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  #11  
Old 08-23-2017, 12:17 PM
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RV7A Flyer RV7A Flyer is offline
 
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Location: US
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Originally Posted by rmartingt View Post
I wanted separate filters for the left and right sides so that if one becomes obstructed, it's not obstructing the entire system. I can switch tanks.
What Walt said. Plus, there seems to be nearly 10,000 RVs flying out there with systems that, for the most part, don't have these added components, and they seem to be doing just fine.

Quote:
I wanted them in the wing roots so they'd be easier to access without spilling fuel everywhere in the cabin; the shutoff valves are to avoid having to burn off or drain gas (the latter is something I really don't want to mess with if I can avoid it). This counts as "easiest to service", no?
Meh. For the once a year at condition inspection time that one has to check the filter, it seems that turning off one valve *in the cockpit where you'll see that it is properly positioned prior to flight*, then checking the filter at the pump, is a pretty easy thing to do.

Didn't someone say that one of the highest causes of engine-related accidents is a non-standard fuel system installation?
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  #12  
Old 08-23-2017, 10:28 PM
terrye terrye is offline
 
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Location: Vancouver, BC, Canada
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Default Fuel filter and shutoff valve in wing root?

Quote:
Originally Posted by rmartingt View Post
Anyone here managed to squeeze a maintenance shutoff valve (normally safety-wired open) and an inline fuel filter into their wing root area? I'm trying to figure out how to squeeze mine in there and I'm just not having luck.

I'm also considering just having the valve in the wing root and then the filter in front of the spar, and draining it out at the wing roots before pulling the filter.
Do a search on this topic and I think you'll find several threads and opinions. My fuel system will be "non-standard" whatever that means and here's why:
1.) Canada has a requirement for a gascolator in the system, whether carb or fuel injected. This is non-negotiable, no matter what you think of gascolators. I consider them to be inspectable (drain before flight to make sure fuel comes out and not something else) fuel filters that have a bypass built into them.
2.) I am using a certified style Weldon high pressure fuel injection boost pump because it is the most reliable cost effective pump I could find. The pump manufacturer recommends a fuel filter upstream to protect the pump. To address this requirement I'm installing an Andair "gascolator" in each of my wing roots. There is maybe more room in the RV-9A wing roots than others. Yes it's a tight fit, but I did a mockup with real parts and am going with them.
3.) Precision Airmotive who makes the Silver Hawk fuel injection system recommends a fuel filter upstream of the servo. Can't remember the micron rating off the top of my head, but it is finer than most inline automotive filters that many install in the cockpit. I sourced a Falls Filtration "gascolator" which features a cleanable filter element, a quick drain for preflight inspection and a clogged filter bypass valve. This gascolator is used in the Beech King Air and similar ones are used in Piper Navajos.

So my fuel system consists of;
Van's finger screen (not the sawcut aluminum tube) in the fuel pickups
Andair GAS375 gascolator in each wingroot
Andair LEFT RIGHT OFF fuel selector valve
Weldon high pressure boost pump
Falls Filtration gascolator mounted on the firewall right side low where the Van's filter for carbs is normally mounted
Lycoming engine driven fuel pump
Precision Airmotive fuel injection servo, spider and lines

This the safest, most reliable, most inspectable, most redundant system I could design that met the micron requirements of the pump and fuel injection manufacturer's recommendations and the Canadian regulatory requirements

I rejected the idea of using shutoff valves in the wingroots so there would absolutely be no chance of them being turned off or vibrating to the off position. The research I did led me to believe that if the fuel tank is below about 1/3 full that the fuel would not siphon through the wing root filters while they are being serviced. Airplane is not finished yet so I have yet to verify this.
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  #13  
Old 08-23-2017, 11:04 PM
gasman gasman is offline
 
