X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 12 May 2014 07:54:12 -0400 Message-ID: X-Original-Return-Path: Received: from [107.14.166.231] (HELO cdptpa-oedge-vip.email.rr.com) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTP id 6867033 for lml@lancaironline.net; Sat, 10 May 2014 13:35:44 -0400 Received-SPF: none receiver=logan.com; client-ip=107.14.166.231; envelope-from=Wolfgang@MiCom.net X-Original-Return-Path: Received: from [74.218.201.50] ([74.218.201.50:1305] helo=lobo) by cdptpa-oedge01 (envelope-from ) (ecelerity 3.5.0.35861 r(Momo-dev:tip)) with ESMTP id A9/53-16163-F436E635; Sat, 10 May 2014 17:35:12 +0000 X-Original-Message-ID: From: "Wolfgang" X-Original-To: "Chris Zavatson" , References: Subject: Re: [LML] Re: Gear Down...INOP X-Original-Date: Sat, 10 May 2014 13:35:04 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0058_01CF6C54.A6863660" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5512 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5512 X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 This is a multi-part message in MIME format. ------=_NextPart_000_0058_01CF6C54.A6863660 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable I'm detecting some OCD going on here . . . let it go already. If you MUST have the last word . . . then take it . . . I'm done. Wolfgang ----- Original Message -----=20 From: Chris Zavatson=20 Sent: Friday, May 09, 2014 7:54 AM Subject: Re: [LML] Re: Gear Down...INOP Wolfgang, I believe the exact words were: =E2=80=9CI see the centering springs but what about the added spring, = eyelet and ball? Where does that fit into the = schematic?=E2=80=9D=E2=80=9D And =E2=80=9CStill, 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?=E2=80=9D I interpreted that to mean you did not understand the purpose of the = ball and spring and were unsure of the purpose of the third port that = houses them. Please correct me if I misunderstood your questions. I support only logic. I base my statements on repeatable, = demonstrated facts and sound logic. I then apply them to reported = observations to help explain anomalies and trouble shoot systems. I am = quite willing to discuss any aspects of hydraulics with you, but no = technical counter arguments have been forthcoming. Without intending any disrespect, observations in the absence of key = data can easily lead to incorrect hypotheses. For example, the early = theories about how pressure would migrate from the high side to the low = side =E2=80=9Cdue to low temperatures=E2=80=9D; or assuming the state of = pressure switches without actually having any way to monitor them; or = assuming 70g vibration levels at the pump; or not knowing the exact = configuration of a pump that is behaving oddly. Without good data, it = is inevitable that incorrect conclusions will be drawn, no matter how = good the intentions of the observer. Chris Zavatson N91CZ 360std www.N91CZ.net =E2=80=9Cpassionate not pationate=E2=80=9D On Tuesday, May 6, 2014 9:21 AM, Wolfgang wrote: Chris, you are clearly pationate about what you do but I still say = here you're not the only, let alone the final answer. I think it improper and do not appreciate you make assumptions on what = others have experienced without first hand knowledge (Lorn) and what I = have or not said in the past (You had asked what their purpose was.) As I have said before, you go to great lengths to support yourself but = give only passing support to the "other side". This is "fair and = balanced" ? Wolfgang ----- Original Message -----=20 From: Chris Zavatson=20 Sent: Monday, May 05, 2014 7:14 AM Subject: Re: [LML] Re: Gear Down...INOP Wolfgang, The concept I have trying to describe here and in my hydraulics = write-up is nothing new. It is however difficult, if not impossible, to = identify without instrumentation. Most often this phenomenon simply = causes what is perceived as a hesitation during gear extension. Sort of = a quick Start-Stop-Start with the gear continuing all the way down. It = becomes quite clear what is happening if one looks at the system = pressures when gear-down is selected. Analog gauges are best for = catching the interaction. What you=EF=BF=BDll see is a pressure pulse = just as the gear starts to fall. The magnitude of the pulse is made = greater by a few factors: =20 1.. Warm/hot hydraulic fluid (lower viscosity) 2.. Outback gear (adds gear down force) 3.. High-side pressure well above nominal (descending into = significantly warmer air) 4.. Original, lower volume gear pump When the landing gear is in the retracted position, it stores a lot = of potential energy. This is from the mass of the landing gear, the = pressure on the high side circuit and, with the outback gear, the aero = loads trying to pull the gear down. It is useful to look at Figures 9 and 10 in the hydraulics write-up = when trying understand the chain of events. =20 http://www.n91cz.com/Hydraulics/Lancair%20Hydraulics.pdf In Figure 9, you=EF=BF=BDll see state of the pump while the gear is = retracted. When beginning the extension cycle, the pump builds up = pressure behind the spool (right side) and pushes it against the poppet = valve on the left as seen in Figure 10. Opening the high side poppet = valve opens a path for fluid from the high side circuit to return back = to the pump. It is not just the pump moving fluid though. All the = stored energy in the system is released and the falling gear, now also = pushing fluid back to the pump. Given the fixed volume nature of the = gear pump, it can only absorb fluid at a certain rate. If the gear = pushes the fluid back faster than the pump can absorb it, back pressure = builds up in the high side circuit. With enough back pressure the spool = is pushed back to the right. As this happens, the high side poppet = starts to close off again. Pressure begins to rise and propagates = backwards through the system. As soon as the low side pressure rises = above the pressure switch set point, the pump is shuts down. =20 Most of the time, the shut-down is momentary. This is because the = pump takes time to spool down and it is still moving fluid as it does = so. At the same time, the falling gear is losing energy. If the = pressure spike was small, the pump side will win, the spool will again = open the poppet all the way and the gear comes down. If the spike was = large, the pump will remain off and you will see equal pressure in the = high and low side, just like in Lorn=EF=BF=BDs photo. Pressure will be = just above the set-point of the low side pressure switch and the gear = will be partially extended. Mitigation simply involves raising the low = side pressure set-point so that the pressure spike can no longer affect = the switch and pump. I really don=EF=BF=BDt expect you to be convinced. I post these = details for the benefit everyone. For many years now, I have been publishing all kinds of reports, = studies, diagrams, maintenance guides and videos of Lancair systems is = to promote a better understanding and safe operation of the LNC2. If I = have made errors somewhere, please point them out. But don=EF=BF=BDt = just say it is wrong or that you don=EF=BF=BDt agree. Please provide = some legitimate, logical reasoning, some data or something that makes = the point. =20 To be honest, I found many of your posts to be a bit worrisome. = They left me with the impression you did not have a full understanding = of the pump operating environment or its operation.=20 For example, when discussing spool movement, you claimed the pump = could be subjected to 70 g=EF=BF=BDs. The actual environment is much = more benign. Vibration peaks are more on the order of 0.1 G=EF=BF=BDs. = Below is a link to a vibration study that looks at airframe vibration = in different phases of flight. The study was done while looking into an = engine isolator issue, but is a useful environmental baseline for = anything mounted to the structure. =20 http://www.n91cz.net/Vibration/Vibration_Summary.pdf Another example was a question regarding the ball and spring in the = return line. You had asked what their purpose was. This would normally = a very legitimate question. My concern was that you had already = designed a circuit to alter pump operation without being aware of or = understanding the function of all the internal parts.=20 Innovation is a good thing, but on an aircraft the level of required = due diligence is quite high. Lorn=EF=BF=BDs pump definitely had issues. Mounting the pump behind = the baggage bulkhead is not ideal. It discourages good maintenance = practices, just as it did in this case. Being unwilling to remove it = from the aircraft to investigate the internals because it was = =EF=BF=BDso hard to get to=EF=BF=BD simply makes it impossible to = properly investigate a problem. When I offered to examine the pump, the = response was that these airplanes were built to fly and two weeks of = down-time was too much of a burden. That was unfortunate. Based on = Lorn=EF=BF=BDs description of the pumps behavior I strongly suspected = the root cause of its problems would have been immediately obvious upon = examination. I have disassembled more pumps that I can remember. All = were made to operate normally once configured and adjusted correctly. =20 Chris Zavatson N91CZ 360std www.N91CZ.net On Monday, April 28, 2014 4:59 AM, Wolfgang = wrote: Chris, I remain unconvinced with your theory. You have suggested that the = pump will somehow shut down immediately after it has started up due to = some pressure pulse. The mechanisim of which you have yet to clarify, = let alone demonstrated. I'm tired of your kibitzing and since you have proven that you can't = let it go, I will and leave you to humor yourself. Wolfgang ----- Original Message -----=20 From: Chris Zavatson=20 To: lml@lancaironline.net=20 Sent: Saturday, April 26, 2014 1:28 PM Subject: Gear Down...INOP Wolfgang, <<=EF=BF=BDI believe in redundancy and it looks like you = don't=EF=BF=BD.=EF=BF=BD>> I am a big proponent of redundancy. That is redundancy defined as = a true back-up to an otherwise trouble-free system. First, I have redundant switches to power the pump solenoids. = This allows me to raise and lower the gear in case of the failure of = either of the pressure switches. It doesn=EF=BF=BDt happen very often, = but it does happen - twice in 17 years of flying my 360. =20 I also have redundant gear down indications. Two completely = separate systems, separate switches, separate wires and separate = indicators. The second set of switches is mounted directly on the = over-center links.=20 I even carry two iPads and a iPhone - just in case <<=EF=BF=BDThe pressure pulse you're talking about will subside = (glad you agree) and as it does, because the cylinder is only partially = extended, the cylinder will continues to extend, the low switch will = close again, and enable the pump to continue . .=EF=BF=BD>> The part you seem to be missing here is that the momentary pulse = is not directly turning off the pump. Thus when the pulse subsides, the = pump doesn=EF=BF=BDt just spring back to life. The pulse pushes the = spool in the wrong direction -against the pump flow. This locks the = poppet that the pump just opened up a fraction of a second earlier. = When this happens, the high side begins to pressurize along with the low = side. As soon as both sides reach the low side pressure setting, the = pump is turned off. This is why you see both high and low circuits = pressurized to the same value in Lorn=EF=BF=BDs photo. To prevent this, the low side pressure settings should be raised. = 800 psi has proven sufficient. The high volume gear pump will reduce = the size of the pulse since the higher volume pump is able to absorb = incoming fluid at a higher rate. I highly recommend pressure gauges for both high and low circuit = be installed in a location visible to the pilot. The state of the = system can always be verified. One can immediately diagnose any = in-flight problem. Leaks can be caught early. And adjusting pressure = settings is no longer guess work. Chris Zavatson N91CZ 360std www.N91CZ.net ------=_NextPart_000_0058_01CF6C54.A6863660 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
I'm detecting some OCD going on here . = . . let it=20 go already.
 
