X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from qmta07.emeryville.ca.mail.comcast.net ([76.96.30.64] verified) by logan.com (CommuniGate Pro SMTP 5.4.5) with ESMTP id 5598477 for flyrotary@lancaironline.net; Wed, 13 Jun 2012 23:21:23 -0400 Received-SPF: pass receiver=logan.com; client-ip=76.96.30.64; envelope-from=hoursaway1@comcast.net Received: from omta04.emeryville.ca.mail.comcast.net ([76.96.30.35]) by qmta07.emeryville.ca.mail.comcast.net with comcast id N3Kl1j0010lTkoCA73LnuH; Thu, 14 Jun 2012 03:20:47 +0000 Received: from sz0081.ev.mail.comcast.net ([76.96.26.137]) by omta04.emeryville.ca.mail.comcast.net with comcast id N3Ln1j00V2xV6SL8Q3LnGg; Thu, 14 Jun 2012 03:20:47 +0000 Date: Thu, 14 Jun 2012 03:20:47 +0000 (UTC) From: hoursaway1@comcast.net To: Rotary motors in aircraft Message-ID: <1386069685.92211.1339644047419.JavaMail.root@sz0081a.emeryville.ca.mail.comcast.net> In-Reply-To: Subject: Re: [FlyRotary] Re: Two possible causes was : [FlyRotary] Re: Fuel presure question. MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_92210_713738325.1339644047417" X-Originating-IP: [71.206.108.115] X-Mailer: Zimbra 6.0.13_GA_2944 (ZimbraWebClient - IE8 (Win)/6.0.13_GA_2944) ------=_Part_92210_713738325.1339644047417 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Thanks Mark, Steve hit on a couple also, I have some testing to do.=C2=A0 D= avid.=20 ----- Original Message ----- From: "Mark Steitle" =20 To: "Rotary motors in aircraft" =20 Sent: Wednesday, June 13, 2012 8:24:05 PM=20 Subject: [FlyRotary] Re: Two possible causes was : [FlyRotary] Re: Fuel pre= sure question.=20 David,=C2=A0=20 Ed covered what I was thinking about a possible bad check-valve in one of y= our pumps. =C2=A0And a bunch of other stuff I hadn't considered.=20 Mark=C2=A0=20 On Wed, Jun 13, 2012 at 6:17 PM, Ed Anderson < eanderson@carolina.rr.com > = wrote:=20 David, don't know whether you have considered this - as you are aware the t= wo pumps are able to work in parallel because the pumps have check valves.= =C2=A0 So if one pump is off and the other on, the on pump does not pump fu= el backwards through the off pump.=C2=A0 Since each pump produces the 42 ps= i pressure by itself, one would assume the pumping elements in both pumps a= re working properly.=C2=A0 Also assuming the pressure change is NOT due to = a malfunctioning pressure sensor.=20 =C2=A0=20 Here are some things that you might want to consider:=20 =C2=A0=20 1.=C2=A0 That somehow when both pumps are on - one of the pumps check valve= s is not closing properly.=C2=A0 Not a=C2=A0 pump expert so not certain thi= s could even happen - but the thought occurred to me.=20 =C2=A0=20 2.=C2=A0 The effect of Increased fuel flow rate due to both pumps=C2=A0may = be=C2=A0causing a pressure drop through an upstream orifice (like perhaps y= our "T").=20 =C2=A0=20 3.=C2=A0 Turning on both pumps (assuming on the same circuit) might cause s= ufficient voltage drop in the line sufficient to decrease the pumping perfo= rmance of both pumps - pump flow rates are sensitive to voltage variations.= =20 =C2=A0=20 4.=C2=A0 The pressure return regulator might be malfunctioning and opening = due to the higher flow rate - easy to check, just temporarily block off the= return.=C2=A0 If the symptom disappears then it=E2=80=99s the regulator.= =20 =C2=A0=20 =C2=A0=20 Theoretically, if the fuel flow rate through the T's and pumps=C2=A0 does n= ot change with both pumps on, then the pressure should remain the same=C2= =A0 - which is what you are expecting, but not seeing.=C2=A0=20 =C2=A0=20 So since the pressure does change (drops) - what could cause this (assuming= the pressure drop is real and not the result some strange malfunction of y= our gauge)?=20 =C2=A0=20 =C2=A0 One thing that could cause it, is if the fuel flow rate increases th= rough an upstream orifice=C2=A0in your fuel line (say at the "T" which=C2= =A0feeds your two pumps) =C2=A0then the pressure on the other (downstream) = side will drop.