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Sun, 12 Feb 2012 19:48:07 PST X-Mailer: YahooMailWebService/0.8.116.338427 References: X-Original-Message-ID: <1329104887.89700.YahooMailNeo@web36904.mail.mud.yahoo.com> X-Original-Date: Sun, 12 Feb 2012 19:48:07 -0800 (PST) From: Chris Zavatson Reply-To: Chris Zavatson Subject: Re: [LML] Re: 320/360 Hydraulic Pressure Switch X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-2114655128-712454210-1329104887=:89700" ---2114655128-712454210-1329104887=:89700 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Wolfgang,=0A=A0=0AI would like nothing better than to get at the root cause= for those pumps exhibitng a system lock-up.=0AWe=A0can=A0show by analysis = and test that when both poppets are allowed to close, the hydraulic system= =A0will lock up on the ground when heated.=0AWe=A0can also show by analysis= and test that if the spool remains=A0in its last commanded position that a= lock up cannot occur.=0AWe have measured the force it takes to move a spoo= l on a number of different pumps and=A0configurations and foud the force fa= r=A0exceeds what can be expected=A0by=A0airframe vibration.=A0=0A=A0=0AIt s= eems to me one should examine in detail any pump that acts differently than= the general fleet.=A0 If I owned=A0one hundred identical=A0aircraft and on= e=A0exhibited low fuel pressure, I would not redesign the fuel system for t= he entire fleet=A0in=A0response.=A0 Rather, I would examine why the=A0one w= as different.=A0=A0Likewise, when=A0a pump allows the hydraulic system to l= ock-up, the proper thing to do would be to examine that pump in great detai= l and determine how it differs from the rest.=A0 I have a standing offer on= the table=A0to examine and test any pump that exhibits this behavior.=A0= =A0While I have=A0examined 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.=A0 I a= m=A0really curious to see what the differences are=A0and if they have any i= mplications for the rest of the Lancair=A0fleet.=A0=0A=A0=0AThere is no nee= d to further test a pump with return springs.=A0=A0We know=A0what can happe= n.=A0 Note 'can happen'.=A0 The system will=A0not lock up every time, in fa= ct, it will be very infrequent.=A0 Several conditions must be met.=A0 While= the return springs, at 26 lb/in, are strong enough=A0 to get the spool mov= ing towards center, they do not always make it all the way.=A0 After all, s= pring force is a function of deflection.=A0 Near center, they run out of st= eam.=A0 On occasion, I had to add some vibration to lock both poppets.=A0 = =0AThe vibration levels required to move a spool without a spring are enorm= ous.=A0 Those levels would likely destroy the motor assembly, not to mentio= n the pressure switches, avionics and so on.=0AUntil we can examine a mis-b= ehaving pump and compare certain parameters, the root cause for that pump w= ill indeed be unknown.=A0 Fortunately, we know a great deal about how prope= rly behaving pumps operate and what configurations will cause problems.=A0 = Hypothesizing about a failure mode without being willing to examine the pum= p itself is rather pointless.=0A=A0=0AChris Zavatson=0AN91CZ=0A360std=0Awww= .N91CZ.net=0A=A0=0A=A0 =0A=0AFrom: Wolfgang =0ATo: lml@= lancaironline.net =0ASent: Friday, February 10, 2012 7:26 AM=0ASubject: [LM= L] Re: 320/360 Hydraulic Pressure Switch=0A=0AIf it takes that much force t= o move the spindle against the O-rings then those springs must be pretty da= rn strong. I find that dificult to accept.=0A=0AStill, that port with the a= dded spring, I believe it's a return port for excess hydraulic fluid that c= an be used with a three port dump valve.=0A. . . but why the spring if it's= plugged anyway ?=0A=0AIf the ultimate answer is to remove the "extra" spri= ngs, then let's demonstrate that by testing a pump with the springs under p= ressure, heat, AND simulated engine vibration. Short of that, this failure = mode remains a question.=0A=0AWolfgang=0A=0A=A0=0AFrom: Chris Zavatson =0ASender: =0ASubject: Re: = [LML] Fw: [LML] Re: 320/360 Hydraulic Pressure Switch =0ADate: Wed, 08 Feb = 2012 08:05:15 -0500 =0ATo: lml@lancaironline.net =0AWolfgang,=0AThe ball a= nd spring go in the port labeled "Cavity "E" Back-Pressure".=A0 This is the= pipe plug that sits in between the two output ports.