Return-Path: Received: from imf21aec.mail.bellsouth.net ([205.152.59.69] verified) by logan.com (CommuniGate Pro SMTP 4.3c1) with ESMTP id 726320 for flyrotary@lancaironline.net; Sat, 12 Feb 2005 13:56:14 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.69; envelope-from=sqpilot@bellsouth.net Received: from [209.214.45.129] by imf21aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20050212185525.TWKG2069.imf21aec.mail.bellsouth.net@[209.214.45.129]> for ; Sat, 12 Feb 2005 13:55:25 -0500 Received: from 127.0.0.1 (AVG SMTP 7.0.300 [265.8.7]); Sat, 12 Feb 2005 12:55:14 -0600 Message-ID: <002701c51134$5e919d20$812dd6d1@paul52u7f5qyav> From: "Paul" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Vapor lock in sump/header tank. Date: Sat, 12 Feb 2005 12:55:06 -0600 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="=======AVGMAIL-420E511210EC=======" --=======AVGMAIL-420E511210EC======= Content-Type: multipart/alternative; boundary="----=_NextPart_000_0024_01C51102.13C9DB90" ------=_NextPart_000_0024_01C51102.13C9DB90 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Hi, Todd....thank you VERY much for going into all that detail regarding = your fuel system and it's problems/fixes. Yes, my main fuel tanks are = the highest point of the system....the sump tank is lower than the 2 = main tanks (both are vented), and the fuel pumps are lower than the sump = tank. The fuel goes out of the bottom of the main tanks and goes = downhill into the fuel selector valve. Then the fuel comes out of the = fuel selector valve , downhill (through a facet low pressure boost pump = that I have yet to use) to the top of the surge tank.The fuel then comes = out of the bottom of the surge tank and runs downhill to the gascolator = and then two EFI pumps. After going uphill through the fuel rail and to = the fuel pressure regulator, it then goes back downhill to the top of = the unvented surge tank. (I hope I didn't confuse everyone with this) As to how long I waited to restart the engine....It never really = quit. It just wouldn't produce any power. Immediately, as the plane = came to a stop in the mud, I applied power and was able to turn around = and taxi back to the hangar. Unfortunately, I didn't try a full power = run-up (just too darned happy to be on the ground in one piece), but I = would have to guess that I used at least 1/2 throttle to pull me out of = the mud, and I was unable to get that in the air, or else I would have = continued to fly the pattern and land on the runway. You have really peaked my curiosity...you stated that you converted = to a returnless fuel system....please educate me a little here....where = does the unused fuel (after the fuel pressure regulator) go? Inquiring = minds need to know. Thanks again for helping out. Paul Conner ----- Original Message -----=20 From: Todd Bartrim=20 To: Rotary motors in aircraft=20 Sent: Saturday, February 12, 2005 5:18 AM Subject: [FlyRotary] Re: Vapor lock in sump/header tank. Hi Paul; Caution this is a long story relating my previous vapour lock = issues and how they may relate to yours. Recent comments have differed = about the need to vent or not to vent a sump/header tank. As I = understand it you have a sump tank in which it is gravity fed from your = mains, then pumped up to your engine. However IIRC a previous post in = which you said you had copied Ed's system which is a header tank that = has boost pumps feeding it. (I may have that incorrect as I couldn't = find the post in question) Now I went through a couple different = versions of a header tank before scrapping the idea altogether. My first = one was always vented, but this required level control, via the boost = pumps as it required fuel to be pumped up to the tank, then it gravity = fed my FI pumps. If not filled by pumps, it would just drain the tank = due to the vent. If pumps were left on it would over fill and fuel would = go out the vent lines which were tied via a common header to the main = tanks so negative draft would draw most of the fuel back to the feed = tank, but not all. I'd planned to use an electronic level control system = to help manage this but supplier problems caused me to look closely at = what was really an unnecessary failure mode.