If you MUST have the last word . . . = then take it .=20 . . I'm done.
 
Wolfgang
 
----- Original Message -----
From:=20 Chris=20 Zavatson
Sent: Friday, May 09, 2014 7:54 = AM
Subject: Re: [LML] Re: Gear=20 Down...INOP

Wolfgang,
I believe the exact words = were:
=E2=80=9CI see=20 the centering springs but what about the added spring, eyelet and = ball? Where=20 does that fit into the schematic?=E2=80=9D=E2=80=9D
And
=E2=80=9CStill,=20 that port with the added spring, I believe it's a return port for = excess=20 hydraulic fluid that can be used with a three port dump=20 valve.
. . . but why the spring if it's plugged=20 anyway?=E2=80=9D
I interpreted that to mean you did not = understand the=20 purpose of the ball and spring and were unsure of the purpose of the = third=20 port that houses them.  = Please=20 correct me if I misunderstood your questions.
I support only logic.  I base my statements on = repeatable,=20 demonstrated facts and sound logic. =20 I then apply them to reported observations to help explain = anomalies=20 and trouble shoot systems.  I am=20 quite willing to discuss any aspects of hydraulics with you, but no = technical=20 counter arguments have been forthcoming.
Without intending any disrespect, observations = in the=20 absence of key data can easily lead to incorrect hypotheses.  For example, the early = theories about=20 how pressure would migrate from the high side to the low side = =E2=80=9Cdue to low=20 temperatures=E2=80=9D; or assuming the state of pressure switches = without actually=20 having any way to monitor them; or assuming 70g vibration levels at = the pump;=20 or not knowing the exact configuration of a pump that is behaving = oddly.  Without good data, it is = inevitable=20 that incorrect conclusions will be drawn, no matter how good the = intentions of=20 the observer.
Chris Zavatson
N91CZ
360std
www.N91CZ.net
=E2=80=9Cpassionate not = pationate=E2=80=9D
On Tuesday, May 6, 2014 = 9:21 AM, Wolfgang=20 <Wolfgang@MiCom.net> wrote:
Chris, you are clearly pationate = about what you=20 do but I still say here you're not the only, let alone the final=20 answer.
 
I think it improper and do not = appreciate you=20 make assumptions on what others have experienced without first hand = knowledge=20 (Lorn) and what I have or not said in the past (You had asked what = their=20 purpose was.)
 
As I have said before, you go to = great lengths to=20 support yourself but give only passing support to the "other side". = This is=20 "fair and balanced" ?
 