=C2=A0 Turn one of the pumps off, the fuel flow rate drops, = therefore there is less pressure drop across this orifice =C2=A0and your fu= el pressure on the downstream side of the orifice will again go up.=20 =C2=A0=20 Its similar to a resistor in a circuit.=C2=A0 The resistor value will remai= n static - the same, but if you pull more current thought it, the voltage d= rop across it will increase resulting in less voltage on the downstream sid= e.=C2=A0 Reduce the current flow back to previous rate=C2=A0and the voltage= drop across the resistor decreases and therefore voltage on the downstream= side increase.=20 =C2=A0=20 Another possible cause might be if both of your pumps are fed off the same = electrical line and there is sufficient resistance that when both pumps are= on the voltage drop causes less performance by both pumps.=20 =C2=A0=20 Just=C2=A0some WAGs that you might consider, if the suggestions make by oth= ers do not result in identifying the cause.=20 =C2=A0=20 Good Luck=20 =C2=A0=20 Ed=20 =C2=A0=20 Edward L. Anderson=20 Anderson Electronic Enterprises LLC=20 305 Reefton Road=20 Weddington, NC 28104=20 http://www.andersonee.com=20 http://www.eicommander.com=20 From: hoursaway1@comcast.net=20 Sent: Wednesday, June 13, 2012 6:43 PM=20 To: Rotary motors in aircraft=20 Subject: [FlyRotary] Re: Fuel presure question.=20 Fuel is gravity routed from tanks to ganged fuel selector out to T-fitting = with each pump on the sides of the T,=C2=A0 to another T,=C2=A0 into main l= ine out to eng., pressure=C2=A0sender is mounted directly after the T=C2=A0= where the two pumps come together.=C2=A0=C2=A0 All this is in front of the= wing spar near the floor in an RV6A. This would make the pumps in parallel= & the pressure is the same from either pump, but both together pressure dr= ops.=C2=A0=C2=A0 David=C2=A0=20 From: "Mark Steitle" msteitle@gmail.com=20 To: "Rotary motors in aircraft" < flyrotary@lancaironline.net >=20 Sent: Wednesday, June 13, 2012 8:36:19 AM=20 Subject: [FlyRotary] Re: Fuel presure question.=20 David,=20 How are your pumps plumbed... in parallel or series? =C2=A0What kind of=20 pressure do you get when running the backup pump only?=20 Mark=20 On 6/13/12, Tracy < rwstracy@gmail.com > wrote:=20 > Hmmmm... =C2=A0Mine goes up about a pound when I switch on the second pum= p. =C2=A0What=20 > happens when you turn both off?=20 >=20 > Tracy=20 >=20 > Sent from my iPad=20 >=20 > On Jun 12, 2012, at 7:11 PM, hoursaway1@comcast.net wrote:=20 >=20 >> Question about fuel pressure indications, at fast idle 2200 RPM, fuel=20 >> pressure is 42 PSI on EM2, if I switch on the back-up pump with the=20 >> primary pump the pressure drops to 35 PSI, can here both pumps running, = if=20 >> I switch off either pump pressure goes back to 42 PSI. =C2=A0My system i= s 13B,=20 >> stock red injectors all four, pressure regulator is stock Mazda on the e= nd=20 >> of fuel rail with vacume connection from dynamic chamber. =C2=A0Thanks, = =C2=A0David=20 >> R. Cook =C2=A0RV6A Rotary.=20 >=20 --=20 Homepage: =C2=A0 http://www.flyrotary.com/=20 Archive and UnSub: =C2=A0 http://mail.lancaironline.net:81/lists/flyrotary/= List.html=20 No virus found in this message.=20 Checked by AVG - www.avg.com=20 Version: 2012.0.2180 / Virus Database: 2433/5068 - Release Date: 06/13/12= =20 ------=_Part_92210_713738325.1339644047417 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable <= div style=3D'font-family: Arial; font-size: 12pt; color: #000000'>Thanks Ma= rk, Steve hit on a couple also, I have some testing to do.  David.
=
From: "Mark Steitle" <msteitle@gmail.com>
To: "Rotar= y motors in aircraft" <flyrotary@lancaironline.net>
Sent: W= ednesday, June 13, 2012 8:24:05 PM
Subject: [FlyRotary] Re: Two p= ossible causes was : [FlyRotary] Re: Fuel presure question.

