Mailing List flyrotary@lancaironline.net Message #63739
From: Todd Bartrim <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] fuel system
Date: Mon, 4 Sep 2017 02:37:45 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
It's been an eventful few days. No disrespect intended to those of you suffering through a hurricane. I hope everybody comes through it ok.
 First Steve;
   That's a very good observation and I'm a little ashamed I overlooked the total fuel flow. I have the same data sheet and when I saw 15 gph my initial thought was " it better not be that much or I can't afford to fly it!". Seriously though, I've only ever measured fuel flow with the EM2, which I'm sure is a pretty accurate way to measure fuel consumption but that doesn't account for total fuel flow through the system. I kinda feel stupid that I didn't think of it. But that's nothing compared to the stupid thing I'll tell you about later.
But that's why I put this out there for peer review. 
OK, so now that it's in there and seems to be working where do I go now. Physically, this filter cartridge is far larger than the old in-line filters that were meant for a HP fuel injection system, so I would assume that it also has a larger filter area. So I think maybe you're right about that flow limit being with regards to it's ability to separate water. So if I exceed this limit where does it leave me? Does it matter much?
Honestly water in fuel isn't really much of a problem. The only time I've had to deal with it was when I was repairing a friends snowmobile and oh yeah that time when I was younger and not quite as good as I thought I was and sunk my own sled while crossing a long stretch of open water. I have seen how ice crystals can plug up filters, but it's generally not a problem.
 Long ago I bought one of these Mr. Funnels (size F-15) http://www.mrfunnel.com/Mr._Funnel/Home.html for use in the airplane and every drop of fuel that's ever gone into that airplane has gone through that funnel (if only cause it cost me $100 and I wanted to get my moneys worth). I've also used that funnel on occasion with snowmobile fuel but not every time. As a testament to how good they are, the aforementioned buddy's sled had close to a gallon of water in his fuel tank. We drained it into a fuel can then transferred it to another through the funnel. The water line in the funnel kept building until the funnel was getting full but not able to pass much more fuel. we dumped the water twice. Then we transferred it back again and had no water. We then put that fuel back in his sled and it ran well (after we cleaned the carbs). So if you're concerned about water in your fuel get one of them.
   So anyways back to airplanes. I'm not really worried about water, I just thought it was a nice feature. Nice enough that I also ordered the water detector. So is that the limiting factor on the fuel flow of this unit? I'm willing to bet that you're right. 2 micron, again I didn't consider ice crystals. Yes I know it's probably more than I need, but without giving it a lot of thought I figured it wouldn't hurt. But maybe it will. I might consider the R12T with a 10 micron rating or even the R12P/30 micron.
Thanks for bringing this up.

   Next. My concern about isolating fuel tanks was somewhat validated today when I had a significant leak from one of the tanks. Or so I thought. It seems like it is actually in the feed tubing from one of the outboard tanks, somewhere near the wing root. The wing will have to come off to find and repair it. This is all one continuous piece of aluminum tubing, so I'm quite curious as to what I'll find. I do recall that it was a challenge to do this tubing when I built these tanks, but that was so long ago I don't remember all the details so I'm not sure what I'll find. It must be significant because I couldn't even draw fuel from this tank, only air, while it was raining under the wing. This really sucks, but if I was in the air and fuel from other tanks was having to be routed through this tank, well that would just be a real bad day :-(

   Next. One of the Gems fuel sensors wasn't showing empty so I reached in to check it and found as I suspected that it was inline with the dihedral of the wing, meaning that it was downhill and so a little fuel was remaining against the sensor, enough to make it think it was still immersed in fuel (well actually it was). In flight this probably wouldn't be a problem, but in case I was in perfectly level flight maybe it would? in any event I pulled the access cover (a landing light, don't ask, another long explanation) and slightly bent the connecting tube up slightly and it was reading empty. But I gave it one more tweak... and it broke off in my hand! ****!!??##?? 
Now these are rated for petrochemical use so am I wrong to assume that means gasoline? But the part that broke off was not exposed to gasoline. I was reaching in there blind but I was certain that I was holding onto the aluminum tee while I was tweaking it, but maybe not. I guess the good news is if this happened in flight it would not have leaked any fuel as the line is still sealed well. But it is in the "wet" condition with light scattering and not being reflected through the prism to the detector. So this would not give me an empty tank alarm. But it's not my only one as the pump inlets also have an optical sensor with audible alarm. So anyways, I figured I'd better mention it, incase others were considering using these. I still think they are a great little sensor, but nothings perfect. So beware.
    
