X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 07 Sep 2012 14:13:06 -0400 Message-ID: X-Original-Return-Path: Received: from nm17-vm0.access.bullet.mail.mud.yahoo.com ([66.94.236.21] verified) by logan.com (CommuniGate Pro SMTP 6.0c1) with SMTP id 5749711 for lml@lancaironline.net; Fri, 07 Sep 2012 13:45:19 -0400 Received-SPF: neutral receiver=logan.com; client-ip=66.94.236.21; envelope-from=ralphlove@stanfordalumni.org Received: from [66.94.237.194] by nm17.access.bullet.mail.mud.yahoo.com with NNFMP; 07 Sep 2012 17:44:42 -0000 Received: from [98.139.221.49] by tm5.access.bullet.mail.mud.yahoo.com with NNFMP; 07 Sep 2012 17:44:42 -0000 Received: from [127.0.0.1] by smtp102.sbc.mail.bf1.yahoo.com with NNFMP; 07 Sep 2012 17:44:42 -0000 X-Yahoo-Newman-Id: 604950.6501.bm@smtp102.sbc.mail.bf1.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: Ymwd2YEVM1lMSalIiuxkMhwsEiT2cSBiS6kTNsHcKjGavdr nkXzl0hZbXetBeMNAFD61gY17hCXuV7dWPhgtz5wyMhSji3ahAi9NhpTEvrz fg9NaDZV3XsYHC3vBmVMPkNQSC8ARHccXt1An0ze6vtaB809u1SSUIHpLcn_ GE.qjx2KRJdHm9VvZ_oUJ6tH6CGB5ZalDg0qlpieaEpa1OrRNaRHYFn5Ra8d zRNbhGKsu6VcGK9zB9PV7iRPvZBxZ9drKHj6u1nfKddxbfT.X_icgP.bB2T6 sh5X.0.Kvs2ye9U.5IXHLwu_fHZmqBo5WptwowEfHYP1tAPpDUa9uNzrv0dZ Txkn2b0G8ILITSzsP3RmVryy3nwXV_VfNphmCXQxn2B1c3UeiNwT_9vN0H5a hVzdaeh.uRZH7ERjWNTfsQ6w_IVAAontx1MuBKpWepHQRp95OuJAFhydeGo3 gHaBp483XnHoBePU4PbW2CmUxF9j2ESFNVVQoG9_uaXWJzrlfbGQKgd334PT Ix9ukEk5rDdRjQBgBYrQGHo2D8DVH3W6lT1mzX9N4J0oE6xMURxm8atkut9v f0_Pnv1ed.pE3XA2iOO9uk247PbafX1mCNCtQ2Q-- X-Yahoo-SMTP: O0s9NnaswBCimploNHufwcJQi58B5NjMy.C2WAjfZjgmjJOd Received: from [10.0.0.135] (ralphlove@99.2.134.5 with plain) by smtp102.sbc.mail.bf1.yahoo.com with SMTP; 07 Sep 2012 10:44:40 -0700 PDT Subject: Re: [LML] Re: Thermal influence on Hydraulic Pressure References: From: Ralph Love Content-Type: multipart/alternative; boundary=Apple-Mail-4B7DC717-3A9C-45AF-9718-5EA04A999C6A X-Mailer: iPad Mail (9B206) In-Reply-To: X-Original-Message-Id: <0614D1E6-F08D-47EE-B9D7-70329F5EE02F@stanfordalumni.org> X-Original-Date: Fri, 7 Sep 2012 10:44:37 -0700 X-Original-To: Lancair Mailing List Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (1.0) --Apple-Mail-4B7DC717-3A9C-45AF-9718-5EA04A999C6A Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 Robert, Do you see a solution here? R On Sep 7, 2012, at 10:38 AM, "Wolfgang" wrote: > I have said it before, removing a pump and taking it apart to fix a suppos= ed design problem, putting the aircraft down for the duration, is not always= the best solution. After it's apart, you're still looking to verify your su= pposition. Installing a fix like mine guarantees a solution in about 30 minu= tes. Pilot's choice. 30 minutes is a small price to pay. > =20 > Wolfgang > =20 > ----- Original Message ----- > From: Chris Zavatson > To: lml@lancaironline.net > Sent: Thursday, September 06, 2012 8:15 AM > Subject: Re: [LML] Re: Thermal influence on Hydraulic Pressure >=20 > Wolfgang, > The =E2=80=98failure to retract=E2=80=99 issue, to which you refer, sounds= like a pump configuration issue.=20 > For example, the current pump sold by Lancair for the 320/360/Legacy conta= ins spool return springs. This configuration has the potential to lock up= due to thermal heating. This configuration is simply not compatible with t= he design of the Lancair two-seat hydraulic systems.=20 > Lock-up video:http://www.n91cz.com/Hydraulics/NewPumpLockUp_0001.wmv > With personnel turn-over at both companies, neither side knows why the ret= urn springs were added. However, both Parker and Lancair agree that a lock u= p on the ground is possible with the springs installed. This lock-up has be= en experienced by some, including the factory Legacy. It just has not been r= eported enough to drive an engineering change at Lancair.=20 > Parker has graciously supplied parts to revert currently sold =E2=80=9CCZZ= =E2=80=9D pumps back to the original 320/360 configuration with respect to s= pool operation. I have been forwarding these parts free of charge to anyone= who needs them. > See conversion instructions here: http://www.n91cz.com/Hydraulics/Pump-Unl= ock.pdf > I applaud your ingenuity in devising your circuit. Unfortunately your ene= rgy seems to be a little misplaced. I would prefer to investigate and fix t= he root cause of any out of the ordinary behavior-especially on an airplane!