X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 09 May 2014 07:54:08 -0400 Message-ID: X-Original-Return-Path: Received: from nm20.bullet.mail.bf1.yahoo.com ([98.139.212.179] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTPS id 6863279 for lml@lancaironline.net; Wed, 07 May 2014 20:46:09 -0400 Received-SPF: pass receiver=logan.com; client-ip=98.139.212.179; envelope-from=chris_zavatson@yahoo.com Received: from [66.196.81.170] by nm20.bullet.mail.bf1.yahoo.com with NNFMP; 08 May 2014 00:45:33 -0000 Received: from [98.139.212.210] by tm16.bullet.mail.bf1.yahoo.com with NNFMP; 08 May 2014 00:45:33 -0000 Received: from [127.0.0.1] by omp1019.mail.bf1.yahoo.com with NNFMP; 08 May 2014 00:45:33 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 628223.44121.bm@omp1019.mail.bf1.yahoo.com Received: (qmail 97756 invoked by uid 60001); 8 May 2014 00:45:33 -0000 X-YMail-OSG: ITx.J4EVM1krcLxQ9ZOMGgEW7XmaT3sLywT_ygxCDQKnQWZ hWg0Ie7C1gPIEqkbmRI4tS6tJlxi1BmTcnn9fsUK_7_Dxx365Um1Y8sXikMr H.hOwn0X2CG0zyGewRLq3C96WBc5Baljvbya9LT_tS8DRIgjtHlS3dn6kXYx nSfJm.WXJWSHy9MX0cX121AkzXOoosvifreoCqBUHBSD5aO2zAouA3ouX.Kp 92mbJ6Pla9h2sd3XByvTGBu5l1GHYPZT08WuACpcP7NjxAGZzV8GcpMoBwya vEoNqx88XC7lixEUGjBdjkvPClBug7N4f2SPbIsFOgZIaLI8uqcVXaH5sEUr LB.M0EGRxuacs06e7IuFTx2TK_jL7Ne_KBe_WhuDB74o6d5QSutzMD0medYd Fb75iMqrxdVyCr44yABW4mMAptjNJA5AYDxO2mBREj5Ar_TD68tVz541VHjT AUJO.0QUk0.RKO24Sfw4YvoCRZYkuLH3iDtmYr8jij6Mpen72jDQ4r91tS9V tL.7k2VftsXhf4cYtNRidM0aWZl8orVlYucdhbBcNmJ6aLaZXTfYqbI8Airq RfUQ7AKa97Zh3.8oaM13EtRvHg38CSZR4KOHSD_9ZjHWLB2u7.JPQmS5jO9w l0zXX17qdeXs5iieseSUIZ8eEIsvQLJTSDWGAX.Jj1B5oPeuVa8E0vKPH67d TZ829y3queUgauVk- Received: from [172.14.16.72] by web161204.mail.bf1.yahoo.com via HTTP; Wed, 07 May 2014 17:45:33 PDT X-Rocket-MIMEInfo: 002.001,V29sZmdhbmcsCkkgYmVsaWV2ZSB0aGUgZXhhY3Qgd29yZHMgd2VyZToK4oCcSSBzZWUgdGhlIGNlbnRlcmluZyBzcHJpbmdzIGJ1dCB3aGF0IGFib3V0IHRoZQphZGRlZCBzcHJpbmcsIGV5ZWxldCBhbmQgYmFsbD8gV2hlcmUgZG9lcyB0aGF0IGZpdCBpbnRvIHRoZSBzY2hlbWF0aWM_4oCd4oCdCkFuZArigJxTdGlsbCwgdGhhdCBwb3J0IHdpdGggdGhlIGFkZGVkIHNwcmluZywKSSBiZWxpZXZlIGl0J3MgYSByZXR1cm4gcG9ydCBmb3IgZXhjZXNzIGh5ZHJhdWxpYyBmbHVpZCB0aGF0IGNhbiBiZSB1c2VkIHcBMAEBAQE- X-Mailer: YahooMailWebService/0.8.188.663 References: <8C361629041546EDBFD428FDB4D0A607@lobo> X-Original-Message-ID: <1399509933.63307.YahooMailNeo@web161204.mail.bf1.yahoo.com> X-Original-Date: Wed, 7 May 2014 17:45:33 -0700 (PDT) From: Chris Zavatson Reply-To: Chris Zavatson Subject: Re: [LML] Re: Gear Down...INOP X-Original-To: "lml@lancaironline.net" In-Reply-To: <8C361629041546EDBFD428FDB4D0A607@lobo> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="1173436188-141858416-1399509933=:63307" --1173436188-141858416-1399509933=:63307 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Wolfgang,=0AI believe the exact words were:=0A=E2=80=9CI see the centering = springs but what about the=0Aadded spring, eyelet and ball? Where does that= fit into the schematic?=E2=80=9D=E2=80=9D=0AAnd=0A=E2=80=9CStill, that por= t with the added spring,=0AI believe it's a return port for excess hydrauli= c fluid that can be used with a=0Athree port dump valve.=0A. . . but=0Awhy = the spring if it's plugged anyway?=E2=80=9D=0AI interpreted that to mean yo= u did not=0Aunderstand the purpose of the ball and spring and were unsure o= f the purpose of=0Athe third port that houses them.=C2=A0 Please=0Acorrect = me if I misunderstood your questions.=0AI support only logic.=C2=A0 I base = my statements on repeatable, demonstrated=0Afacts and sound logic.=C2=A0 I = then apply them=0Ato reported observations to help explain anomalies and tr= ouble shoot systems. =C2=A0I am quite willing to discuss any aspects of=0Ah= ydraulics with you, but no technical counter arguments have been forthcomin= g.=0AWithout intending any disrespect, observations=0Ain the absence of key= data can easily lead to incorrect hypotheses.=C2=A0 For example, the early= theories about how=0Apressure would migrate from the high side to the low = side =E2=80=9Cdue to low=0Atemperatures=E2=80=9D; or assuming the state of = pressure switches without actually having=0Aany way to monitor them; or ass= uming 70g vibration levels at the pump; or not knowing=0Athe exact configur= ation of a pump that is behaving oddly.