David,&n= bsp;

Ed covered what I was thinking about a possible bad check-valve in one= of your pumps.  And a bunch of other stuff I hadn't considered.

Mark 

On Wed, Jun 13, 2012 at 6:17 PM, Ed Anderson <eanderson@carolina.rr.com> wrote:
David, don't know whether you have considered this = - as you are aware the two pumps are able to work in parallel because the p= umps have check valves.  So if one pump is off and the other on, the o= n pump does not pump fuel backwards through the off pump.  Since each = pump produces the 42 psi pressure by itself, one would assume the pumping e= lements in both pumps are working properly.  Also assuming the pressur= e change is NOT due to a malfunctioning pressure sensor.
 
Here are some things that you might want to conside= r:
 
1.  That somehow when both pumps are on - one = of the pumps check valves is not closing properly.  Not a  pump e= xpert so not certain this could even happen - but the thought occurred to m= e.
 
2.  The effect of Increased fuel flow rate due= to both pumps may be causing a pressure drop through an upstream= orifice (like perhaps your "T").
 
3.  Turning on both pumps (assuming on the sam= e circuit) might cause sufficient voltage drop in the line sufficient to de= crease the pumping performance of both pumps - pump flow rates are sensitiv= e to voltage variations.
 
4.  The pressure return regulator might be mal= functioning and opening due to the higher flow rate - easy to check, just t= emporarily block off the return.  If the symptom disappears then it=E2= =80=99s the regulator.
 
 
Theoretically, if the fuel flow rate through the T'= s and pumps  does not change with both pumps on, then the pressure sho= uld remain the same  - which is what you are expecting, but not seeing= . 
 
So since the pressure does change (drops) - what co= uld cause this (assuming the pressure drop is real and not the result some = strange malfunction of your gauge)?
 
  One thing that could cause it, is if the fue= l flow rate increases through an upstream orifice in your fuel line (s= ay at the "T" which feeds your two pumps)  then the pressure on t= he other (downstream) side will drop.  Turn one of the pumps off, the = fuel flow rate drops, therefore there is less pressure drop across this ori= fice  and your fuel pressure on the downstream side of the orifice wil= l again go up.
 
Its similar to a resistor in a circuit.  The r= esistor value will remain static - the same, but if you pull more current t= hought it, the voltage drop across it will increase resulting in less volta= ge on the downstream side.  Reduce the current flow back to previous r= ate and the voltage drop across the resistor decreases and therefore v= oltage on the downstream side increase.
 
Another possible cause might be if both of your pum= ps are fed off the same electrical line and there is sufficient resistance = that when both pumps are on the voltage drop causes less performance by bot= h pumps.
 
Just some WAGs that you might consider, if the= suggestions make by others do not result in identifying the cause.<= /DIV>
 
Good Luck
 
Ed
 
Edward L. Anderson
Anderson Electronic Enterpris= es LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com<= /A>

Sent: Wednesday, June 13, 2012 6:43 PM
Subject: [FlyRotary] Re: Fuel presure question.

Fuel is gravity routed f= rom tanks to ganged fuel selector out to T-fitting with each pump on the si= des of the T,  to another T,  into main line out to eng., pressur= e sender is mounted directly after the T  where the two pumps com= e together.   All this is in front of the wing spar near the floo= r in an RV6A. This would make the pumps in parallel & the pressure is t= he same from either pump, but both together pressure drops.   Dav= id 

From: "Mark Steitle" msteitle@gmail.com
To: "Rotary motors in aircraft" <= ;flyrotary@l= ancaironline.net>
Sent: Wednesday, June 13, 2012 8:36:19 A= M
Subject: [FlyRotary] Re: Fuel presure question.

David,
How are your pumps plumbed... in parallel or series?  What kind = of
pressure do you get when running the backup pump only?

Mark
On 6/13/12, Tracy <rwstracy@gmail.com> wrote:
> Hmmmm...  Mine goes up= about a pound when I switch on the second pump.  What
> happens= when you turn both off?
>
> Tracy
>
> Sent from my= iPad
>
> On Jun 12, 2012, at 7:11 PM, hoursaway1@comcast.net wrote:
>= ;
>> Question about fuel pressure indications, at fast idle 2200 R= PM, fuel
>> pressure is 42 PSI on EM2, if I switch on the back-up = pump with the
>> primary pump the pressure drops to 35 PSI, can he= re both pumps running, if
>> I switch off either pump pressure goe= s back to 42 PSI.  My system is 13B,
>> stock red injectors a= ll four, pressure regulator is stock Mazda on the end
>> of fuel r= ail with vacume connection from dynamic chamber.  Thanks,  David<= BR>>> R. Cook  RV6A Rotary.
>

--
Homepage:  = ;http://www.flyrotary= .com/
Archive and UnSub:   http://mail.lancaironlin= e.net:81/lists/flyrotary/List.html

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0= .2180 / Virus Database: 2433/5068 - Release Date: 06/13/12


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