= If my engine was burning a quart of oil per hour, the fix would not to de= sign a gadget that would pump oil from an onboard supply into the sump and r= eplenish the lost oil. The solution, albeit painful in the short term, woul= d be to open up the engine, find and fix the problem and then fly like other= engines. > I understand that removing a pump, in particular those mounted behind the b= aggage bulkhead is no fun. Poor access is a real deterrent for any maintena= nce activity. That is simply human nature. In the grand scheme of things, i= t is a small price to pay.=20 > My offer still stands to examine your (Lorn=E2=80=99s) pump or any other t= hat is able to lock-up both circuits. I have not yet come across one that d= id not have an obvious cause-like the springs mentioned above, so any such r= eported behavior of great interest to me and is worth investigating. > =20 > Chris Zavatson > N91CZ > 360std > www.N91CZ.net >=20 >=20 > From: Wolfgang > To: lml@lancaironline.net=20 > Sent: Wednesday, September 5, 2012 9:28 AM > Subject: [LML] Re: Thermal influence on Hydraulic Pressure > Let's not forget this thermal influence causing non-function can also happ= en in reverse. It has been reported that a thermal a soak on the ground afte= r a cold night can and has caused a failure to retract after take off. > =20 > A while back I offered a solution of bumping the pump automatically whenev= er both pressure switches, HI and LO, are open due to high pressure. This wo= uld put the system back in normal operation mode without the need for pilot i= ntervention > =20 > Wolfgang > =20 > ----- Original Message ----- > From: Chris Zavatson > To: lml@lancaironline.net > Sent: Tuesday, September 04, 2012 7:53 PM > Subject: Re: [LML] Re: Thermal influence on Hydraulic Pressure >=20 > Fred, > I wish we had an easy way of bleeding just a wee bit of pressure without m= omentarily dumping the gear in cruise. > The 320/360 pumps use a non-adjustable thermal relief valve rated at 2,500= psi. The actual cracking pressure is 2,500 to 2,900 psi. This is the lowe= st set-point Parker has available. 2,900 psi is a lot of pressure for a sys= tem that nominally operates at 1,200 psi. Hopefully the design margin for t= he cylinders etc. was chosen large enough. > The first time I saw a 2,000+ excursion was on the test bench. I was leak= checking a cylinder. The test stand was near the hangar door. The sun swu= ng around and hit the pressurized clyinder. I dont' know what the max press= ure was since that gauge only went to 2,000 psi. > Chris > =20 > Chris Zavatson > N91CZ > 360std > http://www.n91cz.net/ >=20 > From: Frederick Moreno > To: lml@lancaironline.net=20 > Sent: Monday, September 3, 2012 11:54 AM > Subject: [LML] Re: Thermal influence on Hydraulic Pressure > > I have an MPV-50 engine monitor that includes continuous reading of the h= ydraulic system pressure on my Lancair IV/ I have seen the same thing, pa= rticularly on a flight that started on a cool morning departure from my home= drome and took us to the desert for a 110+F day. On descent, pressure rose= from its customary 1250 to 1500 psi at which point Bitching Betty started t= o complain so I bumped my speed brakes which are hydraulic, and lowered pres= sure back down to my customary range. Same thing sometimes happens in reve= rse, a hot soak on the ground, then a climb to 10-11,000 feet for a cool soa= k, and at some point the hydraulic pump kicks on to restore pressure to the d= esired level. My TR-182 used to the the same thing routinely when departing= Phoenix in the summertime. > =20 > It is a real effect, and makes one wonder about very high pressure events a= rising from FL 270 (say) cold soak terminating in Phoenix on a July afternoo= n. Hmmmm.... > =20 > Fred > =20 > =20 > =20 > =20 > -------Original Message------- > =20 > =20 > -took this photo after a descent from 16.5k to 1,500 ft. > OAT went from 42 to 94 degrees. > High Pressure gauge is pegged at 2,000+ psi > -Didn't get a photo, but the opposite happened on the ramp in Spokane. Aft= er sitting for an hour, the low pressure gauge was pegged at 1,200 psi+. Sp= okane might not be the warmest spot in the country, but at 85 deg F, it was 5= 5 degrees warmer than the cold soak on the previous leg. > Temperature changes have a big impact on system pressure.=20 > =20 > Chris Zavatson > N91CZ > 360std > http://www.n91cz.net/ > =20 --Apple-Mail-4B7DC717-3A9C-45AF-9718-5EA04A999C6A Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=utf-8
Robert,
Do you s= ee a solution here?
R