=C2=A0 Without good data, it is inev= itable that=0Aincorrect conclusions will be drawn, no matter how good the i= ntentions of the=0Aobserver.=0AChris=0AZavatson=0AN91CZ=0A360std=0Awww.N91C= Z.net=0A=E2=80=9Cpassionate=0Anot pationate=E2=80=9D=0AOn Tuesday, May 6, 2= 014 9:21 AM, Wolfgang wrote:=0A =0AChris, you are cle= arly pationate about what you do =0Abut I still say here you're not the onl= y, let alone the final =0Aanswer. =0A=C2=A0 =0AI think it improper and do n= ot appreciate you make =0Aassumptions on what others have experienced witho= ut first hand knowledge (Lorn) =0Aand what I have or not said in the past (= You had asked what their purpose =0Awas.) =0A=C2=A0 =0AAs I have said befor= e, you go to great lengths to =0Asupport yourself but give only passing sup= port to the "other side". This is =0A"fair and balanced" ? =0A=C2=A0 =0AWol= fgang =0A=C2=A0 =0A----- Original Message ----- =0A>From: Chris Zavatson = =0A>Sent: Monday, May 05, 2014 7:14 AM =0A>Subject: Re: [LML] Re: Gear Do= wn...INOP =0A>=0A> =0A> =0A>Wolfgang, =0A>The concept I have trying to de= scribe here and in my hydraulics write-up is nothing new.=C2=A0 It is howev= er difficult, if not impossible, to identify without instrumentation.=C2= =A0 Most often this phenomenon simply causes what is perceived as a hesita= tion during gear extension.=C2=A0 Sort of a quick Start-Stop-Start with th= e gear continuing all the way down. =C2=A0It becomes quite clear what is h= appening if one looks at the system pressures when gear-down is selected.= =C2=A0 Analog gauges are best for catching the interaction.=C2=A0 What you= =EF=BF=BDll see is a pressure pulse just as the gear starts to fall.=C2=A0= The magnitude of the pulse is made greater by a few factors:=C2=A0 =0A>= =091. Warm/hot hydraulic fluid (lower viscosity) =0A>=092. Outback gear (a= dds gear down force) =0A>=093. High-side pressure well above nominal (des= cending into significantly warmer air) =0A>=094. Original, lower volume ge= ar pump =0A>When the landing gear is in the retracted position, it stores= a lot of potential energy.=C2=A0 This is from the mass of the landing gea= r, the pressure on the high side circuit and, with the outback gear, the a= ero loads trying to pull the gear down. =0A>It is useful to look at Figur= es 9 and 10 in the hydraulics write-up when trying understand the chain of= events.=C2=A0 =0A>http://www.n91cz.com/Hydraulics/Lancair%20Hydraulics.p= df =0A>In Figure 9, you=EF=BF=BDll see state of the pump while the gear i= s retracted.=C2=A0 When beginning the extension cycle, the pump builds up = pressure behind the spool (right side) and pushes it against the poppet va= lve on the left as seen in Figure 10.=C2=A0 Opening the high side poppet va= lve opens a path for fluid from the high side circuit to return back to th= e pump.=C2=A0 It is not just the pump moving fluid though.=C2=A0 All the = stored energy in the system is released and the falling gear, now also pus= hing fluid back to the pump.=C2=A0 Given the fixed volume nature of the g= ear pump, it can only absorb fluid at a certain rate.=C2=A0 If the gear pu= shes the fluid back faster than the pump can absorb it, back pressure buil= ds up in the high side circuit.=C2=A0 With enough back pressure the spool= is pushed back to the right. =C2=A0=C2=A0As this happens, the high side p= oppet starts to close off again.=C2=A0 Pressure begins to rise and propagat= es backwards through the system.=C2=A0 As soon as the low side pressure rises above the pressure switch set point, the pump= is shuts down.=C2=A0 =0A>Most of the time, the shut-down is momentary.= =C2=A0 This is because the pump takes time to spool down and it is still m= oving fluid as it does so.=C2=A0 At the same time, the falling gear is los= ing energy.=C2=A0 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.