X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-ob0-f180.google.com ([209.85.214.180] verified) by logan.com (CommuniGate Pro SMTP 5.4.5) with ESMTPS id 5598493 for flyrotary@lancaironline.net; Wed, 13 Jun 2012 23:33:29 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.214.180; envelope-from=keltro@gmail.com Received: by obbun3 with SMTP id un3so1609507obb.25 for ; Wed, 13 Jun 2012 20:32:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=5U6Q5RiFzMtTN3ISqS+D2u/0/2AeGFg4WXWc3pU28rs=; b=y82AgeqDqNz9Afo42MZajh0vTmG3nl44m8FGmrLLF0KE8ileLP3JKnWpBXDZd3UYUQ w1pvYbVeicrw0xkNbBjuH14bhmeWTu/sUEOOgefgsUuYr7CFEqW3wSTWMtFBhqEo0zqZ BWLCX0d0GRK8QT7HpFoB4yz0G37vwYFLxVEalXcyCLer0TK0CorR1kwocOGtmjXVRzMv eH5WzFozJfQRH8FnvwTZy5bGWBeyBg7LVuDwdHEgf8fhW0kGV/KEZvJ6v5IuWjD6XP9/ GaV+wFzfa/GHAm9iLqaD6cFJoNOmhSqP6BtkxyiZmuyyh4/GVQrQcqWGy9SgwXOqDLQl 0fag== MIME-Version: 1.0 Received: by 10.60.27.65 with SMTP id r1mr68283oeg.55.1339644772288; Wed, 13 Jun 2012 20:32:52 -0700 (PDT) Received: by 10.60.28.70 with HTTP; Wed, 13 Jun 2012 20:32:52 -0700 (PDT) In-Reply-To: References: Date: Wed, 13 Jun 2012 22:32:52 -0500 Message-ID: Subject: Re: [FlyRotary] Re: Two possible causes was : [FlyRotary] Re: Fuel presure question. From: Kelly Troyer To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=e89a8fb20634c7070904c2665afa --e89a8fb20634c7070904c2665afa Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Just what I was thinking Bill...............Sharing a common feed circuit may also cause a voltage drop that reduces pump output (pressure) when both pumps are powered up as has been stated by Ed Anderson................ Kelly Troyer On Wed, Jun 13, 2012 at 9:07 PM, Bill Bradburry w= rote: > ************** > > David,**** > > ** ** > > If they don=92t, each pump should have its own circuit, otherwise you los= e > your redundancy.**** > > ** ** > > Bill B**** > > ** ** > ------------------------------ > > *From:* **Rotary motors in aircraft** [mailto:flyrotary@lancaironline.net= ] > *On Behalf Of *Mark Steitle > *Sent:* Wednesday, June 13, 2012 8:24 PM > > *To:* **Rotary motors in aircraft** > *Subject:* [FlyRotary] Re: Two possible causes was : [FlyRotary] Re: Fuel > presure question.**** > > ** ** > > David, **** > > ** ** > > 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 > 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 pumps have check > valves. So if one pump is off and the other on, the on pump does not pum= p > fuel backwards through the off pump. Since each pump produces the 42 psi > pressure by itself, one would assume the pumping elements in both pumps a= re > working properly. Also assuming the pressure change is NOT due to a > malfunctioning pressure sensor.**** > > **** > > Here are some things that you might want to consider:**** > > **** > > 1. That somehow when both pumps are on - one of the pumps check valves i= s > not closing properly. Not a pump expert so not certain this could even > happen - but the thought occurred to me.**** > > **** > > 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 same circuit) might cause > sufficient voltage drop in the line sufficient to decrease the pumping > performance of both pumps - pump flow rates are sensitive to voltage > variations.**** > > **** > > 4. The pressure return regulator might be malfunctioning and opening due > to the higher flow rate - easy to check, just temporarily block off the > return. If the symptom disappears then it=92s the regulator.**** > > **** > > **** > > Theoretically, if the fuel flow rate through the T's and pumps does not > change with both pumps on, then the pressure should remain the same - > which is what you are expecting, but not seeing. **** > > **** > > 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 your gauge)?**** > > **** > > One thing that could cause it, is if the fuel flow rate increases > through an upstream orifice in your fuel line (say at the "T" which feeds > your two pumps) then the pressure on the other (downstream) side will > drop. Turn one of the pumps off, the fuel flow rate drops, therefore the= re > is less pressure drop across this orifice and your fuel pressure on the > downstream side of the orifice will again go up.**** > > **** > > Its similar to a resistor in a circuit. The resistor value will remain > static - the same, but if you pull more current thought it, the voltage > drop across it will increase resulting in less voltage on the downstream > side. Reduce the current flow back to previous rate and the voltage drop > across the resistor decreases and therefore voltage on the downstream sid= e > increase.**** > > **** > > Another possible cause might be if both of your pumps are fed off the sam= e > electrical line and there is sufficient resistance that when both pumps a= re > on the voltage drop causes less performance by both pumps.**** > > **** > > Just some WAGs that you might consider, if the suggestions make by others > do not result in identifying the cause.**** > > **** > > Good Luck**** > > **** > > Ed**** > > **** > > Edward L. Anderson > ****Anderson**** Electronic Enterprises LLC > ****305 Reefton Road**** > ****Weddington**, **NC** **28104**** > http://www.andersonee.com > http://www.eicommander.com**** > > ** ** > > *From:* hoursaway1@comcast.net **** > > *Sent:* Wednesday, June 13, 2012 6:43 PM**** > > *To:* Rotary motors in aircraft **** > > *Subject:* [FlyRotary] Re: Fuel presure question.**** > > ** ** > > Fuel is gravity routed from tanks to ganged fuel selector out to T-fittin= g > with each pump on the sides of the T, to another T, into main line out = to > eng., pressure sender is mounted directly after the T where the two pump= s > come together. 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 fr= om > either pump, but both together pressure drops. David **** > ------------------------------ > > *From: *"Mark Steitle" msteitle@gmail.com > *To: *"**Rotary motors in aircraft**" > *Sent: *Wednesday, June 13, 2012 8:36:19 AM > *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**** 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 RPM, 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 here both pumps running= , > if > >> I switch off either pump pressure goes back to 42 PSI. My system is > 13B, > >> stock red injectors all four, pressure regulator is stock Mazda on the > end > >> of fuel rail with vacume connection from dynamic chamber. Thanks, > David > >> R. Cook RV6A Rotary. > > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.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= * > *** > > ** ** > --e89a8fb20634c7070904c2665afa Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
Just what I was thinking Bill...............Sharing a common feed circ= uit may=A0also cause a voltage
drop that reduces pump output (pressure) when both pumps are powered u= p=A0as has been
stated by Ed Anderson................
=A0
Kelly Troyer
On Wed, Jun 13, 2012 at 9:07 PM, Bill Bradburry = <bbradburry@bellsouth.net> wrote:

