Denny Mortensen Posted January 5, 2004 Share Posted January 5, 2004 I have been reading some of the threads floating around about fuel sumps in the back seat area and I find that a bit scary. Seems like it would open up lots of opportunity to take a gasoline bath in the event of a forced landing. However I can see some of the benefits to a sump type of system. Please keep in mind that I am just a new builder getting started and not even a pilot as of yet. But I was thinking, how about if a person fabricated a small tank say half gallon or so out of maybe Thick PVC pipe with end caps. Route fuel lines from the two wing tanks to a left, right, or both fuel valve. From there route the line to this small tank tucked in whatever available space. From this tank run a feed line through the fuel pump and into the filters, ext. You could run a return from the fuel injector rail back into this tank. You would need to vent both wing tanks and probably this sump tank. You could also put water check valves in it as well as the wing tanks to check for water in the system. I am thinking if this works it would allow a person to feed from both tanks or in the event of a bad fuel load they could switch to only one. It would also allow the injector a place to dump the over flow. I’m not sure about the vent line on the sump tank would the injector just cause it to dump the extra returning fuel back out the vent? I am a newbie to this group and I hear that it is not as heated as the other groups so please limit the size of ammunition. Fire at will. Denny Quote Link to comment Share on other sites More sharing options...
Jim Sower Posted January 5, 2004 Share Posted January 5, 2004 <... Seems like it would open up lots of opportunity to take a gasoline bath in the event of a forced landing ...> To keep this in perspective, consider the large number of homebuilt (and certified) tractors that have a header tank of anywhere from 5 to 15 gal between the instrument panel and firewall. Next, consider how many have low wings, which puts the tanks into the rocks and stumps much quicker than our mid wings. Next, examine failure modes. I happen to feel that a strong glass sump just forward of the firewall is a whole lot safer than three large fuel lines plumbed through the back seat from the firewall to the front seat. I'm not completely sure, and there are too many individual variables to make meaningful generalities, but I believe that plumbing fails more often than tanks and connectors more often than "enroute" plumbing. Quote ...Destiny's Plaything... Link to comment Share on other sites More sharing options...
Denny Mortensen Posted January 10, 2004 Author Share Posted January 10, 2004 That is a very interesting viewpoint and yes it does make sense. I guess I just haven’t developed my full faith in fiberglass and gasoline yet. I presume that will come, as I am totally amazed by the “strength” of the fiberglass construction. I have serious doubt that the vent in my idea would work anyway. I think the injector return would just dump it all over board. Not being a pilot yet I question one of the fears of a single tank configuration is vulnerability to contaminated fuel. Just how often does this happen in the real world and how serious is it? Denny Quote Link to comment Share on other sites More sharing options...
Jim Sower Posted January 10, 2004 Share Posted January 10, 2004 <... fears of a single tank configuration is vulnerability to contaminated fuel ...> Not sure I understand the question. In light of the fact that single OR multiple tanks are all fueled from a single source, contaminated fuel could just as likely enter both tanks as one. In any event, a Cozy (like any airplane with wing tanks) has at least two tanks so single tank concerns seem to me irrelevant. It is a given that ALL tanks (including sump) have a moisture drain at the low point. Virtually all of the contaminated fuel problems I have heard of can be neutralized by using the resources available (drain valves) and I've never heard of any that would have been alleviated by a single tank. OTOH a fuel tank outlet that gets plugged up by foriegn matter is extremely difficult to detect until it happens, and multiple tanks can eliminate that single point of failure. Quote ...Destiny's Plaything... Link to comment Share on other sites More sharing options...
LargePrime Posted January 10, 2004 Share Posted January 10, 2004 Another, not quite tangental, thought... You dont NEED the fuel blisters with a header tank. I havent read anything on this, but I would guess that the plans fuel blisters create a decent amount of drag. They are in a high pressure area and at an interference point. Quote We know who you are... Link to comment Share on other sites More sharing options...
Jim Sower Posted January 11, 2004 Share Posted January 11, 2004 Originally posted by LargePrime ... dont NEED the fuel blisters with a header tank ... the plans fuel blisters create a decent amount of drag ... in a high pressure area and at an interference point. I plan on having a sump tank (pretty much a given with an automotive injection system) but I'll retain the blisters (and perhaps clean them up just a little). My reason is, the last few of gallons in the strake is really shallow and spread over a pretty wide area and might not want to transfer very well. My Velocity has sump and no blisters and I don't trust the that last little bit of transfer worth a flip. If one tank empties, I end up kicking a bunch of rudder to make the last little bit of fuel pile up against the fuselage so I have some assurance that it's transferred. Blisters would alleviate (but probably not eliminate) that problem. Extending them back further might clean them up some. Quote ...Destiny's Plaything... Link to comment Share on other sites More sharing options...