Wolfgang
 
-----=20 Original Message -----
From:=20 Chris=20 Zavatson
Sent:=20 Monday, May 05, 2014 7:14 AM
Subject:=20 Re: [LML] Re: Gear Down...INOP

Wolfgang,
The = concept I=20 have trying to describe here and in my hydraulics write-up is = nothing=20 new.  It is however difficult, if not impossible, = to=20 identify without instrumentation.  Most often this = phenomenon simply causes what is perceived as a hesitation during = gear=20 extension.  Sort of a quick Start-Stop-Start with = the gear=20 continuing all the way down.  It becomes quite = clear what=20 is happening if one looks at the system pressures when gear-down is=20 selected.  Analog gauges are best for catching the = interaction.  What you=EF=BF=BDll see is a = pressure pulse just as=20 the gear starts to fall.  The magnitude of the = pulse is=20 made greater by a few factors: =20
  1. Warm/hot = hydraulic=20 fluid (lower viscosity)
  2. Outback = gear (adds=20 gear down force)
  3. High-side pressure=20 well above nominal (descending into significantly warmer = air)
  4. Original, lower=20 volume gear pump
When the landing = gear is in=20 the retracted position, it stores a lot of potential = energy. =20 This is from the mass of the landing gear, the pressure on = the high=20 side circuit and, with the outback gear, the aero loads trying to = pull the=20 gear down.
It=20 is useful to look at Figures 9 and 10 in the hydraulics write-up = when trying=20 understand the chain of events. =20
http://www.n91cz.com/Hydraulics/Lancair%20Hydraulics.pdf
In = Figure 9,=20 you=EF=BF=BDll see state of the pump while the gear is = retracted. =20 When beginning the extension cycle, the pump builds up = pressure=20 behind the spool (right side) and pushes it against the poppet valve = on the=20 left as seen in Figure 10.  Opening the high side = poppet=20 valve opens a path for fluid from the high side circuit to return = back to=20 the pump.  It is not just the pump moving fluid=20 though.  All the stored energy in the system is = released=20 and the falling gear, now also pushing fluid back to the = pump. =20 Given the fixed volume nature of the gear pump, it can only = absorb=20 fluid at a certain rate.  If the gear pushes the = fluid=20 back faster than the pump can absorb it, back pressure builds up in = the high=20 side circuit.  With enough back pressure the spool = is=20 pushed back to the right.   As this happens, = the high=20 side poppet starts to close off again.  Pressure = begins to=20 rise and propagates backwards through the system.  = As soon=20 as the low side pressure rises above the pressure switch set point, = the pump=20 is shuts down. 
Most of the time, = the=20 shut-down is momentary.  This is because the pump = takes=20 time to spool down and it is still moving fluid as it does = so. =20 At the same time, the falling gear is losing = energy. =20 If the pressure spike was small, the pump side will win, the = spool=20 will again open the poppet all the way and the gear comes = down. =20 If the spike was large, the pump will remain off and you will = see=20 equal pressure in the high and low side, just like in Lorn=EF=BF=BDs = photo.  Pressure will be just above the set-point = of the=20 low side pressure switch and the gear will be partially=20 extended.  Mitigation simply involves raising the = low side=20 pressure set-point so that the pressure spike can no longer affect = the=20 switch and pump.
I really = don=EF=BF=BDt expect you to=20 be convinced.  I post these details for the = benefit=20 everyone.
For = many years=20 now, I have been publishing all kinds of reports, studies, diagrams, = maintenance guides and videos of Lancair systems is to promote a = better=20 understanding and safe operation of the LNC2.  If = I have=20 made errors somewhere, please point them out.  But = don=EF=BF=BDt=20 just say it is wrong or that you don=EF=BF=BDt agree. Please provide = some=20 legitimate, logical reasoning, some data or something that makes the = point. 
To be honest, I = found many of=20 your posts to be a bit worrisome.  They left me = with the=20 impression you did not have a full understanding of the pump = operating=20 environment or its operation.
For = example,=20 when discussing spool movement, you claimed the pump could be = subjected to=20 70 g=EF=BF=BDs.  The actual environment is much = more=20 benign.   Vibration peaks are more on the = order of=20 0.1 G=EF=BF=BDs.  Below is a link to a vibration = study that looks=20 at airframe vibration in different phases of flight.  = The=20 study was done while looking into an engine isolator issue, but is a = useful=20 environmental baseline for anything mounted to the=20 structure.    =
http://www.n91cz.net/Vibration/Vibration_Summary.pdf<= /FONT>
Another example was = a=20 question regarding the ball and spring in the return = line. =20 You had asked what their purpose was.  This = would=20 normally a very legitimate question.  My concern = was that=20 you had already designed a circuit to alter pump operation without = being=20 aware of or understanding the function of all the internal parts.=20
Innovation is a = good thing,=20 but on an aircraft the level of required due diligence is quite=20 high.
Lorn=EF=BF=BDs pump=20 definitely had issues.  Mounting the pump behind = the=20 baggage bulkhead is not ideal. It discourages good maintenance = practices,=20 just as it did in this case.  Being unwilling to = remove it=20 from the aircraft to investigate the internals because it was = =EF=BF=BDso hard to=20 get to=EF=BF=BD simply makes it impossible to properly investigate a = problem.  When I offered to examine the pump, the = response=20 was that these airplanes were built to fly and two weeks of = down-time was=20 too much of a burden.  That was = unfortunate. =20 Based on Lorn=EF=BF=BDs description of the pumps behavior I = strongly=20 suspected the root cause of its problems would have been immediately = obvious=20 upon examination.  I have disassembled more pumps = that I=20 can remember.  All were made to operate normally = once=20 configured and adjusted correctly. =20
Chris = Zavatson
N91CZ
360std
www.N91CZ.net
 
