X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 16 Feb 2012 08:08:48 -0500 Message-ID: X-Original-Return-Path: Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTP id 5398389 for lml@lancaironline.net; Wed, 15 Feb 2012 10:13:38 -0500 Received-SPF: none receiver=logan.com; client-ip=71.74.56.122; envelope-from=Wolfgang@MiCom.net X-Original-Return-Path: X-Authority-Analysis: v=2.0 cv=fNy7LOme c=1 sm=0 a=MHZY6FYWMEQOp7S43i2QIw==:17 a=rOJFdwVDlGUA:10 a=ttCsPuSJ-FAA:10 a=Ia-xEzejAAAA:8 a=5FIZSGrRAAAA:8 a=rTjvlri0AAAA:8 a=CjxXgO3LAAAA:8 a=ndVRne3UAAAA:8 a=F22R_m7Oonoy157JKRUA:9 a=wyy1w6QF0HrfCeLOdAAA:7 a=wPNLvfGTeEIA:10 a=VQWZxD7wvt0A:10 a=nrXl3C1RZZ4A:10 a=wR8WdYEwGqoA:10 a=EzXvWhQp4_cA:10 a=Dr9Wx-Q63l4A:10 a=rC2wZJ5BpNYA:10 a=Whv8HLVs5OMA:10 a=q3bnT8Mu3NyNlyRA:21 a=SI0TZ28O0wK_l7uw:21 a=b2dJBuweSB6SsgpNPU4A:9 a=aoW0HKAYHfB_G-bOVwIA:7 a=tXsnliwV7b4A:10 a=MHZY6FYWMEQOp7S43i2QIw==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.218.201.50 Received: from [74.218.201.50] ([74.218.201.50:1206] helo=lobo) by hrndva-oedge03.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id ED/27-11045-E7BCB3F4; Wed, 15 Feb 2012 15:13:03 +0000 X-Original-Message-ID: <008101ccebf4$4aee71b0$6701a8c0@lobo> From: "Wolfgang" X-Original-To: Subject: Fw: 320/360 Hydraulic Pressure Switch X-Original-Date: Wed, 15 Feb 2012 10:12:54 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_007E_01CCEBCA.61EB1820" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_007E_01CCEBCA.61EB1820 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Chris, We would all like to get at the root cause of the problem but, as yet, = that hasn't happened. Likely because it's too much work to track down = the actual cause and fix it. The questionable pump has to be removed and = forensically examined by someone who knows what they're doing. You have = offered to do the examination but the questionable pump still has to be = removed and shipped to the examination and while it's away, the aircraft = is useless in the hangar. So far we only have a good plausible theory missing only demonstratable = proof. The problem is infrequent enough that most people "take their = chances" and figure that the dump valve will solve the problem. However, for the problem in question, the dump valve does not work. If = the spool & poppet valve comes off it's end position, for whatever = reason, and traps the fluid volume in the lines and the hydraulic system = sees a large temperature rise, the pressure in both the HI and LO side = can exceed the pressure switch settings rendering the pump inoperable. = With the pressure excessively high in both the HI and LO side, = activating the dump valve has no effect. The way I see it there are three ways to fix the problem, 1) Test the pump under the offending conditions and if it fails, apply = the suggested repairs and test it again until it passes operational = test. This means removing the pump and testing in a controlled = environment while the aircraft is laid up. 2) Install a three port dump valve with the third line going back to the = pump's fluid reservoir so when actuated both HI and LO sides dump back = to the pump instead of simply cross connecting the HI and LO sides. This = still requires pilot intervention if/when the problem occurs. 3) Shameless plug - - install my safe module on top of your pressure = switches, a 30 minute operation. This module monitors both pressure = switches and if both come open (high pressure) then activate the pump in = the direction currently selected by the gear switch forcing the spool & = poppet valves back into the required position and relieving the = offending pressure in the lines. This monitoring is a continuous = operation on the ground and in the air and does not require any pilot = intervention. Wolfgang ----- Original Message -----=20 From: Chris Zavatson=20 To: lml@lancaironline.net=20 Sent: Monday, February 13, 2012 9:23 AM Subject: Re: [LML] Re: 320/360 Hydraulic Pressure Switch Wolfgang, I would like nothing better than to get at the root cause for those = pumps exhibitng a system lock-up. We can show by analysis and test that when both poppets are allowed to = close, the hydraulic system will lock up on the ground when heated. We can also show by analysis and test that if the spool remains in its = last commanded position that a lock up cannot occur. We have measured the force it takes to move a spool on a number of = different pumps and configurations and foud the force far exceeds what = can be expected by airframe vibration.=20 It seems to me one should examine in detail any pump that acts = differently than the general fleet. If I owned one hundred identical = aircraft and one exhibited low fuel pressure, I would not redesign the = fuel system for the entire fleet in response. Rather, I would examine = why the one was different. Likewise, when a pump allows the hydraulic = system to lock-up, the proper thing to do would be to examine that pump = in great detail and determine how it differs from the rest. I have a = standing offer on the table to examine and test any pump that exhibits = this behavior. While I have examined pumps for other reasons, I have = not yet had the opportunity to look at one that has been known to a = cause a lock up. I am really curious to see what the differences are = and if they have any implications for the rest of the Lancair fleet.