All, 

We have a viking 130 with a mini dual pump tank.  We have the location of where we are mounting the tank underneath behind the radiator in our 750.  What we are debating is where to run our fuel lines from.  They are initially running down the side pillar channels and then out the bottom somewhere.  My question is, Is there any harm in running the fuel lines out near the access panel and then crossing them over the landing gear.  The only harm I could see is if it crashed it would rip the lines off but there would be no fuel in the cockpit area. 

Otherwise our option in to maybe run the inlet lines through the center console area however we are not sure if we like that idea nor have enough room?

We would like to keep as much on the outside as possible.

Any ideas?

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Otherwise our option in to maybe run the inlet lines through the center console area however we are not sure if we like that idea nor have enough room?

I have a gravity-feed system with my Jab 3300 and ran stainless braided PTFE lines separately from each tank, down the inside of the side pillar channels (I grommeted the hole and slid a piece of black corrugated plastic loom over the line to prevent chafing - probably not necessary but I thought it might prevent any rattles, etc.):

... then across (inside) the bottom skin, and then through the center console on each side and up to an Andair L/R/Both/Off fuel selector valve.  I used padded Adel clamps to secure the fuel lines to the sides of the inside of the center console (I actually used 2 Adel's to make a "butterfly" and ran the brake line above the fuel line):

I delayed attaching the Earl's AN-6 fitting to the other end of the line until I had run the line.  That let me use smaller grommeted holes which was helpful - especially where the line passes through the support at the forward end of the tunnel underneath the torque tube) - in the picture below, you can see the grommeted holes under the brake lines where the fuel line came through (but obviously not installed in the first photo below!):

This is do-able with flexible lines such as braided stainless PTFE or rubber lines - probably would be tough to do with aluminum lines unless you had a lot of connectors.  By using the flexible braided stainless PTFE, I was able to run just one continuous line on each side from my bulkhead fitting to my fuel selector valve.  I've never had a leak or even a single whiff of gas fumes in 6+ years - and I suspect the braided stainless would be the last thing to let go inside the cabin in the event of a catastrophic event, so I'm comfortable with it inside the cabin!

This may not all be directly applicable to your plumbing configuration, but I thought it might at least give you some ideas!

John

N750A

Can't help thinking that steel braided fuel lines in a teflon loom might be a nice choice for routing underneath the aircraft.  If you crashed hard enough for a landing gear failure then you'll likely have no other concerns anyway.  

Curious, is this aircraft still being built?  If so, why are you using a mini dual pump tank under the fuselage instead of the 2.5 gal header tank mounted behind the baggage bulkhead?  The mini dual pump tank should work fine, but you'll also probably want to enclose the assembly, and after T'ing the pump discharge lines, route the single fuel supply line and fuel pump electrical wires in separate looms above the radiator towards the firewall.  I'm just trying to visualize.  Be interesting to hear what Jan has to say?

When we bought the engine that is what it came with. We are enclosing it behind the radiator and then running a single line up to the engine. We think we had that plan figured out. I think our main question was the routing from the wings to the pumps. We have looked at the header tank and did not think it would be much of any benefit for the price costs for what we already have as we won’t be running that low on fuel 99% of our flying. 

Did you buy directly from Viking?  I don't see why the fuel lines cannot be routed under the landing gear, but be interested to hear other opinions.

Bought from a guy who bought from Viking and then decided building took too much time and he'd rather fly. So we confirmed everything with viking before purchasing, but got a great deal and hopefully have it fired up soon. 

The more I think about it I don't see why a protected fuel line running under the gear should be any harm. 

The more I think about it I don't see why a protected fuel line running under the gear should be any harm. 

Something durable like stainless braided should be fine - I believe some that have run external lines and wanted a "cleaner" look ran them up the midline c-channel and made a cover (thus creating a box section) to enclose the lines in the channel.

John

Right the channel is present, it just is not present from the gear back but I am thinking we can make some sort of box to house them in on the back side and enclose the channel to the pumps then just leave it open where it crosses over the gear. I see braided hose is probably a must. 

Not that you're asking, but bulkhead elbows like AN833 through the lower fuselage should work well.

I ran my fuel line through the cabin; see attach photos of my 701 with a Viking 130. Note 2 gasulators, one each main tank at the fuel low point. Two mini tanks with fuel pumps. Fuel manifold with bleeder. Fuel selector with return to selected tank.

Attachments:

Looks like some fine work.

Great discussion,

Kudos to John and Ron for providing photos of their installs. Jan's install with the header tank under the belly is interesting too.   Some may really not like fuel lines, and "header"  tanks in the belly considering the risk if you crash, but there are risks for lines in the cabin too.  There have been fuel related cabin fires and that is nothing to scoff at either.  

  As a hopeful 750 builder I am interested in this    I have never liked the idea of fuel lines in the cabin, yet this is how most people route them.   I think this is necessary when considering the need for a selector valve.   Although it gets even more interesting when considering the decision to use a header tank, or not.   And add in the complexity of a fuel return line for FI engines and you have a fascinating discussion on your hands. 

I would be interested to know what Zenith calls out in their plans?

Charlie 

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