On Sep 7, 2012, at 10:38 AM, "= Wolfgang" <Wolfgang@MiCom.net&g= t; wrote:

I have said it before, removing a pump a= nd taking=20 it apart to fix a supposed design problem, putting the aircraft down for the= =20 duration, is not always the best solution. After it's apart, you're still=20= looking to verify your supposition. Installing a fix like mine guarantees a=20= solution in about 30 minutes. Pilot's choice. 30 minutes is a small price to= =20 pay.
 
Wolfgang
 
----- Original Message -----
Sent: Thursday, September 06, 2012 8= :15=20 AM
Subject: Re: [LML] Re: Thermal infl= uence=20 on Hydraulic Pressure

Wolfgang,
The=20 =E2=80=98failure to retract=E2=80=99 issue, to which you refer, sounds lik= e a pump=20 configuration issue. =20
For example, the current pump sold b= y Lancair=20 for the 320/360/Legacy contains spool return springs.    This configuration has the=20 potential to lock up due to thermal heating.  This configuration is simply not=20 compatible with the design of the Lancair two-seat hydraulic systems. 
Loc= k-up video:http://www.n91cz.com/Hydraulics/NewPumpLockUp_0001.wmv
With personnel turn-over at both com= panies,=20 neither side knows why the return springs were added.  However, both Parker and Lancair agree=20 that a lock up on the ground is possible with the springs installed.  This lock-up has been experienced b= y=20 some, including the factory Legacy. = ;=20 It just has not been reported enough to drive an engineering change= at=20 Lancair. 
Parker=20 has graciously supplied parts to revert currently sold =E2=80=9CCZZ=E2=80=9D= pumps back to the=20 original 320/360 configuration with respect to spool operation.  I have been forwarding these parts=20 free of charge to anyone who needs them.
See conversion instructions here: http://www.n91cz.com/Hydraulics/Pump-Unlock.pdf
I applaud your ingenuity in devising= your=20 circuit.  Unfortunately your= =20 energy seems to be a little misplaced.&n= bsp;  I would prefer to investigate=20 and fix the root cause of any out of the ordinary behavior-especially on a= n=20 airplane!   If my engin= e was=20 burning a quart of oil per hour, the fix would not to design a gadget= =20 that would pump oil from an onboard supply into the sump and replenish the= =20 lost oil.  The solution, alb= eit=20 painful in the short term, would be to open up the engine, find a= nd=20 fix the problem and then fly like other engines.
I understand that removing a pump, i= n=20 particular those mounted behind the baggage bulkhead is no fun.  Poor access is a real deterrent for=20 any maintenance activity.  T= hat is=20 simply human nature.  In the= grand=20 scheme of things, it is a small price to pay. 
My offer still stands to examine you= r=20 (Lorn=E2=80=99s) pump or any other that is able to lock-up both circuits.<= span style=3D"RIGHT: auto; mso-spacerun: yes">  I have not yet c= ome=20 across one that did not have an obvious cause-like the springs mentioned=20= above, so any such reported behavior of great interest to me and is worth=20= investigating.
 
