X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 20 Feb 2012 11:32:53 -0500 Message-ID: X-Original-Return-Path: Received: from imr-ma04.mx.aol.com ([64.12.206.42] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTP id 5406104 for lml@lancaironline.net; Mon, 20 Feb 2012 08:38:38 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.42; envelope-from=Sky2high@aol.com Received: from mtaomg-ma02.r1000.mx.aol.com (mtaomg-ma02.r1000.mx.aol.com [172.29.41.9]) by imr-ma04.mx.aol.com (8.14.1/8.14.1) with ESMTP id q1KDbsKL032583 for ; Mon, 20 Feb 2012 08:37:54 -0500 Received: from core-mtc004c.r1000.mail.aol.com (core-mtc004.r1000.mail.aol.com [172.29.235.13]) by mtaomg-ma02.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id DF687E000081 for ; Mon, 20 Feb 2012 08:37:50 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <2e374.1c620f86.3c73a6ae@aol.com> X-Original-Date: Mon, 20 Feb 2012 08:37:50 -0500 (EST) Subject: Re: [LML] Vision Micro X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_2e374.1c620f86.3c73a6ae_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [67.175.156.123] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:0:0:0 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d29094f424cae4d2c --part1_2e374.1c620f86.3c73a6ae_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en The MAP gauge (sensor) is an absolute pressure sensor. In order to check= =20 that it is reasonable with the engine off, set your sensitive altimeter to = =20 zero altitude (sea level) and read the Kollsman window for the pressure =20 indication - this should match the pressure indication on the MAP display.= =20 The sensor should not match the baro at the altitude you are parked at unl= ess=20 you are at the shoreline on the east, west or southern coast -- i.e. sea= =20 level. =20 Grayhawk=20 =20 =20 In a message dated 2/20/2012 7:01:53 A.M. Central Standard Time, =20 BGray@glasair.org writes: =20 Cross post from Glasair.org=20 From: "Reggie Smith" =20 This is the second in a series of informational articles on the Vision=20 Microsystems EPI-800 and VM1000 Engine Management Systems. As a reminder= , I=E2=80=99 m not a certified avionics technician but an experimental aircraft owner= =20 and enthusiast like many of you. My intention with these posts is to pass= =20 along the information I=E2=80=99ve learned over the years to help keep you= r EPI-800=20 or VM1000 system alive and well, giving back to the community that has giv= en=20 so much to me. This writing will cover aspects of the manifold pressure= =20 transducer =E2=80=9Ccare and feeding=E2=80=9D to help you avoid the =E2=80= =9CMPT Blues.=E2=80=9D=20 The VMS engine management system receives manifold pressure (MP)=20 information from a manifold pressure transducer (MPT), VMS part number 301= 0015. The=20 MPT receives 5VDC input from the VMS data processing unit (DPU) and=20 returns a low level signal proportionate to the pressure differential betw= een=20 ambient and sensed intake manifold pressure. The DPU processes this sign= al=20 to provide the cockpit indication of MP in inches of mercury. If properly= =20 installed and maintained, the MPT is a robust and reliable unit giving=20 decades of trouble free service.=20 The MPT consists of an electrical sensing unit soldered to a PC board and= =20 this assembly attached to a machined aluminum block. The first generatio= n=20 units had a tan PC board with red-green-white-black wires; later units had= =20 a green PC board with four blade connectors. The sensing unit is a 0-15=20 psi differential sensor with two sensing ports. In VMS installations, one= =20 port remains open to ambient pressure while the other is connected to a br= ass=20 nipple in the mounting block, a snubber fitting to dampen pressure =20 transients, and to the aircraft manifold via owner installed fittings.=20 For longest service life, guidelines in the VMS installation manual must= =20 be followed. Specifically, it is essential that the MPT be mounted in a= =20 position vertically higher than the manifold pressure port on the engine. = If=20 the MPT is mounted level with the engine MP port, or worse yet lower than= =20 the port, it is possible for liquid fuel and/or heavy fuel vapors to=20 condense and accumulate in the MPT assembly. Over time, the blue dye pre= sent in=20 100LL fuel accumulates and congeals contaminating the snubber, sensing=20 tube, and eventually the sensor itself. Picture 1 below shows a MPT that= came=20 to me for repair with about 15 years time in service, the owner complaint= =20 was sluggish and inaccurate indications. The owner had also attempted to = =20 dismantle the unit himself breaking both the plastic sensor pressure ports = in=20 the process. Note the yellow pressure tube contaminated on both ends=20 with blue dye. Also note the dye residue around the brass nipple and sens= or=20 ports. Picture 2 shows the bottom of the aluminum block where the snubber= =20 assembly and aircraft MP port are connected. Note the excessive amount of= =20 congealed blue dye inside the cavity. After consulting with the owner, I= =20 found that his installation was in the engine compartment and below the le= vel=20 of the engine MP port, the worst possible location; it is a wonder the=20 sensor lasted as long as it did. On the test bench, as received the MPT = =20 provided and indicated MP of 24.1 inches when actual pressure was 30.15, in= =20 excess of 20% error. Makes one wonder how long an engine would hold up if= it=20 is consistently overpowered in cruise by 6+ inches MP?