= =C2=A0 If the spike was large, the pump will remain off and you will see eq= ual pressure in the high and low side, just like in Lorn=EF=BF=BDs photo.= =C2=A0 Pressure will be just above the set-point of the low side pressure = switch and the gear will be partially extended.=C2=A0 Mitigation simply i= nvolves raising the low side pressure set-point so that the pressure spike = can no longer affect the switch and pump. =0A>I really don=EF=BF=BDt expe= ct you to be convinced.=C2=A0 I post these details for the benefit everyo= ne. =0A>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.=C2=A0 If I = have made errors somewhere, please point them out.=C2=A0 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 poin= t.=C2=A0 =0A>To be honest, I found many of your posts to be a bit worris= ome.=C2=A0 They left me with the impression you did not have a full underst= anding of the pump operating environment or its operation. =0A>For examp= le, when discussing spool movement, you claimed the pump could be subjecte= d to 70 g=EF=BF=BDs. =C2=A0The actual environment is much more benign.=C2= =A0=C2=A0 Vibration peaks are more on the order of 0.1 G=EF=BF=BDs.=C2=A0 = Below is a link to a vibration study that looks at airframe vibration in d= ifferent phases of flight.=C2=A0 The study was done while looking into an e= ngine isolator issue, but is a useful environmental baseline for anything = mounted to the structure.=C2=A0=C2=A0=C2=A0 =0A>http://www.n91cz.net/Vibr= ation/Vibration_Summary.pdf =0A>Another example was a question regarding = the ball and spring in the return line.=C2=A0 You had asked what their purp= ose was.=C2=A0 This would normally a very legitimate question.=C2=A0 My c= oncern 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. =0A>Innovation is a good thing, but on an aircraft the level of r= equired due diligence is quite high. =0A>Lorn=EF=BF=BDs pump definitely h= ad issues.=C2=A0 Mounting the pump behind the baggage bulkhead is not idea= l. It discourages good maintenance practices, just as it did in this case.= =C2=A0 Being unwilling to remove it from the aircraft to investigate the i= nternals because it was =EF=BF=BDso hard to get to=EF=BF=BD simply makes i= t impossible to properly investigate a problem.=C2=A0 When I offered to exa= mine the pump, the response was that these airplanes were built to fly and= two weeks of down-time was too much of a burden.=C2=A0 That was unfortuna= te.=C2=A0 Based on Lorn=EF=BF=BDs description of the pumps behavior I stron= gly suspected the root cause of its problems would have been immediately o= bvious upon examination.=C2=A0 I have disassembled more pumps that I can = remember.=C2=A0 All were made to operate normally once configured and adjus= ted correctly.=C2=A0 =0A>Chris Zavatson =0A>N91CZ =0A>360std =0A>www.= N91CZ.net =0A>=C2=A0 =0A>On Monday, April 28, 2014 4:59 AM, Wolfgang wrote:=0A> =0A> =0A>Chris, =0A>=C2=A0 =0A>I remain uncon= vinced with your theory. You have suggested that the pump will somehow shu= t down immediately after it has started up due to some pressure pulse. The= mechanisim of which you have yet to clarify, let alone demonstrated. =0A>= =C2=A0 =0A>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. =0A>=C2=A0 =0A>Wo= lfgang =0A>=C2=A0 =0A>----- Original Message ----- =0A>>From: Chris Zava= tson =0A>>To: lml@lancaironline.net =0A>>Sent: Saturday, April 26, 2014 1= :28 PM =0A>>Subject: Gear Down...INOP =0A>>=0A>> =0A>>Wolfgang, =0A>>=0A>> = =0A>><<=EF=BF=BDI believe in redundancy and it looks like you don't=EF=BF= =BD.=EF=BF=BD>> =0A>>=0A>> =0A>>I am a big proponent of redundancy.=C2=A0 = That is redundancy defined as a true back-up to an otherwise trouble-free = system. =0A>>=0A>> =0A>>First, I have redundant switches to power the pump= solenoids.=C2=A0 This allows me to raise and lower the gear in case of t= he failure of either of the pressure switches.=C2=A0 It doesn=EF=BF=BDt hap= pen very often, but it does happen - twice in 17 years of flying my 360.= =C2=A0 =0A>>=0A>> =0A>>I also have redundant gear down indications.=C2=A0= Two completely separate systems, separate switches, separate wires and se= parate indicators.