X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 31 Jan 2013 01:48:58 -0500 Message-ID: X-Original-Return-Path: Received: from [202.154.122.98] (HELO extmail-03.people.net.au) by logan.com (CommuniGate Pro SMTP 6.0.1) with SMTP id 6037920 for lml@lancaironline.net; Thu, 31 Jan 2013 00:19:28 -0500 Received-SPF: pass receiver=logan.com; client-ip=202.154.122.98; envelope-from=stevens5@swiftdsl.com.au Received: (qmail 19599 invoked from network); 31 Jan 2013 05:18:48 -0000 Received: from unknown (HELO StevensPC) (218.215.205.199) by extmail-03.people.net.au with SMTP; 31 Jan 2013 05:18:48 -0000 From: "Stevens Family" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: RE: [LML] Re: Thermal influence on Hydraulic Pressure X-Original-Date: Thu, 31 Jan 2013 13:18:50 +0800 X-Original-Message-ID: <004b01cdff72$7488f620$5d9ae260$@swiftdsl.com.au> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_004C_01CDFFB5.82B33B00" X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQEhhSDVDx2GIuDTMlVLEI8IlamC15m72hEQ Content-Language: en-au This is a multipart message in MIME format. ------=_NextPart_000_004C_01CDFFB5.82B33B00 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Thanks for your reply Gary. I hadn=E2=80=99t realised until = Chris=E2=80=99s comment that these pressure switches had been = superseded. Between his comments and yours, I have decided to just = forget the old switches and go for the new ones. =20 Isn=E2=80=99t the LML great! =20 Thanks again. =20 Rob. =20 =20 From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of = Gary Edwards Sent: Thursday, 31 January 2013 1:31 AM To: lml@lancaironline.net Subject: [LML] Re: Thermal influence on Hydraulic Pressure =20 Rob, =20 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. =20 Gary Edwards LNC2=20 =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 =20 Rob, Lancair carries a new type that is much more reliable. I forget the = brand name. =20 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 =20 Chris, =20 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? =20 Thanks again. =20 Rob Stevens Perth, Western Australia. =20 =20 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 =20 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. =20 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. =20 Chris Zavatson N91CZ 360std 1,400hrs http://www.n91cz.net/ =20 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 =20 Chris, =20 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. =20 To allow people to be more comfortable about the hydro-electric system = they should be reminded of this =20 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. =20 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. =20 Failing to retract is a nuisance. Failing to extend is, uh, more = serious, but resolvable.=20 =20 Scott Krueger AKA Grayhawk =20 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>> =20 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. =20 Chris Zavatson N91CZ 360std, 1,400 hrs http://www.n91cz.net/ =20 From: Wolfgang To: lml@lancaironline.net=20 Sent: Saturday, January 26, 2013 11:24 AM Subject: [LML] Re: Thermal influence on Hydraulic Pressure =20 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. =20 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 =20 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. =20 Nasty when the gear won't retract just after blasting off into a low = overcast. =20 Charley Brown Legacy #299 200 hr =20 On Jan 25, 2013, at 7:23 AM, randy snarr wrote: =20 . 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. =20 =20 -- For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html =20 =20 =20 -- For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html ------=_NextPart_000_004C_01CDFFB5.82B33B00 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable

Thanks for your reply Gary. I hadn=E2=80=99t realised until = Chris=E2=80=99s comment that these pressure switches had been = superseded. Between his comments and yours, I have decided to just = forget the old switches and go for the new ones.

 

Isn=E2=80=99t the LML great!

 

Thanks again.

 

Rob.

 

 

From:= Lancair = Mailing List [mailto:lml@lancaironline.net] On Behalf Of Gary = Edwards
Sent: Thursday, 31 January 2013 1:31 AM
To: = lml@lancaironline.net
Subject: [LML] Re: Thermal influence on = Hydraulic Pressure

 

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 

 

F= rom: = Chris Zavatson =

S= ent: = Wednesday, January 30, 2013 5:28 AM

S= ubject: = [LML] Re: Thermal influence on Hydraulic = Pressure

 

Rob,

Lancair carries a = new type that is much more reliable.  I forget the brand = name.

 <= /span>

Chris = Zavatson

N91CZ

360std 1,400 = hrs


 

F= rom: = Stevens Family <stevens5@swiftdsl.com.au>= ;
To: lml@lancaironline.net =
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
Sub= ject: [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. 

Failure to = retract can be a bit more serious if in IMC or taking off at high = density altitude.

 

<= p class=3DMsoNormal style=3D'background:white'>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.

 

<= p class=3DMsoNormal style=3D'background:white'>Chris = Zavatson

N91CZ

360std = 1,400hrs

 

<= div>

F= rom: = "Sky2high@aol.com" <Sky2high@aol.com>
To: = lml@lancaironline.net =
Sent: Tuesday, January 29, 2013 5:27 AM
Subject: = [LML] Re: Thermal influence on Hydraulic Pressure

 

C= hris,

 

<= p class=3DMsoNormal style=3D'background:white'>W= hile 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.

 

<= p class=3DMsoNormal style=3D'background:white'>T= o allow people to be more comfortable about the hydro-electric system = they should be reminded of this

 

<= p class=3DMsoNormal style=3D'background:white'>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.

 

<= p class=3DMsoNormal style=3D'background:white'>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.

 

<= p class=3DMsoNormal style=3D'background:white'>F= ailing to retract is a nuisance.  Failing to extend is, uh, more = serious, but resolvable.

 

<= p class=3DMsoNormal style=3D'background:white'>S= cott Krueger AKA Grayhawk

 

<= div>

I= n 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.

<<That's a sound and positive fix. =

- - However it = requires changing the dump valve, running a return line and pump = modification (replace the = reservoir).

...................................

Wolfgang>>

<= div>

<<..........Automatic = action by my module can prevent these problems for both up and down gear = operation.

Wolfgang>>

<= p class=3DMsoNormal style=3D'background:white'> 

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

 

F= rom: = Wolfgang <Wolfgang@MiCom.net>
To:<= /b> lml@lancaironline.net =
Sent: Saturday, January 26, 2013 11:24 AM
Subject: = [LML] Re: Thermal influence on Hydraulic Pressure

 

T= his 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.

 

<= p class=3DMsoNormal style=3D'background:white'>W= olfgang

-= ---- Original Message -----

F= rom: = Charles Brown

S= ent: = Saturday, January 26, 2013 2:07 AM

S= ubject: = Re: [LML] Re: Thermal influence on Hydraulic Pressure

 

<= p class=3DMsoNormal style=3D'background:white'>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.

 

<= p class=3DMsoNormal style=3D'background:white'>Nasty when the gear won't retract just after = blasting off into a low = overcast.

 

<= p class=3DMsoNormal style=3D'background:white'>Charley = Brown

Legacy #299 =  200 hr

 

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

 

<= p class=3DMsoNormal style=3D'background:white'>. 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

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