=0A=A0=0AYou might con= sider securing the dump valve with a secondary locking feature.=A0 It too r= elies on friction alone to stay in position.=A0 Seriously, given the force = it takes to move the spool, if mine were not staying put, I would=A0want to= know why.=A0 =0A=A0=0AFrom previous measurements:=0AUsing O-ring=A0013-70 = requires 30 g's to move the spool.=0AUsing O-ring=A0013-90 requires 70 g's = to move the spool. =0AThe 013-90 is=A0specified for pumps with back pressur= e circuits such as we have.=0A=A0=0AChris Zavatson=0AN91CZ=0A360std=0Awww.N= 91CZ.net=0A=A0=0AFrom: Wolfgang =0ATo: lml@lancaironlin= e.net =0ASent: Monday, February 6, 2012 9:24 AM=0ASubject: [LML] Fw: [LML] = Re: 320/360 Hydraulic Pressure Switch=0A=0AI see the centering springs but = what about the added spring, eyelet and ball ? Where does that fit into the= schematic ?=0A=0AI still don't like the idea of friction being the only th= ing 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 posi= tion automatically as needed still seems prudent.=0A=0AWolfgang=0A=0A----- = Original Message ----- =0AFrom: Chris Zavatson =0ATo: lml@lancaironline.net= =0ASent: Sunday, February 05, 2012 8:34 AM=0ASubject: Re: [LML] Re: 320/36= 0 Hydraulic Pressure Switch=0ASeveral folks have been asking privately abou= t the spool centering springs mentioned below.=A0 This link contains both s= chematics and photos=A0showing how to revert=A0a new pump back to=A0the ori= ginal 320/360 functionality.=A0 =0Ahttp://www.n91cz.com/Hydraulics/Pump-Unl= ock.pdf=0A=0AChris Zavatson=0AN91CZ=0A360std=0Awww.N91CZ.net=0AFrom: Chris = Zavatson =0ATo: lml@lancaironline.net =0ASent: We= dnesday, February 1, 2012 12:46 PM=0ASubject: [LML] Re: 320/360 Hydraulic P= ressure Switch=0A=0ALorn,=0AHad the temperature been 90 or 100 degrees your= pressure would have been even higher.=A0 In some of my hydraulics videos, = you will=A0see the 2,000 psi gauge pegged on occasion during thermal heatin= g tests.=0A=0Ahttp://www.n91cz.com/Hydraulics/Lancair_Hydraulics.htm=0A=0AY= our predicament=A0of having to crack a hydraulic line is exactly what can h= appen if the spool centers after pump shut down.=A0 I find that a completel= y unacceptable design.=A0 Imagine taking off into IMC and the gear won't co= me up.=A0 I had the opportunity to test out a pump in this configuration la= st summer.=A0 Just as you experienced, I was able to reproduce a complete l= ock up.=A0 =0Ahttp://www.n91cz.com/Hydraulics/NewPumpLockUp_0001.wmv=A0- hi= res=0Ahttp://www.n91cz.com/Hydraulics/NewPumpLockUp_0002.wmv=A0- low res= =0A=0AAfter discussions with Lancair and Parker, I reverted the configurati= on back to the original 320/360 config and all is good now.=A0 Only one sid= e can ever be pressurized at a time.=A0 Unfortunately due to employee turn-= over, no one currently at Parker or Lancair knows why the centering springs= were added.=A0 After reviewing the 320/360 system both agreed that a syste= m lock up is possible using replacement pumps currently sold (108AMS32-CZZ-= 3V-14-08-Y).=A0 Parker sent me parts to revert three pumps back to the orig= inal configuration.=A0=0A=A0=0AThe TRVs in our pumps are the lowest availab= le -fixed setting of 2,500 psi.=A0 This may be too high=A0to protect=A0some= of our components.=A0 I=A0have=A0run them up=A0to 2,000 psi.=A0 In flight,= I have seen 1,800 psi, descending from 18k into the southwest deserts.=0A= =0AChris Zavatson=0AN91CZ=0A360std=0Awww.N91CZ.net=0A=0A=0AFrom: Lorn H Ols= en =0ATo: lml@lancaironline.net =0ASent: Wednesday, Febru= ary 1, 2012 6:33 AM=0ASubject: [LML] Re: 320/360 Hydraulic Pressure Switch= =0AAgain,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 t= he evening. The temperature was 40=B0F. 3 days later, when I was going to t= ake off. The temperature was 80=B0F. I looked at my pressure gauges. Both t= he 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 wo= uld not run at all, at this pressure.Now, I have Wolfgang's high pressure a= dapter in the system. It runs the pump whenever the pressure is high on bot= h the up and the down side.There is no speculation here. Just the facts, ma= m.--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, N= 31161, Y47, SE Michigan ---2114655128-712454210-1329104887=:89700 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Wolfgang,
 