=C2=A0 The second set of switches is mounted directly o= n the over-center links. =0A>>=0A>> =0A>>I even carry two iPads and a iPh= one - just in case =0A>>=0A>> =0A>><<=EF=BF=BDThe pressure pulse you're ta= lking about will subside (glad you agree) and as it does, because the cyli= nder is only partially extended,=C2=A0the cylinder will continues to exten= d, the low switch will close again, and enable the pump to continue . .=EF= =BF=BD>> =0A>>=0A>> =0A>>The part you seem to be missing here is that the = momentary pulse is not directly turning off the pump.=C2=A0 Thus when the = pulse subsides, the pump doesn=EF=BF=BDt just spring back to life.=C2=A0 T= he pulse pushes the spool in the wrong direction -against the pump flow.= =C2=A0 This locks the poppet that the pump just opened up a fraction of a = second earlier.=C2=A0 When this happens, the high side begins to pressuriz= e along with the low side.=C2=A0 As soon as both sides reach the low side = pressure setting, the pump is turned off.=C2=A0 This is why you see both h= igh and low circuits pressurized to the same value in Lorn=EF=BF=BDs photo= . =0A>>=0A>> =0A>>To prevent this, the low side pressure settings should b= e raised.=C2=A0 800 psi has proven sufficient.=C2=A0 The high volume gear = pump will reduce the size of the pulse since the higher volume pump is abl= e to absorb incoming fluid at a higher rate. =0A>>=0A>> =0A>>I highly reco= mmend pressure gauges for both high and low circuit be installed in a loca= tion visible to the pilot.=C2=A0 The state of the system can always be ver= ified.=C2=A0 One can immediately diagnose any in-flight problem.=C2=A0 Lea= ks can be caught early.=C2=A0 And adjusting pressure settings is no longer= guess work. =0A>>Chris Zavatson =0A>>N91CZ =0A>>360std =0A>>www.N91CZ.ne= t=0A>=0A> --1173436188-141858416-1399509933=:63307 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
=0A=0A
Wolfgang,
=0A=0A
I believe the exact words were:
=0A=0A
=E2=80=9CI see the centering springs but what about the=0Aadded spring, = eyelet and ball? Where does that fit into the schematic?=E2=80=9D=E2=80=9D<= /i>
=0A=0A
= And
=0A=0A
=E2=80=9CStill, that port with the added sp= ring,=0AI believe it's a return port for excess hydraulic fluid that can be= used with a=0Athree port dump valve.
=0A=0A
. . . but=0Awhy the spring if it's plugged anyway?=E2=80=9D
=0A=0A
I interpreted that to mean you did not=0Aunderstand the purpose of t= he ball and spring and were unsure of the purpose of=0Athe third port that = houses them.  Please=0Acorre= ct me if I misunderstood your questions.
=0A=0A
I support only logic.  I base my statements on repeata= ble, demonstrated=0Afacts and sound logic.&= nbsp;I am quite willing to discuss any aspects of=0Ahydraulics with = you, but no technical counter arguments have been forthcoming.
=0A=0A
Withou= t intending any disrespect, observations=0Ain the absence of key data can e= asily lead to incorrect hypotheses. = ; For example, the early theories about how=0Apressure would migrate= from the high side to the low side =E2=80=9Cdue to low=0Atemperatures=E2= =80=9D; or assuming the state of pressure switches without actually having= =0Aany way to monitor them; or assuming 70g vibration levels at the pump; o= r not knowing=0Athe exact configuration of a pump that is behaving oddly.  Without good data, it is ine= vitable that=0Aincorrect conclusions will be drawn, no matter how good the = intentions of the=0Aobserver.
=0A= =0A
Chris=0AZavatson
=0A=0A
= N91CZ
=0A=0A
360= std
=0A=0A
=0A=0A
=E2=80=9Cpassionate=0Anot pationate=E2=80=9D
=0A=0A
= On Tuesday, May 6, 2014 9:21 AM, Wolfgang <Wolfgang@MiCom.net> wrote:=
=0A=0A =0A =0A
=0A<= div>Chris, you are clearly pationate about = what you do =0Abut I still say here you're not the only, let alone the fina= l =0Aanswer.
=0A
&nb= sp;
=0A
I think it improper and do= not appreciate you make =0Aassumptions on what others have experienced wit= hout first hand knowledge (Lorn) =0Aand what I have or not said in the past= (You had asked what their purpose =0Awas.)
=0A
 