=20 There is no need to further test a pump with return springs. We know = what can happen. Note 'can happen'. The system will not lock up every = time, in fact, it will be very infrequent. Several conditions must be = met. While the return springs, at 26 lb/in, are strong enough to get = the spool moving towards center, they do not always make it all the way. = After all, spring force is a function of deflection. Near center, they = run out of steam. On occasion, I had to add some vibration to lock both = poppets. =20 The vibration levels required to move a spool without a spring are = enormous. Those levels would likely destroy the motor assembly, not to = mention the pressure switches, avionics and so on. Until we can examine a mis-behaving pump and compare certain = parameters, the root cause for that pump will indeed be unknown. = Fortunately, we know a great deal about how properly behaving pumps = operate and what configurations will cause problems. Hypothesizing = about a failure mode without being willing to examine the pump itself is = rather pointless. Chris Zavatson N91CZ 360std www.N91CZ.net =20 From: Wolfgang To: lml@lancaironline.net=20 Sent: Friday, February 10, 2012 7:26 AM Subject: [LML] Re: 320/360 Hydraulic Pressure Switch If it takes that much force to move the spindle against the O-rings = then those springs must be pretty darn strong. I find that dificult to = accept. Still, that port with the added spring, I believe it's a return port = for excess hydraulic fluid that can be used with a three port dump = valve. . . . but why the spring if it's plugged anyway ? If the ultimate answer is to remove the "extra" springs, then let's = demonstrate that by testing a pump with the springs under pressure, = heat, AND simulated engine vibration. Short of that, this failure mode = remains a question. Wolfgang =20 From: Chris Zavatson =20 Sender: =20 Subject: Re: [LML] Fw: [LML] Re: 320/360 Hydraulic = Pressure Switch=20 Date: Wed, 08 Feb 2012 08:05:15 -0500=20 To: lml@lancaironline.net=20 =20 Wolfgang, The ball and spring go in the port labeled "Cavity "E" = Back-Pressure". This is the pipe plug that sits in between the two = output ports. You might consider securing the dump valve with a secondary = locking feature. It too relies on friction alone to stay in position. = Seriously, given the force it takes to move the spool, if mine were not = staying put, I would want to know why. =20 From previous measurements: Using O-ring 013-70 requires 30 g's to move the spool. Using O-ring 013-90 requires 70 g's to move the spool.=20 The 013-90 is specified for pumps with back pressure circuits = such as we have. Chris Zavatson N91CZ 360std www.N91CZ.net =20 From: Wolfgang To: lml@lancaironline.net=20 Sent: Monday, February 6, 2012 9:24 AM Subject: [LML] Fw: [LML] Re: 320/360 Hydraulic Pressure Switch I see the centering springs but what about the added spring, = eyelet and ball ? Where does that fit into the schematic ? I still don't like the idea of friction being the only thing = keeping spindle at it's end point. Sure, removing the springs will help = but a positive system to pressure the spindle back into it's required = position automatically as needed still seems prudent. Wolfgang ----- Original Message -----=20 From: Chris Zavatson=20 To: lml@lancaironline.net=20 Sent: Sunday, February 05, 2012 8:34 AM Subject: Re: [LML] Re: 320/360 Hydraulic Pressure Switch Several folks have been asking privately about the spool = centering springs mentioned below. This link contains both schematics = and photos showing how to revert a new pump back to the original 320/360 = functionality. =20 http://www.n91cz.com/Hydraulics/Pump-Unlock.pdf Chris Zavatson N91CZ 360std www.N91CZ.net From: Chris Zavatson To: lml@lancaironline.net=20 Sent: Wednesday, February 1, 2012 12:46 PM Subject: [LML] Re: 320/360 Hydraulic Pressure Switch Lorn, Had the temperature been 90 or 100 degrees your pressure would = have been even higher. In some of my hydraulics videos, you will see = the 2,000 psi gauge pegged on occasion during thermal heating tests. http://www.n91cz.com/Hydraulics/Lancair_Hydraulics.htm Your predicament of having to crack a hydraulic line is exactly = what can happen if the spool centers after pump shut down. I find that = a completely unacceptable design. Imagine taking off into IMC and the = gear won't come up. I had the opportunity to test out a pump in this = configuration last summer. Just as you experienced, I was able to = reproduce a complete lock up. =20 http://www.n91cz.com/Hydraulics/NewPumpLockUp_0001.wmv - hi res http://www.n91cz.com/Hydraulics/NewPumpLockUp_0002.wmv - low res After discussions with Lancair and Parker, I reverted the = configuration back to the original 320/360 config and all is good now. = Only one side can ever be pressurized at a time. Unfortunately due to = employee turn-over, no one currently at Parker or Lancair knows why the = centering springs were added. After reviewing the 320/360 system both = agreed that a system lock up is possible using replacement pumps = currently sold (108AMS32-CZZ-3V-14-08-Y). Parker sent me parts to = revert three pumps back to the original configuration.=20 The TRVs in our pumps are the lowest available -fixed setting of = 2,500 psi. This may be too high to protect some of our components. I = have run them up to 2,000 psi. In flight, I have seen 1,800 psi, = descending from 18k into the southwest deserts. Chris Zavatson N91CZ 360std www.N91CZ.net From: Lorn H Olsen To: lml@lancaironline.net=20 Sent: Wednesday, February 1, 2012 6:33 AM Subject: [LML] Re: 320/360 Hydraulic Pressure Switch Again,My Oildyne internal pressure switch came (set by Oildyne) = at 1,500 PSI. How do I know? I parked my plane on the ramp at Newport = News, Va in the evening. The temperature was 40=B0F. 3 days later, when = I was going to take off. The temperature was 80=B0F. I looked at my = pressure gauges. Both the up and down were at 1,500 PSI. I had to crack = a nut in a hydraulic line to release the pressure. The gear would not go = up or down, at this pressure. The emergency dump valve would not = release, at this pressure. The pump would not run at all, at this = pressure.Now, I have Wolfgang's high pressure adapter in the system. It = runs the pump whenever the pressure is high on both the up and the down = side.There is no speculation here. Just the facts, mam.--Lorn H. = 'Feathers' Olsen, MAA, ASMEL, ASES, Comm, InstDynaComm, Corp., = 248-345-0500, mailto:lorn@dynacomm.usLNC2, FB90/92, O-320-D1F, 1,800 = hrs, N31161, Y47, SE Michigan=20 ------=_NextPart_000_007E_01CCEBCA.61EB1820 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hi Chris,
 