=20 The MPT has two basic failure modes, gradual and sudden. Sudden failure= =20 results in a cockpit indication of 00.0 MP with the engine running. This= =20 is usually caused by wiring issues such as a grounded signal wire, breaks = or=20 shorts, loose wires at the DPU terminal, etc. It can also be caused by= =20 complete failure of the sensing unit, although this is rare. Gradual=20 failure is the more common mode. Gradual failure is characterized by slo= wly=20 decreasing indicated MP over a period of time for a given throttle setting= . =20 It can be very insidious occurring over a period of weeks or months. =20 Eventually the cockpit indication may be near zero or even negative MP at = idle. =20 The telltale way to diagnose this failure is to check the indicated MP on= =20 your VMS display against the local altimeter setting. The two numbers=20 should agree within 0.2 in Hg, or about 0.5% if the MPT is functioning=20 correctly; outside this range and you have an inaccurate sensor that needs= to be=20 repaired.=20 Now back to our poor old MPT that had to endure a life of hardship in the= =20 engine compartment. I did a thorough cleaning of the unit after=20 dismantling all the parts. I removed and discarded the old sensor unit an= d replaced=20 with new. FYI, you can=E2=80=99t use your =E2=80=9CRadio Shack=E2=80=9D s= oldering iron on the=20 sensor unit. It=E2=80=99s very heat sensitive, the tech specs allow no mo= re than 2=20 seconds contact at 482F requiring a highly accurate variable temperature= =20 soldering iron, precision tip, and special low temp/no acid solder. I kno= w of=20 owners who have shelled out $85+ for a brand new sensor, =E2=80=9Cglopped= =E2=80=9D on=20 hardware store solder to get it to stick to the new sensor and PC board, t= hen=20 reinstall only to find it does not work; the sensor was internally destroy= ed=20 by excessive heat and incorrect assembly procedures. Now back to the=20 repair job: after I replaced the old sensor, I reassembled the MPT and=20 replaced the old yellow tube with a clear tube making it easier to detect = any blue=20 dye contamination (see pictures 3 & 4 below). On the test bench this now= =20 =E2=80=9Clike new=E2=80=9D unit is spot on to the local altimeter setting a= nd the owner is=20 happy to know with his new MPT and corrected installation, he should get= =20 at least 20 or more years of reliable service and accurate cockpit MP =20 indications.=20 So, what can you do to help your MPT give you long and reliable service=20 life? First, avoid the =E2=80=9CMPT Blues=E2=80=9D by making sure your in= stallation is IAW=20 the VMS VM1000 or EPI-800 installation manual guidelines. Never install= =20 your MPT in the engine compartment and never install lower than the engine= MP=20 port. Some owners have gone so far as to install a small lawn mower=20 style clear plastic/paper element filter between the engine MP port and th= e=20 line going to the VMS MPT, I don=E2=80=99t see this as necessary plus it i= ntroduces=20 another point of possible vacuum leak, but others swear by it. During you= r =20 annual condition inspection, take a look at the plastic sensor tube for =20 indications of dye contamination. If present, check your MP line for any= =20 areas where residual fuel or vapors can condense and accumulate, correct y= our=20 installation as necessary.=20 Next, remove the MPT for cleaning=E2=80=94be sure to discharge yourself to= ground=20 to avoid static electric damage to the sensor before starting work. After= =20 removing the MPT from the aircraft, carefully pull the plastic sensor tube= =20 from the brass nipple only, DO NOT try to remove it from the plastic senso= r=20 port or you will likely break it off. If the tube has become too=20 hard/brittle to remove, use an exacto knife, score the tube longitudinally = up the=20 brass nipple, and pull it off the nipple. Remove the 4 screws holding th= e=20 electric sensor/PC board assembly and set it to the side. You now are =20 able to clean the brass nipple port and the MP port connection on the back = =20 side. Use a mild solvent such as mineral spirits, denatured alcohol, or= =20 acetone to dissolve the congealed blue dye. You can use a dropper to fil= l the=20 pressure port, wait a few moments, and drain onto a paper towel, when it= =20 comes out clear, your port is clean. Try to clean both directions, i.e.= =20 pressure port toward snubber fitting, and snubber fitting toward pressure = port.=20 If you suspect excessive contamination inside the block, then disassemble= =20 the snubber and clean separately from the block. Gently blow out the=20 port, allow to dry thoroughly, and reassemble. If the tube had to be cut, = or if=20 you cannot clean out the dye contamination, replace the plastic sensor=20 tube with new. To remove it from the plastic sensor port, score the tube= =20 with an exacto knife as before and carefully remove.=20 Finally, get in the habit of comparing your altimeter setting to the=20 indicated MP before engine start making it part of your power-on pre-start= =20 checklist. This will preclude you flying with an inaccurate MP setting an= d=20 possibly overpowering your engine in cruise. If you are out in the middle = of =20 nowhere and notice a bad indication, you=E2=80=99ll at least have an idea o= f the =20 magnitude of the error and be able to power conservatively until you can ge= t =20 somewhere for repairs.=20 Hopefully these tips will keep you and your MPT be happy for years to=20 come, no =E2=80=9CMPT Blues=E2=80=9D is a good thing! If I can help you w= ith a manifold=20 pressure transducer repair or any other Vision Microsystems issues, please= don=E2=80=99 t hesitate to contact me at mooney37v@juno.com=20 Reggie=20 Glasair I-RG Flying!=20 Mooney M-20E SOLD=20 Grumann Yankee SOLD=20 =20 Bruce WWW.Glasair.org =20 > =20 -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.htm= l --part1_2e374.1c620f86.3c73a6ae_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
The MAP gauge (sensor) is an absolute pressure sensor.  In order = to=20 check that it is reasonable with the engine off, set your sensitive altimet= er to=20 zero altitude (sea level) and read the Kollsman window for the pressure=20 indication - this should match the pressure indication on the MAP=20 display.  The sensor should not match the baro at the altitude you are= =20 parked at unless you are at the shoreline on the east, west or souther= n=20 coast -- i.e. sea level.
 