=20 At this time I decided to use a non-vented system much like Ed's, = however I was certain that I could improve upon it by increasing the = size of the header tank and having it located on the cool side of the = firewall. But I found that it required a vent as there was no other way = to purge out the air from the tank which would accumulate there when one = would run a tank dry before switching tanks (I have 6 tanks so it is = important to completely empty the aux tanks). So I installed a vent with = a pilot accessible valve. This allowed the venting of all air out of the = tank at which time it would be closed. Then the fuel would draw up from = the main tanks to replace the fuel that had been drawn out and not = returned through the return line from the fuel reg, without the need for = pumps. I had a clear sight tube to see the level of the header tank and = another short clear section of hose on the vent line, so that I could = see whether I was venting air or fuel.=20 This seemed like a fine system, until it began seeing the heat of = flight operations. Ground runs seemed mostly successful and running a = tank dry until the header tank was empty resulted in approximately a 20 = second delay in getting fresh fuel to restart the engine and completely = purging the air within 2-3 minutes. But under flight conditions it was = much different. Heat would cause vapour problems that were very = difficult to deal with. The pressure would build within the header tank = and the sight tube would not always give a true reading as it should. = Twice I ran a tank dry while at +10000' above the airport and had a very = difficult time in getting fuel back resulting in approx 6000' of glider = alt loss each time. Another time I was doing circuits and was on my = downwind leg when the pressure in the tank caused a vapour lock even = though I had plenty of fuel in the tank(s) feeding the header tank. The = pressure had just built up to the point where even the 7 psi = boost/transfer pumps couldn't overcome it to keep fuel in the tank. In = this case I was able to make an emergency deadstick landing on an = intersecting runway and fortunately I even kept my speed up enough to = coast all the way to my tie-down spot. That's where the firetrucks met = me... kinda embarrassing!=20 In each of these cases, I found that when opening the vent valve = to release the pressure, I could see through the clear vent tube section = that I was venting a boiling fuel (air/fuel) mixture. And it took an = uncomfortably long period of time to relieve that pressure and refill = the tank with fresh fuel. I then installed optical fuel level sensors = (hi/low) on the header tank, a vacuum/pressure gauge and a temp sensor. = I found that it would begin by having a vacuum in the tank as the system = would draw in new fuel to replace that which was being consumed, but it = would soon begin to build as a pressure as the fuel heated and would = then begin to push the level down. Opening the vent relived this = pressure but it couldn't be left open, or it would just empty the header = tank. Keeping the pump(s) running would over flow the tank.=20 Can you see where all this was going? I surmise that the greater = capacity of the header tank (as compared to Ed's) allowed some heat = absorption as it took longer to become affected, but once heated it was = far less manageable. My pilot workload was too great and became centred = around fuel management. I had so much time, effort and $$$ invested in = making that header tank work that I didn't want to let go of the idea, = but one day I just had enough and tore it out of there. I've now = converted to a returnless system with no header tank and I couldn't be = happier. What I'm trying to show is that there is more going on with heat = in the fuel system than expected. I'm not familiar with your system, but = the way I understand it, you have your main tanks draining by gravity = into your sump tank. Your FI return line feeds into this tank bringing = heat from the engine with it. I surmise that it is bringing enough heat = to begin a vapour build-up in your sump tank overcoming the gravity = feed. How long after your emergency landing did you restart your engine? = If it was immediately and it ran fine, then this theory may not be = valid, however if there was sometime elapse (while you kissed the ground = & changed your shorts :-), then it could be that the tank had time = enough to cool and/or relive the pressure allowing more fuel to enter = the tank. One way that I could see overcoming this would be..... A vent line from the top of your sump tank up to the top of both of = your main tanks, but not tied into the main tank vent system. This would = allow any fuel vapours to immediately flow out of the sump tank, = eliminating any chance of vapour build-up, while allowing the cool fuel = to continue to be gravity fed to the sump tank. These fuel vapours would = then flow into the main tanks where they should immediately condense, = preventing the loss of any fuel through a direct atmosphere vent system. = This would (may) only work if you have your main tanks located above the = sump tank. Having your FI pumps located at or below the sump pump would = surely be a help as well. But I would not expect the tank to work = without a vent or with a vent to atmosphere. I hope some of this is relevant to you and helps. Todd Bartrim (top posted all the way to the bottom) -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.8.7 - Release Date: 2/10/2005 ------=_NextPart_000_0024_01C51102.13C9DB90 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Hi, Todd....thank you VERY much for = going into all=20 that detail regarding your fuel system and it's problems/fixes.  = Yes, my=20 main fuel tanks are the highest point of the system....the sump tank is = lower=20 than the 2 main tanks (both are vented), and the fuel pumps are lower = than the=20 sump tank.  The fuel goes out of the bottom of the main tanks and = goes=20 downhill into the fuel selector valve. Then the fuel comes out = of the=20 fuel selector valve , downhill (through a facet low pressure boost pump = that I=20 have yet to use) to the top of the surge tank.The fuel then comes out of = the=20 bottom of the surge tank and runs downhill to the gascolator and then = two EFI=20 pumps.  After going uphill through the fuel rail and to the fuel = pressure=20 regulator, it then goes back downhill to the top of the = unvented surge=20 tank.  (I hope I didn't confuse everyone with this)
    As to how long I = waited to=20 restart the engine....It never really quit.  It just wouldn't = produce any=20 power.  Immediately, as the plane came to a stop in the mud, I = applied=20 power and was able to turn around and taxi back to the hangar. =20 Unfortunately, I didn't try a full power run-up (just too darned happy = to be on=20 the ground in one piece), but I would have to guess that I used at least = 1/2=20 throttle to pull me out of the mud, and I was unable to get that in the = air, or=20 else I would have continued to fly the pattern and land on the=20 runway.
    You have really = peaked my=20 curiosity...you stated that you converted to a returnless fuel = system....please=20 educate me a little here....where does the unused fuel (after the fuel = pressure=20 regulator) go?  Inquiring minds need to know.  Thanks again = for=20 helping out.  Paul Conner
----- Original Message -----
From:=20 Todd = Bartrim=20
Sent: Saturday, February 12, = 2005 5:18=20 AM
Subject: [FlyRotary] Re: Vapor = lock in=20 sump/header tank.

Hi=20 Paul;
    Caution this is a long story relating my = previous vapour=20 lock issues and how they may relate to yours. Recent comments have = differed=20 about the need to vent or not to vent a sump/header tank. As I = understand it=20 you have a sump tank in which it is gravity fed from your mains, then = pumped=20 up to your engine. However IIRC a previous post in which you said you = had=20 copied Ed's system which is a header tank that has boost pumps feeding = it. (I=20 may have that incorrect as I couldn't find the post in question) Now I = went=20 through a couple different versions of a header tank before scrapping = the idea=20 altogether. My first one was always vented, but this required level = control,=20 via the boost pumps as it required fuel to be pumped up to the tank, = then it=20 gravity fed my FI pumps. If not filled by pumps, it would just drain = the tank=20 due to the vent. If pumps were left on it would over fill and fuel = would go=20 out the vent lines which were tied via a common header to the main = tanks so=20 negative draft would draw most of the fuel back to the feed = tank, but=20 not all. I'd planned to use an electronic level control system to help = manage=20 this but supplier problems caused me to look closely at what was = really an=20 unnecessary failure mode.
    At this time I decided to use a non-vented = system=20 much like Ed's, however I was certain that I could improve upon it by=20 increasing the size of the header tank and having it located on the = cool side=20 of the firewall. But I found that it required a vent as there was no = other way=20 to purge out the air from the tank which would accumulate there when = one would=20 run a tank dry before switching tanks (I have 6 tanks so it is = important to=20 completely empty the aux tanks). So I installed a vent with a=20 pilot accessible valve. This allowed the venting of all air out = of the=20 tank at which time it would be closed. Then the fuel would draw up = from the=20 main tanks to replace the fuel that had been drawn out and not = returned=20 through the return line from the fuel reg, without the need for pumps. = I had a=20 clear sight tube to see the level of the header tank and another short = clear=20 section of hose on the vent line, so that I could see whether I was = venting=20 air or fuel.