We would all like to get at the root = cause of the=20 problem but, as yet, that hasn't happened. Likely because it's too much = work to=20 track down the actual cause and fix it. The questionable pump has to be = removed=20 and forensically examined by someone who knows what they're doing. You = have=20 offered to do the examination but the questionable pump still has to be = removed=20 and shipped to the examination and while it's away, the aircraft is = useless in=20 the hangar.
 
So far we only have a good plausible = theory missing=20 only demonstratable proof. The problem is infrequent enough that most = people=20 "take their chances" and figure that the dump valve will solve the=20 problem.
 
However, for the problem in question, = the dump=20 valve does not work. If the spool & poppet valve comes off it's = end=20 position, for whatever reason, and traps the fluid volume in the lines = and the=20 hydraulic system sees a large temperature rise, the pressure in both the = HI and=20 LO side can exceed the pressure switch settings rendering the pump=20 inoperable. With the pressure excessively high in both the HI and LO=20 side, activating the dump valve has no effect.
 
The way I see it there are three ways = to fix the=20 problem,
 
1) Test the pump under the offending = conditions and=20 if it fails, apply the suggested repairs and test it again until it = passes=20 operational test. This means removing the pump and testing in a = controlled=20 environment while the aircraft is laid up.
 
2) Install a three port dump valve = with the=20 third line going back to the pump's fluid reservoir so when actuated = both HI and=20 LO sides dump back to the pump instead of simply cross connecting the HI = and LO=20 sides. This still requires pilot intervention if/when the problem=20 occurs.
 
3) Shameless plug - - install my safe = module on top=20 of your pressure switches, a 30 minute operation. This module monitors = both=20 pressure switches and if both come open (high pressure) then activate = the pump=20 in the direction currently selected by the gear switch = forcing the spool & poppet valves back into the = required position=20 and relieving the offending pressure in the lines. This monitoring is a=20 continuous operation on the ground and in the air and does not require = any pilot=20 intervention.
 
