Thermal influence on Hydraulic Pressure
 
This=20 has been covered at great length before. Some take the position that = "real=20 pilots" don't need anything but the dump valve.
I=20 have proposed two answers,
1)=20 replace the dump valve that only opens a port between the HI and LO = sides=20 with a dump valve that dumps back to the pump reservoir.
2)=20 install a small electric module I make across the pressure switches=20 that runs the pump to relieve the over pressure in the = "wrong"=20 line automatically.
 
Wolfgang
-----=20 Original Message -----
From:=20 Charles=20 Brown
Sent:=20 Saturday, January 26, 2013 2:07 AM
Subject:=20 Re: [LML] Re: Thermal influence on Hydraulic = Pressure
 
This has happened to me even at the = beginning of a=20 flight, if the temps in the hangar have gone from cold on a = previous day,=20 to warm on flight day.  I guess cold temps shrink the fluid = and suck=20 more from the reservoir into the lines, and when it warms, the = pressure=20 builds on both sides of the system, so that the "up" and "down" = pressure=20 switches are both open and the gear won't move until I pop the = bleed=20 valve.
 
Nasty when the gear won't retract just = after blasting=20 off into a low overcast.
 
Charley Brown
Legacy #299  200 hr
 
On Jan 25, 2013, at 7:23 AM, randy snarr=20 wrote:
 
. = I dont like=20 having to open the dump valve but it is necessary once in a while=20 especially when it is cold. The pressures on both sides of the = system=20 climb due to the engine heat and the gear sometimes will not move = without=20 dumping the pressure.
 
 


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