X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from poplet2.per.eftel.com ([203.24.100.45] verified) by logan.com (CommuniGate Pro SMTP 5.3.7) with ESMTP id 4341187 for flyrotary@lancaironline.net; Wed, 09 Jun 2010 04:01:11 -0400 Received-SPF: none receiver=logan.com; client-ip=203.24.100.45; envelope-from=lendich@aanet.com.au Received: from sv1-1.aanet.com.au (mail.aanet.com.au [203.24.100.34]) by poplet2.per.eftel.com (Postfix) with ESMTP id 2F7AE173744 for ; Wed, 9 Jun 2010 16:00:25 +0800 (WST) Received: from ownerf1fc517b8 (203.171.92.134.static.rev.aanet.com.au [203.171.92.134]) by sv1-1.aanet.com.au (Postfix) with SMTP id A3230BEC081 for ; Wed, 9 Jun 2010 16:00:15 +0800 (WST) Message-ID: <9FE9C527ABC74B2590A369F512A354E3@ownerf1fc517b8> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: high/low pressure pumps question Date: Wed, 9 Jun 2010 18:00:18 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0011_01CB07FD.9EC51EB0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5931 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5931 X-Antivirus: avast! (VPS 100608-1, 06/08/2010), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_0011_01CB07FD.9EC51EB0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Well said Todd. George ( down under) Hi Al; Returning the fuel to the fuel line rather than the tank (thereby = to the fuel suction), is I admit not ideal. Not by a long shot. However = in some cases it may be a necessary evil that can (and so far has) been = made to work. In most vehicles there is one tank, sometimes two so it is = relatively simple to return fuel to the source fuel tank. Most airplanes = also have 2 tanks and occasionally one, so returning to the source tank = is again fairly simple and should be the first choice. where it becomes = more complicated is when you have to manage 4 or even 6 tanks. It's = difficult enough to come up with a simple, safe, light and affordable = for the average home builder, way to manage selection of these 6 tanks, = but to return the fuel to the source tank, would become a potential = problem. Some builders simply return to a single tank which they draw = down first then switch back to before it overflows, while others always = drawn out of the same tank, and simply transfer fuel to that tank. = Nothing wrong with that and it is ideal for many. Fortunately were not = all the same, which is why were here on this list. My reason for 6 tanks is to increase range for either flights to = remote areas with no fuel service or over long stretches of inhospitable = terrain (like passing over my mother-in-law's). The plan of transferring = fuel in my mind allows the distinct possibility of pumping precious fuel = overboard whether it be from directly transferring fuel or via a fuel = return to a tank that is not the source. There is also the possibility = of failure of the transfer equipment, which would result in inaccessible = fuel on board. Sure these are remote possibilities and could be lessened = by the addition of various safety checks and devices all which add = complexity and/or workload to the pilot. Not much but some. So I chose = to try to implement a variation of a return-less system.=20 Sure as you've said the failure frequency could be in the hundreds = of hours, so in my short time it has been just fine, but still not = proven. However what would be the incident frequency of lost or = inaccessible fuel? More, less? I can't say, but I do know that if it = happened there would be absolutely nothing I could do about it in = flight, so I'd better hope that I didn't really need it. With my current = system design, I have 2 facet pumps and 2 FI pumps that are plumbed in = such a way that is fairly simple for fuel management, but also allows = full redundancy in that any pump failure would not prevent me from being = accessing fuel. The issue of vapour lock remains but the facet pumps = 7psi of pressure has so far proven to be more than adequate for = elimination of this threat. So if this were to happen at least I would = have options to try to clear the vapour. Better to be able to do = something than nothing. Now with that said, I feel the chances of a = vapour issue developing halfway through a flight are even more remote. = This would be most likely to rear it's ugly head during the take-off you = described after a long taxi and wait in the south Texas sun. Or in my = case more likely while flying in mountain valleys when working it a = little harder. Exactly the time I wouldn't want it to happen. That's why = the facet boost pumps are always on at these times. So as Ed has pointed out, while millions of cars return the fuel = to the tank, millions don't. But, I must add, most or all of them have a = true return-less fuel system which we don't. Some of us are trying to = copy that within the limitation placed upon us. Could we make it a true = return-less system? Sure we could. At the low, low, price of a few more = pounds and cost and complexity per tank. There is no free lunch here. = Would I be willing to pay that price, while dead-sticking it down into a = mountain valley. Of course I would, but using that logic would result in = an ultimate safe plane, as it would never get finished. So here we are = discussing ways to make it work without returning fuel to the tank. And = I can say that it has worked well. I just can't say that it will always = work well. I would never suggest to anyone that the way I did it is the best, = but when asked about it, I'm happy to report my knowledge based on my = experience along with any cautions based on that same experience. Then = in the ensuing discussion I may learn something. Which seems to be the = case here, as Charlie, who started this thread with his question has = shown his idea based on what he's learnt from the discussion and it has = his own subtle differences, with regards to regulator plumbing, that I'm = surprised I overlooked and I think it has real promise. So much so that = I'll consider a possible change to my current system.=20 Other commitments these days usually restrict me to lurker status = (that always sounds creepy), but the occasional questions directed at me = usually don't go unnoticed and I enjoy the free exchange of ideas that = happen on this list. I appreciate the words of caution, but when phrased = as a command not to go against the grain, it loses it's validity as it = is reminiscent of another place where free thinking is discouraged. = We're all aware of the risks of venturing from the beaten path, which is = why we're here to discuss, dissect and hopefully come up with a better = way. Al, I do value much of your advice even if it comes across as = harsh, but I figured I'd explain my mindset which I suspect is shared by = a few others here, which is to minimize and take calculated risks, but = not reckless risks. Todd C-FSTB ------=_NextPart_000_0011_01CB07FD.9EC51EB0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
 Well said Todd.
George ( down under)
Hi=20 Al;
    Returning the fuel to the fuel line rather = than the=20 tank (thereby to the fuel suction), is I admit not ideal. Not by a = long shot.=20 However in some cases it may be a necessary evil that can (and so far = has)=20 been made to work. In most vehicles there is one tank, sometimes two = so it is=20 relatively simple to return fuel to the source fuel tank. Most = airplanes also=20 have 2 tanks and occasionally one, so returning to the source tank is = again=20 fairly simple and should be the first choice. where it becomes more=20 complicated is when you have to manage 4 or even 6 tanks. It's = difficult=20 enough to come up with a simple, safe, light and affordable for the = average=20 home builder, way to manage selection of these 6 tanks, but to return = the fuel=20 to the source tank, would become a potential problem. Some builders = simply=20 return to a single tank which they draw down first then switch back to = before=20 it overflows, while others always drawn out of the same tank, and = simply=20 transfer fuel to that tank. Nothing wrong with that and it is ideal = for many.=20 Fortunately were not all the same, which is why were here on this=20 list.