Grayhawk 
 
In a message dated 2/20/2012 7:01:53 A.M. Central Standard Time,=20 BGray@glasair.org writes:
=

Cross post fro= m=20 Glasair.org

 

 

From: "Reggie Smith= "=20 <mooney37v@juno.com>

 

This is the second = in a=20 series of informational articles on the Vision Microsystems EPI-800 and V= M1000=20 Engine Management Systems.  As a=20 reminder, I=E2=80=99m not a certified avionics technician but an experime= ntal aircraft=20 owner and enthusiast like many of you.&= nbsp;=20 My intention with these posts is to pass along the information I= =E2=80=99ve=20 learned over the years to help keep your EPI-800 or VM1000 system alive a= nd=20 well, giving back to the community that has given so much to me.  This writing will cover aspects= of the=20 manifold pressure transducer =E2=80=9Ccare and feeding=E2=80=9D to help y= ou avoid the =E2=80=9CMPT=20 Blues.=E2=80=9D

 

The VMS engine mana= gement=20 system receives manifold pressure (MP) information from a manifold pressu= re=20 transducer (MPT), VMS part number 3010015.  The MPT receives 5VDC input fro= m the=20 VMS data processing unit (DPU) and returns a low level signal proportiona= te to=20 the pressure differential between ambient and sensed intake manifold=20 pressure.  The DPU processe= s this=20 signal to provide the cockpit indication of MP in inches of mercury.  If properly installed and maint= ained,=20 the MPT is a robust and reliable unit giving decades of trouble free=20 service.