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Originally Posted by terrye View Post
I rejected the idea of using shutoff valves in the wingroots so there would absolutely be no chance of them being turned off or vibrating to the off position. The research I did led me to believe that if the fuel tank is below about 1/3 full that the fuel would not siphon through the wing root filters while they are being serviced. Airplane is not finished yet so I have yet to verify this.
If you seal off the fuel cap, and cap off the vent line, you can drain off a small amount of fuel and the flow will stop until you allow air to enter the tank again.
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  #14  
Old 08-23-2017, 11:52 PM
Evolution10 Evolution10 is offline
 
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I have placed a gascolator and shut off in each wingroot of my -10. Originally I had only the gascolator and found issues checking the seals in condition inspection (reason for installing the shut-off valves). It all fits but it is tight.
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  #15  
Old 10-23-2017, 07:39 AM
supik supik is offline
 
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Can you post pictures of your wing root installs? thx!
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  #16  
Old 10-23-2017, 11:19 AM
BillL BillL is offline
 
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Location: Central IL
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Default Well- you can . . .

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Originally Posted by rmartingt View Post
. . . Trying to do both is right on the ragged edge of "maybe possible" and I can't tell without fitting the wing in place.
But it will be a time consuming PITA. Take a large slab of plywood and make another the shape of the tank forward of the spar and place it on the plywood. See what you can fit in there and service from either the top of bottom. If you used hoses and vertical fasteners, you might be able to make an assembly that can be released and rotated out of the slot for proper access. Balance between the issues solved and negatives generated.

Also, you know that all this tubing/fittings will add to suction head loss at the mechanical fuel pump, right?
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  #17  
Old 10-23-2017, 11:38 AM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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Default Just to throw a little more fuel on the fire....

One thing that I didn't see in this discussion is resistance to flow. I don't recall the exact figure, but most individual bends in tubing add the equivalent to several *feet* of straight tubing. Using any angle-fittings make it worse. All the systems described so far are 'sucking' on the wing root plumbing. If you fear vapor lock at all, at least give this some thought.

Now, if you were using automotive style in-tank pumps, that concern would go away.
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  #18  
Old 10-23-2017, 11:41 AM
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rmartingt rmartingt is offline
 
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Quote:
Originally Posted by BillL View Post
But it will be a time consuming PITA. Take a large slab of plywood and make another the shape of the tank forward of the spar and place it on the plywood. See what you can fit in there and service from either the top of bottom. If you used hoses and vertical fasteners, you might be able to make an assembly that can be released and rotated out of the slot for proper access. Balance between the issues solved and negatives generated.

Also, you know that all this tubing/fittings will add to suction head loss at the mechanical fuel pump, right?
1. I've decided to ditch the shutoff valve and just go with the filters. I'll burn the tanks down and that should be sufficient.
2. I won't be using a mechanical pump--the SDS system uses dual electrical pumps on the cabin floor. I'm avoiding hard angle fittings before the pumps, as well.
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  #19  
Old 10-23-2017, 12:21 PM
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rv8ch rv8ch is offline
 
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Default in tank pumps

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Originally Posted by rv7charlie View Post
...
Now, if you were using automotive style in-tank pumps, that concern would go away.
indeed - would love to see one of the entrepreneurs on this forum come up with a sexy in-tank kit that does it like cars - with the fuel filter sock and in-tank pumps. That's the right place for the pumps - in the tanks.
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  #20  
Old 10-23-2017, 01:13 PM
rv7charlie rv7charlie is offline
 
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Don't know about 'sexy', but I can send you a couple of pics showing dual Walbro gerotor pumps (as used in some of the boost pumps, & EFI pumps) mounted in a 'prototyping' (wrecked) fuel tank. The trickiest thing is you need the output line to be on the rib, instead of the cover, so you can remove the cover without affecting the plumbing.

I'm aware of some installs using the little turbine pumps, also. Those are smaller & lighter, with lower current consumption. They're probably the better solution, but you'd need a positive shutoff fuel valve with them. The Walbros do their own shutoff when they're not running.
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