Chapter 6

[CFernandez]

I'm coming up on Chapter 6 and was thinking about the fuel valve installation.

 

I would like to do away with the fuel valve and sump blisters and go to a sump tank mounted ahead of the firewall, aft of the aft lg bulkhead. The only valve in the system would be an on/off valve.

 

I have not decided on or figured what size the sump tank would be, but somewhere in the 3-5 gallon range.

 

My reasoning is to eliminate the fuel tank switching and fuel lines into the cockpit.

 

Your thoughts...

 

Carlos Fernandez

AeroCanard FG

Plans #206

Chp. 5

[Jon Matcho]

Sounds like you're cruising... good for you! I'm about ready to hit the start button again as well, and will do my best to catch up w/you.

 

I would like to do away with the fuel valve and sump blisters and go to a sump tank mounted ahead of the firewall, aft of the aft lg bulkhead. The only valve in the system would be an on/off valve.

I think this is how the molded AeroCanard FG is setup, so of course it can be done.

 

Steve Wright has a similar setup, as described in a recent issue of SportAviation:

 

Steve designed his own 40-gallon fuel system, which consists of two wing-strake tanks and a 2-gallon fuselage sump. A 2-inch square transfer plenum connects the wing tanks, and one-way flapper valves prevent fuel from sloshing out of the sump in turbulence. A cable extends from the inward opening right-tank flapper valve to the left-side gas cap. Removing the cap opens the flapper and allows single-point refueling. A large 70-micron diesel engine fuel filter is employed to counter the argument for multiple fuel tanks in case one is filled with contaminated gasoline.

That sounds interesting, but I wonder how long-term those flapper valves are, and how they would be serviced?

 

My reasoning is to eliminate the fuel tank switching and fuel lines into the cockpit.

What concerns do you have about these two things? I'm not feeling the same motivation as you. Anything that could be simplified would be a good thing, with fewer moving parts and checklists, but I don't think that's what you're after... what is it?

[CFernandez]

What concerns do you have about these two things? I'm not feeling the same motivation as you. Anything that could be simplified would be a good thing, with fewer moving parts and checklists, but I don't think that's what you're after... what is it?

My concern is the placement of the valve, remembering to switch tanks (something that can be learned) and being able to reach and turn it with two "good size" people up front. I also want clean lines underneath the strakes (less drag...). That's what I'm thinking anyways.

 

(The Cozy Maillist has a nice long string on this very idea.)

 

Carlos Fernandez

AeroCanard FG

Plans #206 Chp. 5

[Jon Matcho]

(The Cozy Maillist has a nice long string on this very idea.)

Can you point me to it? Subject/thread name?

[CFernandez]

Can you point me to it? Subject/thread name?

Go to www.maddyhome.com/cozysrch and enter this: .*to switch or not to switch\\. the question\\..* in the subject line.

[Jon Matcho]

I couldn't get that string to work, but if you search on 'switch' in the Subject, you'll find the thread.

 

One comment in there that got my attention was a caution for the scenario where the left tank might spring a leak, and siphon all the gas out of the right tank via a sump (in a system setup with a sump).

 

My two options for this are developing into:

• Shared sump with whatever valves and switches are needed
• Per-plans (with an Andair valve)

I'm not sure the concern will exist for "remembering to switch tanks". With the glass panel stuff coming out, the glass gas gauges will go from green to yellow to red to blinking-red to beeping-blinking-red. In this case the panel buys you simplicity.

 

However, I would like to remove any blisters on the outside of the plane to be cleaner through the air. This would be a case for a sump IMO.

[CFernandez]

 

One comment in there that got my attention was a caution for the scenario where the left tank might spring a leak, and siphon all the gas out of the right tank via a sump (in a system setup with a sump).

 

I suppose. The sump tank system works well for the Velocity aircraft and I will be using a similar setup. No switching, only on/off.

 

(Brett F. join in anytime)

[bferrell]

I suppose. The sump tank system works well for the Velocity aircraft and I will be using a similar setup. No switching, only on/off.

 

(Brett F. join in anytime)

Don't mind if I do, Carlos!

 

Although it's true that with both tanks connected to a single sump there's some possibility of issues (lost cap pulling a vaccum or siphon, though I think that's less likely since you'd be going uphill through a straw with very small pressure differences), I don't recall any actual reports of trouble in the Velocity. I also think they pale in comparison to having valves in the system. I've read many reports of accidents where there was fuel in the tank not selected, for whatever reason.

 

A single sump does work quite well for most of the Velocity fleet, and people with a loose cap usually just notice that this tank will not drain. I don't know of any leak-related incidents. I think that Jim S has made some significant mods to his aircraft to resolve some sort of fuel flow issue, but I don't have the details committed to memory, I think it was a tank imbalance of some sort.

 

It really is a personal choice, but a sump is pretty brainless. Like they said in engineering school, gravity is generally reliable.

 

B