   So now unrelated to rotary aviation or fuel supply... I got an odd warning on the display of my X-Com radio today and it seems that it wants to take an Australian vacation without me! Seriously though, it gave me a "PLL fail" warning that wasn't in the manual or online so I emailed them not expecting a reply till after labour day, but shortly after I got a reply saying it is an internal error and to send it in for repair. The warning is now gone and I cant duplicate it. With winter coming, I'd like to not be sitting around while my radio goes down under to enjoy their spring sun. On the X-Com website they have this quote from Leonardo Da Vinci, "For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return". So I told him I've been walking the earth with my skyward for the last 12 years, so unless failure is imminent i'd rather not send it back to the other side of this rock without me accompanying it.

  Ok, now for the stupid human tricks part of the show....
As everything seemed to be inline (earlier in the day, before all this other s*#!) for a return to flight I figured it was a good time to do a new weight & balance. But my driveway has a slight slope to it. Close to the garage it is level laterally, so hey a few pieces of plywood and a shallow ramp and I'll get her perfectly level. I used a level and carefully measured and cut all the appropriate pieces. I have 5 electronic 440# scales so I had to use a bridge over 2 for each of the mains anyways. It all looked good. The problem with these electronic scales is that they time out and shut off. and they tare when they turn on. So I had to turn on all the scales then quickly push the airplane on and take the measurements (had my phone camera ready to just take a quick shot of each). Here's the stupid part.... it took more effort than I expect to push it onto the scales so when I really put my shoulder into it I pushed it right off the other end. The carnage can be seen here 
Stupid is as stupid does!  Horizontal stabilizer needs to be partially rebuilt and the trim tab needs to be replaced. This will put me back a little. I think next time I'll put a stop block on the back side of those scale blocks.... or wait till I get to the airport and find some more level ground.

  Now with all the bad news I am happy to report that after I'd pumped all the tanks dry by taking off one line from my fuel header and connecting it to another hose into a fuel can, I then found less than a tablespoon of fuel in each of the tanks.The wingtip tanks were especially difficult to ensure that they would draw from the lowest point, but it seems like I got it right, so I'll not be carrying unusable fuel.

Todd..........   I think I'll go fishing tomorrow


Todd Bartrim

On Sun, Sep 3, 2017 at 8:34 AM, Steven W. Boese <flyrotary@lancaironline.net> wrote:

Todd,


The fuel filter and water separator that you specify has a max flow rate spec of 15 gph (data sheet is attached).  The fuel flow required by the engine would be more than that at times.  Since you are returning the regulator bypass to the inlet of the unit, the flow rate through it would always be more than the rating.  The unit must be capable of flowing more than the rating since it is working in your system.  It is possible that the flow limit is based on the unit's inability to separate water at higher flow rates.  The filter media is described as not allowing water to pass through it.  Does the media become impermeable to fuel if water is trapped on it due to the high flow rate?


The filter cartridge you specify has a 2 micron particle rating.  While this is appropriate for the diesel application that the unit was designed for, this seems much smaller than necessary for your application.  In subfreezing temperatures, I have observed fine suspended crystals when sumping the tanks. They are most likely ice since they disappear at warmer temperatures although no liquid water has been recovered when sumping the tanks.  Y'all who've never seen a snowflake would not run into this (sorry Charlie). The crystals have not caused any  problems in my system that I am aware of.  It is possible that they may be trapped by the fine filter media that you are using.  Whether or not this might be a problem remains to be seen.


The above concerns may be worth considering if you have not already resolved them to your satisfaction.


Dave,


Thank you for your explanation of the use of the fuel flow transducer in the fuel return line.  I have a single fuel flow transducer in the line leading to the dead headed fuel rail for fuel flow and fuel remaining purposes.  At the condition inspection, I temporarily attach a fuel line from the fuel rail to a tank filler opening allowing a check on the fuel system condition using that fuel flow transducer in conjunction with the fuel pressure reading.  Your system allows continuous monitoring while eliminating the need to install temporary plumbing to check the fuel system health.


Steve Boese 


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