=0A
As I have said before, you go to great lengths to =0Asupport yoursel= f but give only passing support to the "other side". This is =0A"fair and b= alanced" ?
=0A
 = ;
=0A
Wolfgang
=0A 
=0A
=0A
----- Original Message -----
=0A =0A
Sent: Monday, May 05, 2014 7:14 AM
=0A=
Subject: Re: [LML] Re: Gear =0A Down...INOP
=0A =

=0A
=0A
=0A
=0A
Wolfgang,<= /div>=0A
=0A
Th= e concept I have =0A trying to describe here and in my hydraulics write-up= is nothing new.  It is however difficult, if not =0A im= possible, to identify without instrumentation.  Most ofte= n this phenomenon simply =0A causes what is perceived as a hesitation duri= ng gear extension.  Sort of a quick Start-Stop-Start with= =0A the gear continuing all the way down.  It becomes q= uite clear what is =0A happening if one looks at the system pressures when= gear-down is =0A selected.  Analog gauges are best =0A = for catching the interaction.  =0A What you=EF=BF=BDll = see is a pressure pulse just as the gear starts to =0A fall.  <= /span>The magnitude of the pulse =0A is made greater by a few factors:  =0A =0A
=0A
    =0A
  1. =0A
    Warm/hot hydraulic =0A fluid (lower viscosity)
    =0A =
  2. =0A
    Outback gear (adds =0A gear down force)
    =0A
  3. =0A <= div style=3D"color: rgb(0, 0, 0); font-style: normal; font-weight: normal;"= >High-sid= e pressure =0A well above nominal (descending into significantly warmer = air)
=0A
  • =0A
    Original, lower volume =0A gear pump
    • =0A
    =0A
    When the landing = gear is in the =0A retracted position, it stores a lot of potential energy= .  This is from the mass of the landing =0A gear, the pr= essure on the high side circuit and, with the outback gear, the =0A aero l= oads trying to pull the gear down.
    =0A
    =0A
    It =0A is useful to look at Figures 9 and 10 in the hydraulics write-= up when trying =0A understand the chain of events.  =0A =
    =0A
    =0A     =0A
    =0A=
    <= font face=3D"times new roman, new york, times, serif">In F= igure 9, =0A you=EF=BF=BDll see state of the pump while the gear is retrac= ted.  When beginning the extension cycle, =0A the pump b= uilds up pressure behind the spool (right side) and pushes it =0A against = the poppet valve on the left as seen in Figure 10.  Openi= ng the high side poppet valve =0A opens a path for fluid from the high sid= e circuit to return back to the =0A pump.  It is not jus= t the pump =0A moving fluid though.  All the =0A stored= energy in the system is released and the falling gear, now also pushing = =0A fluid back to the pump.  Given the =0A fixed volume= nature of the gear pump, it can only absorb fluid at a certain =0A rate.<= span>  If the gear pushes the =0A fluid back faster than the p= ump can absorb it, back pressure builds up in the =0A high side circuit.  With enough =0A back pressure the spool is pushed back t= o the right.   As this happens, the high side =0A p= oppet starts to close off again.  =0A Pressure begins to= rise and propagates backwards through the =0A system.  = As soon as the low side =0A pressure rises above the pressure switch set p= oint, the pump is shuts =0A down.  =0A
    =0A
    =0A
    Most of the= time, the shut-down =0A is momentary.  This is because = the =0A pump takes time to spool down and it is still moving fluid as it d= oes so.  At the same time, the falling gear is =0A losin= g energy.  If the pressure =0A spike was small, the pump= side will win, the spool will again open the poppet =0A all the way and t= he gear comes down.  =0A If the spike was large, the pum= p will remain off and you will see equal =0A pressure in the high and low = side, just like in Lorn=EF=BF=BDs photo.  Pressure will b= e just above the =0A set-point of the low side pressure switch and the gea= r will be partially =0A extended.  Mitigation simply =0A= involves raising the low side pressure set-point so that the pressure spi= ke =0A can no longer affect the switch and pump.