I would like nothing= better than to get at the root cause for those pumps exhibitng a system lo= ck-up.
We can sho= w by analysis and test that when both poppets are allowed to close, the hyd= raulic system will lock up on the ground when heated.
We can also sho= w by analysis and test that if the spool rema= ins 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 con= figurations and foud the force far exceeds what can be expected b= y airframe vibration. 
 
It seems to me one s= hould examine in detail any pump that acts differently than the general fle= et.  If I owned one hundred identical aircraft and one = exhibited low fuel pressure, I would not redesign the fuel system for the e= ntire fleet in response.  Rather, I would examine why the&nb= sp;one was different.  Likewise, when a pump allows the = hydraulic system to lock-up, the proper thing to do wou= ld be to examine that pump in great detail and determine how it differs fro= m the rest.  I have a standing offer on the table to examine and = test any pump that exhibits this behavior.  While I have exa= mined pumps for other reasons, I have not yet had the opportunity to look a= t one that has been known to a cause a lock up.  I am really curi= ous to see what the differen= ces are and if they have any implications for the rest o= f the Lancair fleet. 
 
There is no need to = further test a pump with return springs.  We know what can h= appen.  Note 'can happen'.  The system will not lock up ever= y 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 th= e way.  After all, spring force is a function of deflection.  Nea= r center, they run out of steam.  On occasion, I had to add some vibration to loc= k both poppets. 
The vibration levels= required to move a spool without a spring are enormous.  Those levels would like= ly destroy the motor assembly, not to mention the pressure switches, avioni= cs and so on.
Until we can examine= a mis-behaving pump and compare certain parameters, the root cause for tha= t pump will indeed be unknown.  Fortunately, we know a great deal abou= t how properly behaving pumps operate and what configurations will cause pr= oblems.  Hypothesizing about a failure mode without being willing to e= xamine the pump itself is rather pointless.
 
Chris Zavatson
N91CZ
360std
 
 

From:= Wolfgang <Wolfgang@MiCom.net>
To: lml@lancaironline.net
Sent: Friday, February 10, 2012 7:26 AM
Subject: [LML] Re: 320/360 Hydra= ulic Pressure Switch
If it takes that much force to move the spindle against the O-rings th= en 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 f= or 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 de= monstrate that by testing a pump with the springs under pressure, heat, AND= simulated engine vibration. Short of that, this failure mode remains a que= stion.
 
Wolfgang

 
From: Chris Zavatson <chris_zavatson@yaho= o.com>
Sender: <marv@lancaironline.net>
Subject: Re: [LML] Fw: [LML] Re: 320/360 Hydrau= lic Pressure Switch
Date: Wed, 08 Feb 2012 08:05:15 -0500
To: lml@lancaironline.net
Wolfgang,
The ball and spring go in the port labeled "Cavity "E" Back-Pres= sure".  This is the pipe plug that sits in between the two output port= s.
 
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, i= f mine were not staying put, I would want 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.=20
The 013-90 is specified for pumps with back pressure circuits suc= h as we have.
 
Chris Zavatson
N91CZ
360std
www.N91CZ.net
 
From: Wolfgang <Wolfgang@MiCom.net= >
To: lml@lancaironline.net
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 an= d ball ? Where does that fit into the schematic ?
 
I still don't like the idea of friction being the only thing keeping s= pindle at it's end point. Sure, removing the springs will help but a positi= ve system to pressure the spindle back into it's required position automati= cally 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 Switch
<= /DIV>
Several folks have been asking privately about the spool centering spr= ings mentioned below.  This link contains both schematics and photos&n= bsp;showing how to revert a new pump back to the original 320/360= functionality. 
http://www.n91cz.com/Hydraulics/Pump-Unlock.pdf
 
Chris Zavatson
N91CZ
360std
From: Chris Zavatson &= lt;chris_z= avatson@yahoo.com>
To: lml@lancaironli= ne.net
Sent: Wednesday, February 1, 2012 12:46 PMSubject: [LML] Re: 320/360 Hydraulic Pressure Switch<= BR>
Lorn,
Had the temperature been 90 or 100 degrees your pressure would have be= en even higher.  In some of my hydraulics videos, you will see th= e 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 w= hat can happen if the spool centers after pump shut down.  I find that= a completely unacceptable design.  Imagine taking off into IMC and th= e gear won't come up.  I had the opportunity to test out a pump in thi= s configuration last summer.  Just as you experienced, I was able to r= eproduce a complete lock up. 
http://www.n91cz.com/Hydraulics/NewPumpLockUp_0001.wmv - hi res
http://www.n91cz.com/Hydraulics/NewPumpLockUp_0002.wmv - low res<= /DIV>
 
After discussions with Lancair and Parker, I reverted the config= uration back to the original 320/36= 0 config and all is good now.  Only one side can ever be pressurized a= t a time.  Unfortunately due to employee turn-over, no one currently a= t 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).  Pa= rker sent me parts to revert three pumps back to the original configuration= . 
 
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 component= s.  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
 
 
F= rom: Lorn H Olsen <lorn@dynacomm.us>
To: lml@lancaironline.net
Sent: Wednesday, Februa= ry 1, 2012 6:33 AM
Subject: [LML] Re: 320/360 Hydrau= lic Pressure Switch
Again,My Oildyne interna= l pressure switch came (set by Oildyne) at 1,500 PSI. How do I know? I park= ed 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 wa= s 80=B0F. I looked at my pressure gauges. Both the up and down were at 1,50= 0 PSI. I had to crack a nut in a hydraulic line to release the pressure. Th= e 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.<= WBR>--Lorn H. 'Feathers' Olsen, MAA, ASMEL, ASES, Comm, Inst= DynaComm, Corp., 248-345-0500, mailto:lorn= @dynacomm.usLNC2, FB90/92, O-320-D1F, 1,800 hrs, N31161, Y47, SE M= ichigan
---2114655128-712454210-1329104887=:89700--