 

The MPT consists of= an=20 electrical sensing unit soldered to a PC board and this assembly attached= to a=20 machined aluminum block.  T= he=20 first generation units had a tan PC board with red-green-white-black wire= s;=20 later units had a green PC board with four blade connectors.  The sensing unit is a 0-15 psi differential sensor with two sensing ports.  In VMS installations, one port = remains=20 open to ambient pressure while the other is connected to a brass nipple i= n the=20 mounting block, a snubber fitting to dampen p= ressure=20 transients, and to the aircraft manifold via owner installed=20 fittings.

 

For longest service= life,=20 guidelines in the VMS installation manual must be followed.  Specifically, it is essential t= hat the=20 MPT be mounted in a position vertically higher than the manifold pressure= port=20 on the engine.  If the MPT = is=20 mounted level with the engine MP port, or worse yet lower than the port, = it is=20 possible for liquid fuel and/or heavy fuel vapors to condense and accumul= ate=20 in the MPT assembly.  Over = time,=20 the blue dye present in 100LL fuel accumulates and congeals contaminating= the=20 snubber, sensing tube, and eventually the sen= sor=20 itself.  Picture 1 below sh= ows a=20 MPT that came to me for repair with about 15 years time in service, the o= wner=20 complaint was sluggish and inaccurate indications.  The owner had also attempted to= =20 dismantle the unit himself breaking both the plastic sensor pressure port= s in=20 the process.  Note the yell= ow=20 pressure tube contaminated on both ends with blue dye.  Also note the dye residue aroun= d the=20 brass nipple and sensor ports. =20 Picture 2 shows the bottom of the aluminum block where the snubber assembly and aircraft MP port are connected= .  Note the excessive amount of co= ngealed=20 blue dye inside the cavity.  After=20 consulting with the owner, I found that his installation was in the engin= e=20 compartment and below the level of the engine MP port, the worst possible= =20 location; it is a wonder the sensor lasted as long as it did.  On the test bench, as received = the MPT=20 provided and indicated MP of 24.1 inches when actual pressure was 30.15, = in=20 excess of 20% error.  Makes= one=20 wonder how long an engine would hold up if it is consistently overpowered= in=20 cruise by 6+ inches MP?

 

The MPT has two bas= ic=20 failure modes, gradual and sudden. = ;=20 Sudden failure results in a cockpit indication of 00.0 MP with the= =20 engine running.  This is us= ually=20 caused by wiring issues such as a grounded signal wire, breaks or shorts,= =20 loose wires at the DPU terminal, etc.&n= bsp;=20 It can also be caused by complete failure of the sensing unit, alt= hough=20 this is rare.  Gradual fail= ure is=20 the more common mode.  Grad= ual=20 failure is characterized by slowly decreasing indicated MP over a period = of=20 time for a given throttle setting. = ;=20 It can be very insidious occurring over a period of weeks or=20 months.  Eventually the coc= kpit=20 indication may be near zero or even negative MP at idle.  The telltale way to diagnose th= is=20 failure is to check the indicated MP on your VMS display against the loca= l=20 altimeter setting.  The two= =20 numbers should agree within 0.2 in Hg, or abou= t 0.5%=20 if the MPT is functioning correctly; outside this range and you have an= =20 inaccurate sensor that needs to be repaired.

 

Now back to our poo= r old=20 MPT that had to endure a life of hardship in the engine compartment.  I did a thorough cleaning of th= e unit=20 after dismantling all the parts. = =20 I removed and discarded the old sensor unit and replaced with new.=   FYI, you can=E2=80=99t use your= =E2=80=9CRadio Shack=E2=80=9D=20 soldering iron on the sensor unit. = ;=20 It=E2=80=99s very heat sensitive, the tech specs allow no more tha= n 2 seconds=20 contact at 482F requiring a highly accurate variable temperature solderin= g=20 iron, precision tip, and special low temp/no acid solder.  I know of owners who have shell= ed out=20 $85+ for a brand new sensor, =E2=80=9Cglopped= =E2=80=9D on hardware=20 store solder to get it to stick to the new sensor and PC board, then rein= stall=20 only to find it does not work; the sensor was internally destroyed by=20 excessive heat and incorrect assembly procedures.  Now back to the repair job:  after I replaced the old sensor= , I=20 reassembled the MPT and replaced the old yellow tube with a clear tube ma= king=20 it easier to detect any blue dye contamination (see pictures 3 & 4=20 below).  On the test bench = this=20 now =E2=80=9Clike new=E2=80=9D unit is spot on to the local altimeter set= ting and the owner is=20 happy to know with his new MPT and corrected installation, he should get = at=20 least 20 or more years of reliable service and accurate cockpit MP=20 indications.