Chr= is=20 Zavatson
N91CZ
360std
www.N91CZ.net

=

=
From: Wolfgang=20 <Wolfgang@MiCom.net>
To: lml@lancaironline.net
Sent: Wednesday, September 5, 2012 9:28=20 AM
Subject: [LML] Re: T= hermal=20 influence on Hydraulic Pressure
Let's not forget this thermal influen= ce causing=20 non-function can also happen in reverse. It has been reported that a therm= al a=20 soak on the ground after a cold night can and has caused a failure to retr= act=20 after take off.
 
A while back I offered a solution of b= umping the=20 pump automatically whenever both pressure switches, HI and LO, are open du= e to=20 high pressure. This would put the system back in normal operation mod= e=20 without the need for pilot intervention
 
Wolfgang
 
----- Original Message -----
=
Sent: Tuesday, September 04, 2012= 7:53=20 PM
Subject: Re: [LML] Re: Thermal=20= influence on Hydraulic Pressure

Fred,
I wish we had an easy way of bleeding just a wee bit of pressure=20 without momentarily dumping the gear in cruise.
The=20 320/360 pumps use a non-adjustable thermal relief valve rated at 2,500=20= psi.  The actual cracking pressure is 2,500 to 2,900 psi.  Thi= s is=20 the lowest set-point Parker has available.  2,900 psi is a lot= of=20 pressure for a system that nominally operates at 1,200 psi.  Hopefu= lly=20 the design margin for the cylinders etc. was chosen large=20 enough.
The=20 first time I saw a 2,000+ excursion was on the test bench.  I was l= eak=20 checking a cylinder.  The test stand was near the hangar door. = ;=20 The sun swung around and hit the pressurized clyinder.  I dont= '=20 know what the max pressure was since that gauge only went to 2,000=20 psi.
Chris
 
Chris=20 Zavatson
N91CZ
360std

From: Frederick Moreno=20= <frederickmoreno@bigpo= nd.com>
To: lml@lancaironline.net
Sent: Monday, September 3, 2012 11:54=20= AM
Subject: [LML] Re:= =20 Thermal influence on Hydraulic Pressure
<SENDER_EMAILfrederickmoreno>
I have an MPV-50  engine monitor that includes continuou= s=20 reading of the hydraulic system pressure on my Lancair IV/ &n= bsp;=20  I have seen the same thing, particularly on a flight that=20= started on a cool morning departure from my home drome and took us= to=20 the desert for a 110+F day.  On descent, pressure rose from i= ts=20 customary 1250 to 1500 psi at which point Bitching Betty started t= o=20 complain so I bumped my speed brakes which are hydraulic, and=20 lowered pressure back down to my customary range.  = =20 Same thing sometimes happens in reverse, a hot soak on the ground,= =20 then a climb to 10-11,000 feet for a cool soak, and at some point=20= the hydraulic pump kicks on to restore pressure to the desire= d=20 level.  My TR-182 used to the the same thing routinely when=20= departing Phoenix in the summertime.
 
It is a real effect, and makes one wonder about very high=20 pressure events arising from FL 270 (say) cold soak terminating in= =20 Phoenix on a July afternoon.  Hmmmm....
 
Fred
 
 
 
 
-------Original=20 Message-------
 
 
-took this photo after a descent from 16.5k to 1,500=20 ft.
OAT went from 42 to 94 degrees.
High Pressure gauge is pegged at 2,000+ psi
-Didn't get a photo, but the opposite happened on the ramp in= =20 Spokane. After sitting for an hour, the low pressure gauge wa= s=20 pegged at 1,200 psi+.  Spokane might not be the warmest spot i= n=20 the country, but at 85 deg F, it was 55 degrees warmer than the co= ld=20 soak on the previous leg.
Temperature changes have a big impact on system=20 pressure. 
 
Chris Zavatson
N91CZ
360std
 
<= /blockquote>
= --Apple-Mail-4B7DC717-3A9C-45AF-9718-5EA04A999C6A--