David,

=A0=

If they don=92t, each pump shou= ld have its own circuit, otherwise you lose your redundancy.<= /span>

=A0=

Bill B

=A0=

From: Rotar= y motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark Steitle
Sent: Wednesday, June 13, 20= 12 8:24 PM=20


To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Two possible causes was : [FlyR= otary] Re: Fuel presure question.=20

=A0

David,=A0

=A0

Ed covered what I was thinking about a possible bad ch= eck-valve in one of your pumps. =A0And a bunch of other stuff I hadn't = considered.

=A0

Mark=A0

On Wed, Jun 13, 2012 at 6:17 PM, Ed Anderson <eanderson@carolin= a.rr.com> wrote:

David, don't know whether you have conside= red this - as you are aware the two pumps are able to work in parallel beca= use the pumps have check valves.=A0 So if one pump is off and the other on,= the on pump does not pump fuel backwards through the off pump.=A0 Since ea= ch pump produces the 42 psi pressure by itself, one would assume the pumpin= g elements in both pumps are working properly.=A0 Also assuming the pressur= e change is NOT due to a malfunctioning pressure sensor.

=A0

Here are some things that you might want to co= nsider:

=A0

1.=A0 That somehow when both pumps are on - on= e of the pumps check valves is not closing properly.=A0 Not a=A0 pump exper= t so not certain this could even happen - but the thought occurred to me.