LargePrime Posted January 11, 2004 Share Posted January 11, 2004 I had been kicking around this idea for a while. It just popped out here, half baked at that! I agree totaly about the strakes. The lines are so clean it will be tuff for the fuel to fall in any hole. I thought that if the fuel pooled into the blister, or flowed down to a header, it was the same differance, so no blister needed, as it just acts like a mini header. But then I thought that the blister might provide a larger edge for the fuel to fall over (4" vs 3/8") and into the blister, and this might be more effective in getting the last of the fuel out. Like the kid games with the balls you try to get in the little holes. But then I thought about the lessons Denver taught us. If I have so little fuel that this is an issue, the problem is not the fuel system. Quote We know who you are... Link to comment Share on other sites More sharing options...
LargePrime Posted January 11, 2004 Share Posted January 11, 2004 no edit after 30 min. Smart N E WAY... Sump better than blister?? Click for link Quote We know who you are... Link to comment Share on other sites More sharing options...
dust Posted January 12, 2004 Share Posted January 12, 2004 Now, let me catch up, fuel goes to header, then to injector, then to header or from tank to injector to header, how is header emptied and how much as a percent of the fuel to the injector goes to the header. Does the header tank empty to a strake tank? enjoy the build mike Quote maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build i can be reached at http://www.canardcommunity.com/ Link to comment Share on other sites More sharing options...
Jim Sower Posted January 12, 2004 Share Posted January 12, 2004 Mike, I overstated my case a little when I said that a sump "... was a given ..." with automotive conversions. I plan on having one for a couple of reasons: a) I mean to have retractable main mounts, so a sump will give back the fuel that I give away in the wheel wells; b) In the event I need to have submerged pumps, it is far and away the best place to put them. Sump would occupy the hell hole area where the MLG bow is in FG airplanes. I could make it removable and have access to the submerged pumps if that was deemed necessary. Routing of fuel would be: Right strake => gravity flow to sump => pumped to fuel rails => excess from rails back to Right strake. I would have a Facet pump to transfer on demand from Left strake to Right strake. I think it's a good idea to have the transfer process on an automatic 3-min or so timer. Since that would be an unacceptable (to me) failure mode, I am at this stage planning a 3-position Momentary-ON - OFF - Full-ON switch for Facet. I could flip it once in a while to keep things even and go on about my business, but if it failed, I could turn it on manually and monitor it closely for a few minutes. I would retain the plans blisters in some form (perhaps cleaned up a little) to accumulate fuel. As fuel state decays, the fuel gets progressively more shallow in the strakes and any sloshing becomes really significant. With the blisters, I can kick a little rudder and slosh the blister full and with a couple of those maneuvers I'll have the (Left) strake empty. Sump will have a warning light that it is a half gal or gal shy of full so I can similarly scavenge the last little bit of fuel from the Right strake in the unlikely event I need that last drop. It is VERY important to me that late in the flight I have EVERY DROP of fuel in the "selected" tank. I believe that this scheme minimizes the amount of plumbing in the fuel system: ONE line from strake to engine to strake, ONE line from strake to strake. NO valves (other than manual maintenance isolation valves and perhaps an electrical emergency cutoff between the sump and the engine). Quote ...Destiny's Plaything... Link to comment Share on other sites More sharing options...
dust Posted January 12, 2004 Share Posted January 12, 2004 ok that makes sence, most fuel injected systems pump way more than the header can handle and it seemed that people were thinking that it would handle all of the extra fuel. I agree with you wanting all of the fuel, my safty investigator buddy completely empties a tank to the engine stopping and then restarting on the tak with 1/4-1/3 full on all long cross countries so that ALL remaining fuel is in one place. Scrapped too many pilots off ground that ran out on final on the tank they were on. Can't resist, don't like the fuel management scheme, prefer simple one, double throw valve at my shouldertips enjoy the build Mike Quote maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build i can be reached at http://www.canardcommunity.com/ Link to comment Share on other sites More sharing options...
Jim Sower Posted January 12, 2004 Share Posted January 12, 2004 ... my safty investigator buddy completely empties a tank to the engine stopping and then restarting ... Couldn't agree more. I used to run my EZ tanks "pump empty" so the motor wouldn't stop (which is one argument for lots of fuel line in the cabin) don't like the fuel management scheme, prefer simple one, double throw valve at my shouldertips To each his own. I could have my "momentary 3-min" switch on stick grip or throttle. I don't like lots of feets of fuel line snaking around in the cabin. Definitely a personal value judgement. Quote ...Destiny's Plaything... Link to comment Share on other sites More sharing options...
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