Wolfgang
 
----- Original Message -----
From:=20 Chris=20 Zavatson
Sent: Monday, February 13, 2012 = 9:23=20 AM
Subject: Re: [LML] Re: 320/360 = Hydraulic=20 Pressure Switch

Wolfgang,
 
I would like = nothing better=20 than to get at the root cause for those pumps exhibitng a system=20 lock-up.
We can show by=20 analysis and test that when both poppets are allowed to close, the = hydraulic=20 system will lock up on the ground when heated.
We can = also show by=20 analysis and test that if the spool=20 remains in its last commanded position that a lock up cannot=20 occur.
We have = measured the force=20 it takes to move a spool on a number of different pumps=20 and configurations and foud the force far exceeds what can = be=20 expected by airframe vibration. 
 
It seems to me = one should=20 examine in detail any pump that acts differently than the general = fleet. =20 If I owned one hundred identical aircraft and = one exhibited low=20 fuel pressure, I would not redesign the fuel system for the entire=20 fleet in response.  Rather, I would examine why = the one=20 was different.  Likewise, when a pump allows the hydraulic system to lock-up, the = proper=20 thing to do would be to examine that pump in great detail and = determine how it=20 differs from the rest.  I have a standing offer on the = table to=20 examine and test any pump that exhibits this = behavior.  While I=20 have examined pumps for other reasons, I have not yet had the = opportunity=20 to look at one that has been known to a cause a lock up.  I=20 am really curious to see what the differences are and if they = have any=20 implications for the rest of the = Lancair fleet. 
 
There is no = need to further=20 test a pump with return springs.  We know what can=20 happen.  Note 'can happen'.  The system will not lock = up every=20 time, in fact, it will be very infrequent.  Several conditions = must be=20 met.  While the return springs, at 26 lb/in, are strong = enough  to=20 get the spool moving towards center, they do not always make it all = the=20 way.  After all, spring force is a function of deflection.  = Near=20 center, they run out of steam.  On occasion, I had to add some = vibration to=20 lock both poppets. 
The vibration = levels=20 required to move a spool without a spring are enormous.  Those levels would = likely=20 destroy the motor assembly, not to mention the pressure switches, = avionics and=20 so on.
Until we can = examine a=20 mis-behaving pump and compare certain parameters, the root cause for = that pump=20 will indeed be unknown.  Fortunately, we know a great deal about = how=20 properly behaving pumps operate and what configurations will cause=20 problems.  Hypothesizing about a failure mode without being = willing to=20 examine the pump itself is rather pointless.
 
Chris = Zavatson
N91CZ
360std
www.N91CZ.net
 
  =

From: Wolfgang=20 <Wolfgang@MiCom.net>
To: lml@lancaironline.net =
Sent: Friday, February 10, 2012 = 7:26=20 AM
Subject: [LML] = Re: 320/360=20 Hydraulic Pressure Switch
If it takes that much force to move the spindle against the = O-rings then=20 those springs must be pretty darn strong. I find that dificult to=20 accept.
 
Still, that port with the added spring, I believe it's a return = port for=20 excess hydraulic fluid that can be used with a three port dump = valve.
. . . but why the spring if it's plugged anyway ?
 
If the ultimate answer is to remove the "extra" springs, then = let's=20 demonstrate that by testing a pump with the springs under pressure, = heat, AND=20 simulated engine vibration. Short of that, this failure mode remains a = question.
 
Wolfgang

 
<marv@lancaironline.net>= lml@lancaironline.net<= /TABLE>
From: Chris Zavatson=20 <chris_zavatson@yahoo.com>
Sender:
Subject: Re: [LML] Fw: [LML] Re: = 320/360=20 Hydraulic Pressure Switch
Date: Wed, 08 Feb 2012 = 08:05:15=20 -0500
To:
Wolfgang,
The ball and spring go in the port labeled "Cavity = "E"=20 Back-Pressure".  This is the pipe plug that sits in between = the two=20 output ports.
 
You might consider = securing=20 the dump valve with a secondary locking feature.  It too = relies on=20 friction alone to stay in position.  Seriously, given the = force it=20 takes to move the spool, if mine were not staying put, I = would want=20 to know why. 
 
From previous measurements:
Using O-ring 013-70 requires 30 g's to move the = spool.
Using O-ring 013-90 requires 70 g's to move the spool. =
The 013-90 is specified for pumps with back pressure = circuits=20 such as we have.
 