    My reason for 6 tanks is to increase = range for=20 either flights to remote areas with no fuel service or over long = stretches of=20 inhospitable terrain (like passing over my mother-in-law's). The plan = of=20 transferring fuel in my mind allows the distinct possibility of = pumping=20 precious fuel overboard whether it be from directly transferring fuel = or via a=20 fuel return to a tank that is not the source. There is also the = possibility of=20 failure of the transfer equipment, which would result in inaccessible = fuel on=20 board. Sure these are remote possibilities and could be lessened by = the=20 addition of various safety checks and devices all which add complexity = and/or=20 workload to the pilot. Not much but some. So I chose to try to = implement a=20 variation of a return-less system.

    Sure as = you've=20 said the failure frequency could be in the hundreds of hours, so in my = short=20 time it has been just fine, but still not proven. However what would = be the=20 incident frequency of lost or inaccessible fuel? More, less? I can't = say, but=20 I do know that if it happened there would be absolutely nothing I = could do=20 about it in flight, so I'd better hope that I didn't really need it. = With my=20 current system design, I have 2 facet pumps and 2 FI pumps that are = plumbed in=20 such a way that is fairly simple for fuel management, but also allows = full=20 redundancy in that any pump failure would not prevent me from being = accessing=20 fuel. The issue of vapour lock remains but the facet pumps 7psi of = pressure=20 has so far proven to be more than adequate for elimination of this = threat. So=20 if this were to happen at least I would have options to try to clear = the=20 vapour. Better to be able to do something than nothing.  Now with = that=20 said, I feel the chances of a vapour issue developing halfway through = a flight=20 are even more remote. This would be most likely to rear it's ugly head = during=20 the take-off you described after a long taxi and wait in the south = Texas sun.=20 Or in my case more likely while flying in mountain valleys when = working it a=20 little harder. Exactly the time I wouldn't want it to happen. That's = why the=20 facet boost pumps are always on at these = times.

    So=20 as Ed has pointed out, while millions of cars return the fuel to the = tank,=20 millions don't. But, I must add, most or all of them have a true = return-less=20 fuel system which we don't. Some of us are trying to copy that within = the=20 limitation placed upon us. Could we make it a true return-less system? = Sure we=20 could. At the low, low, price of a few more pounds and cost and = complexity per=20 tank. There is no free lunch here. Would I be willing to pay that = price, while=20 dead-sticking it down into a mountain valley. Of course I would, but = using=20 that logic would result in an ultimate safe plane, as it would never = get=20 finished. So here we are discussing ways to make it work without = returning=20 fuel to the tank. And I can say that it has worked well. I just can't = say that=20 it will always work well.
    I would never suggest = to=20 anyone that the way I did it is the best, but when asked about it, I'm = happy=20 to report my knowledge based on my experience along with any cautions = based on=20 that same experience. Then in the ensuing discussion I may learn = something.=20 Which seems to be the case here, as Charlie, who started this thread = with his=20 question has shown his idea based on what he's learnt from the = discussion and=20 it has his own subtle differences, with regards to regulator plumbing, = that=20 I'm surprised I overlooked and I think it has real promise. So much so = that=20 I'll consider a possible change to my current system.=20

    Other commitments these days usually = restrict me to=20 lurker status (that always sounds creepy), but the occasional = questions=20 directed at me usually don't go unnoticed and I enjoy the free = exchange of=20 ideas that happen on this list. I appreciate the words of caution, but = when=20 phrased as a command not to go against the grain, it loses it's = validity as it=20 is reminiscent of another place where free thinking is discouraged. = We're all=20 aware of the risks of venturing from the beaten path, which is why = we're here=20 to discuss, dissect and hopefully come up with a better=20 way.

    Al, I do value much of your advice even = if it=20 comes across as harsh, but I figured I'd explain my mindset which I = suspect is=20 shared by a few others here, which is to minimize and take calculated = risks,=20 but not reckless risks.

Todd
C-FSTB



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