 

So, what can you do= to=20 help your MPT give you long and reliable service life?  First, avoid the =E2=80=9CMPT B= lues=E2=80=9D by making=20 sure your installation is IAW the VMS VM1000 or EPI-800 installation manu= al=20 guidelines.  Never install = your=20 MPT in the engine compartment and never install lower than the engine MP= =20 port.  Some owners have gon= e so=20 far as to install a small lawn mower style clear plastic/paper element fi= lter=20 between the engine MP port and the line going to the VMS MPT, I don=E2=80= =99t see this=20 as necessary plus it introduces another point of possible vacuum leak, bu= t=20 others swear by it.  During= your=20 annual condition inspection, take a look at the plastic sensor tube for= =20 indications of dye contamination. = =20 If present, check your MP line for any areas where residual fuel o= r=20 vapors can condense and accumulate, correct your installation as=20 necessary.

 

Next, remove the MP= T for=20 cleaning=E2=80=94be sure to discharge yourself to ground to avoid static = electric=20 damage to the sensor before starting work.  After removing the MPT from the= =20 aircraft, carefully pull the plastic sensor tube from the brass nipple on= ly,=20 DO NOT try to remove it from the plastic sensor port or you will likely b= reak=20 it off.  If the tube has be= come=20 too hard/brittle to remove, use an exacto knife, score the tube longitudinally up the = brass=20 nipple, and pull it off the nipple.&nbs= p;=20 Remove the 4 screws holding the electric sensor/PC board assembly = and=20 set it to the side.  You no= w are=20 able to clean the brass nipple port and the MP port connection on the bac= k=20 side.  Use a mild solvent s= uch as=20 mineral spirits, denatured alcohol, or acetone to dissolve the congealed = blue=20 dye.  You can use a dropper= to=20 fill the pressure port, wait a few moments, and drain onto a paper towel,= when=20 it comes out clear, your port is clean.=  =20 Try to clean both directions, i.e. pressure port toward snubber fitting, and snubber=20 fitting toward pressure port.  If=20 you suspect excessive contamination inside the block, then disassemble th= e=20 snubber and clean separately from the block.<= SPAN=20 style=3D"mso-spacerun: yes">  Gently blow out the port, allow= to dry thoroughly, and reassemble.  If the tube had to be cut, or i= f you=20 cannot clean out the dye contamination, replace the plastic sensor tube w= ith=20 new.  To remove it from the= =20 plastic sensor port, score the tube with an exacto=20 knife as before and carefully remove.

 

Finally, get in the= habit=20 of comparing your altimeter setting to the indicated MP before engine sta= rt=20 making it part of your power-on pre-start checklist.  This will preclude you flying w= ith an=20 inaccurate MP setting and possibly overpowering your engine in cruise.  If you are out in the middle of= =20 nowhere and notice a bad indication, you=E2=80=99ll at least have an idea= of the=20 magnitude of the error and be able to power conservatively until you can = get=20 somewhere for repairs.

 

Hopefully these tip= s will=20 keep you and your MPT be happy for years to come, no =E2=80=9CMPT Blues= =E2=80=9D is a good=20 thing!  If I can help you w= ith a=20 manifold pressure transducer repair or any other Vision Microsystems issu= es,=20 please don=E2=80=99t hesitate to contact me at=20 mooney37v@juno.com

 

Reggie

Glasair I-RG=20 Flying!

Mooney M-20E=20 SOLD

Grumann Yankee=20 SOLD

 

 

 

 

Bruce
WWW.Glasair.org=20

>=20



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For archives and unsub= =20 http://mail.lancaironline.net:81/lists/lml/List.html
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