    =0A
    =0A
    I really don=EF=BF=BDt expect you to be = =0A convinced.  I post these details =0A for the benefi= t everyone.
    =0A
    =0A
    For many years =0A now, I have been p= ublishing all kinds of reports, studies, diagrams, =0A maintenance guides = and videos of Lancair systems is to promote a better =0A understanding and= safe operation of the LNC2.  If I have made errors somew= here, =0A please point them out.  But don=EF=BF=BDt =0A = just say it is wrong or that you don=EF=BF=BDt agree. Please provide some = legitimate, =0A logical reasoning, some data or something that makes the p= oint. 
    =0A
    = =0A
    To be honest, I found many of =0A your pos= ts to be a bit worrisome.  =0A They left me with the imp= ression you did not have a full understanding =0A of the pump operating en= vironment or its operation.
    =0A
    =0A
    For example, when =0A= discussing spool movement, you claimed the pump could be subjected to 70 = g=EF=BF=BDs. =0A  The actual environment is much =0A mo= re benign.   Vibration =0A peaks are more on the or= der of 0.1 G=EF=BF=BDs.  =0A Below is a link to a vibrat= ion study that looks at airframe vibration =0A in different phases of flig= ht.  =0A The study was done while looking into an engine= isolator issue, but is =0A a useful environmental baseline for anything m= ounted to the structure.    =0A =
    =0A
    =0A =0A
    =0A
    Another example w= as a question =0A regarding the ball and spring in the return line.&= nbsp; You had asked what their purpose =0A was.  = This would normally a very =0A legitimate question.  My = concern =0A was that you had already designed a circuit to alter pump oper= ation without =0A being aware of or understanding the function of all the = internal parts. =0A
    =0A
    =0A
    Innovation is a good thing, but =0A on an aircraft the level of req= uired due diligence is quite high.
    =0A
    =0A
    Lorn=EF=BF=BD= s pump =0A definitely had issues.  Mounting =0A the pum= p behind the baggage bulkhead is not ideal. It discourages good =0A mainte= nance practices, just as it did in this case.  Being unwi= lling to remove it from the =0A aircraft to investigate the internals beca= use it was =EF=BF=BDso hard to get to=EF=BF=BD =0A simply makes it impossi= ble to properly investigate a problem.  When I offered to= examine the pump, =0A the response was that these airplanes were built to= fly and two weeks of =0A down-time was too much of a burden.  = =0A That was unfortunate.  Based on =0A Lorn=EF= =BF=BDs description of the pumps behavior I strongly suspected the root =0A= cause of its problems would have been immediately obvious upon =0A exami= nation.  I have disassembled =0A more pumps that I can r= emember.  =0A All were made to operate normally once con= figured and adjusted =0A correctly.  =0A =
    =0A
    =0A
    = Chris Zav= atson
    =0A
    =0A
    N91CZ
    =0A
    =0A
    360std
    =0A=
    =0A
    www.N91CZ.net
    =0A <= div>
    =0A
    =  
    =0A
    =0A
    =0A
    =0A
    =0A
    =0A =
    On Monday, April 28, 2014= 4:59 AM, =0A Wolfgang <Wolfgang@MiCom.net> wrote:
    = =0A
    =0A
    =0A =0A=0A
    = =0A
    Chris,
    =0A
     