=A0

2.=A0 The effect of Increased fuel flow rate d= ue to both pumps=A0may be=A0causing a pressure drop through an upstream ori= fice (like perhaps your "T").

=A0

3.=A0 Turning on both pumps (assuming on the s= ame circuit) might cause sufficient voltage drop in the line sufficient to = decrease the pumping performance of both pumps - pump flow rates are sensit= ive to voltage variations.

=A0

4.=A0 The pressure return regulator might be m= alfunctioning and opening due to the higher flow rate - easy to check, just= temporarily block off the return.=A0 If the symptom disappears then it=92s= the regulator.

=A0

=A0

Theoretically, if the fuel flow rate through t= he T's and pumps=A0 does not change with both pumps on, then the pressu= re should remain the same=A0 - which is what you are expecting, but not see= ing.=A0

=A0

So since the pressure does change (drops) - wh= at could cause this (assuming the pressure drop is real and not the result = some strange malfunction of your gauge)?

=A0

=A0 One thing that could cause it, is if the f= uel flow rate increases through an upstream orifice=A0in your fuel line (sa= y at the "T" which=A0feeds your two pumps) =A0then the pressure o= n the other (downstream) side will drop.=A0 Turn one of the pumps off, the = fuel flow rate drops, therefore there is less pressure drop across this ori= fice =A0and your fuel pressure on the downstream side of the orifice will a= gain go up.

=A0

Its similar to a resistor in a circuit.=A0 The= resistor value will remain static - the same, but if you pull more current= thought it, the voltage drop across it will increase resulting in less vol= tage on the downstream side.=A0 Reduce the current flow back to previous ra= te=A0and the voltage drop across the resistor decreases and therefore volta= ge on the downstream side increase.

=A0

Another possible cause might be if both of you= r pumps are fed off the same electrical line and there is sufficient resist= ance that when both pumps are on the voltage drop causes less performance b= y both pumps.

=A0

Just=A0some WAGs that you might consider, if t= he suggestions make by others do not result in identifying the cause.

=A0

Good Luck

=A0

Ed

=A0

Edward L. Anderson
Anderson Electronic Enterprises LLC
305 Reefton Road
Weddington, NC 28104
http://www.an= dersonee.com
http://www.eicommander.com

=A0

Fro= m: hoursaway1@comcast.net

Sen= t: Wednesday, June 13, 2012 6:43 PM

Sub= ject: [FlyRotary] Re: Fuel presure question.

=A0

Fuel is gravity= routed from tanks to ganged fuel selector out to T-fitting with each pump = on the sides of the T,=A0 to another T,=A0 into main line out to eng., pres= sure=A0sender is mounted directly after the T=A0 where the two pumps come t= ogether.=A0=A0 All this is in front of the wing spar near the floor in an R= V6A. This would make the pumps in parallel & the pressure is the same f= rom either pump, but both together pressure drops.=A0=A0 David=A0=

From: "Mark Steitle&quo= t; msteitle@gmail.c= om
To: "Rotary moto= rs in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, June 13, 2012 8:36:19 AM<= br> Subject: [FlyRotary] Re: Fue= l presure question.

David,

How are your pumps plumbed... in p= arallel or series? =A0What kind of
pressure do you get when running the = backup pump only?

Mark

On 6/13/12, Tracy <rwstracy@gmail.com>= wrote:
> Hmmmm... =A0Mine goes up about a pound when I switch on the= second pump. =A0What
> happens when you turn both off?
>
> Tracy=
>
> Sent from my iPad
>
> On Jun 12, 20= 12, at 7:11 PM, hoursaway1@comcast.net wrote:
>
>> Question about fuel pressure indications, at fast idle 220= 0 RPM, 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= here both pumps running, if
>> I switch off either pump pressure goes back to 42 PSI. =A0My syste= m is 13B,
>> stock red injectors all four, pressure regulator is s= tock Mazda on the end
>> of fuel rail with vacume connection from = dynamic chamber. =A0Thanks, =A0David
>> R. Cook =A0RV6A Rotary.
>

--
Homepage: =A0http://www.flyrotary.com/<= /a>
Archive and UnSub: =A0 http://mail.lancaironline.net:8= 1/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<= /u>

=A0

<= /div>



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