On Monday, April 28, 2014 = 4:59 AM,=20 Wolfgang <Wolfgang@MiCom.net> wrote:
Chris,
 
I remain unconvinced with your = theory. You have=20 suggested that the pump will somehow shut down immediately after it = has=20 started up due to some pressure pulse. The mechanisim of which you = have yet=20 to clarify, let alone demonstrated.
 
I'm tired of your kibitzing and = since you have=20 proven that you can't let it go, I will and leave you to humor=20 yourself.
 
Wolfgang
 
-----=20 Original Message -----
From:=20 Chris=20 Zavatson
To:=20 lml@lancaironline.net =
Sent:=20 Saturday, April 26, 2014 1:28 PM
Subject:=20 Gear Down...INOP

Wolfgang,

<<=EF=BF=BDI=20 believe in redundancy and it looks like you=20 don't=EF=BF=BD.=EF=BF=BD>>

I=20 am a big proponent of redundancy.  That is = redundancy=20 defined as a true back-up to an otherwise trouble-free=20 system.

First, I have redundant switches to power the pump=20 solenoids.  This allows me to raise and lower = the gear=20 in case of the failure of either of the pressure = switches. =20 It doesn=EF=BF=BDt happen very often, but it does happen - = twice in 17=20 years of flying my 360.  =

I=20 also have redundant gear down indications.  Two=20 completely separate systems, separate switches, separate wires and = separate indicators.  The second set of switches = is=20 mounted directly on the over-center links.

I=20 even carry two iPads and a iPhone - just in case

<<=EF=BF=BDThe=20 pressure pulse you're talking about will subside (glad you agree) = and as=20 it does, because the cylinder is only partially extended, the = cylinder will continues to extend, the low switch will close = again, and=20 enable the pump to continue . = .=EF=BF=BD>>

The=20 part you seem to be missing here is that the momentary pulse is = not=20 directly turning off the pump.  Thus when the = pulse=20 subsides, the pump doesn=EF=BF=BDt just spring back to = life. =20 The pulse pushes the spool in the wrong direction -against = the pump=20 flow.  This locks the poppet that the pump just = opened=20 up a fraction of a second earlier.  When this = happens,=20 the high side begins to pressurize along with the low = side. =20 As soon as both sides reach the low side pressure setting, = the pump=20 is turned off.  This is why you see both high = and low=20 circuits pressurized to the same value in Lorn=EF=BF=BDs=20 photo.

To=20 prevent this, the low side pressure settings should be = raised. =20 800 psi has proven sufficient.  The high = volume=20 gear pump will reduce the size of the pulse since the higher = volume pump=20 is able to absorb incoming fluid at a higher = rate.

I=20 highly recommend pressure gauges for both high and low circuit be=20 installed in a location visible to the pilot.  = The state=20 of the system can always be verified.  One can=20 immediately diagnose any in-flight problem.  = Leaks can=20 be caught early.  And adjusting pressure = settings is no=20 longer guess work.
Chris=20 Zavatson
N91CZ 360std www.N91CZ.net
=


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