    This seemed like a fine system, until it = began seeing the=20 heat of flight operations. Ground runs seemed mostly successful and = running a=20 tank dry until the header tank was empty resulted in approximately a = 20 second=20 delay in getting fresh fuel to restart the engine and completely = purging the=20 air within 2-3 minutes. But under flight conditions it was much = different.=20 Heat would cause vapour problems that were very difficult to deal = with. The=20 pressure would build within the header tank and the sight tube would = not=20 always give a true reading as it should. Twice I ran a tank dry while = at=20 +10000' above the airport and had a very difficult time in getting = fuel back=20 resulting in approx 6000' of glider alt loss each time. Another time I = was=20 doing circuits and was on my downwind leg when the pressure in the = tank caused=20 a vapour lock even though I had plenty of fuel in the tank(s) feeding = the=20 header tank. The pressure had just built up to the point where even = the 7 psi=20 boost/transfer pumps couldn't overcome it to keep fuel in the tank. In = this=20 case I was able to make an emergency deadstick landing on an = intersecting=20 runway and fortunately I even kept my speed up enough to coast all the = way to=20 my tie-down spot. That's where the firetrucks met me... kinda = embarrassing!=20
    In each of these cases, I found that when = opening the=20 vent valve to release the pressure, I could see through the clear vent = tube=20 section that I was venting a boiling fuel (air/fuel) mixture. And it = took an=20 uncomfortably long period of time to relieve that pressure and refill = the tank=20 with fresh fuel. I then installed optical fuel level sensors (hi/low) = on the=20 header tank, a vacuum/pressure gauge and a temp sensor. I found that = it would=20 begin by having a vacuum in the tank as the system would draw in new = fuel to=20 replace that which was being consumed, but it would soon begin to = build as a=20 pressure as the fuel heated and would then begin to push the level = down.=20 Opening the vent relived this pressure but it couldn't be left open, = or it=20 would just empty the header tank. Keeping the pump(s) running would = over flow=20 the tank.
    Can you see where all this was going? I = surmise that the=20 greater capacity of the header tank (as compared to Ed's) allowed some = heat=20 absorption as it took longer to become affected, but once heated it = was far=20 less manageable. My pilot workload was too great and became centred = around=20 fuel management. I had so much time, effort and $$$ invested in making = that=20 header tank work that I didn't want to let go of the idea, but one day = I just=20 had enough and tore it out of there. I've now converted to a = returnless system=20 with no header tank and I couldn't be happier.
    What I'm trying to show is that there is more = going on=20 with heat in the fuel system than expected. I'm not familiar with your = system,=20 but the way I understand it, you have your main tanks draining by = gravity into=20 your sump tank. Your FI return line feeds into this tank bringing heat = from=20 the engine with it. I surmise that it is bringing enough heat to begin = a=20 vapour build-up in your sump tank overcoming the gravity feed. How = long after=20 your emergency landing did you restart your engine? If it was = immediately and=20 it ran fine, then this theory may not be valid, however if there was = sometime=20 elapse (while you kissed the ground & changed your shorts :-), = then it=20 could be that the tank had time enough to cool and/or relive the = pressure=20 allowing more fuel to enter the tank.
    One way that I could see overcoming this = would=20 be.....
A=20 vent line from the top of your sump tank up to the top of both of = your=20 main tanks, but not tied into the main tank vent system. This would = allow any=20 fuel vapours to immediately flow out of the sump tank, eliminating any = chance=20 of vapour build-up, while allowing the cool fuel to continue to be = gravity fed=20 to the sump tank. These fuel vapours would then flow into the main = tanks where=20 they should immediately condense, preventing the loss of any fuel = through a=20 direct atmosphere vent system. This would (may) only work if you = have=20 your main tanks located above the sump tank. Having your FI pumps = located at=20 or below the sump pump would surely be a help as well. But I would not = expect=20 the tank to work without a vent or with a vent to=20 atmosphere.
 
    I hope some of this is relevant to you and = helps.
 
Todd=20 Bartrim  (top posted all the way to the = bottom)

No virus found in this incoming message.
Checked by AVG=20 Anti-Virus.
Version: 7.0.300 / Virus Database: 265.8.7 - Release = Date:=20 2/10/2005
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