    =0A
    I remain unconvinced with your theory. You have =0A suggeste= d that the pump will somehow shut down immediately after it has =0A starte= d up due to some pressure pulse. The mechanisim of which you have yet to = =0A clarify, let alone demonstrated.
    =0A
     
    =0A
    I'm tired of your kibitzing and since you have =0A proven that you can'= t let it go, I will and leave you to humor =0A yourself.
    =0A =
     
    =0A
    Wolfgang
    =0A
     
    =0A
    =0A
    From: =0A Chris =0A Zavatson =0A =0A =
    Sent: =0A Saturday, April 26, 2014 1:28 PM
    =0A=
    Subject: =0A Gear Down...INOP
    =0A
    =0A
    =0A
    Wolfgang,
    =0A

    =0A
    <<=EF=BF=BDI =0A believe in = redundancy and it looks like you =0A don't=EF=BF=BD.=EF=BF=BD>>
    =0A

    =0A=
    = I =0A am a big proponent of redundancy.&= nbsp; That is redundancy =0A defined as a true back-up to an othe= rwise trouble-free =0A system.
    =0A

    =0A
    First, = I have redundant switches to power the pump =0A solenoids.  <= /span>This allows me to raise and lower the gear in =0A case of the fail= ure of either of the pressure switches.  =0A It doesn= =EF=BF=BDt happen very often, but it does happen - twice in 17 years =0A = of flying my 360. 
    =0A
    =0A
    I= =0A also have redundant gear down indications.  Two c= ompletely =0A separate systems, separate switches, separate wires and se= parate =0A indicators.  The second set of switches is = mounted =0A directly on the over-center links.
    =0A =

    =0A
    I =0A even carry two iPads a= nd a iPhone - just in case
    =0A

    =0A
    <<=EF=BF=BDThe =0A pressure pulse you're talking about will su= bside (glad you agree) and as it =0A does, because the cylinder is only = partially extended, the cylinder =0A will continues to extend, the = low switch will close again, and enable the =0A pump to continue . .=EF= =BF=BD>>
    =0A

    =0A
    The =0A part you seem = to be missing here is that the momentary pulse is not directly =0A turni= ng off the pump.  Thus when the pulse subsides, the =0A = pump doesn=EF=BF=BDt just spring back to life.  The pul= se pushes =0A the spool in the wrong direction -against the pump flow.  =0A This locks the poppet that the pump just opened up= a fraction of a =0A second earlier.  When this happen= s, the high side begins =0A to pressurize along with the low side.=   As soon as both =0A sides reach the low side pressure sett= ing, the pump is turned =0A off.  This is why you see = both high and low circuits =0A pressurized to the same value in Lorn=EF= =BF=BDs photo.
    =0A
    =0A
    To =0A prevent this, the low = side pressure settings should be raised.  =0A 800 psi = has proven sufficient.  The high volume =0A gear pump = will reduce the size of the pulse since the higher volume pump is =0A ab= le to absorb incoming fluid at a higher rate.
    =0A
    =0A
    I= =0A highly recommend pressure gauges for both high and low circuit be i= nstalled =0A in a location visible to the pilot.  The = state of the =0A system can always be verified.  One c= an immediately =0A diagnose any in-flight problem.  Le= aks can be caught =0A early.  And adjusting pressure s= ettings is no longer guess =0A work.
    =0A
    Chris =0A Zavatson
    =0A
    N91CZ
    =0A
    360std
    =0A
    www.N91CZ.net




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