Chris=20 Zavatson
N91CZ
360std
www.N91CZ.net
 
From: = Wolfgang=20 <Wolfgang@MiCom.net>
To:=20 lml@lancaironline.net
Sent: Monday, = February 6,=20 2012 9:24 AM
Subject: [LML] Fw: [LML] Re: = 320/360=20 Hydraulic Pressure Switch
I see the centering springs but what about the added = spring, eyelet=20 and ball ? Where does that fit into the schematic ?
 
I still don't like the idea of friction being the only = thing=20 keeping spindle at it's end point. Sure, removing the springs = will help=20 but a positive system to pressure the spindle back into it's = required=20 position automatically as needed still seems prudent.
 
Wolfgang
 
----- Original Message -----=20
Sent: Sunday, February 05, 2012 8:34 AM
Subject: Re: [LML] Re: 320/360 Hydraulic Pressure=20 Switch
Several folks have been asking privately about the spool = centering=20 springs mentioned below.  This link contains both = schematics and=20 photos showing how to revert a new pump back = to the=20 original 320/360 functionality. 
http://www.n91cz.com/Hydraulics/Pump-Unlock.pdf
 
Chris Zavatson
N91CZ
360std
From: Chris = Zavatson=20 <chris_zavatson@yahoo.com>
To:=20 lml@lancaironline.net
Sent: Wednesday, = February=20 1, 2012 12:46 PM
Subject: [LML] Re: = 320/360=20 Hydraulic Pressure Switch
Lorn,
Had the temperature been 90 or 100 degrees your pressure = would have=20 been even higher.  In some of my hydraulics videos, you=20 will see the 2,000 psi gauge pegged on occasion during = thermal=20 heating tests.
 
=
http://www.n91cz.com/Hydraulics/Lancair_Hydraulics.htm
 
Your predicament of having to crack a hydraulic line = is=20 exactly what can happen if the spool centers after pump shut = down. =20 I find that a completely unacceptable design.  Imagine = taking off=20 into IMC and the gear won't come up.  I had the opportunity = to test=20 out a pump in this configuration last summer.  Just as you=20 experienced, I was able to reproduce a complete lock up.  =
=
http://www.n91cz.com/Hydraulics/NewPumpLockUp_0001.wmv - hi=20 res
=
http://www.n91cz.com/Hydraulics/NewPumpLockUp_0002.wmv - low=20 res
 
After discussions with Lancair and Parker, I reverted = the=20 configuration back to the original=20 320/360 config and all is good now.  Only one side can ever = be=20 pressurized at a time.  Unfortunately due to employee = turn-over, no=20 one currently at Parker or Lancair knows why the centering = springs were=20 added.  After reviewing the 320/360 system both agreed that = a=20 system lock up is possible using replacement pumps currently = sold=20 (108AMS32-CZZ-3V-14-08-Y).  Parker sent me parts to revert = three=20 pumps back to the original configuration. 
 
The TRVs in our pumps are the lowest available -fixed = setting of=20 2,500 psi.  This may be too high to protect some = of our=20 components.  I have run them up to 2,000 = psi. =20 In flight, I have seen 1,800 psi, descending from 18k into the = southwest=20 deserts.
 
Chris Zavatson
N91CZ
360std
 
 
From: Lorn H Olsen=20 <lorn@dynacomm.us>
To:=20 lml@lancaironline.net
Sent: Wednesday, = February=20 1, 2012 6:33 AM
Subject: [LML] Re: = 320/360=20 Hydraulic Pressure = Switch
Again,My=20 Oildyne internal pressure switch came (set by Oildyne) at 1,500 = PSI. How=20 do I know? I parked my plane on the ramp at Newport News, Va in = the=20 evening. The temperature was 40=B0F. 3 days later, when I was = going to=20 take off. The temperature was 80=B0F. I looked at my pressure = gauges. Both=20 the up and down were at 1,500 PSI. I had to crack a nut in a = hydraulic=20 line to release the pressure. The gear would not go up or down, = at this=20 pressure. The emergency dump valve would not release, at this = pressure.=20 The pump would not run at all, at this pressure.Now, I = have=20 Wolfgang's high pressure adapter in the system. It runs the pump = whenever the pressure is high on both the up and the down=20 side.There is no speculation here. Just the facts,=20 mam.--Lorn H. 'Feathers' Olsen, MAA, ASMEL, = ASES,=20 Comm, InstDynaComm, Corp., 248-345-0500, mailto:lorn@dynacomm.usLNC2,=20 FB90/92, O-320-D1F, 1,800 hrs, N31161, Y47, SE=20 = Michigan
=
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