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Question: 4 way Newton Fuel Valve

dmat

Well Known Member
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Would the Newton 4 way valve with “both” work with the Rv6 fuel system?

I don’t think I have ever seen a “both” on low wing aircraft, only in cessna’s.

D
 
Would the Newton 4 way valve with “both” work with the Rv6 fuel system?

I don’t think I have ever seen a “both” on low wing aircraft, only in cessna’s.

D

Low wing's shouldn't have a "both". If you're on both and one tank runs dry, the fuel pump will suck air from the empty tank before it pumps fuel from the tank with gas in it. On high wings, gravity will always keep liquid present at the entry to the fuel pump/engine so "both" is allowable. It's the difference between having a small but positive pressure in the feeder lines in a high wing, and having a small but negative pressure in the feed lines in a low wing.
 
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One of the 3 way Newton valves (Left-Right-Off) would work fine in your RV.
I have one (actually a duplex valve) in my current 6A & have no issues with it.

Putting a 4 way valve in the RV and placing an Off label in the Both position may work for you, but may be a trap to the next pilot that knowingly (or unknowingly) miss uses the valve and causes a potentially major problem.
 
Thanks guys!

Yeah, I have a 3 way valve from Newton on my 6A but I noticed a 4-way and wanted to throw the question out there.

Thanks, and will be going with another 3-way valve for the 6.

D
 
Except for...

The Rockwell Commander has a “both” position, as does the Beech Skipper (if memory serves). Both low wings. Not sure how they are plumbed to avoid the problem you mention.

Low wing's shouldn't have a "both". If you're on both and one tank runs dry, the fuel pump will suck air from the empty tank before it pumps fuel from the tank with gas in it. On high wings, gravity will always keep liquid present at the entry to the fuel pump/engine so "both" is allowable. It's the difference between having a small but positive pressure in the feeder lines in a high wing, and having a small but negative pressure in the feed lines in a low wing.
 
The Rockwell Commander has a “both” position, as does the Beech Skipper (if memory serves). Both low wings. Not sure how they are plumbed to avoid the problem you mention.

Wing root forwarding pumps or similar?
 
Like this...

...perhaps a header tank like my Cessna Agwagon and my Air Tractor had...They’re both low wing aircraft and only had an “On-off” fuel valve. Both airplanes fed from both tanks all the time and never ‘burped’ when one tank was low, because the header tank was always full.

Cheers,
 
How did the Air Tractor and Agwagon keep fuel in the header tank? Were the fuel tanks still high enough to gravity feed the header?
 
Thanks guys!

Yeah, I have a 3 way valve from Newton on my 6A but I noticed a 4-way and wanted to throw the question out there.

Thanks, and will be going with another 3-way valve for the 6.

D

Actually, with the 3-way valve, if you leave the selector between the left and the right positions (not off position), you will be drawing fuel from both tanks at once, even though there is no detention there. It says this on their website. This is not a normal way to operate, but it will work - until one tank runs dry - then you’ll be sucking air. These are ‘make before break’ valves. When switching tanks, the one you are switching from isn’t completely closed off until you reach the detent slot in the selected tank.
 
The Rockwell Commander has a “both” position, as does the Beech Skipper (if memory serves). Both low wings. Not sure how they are plumbed to avoid the problem you mention.

They put the tanks midboard in the wing, not in the wing root. With the dihedral of the wing, this put the lowest part of the tank above the fuel selector valve. The fuel selector valve in the Rockwell also uses an extended actuator tube, putting the actual valve just above the lower skin. While it's a low wing airplane, with some design choices, they were still able to keep the fuel above the valve and treat the system as a "high wing" design as far as fuel is concerned. The older selector valve design also had a drain on it, and you could sump both tanks at the same time through the selector valve. This also supports the idea that the selector valve is the low point in that system.

The RV does both different, the fuel is in the wing root and the selector valve mounts to the top of the spar (at least in the 6 and 7, not sure about 10,12,14), not the bottom skin. I should have been more specific in my original post. I stated "low wings" should not have a both, but there are some low wings that have done the design correctly to support "both". The RVs don't support that option.
 

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Thanks!

I always wondered how this design worked.

They put the tanks midboard in the wing, not in the wing root. With the dihedral of the wing, this put the lowest part of the tank above the fuel selector valve. The fuel selector valve in the Rockwell also uses an extended actuator tube, putting the actual valve just above the lower skin. While it's a low wing airplane, with some design choices, they were still able to keep the fuel above the valve and treat the system as a "high wing" design as far as fuel is concerned. The older selector valve design also had a drain on it, and you could sump both tanks at the same time through the selector valve. This also supports the idea that the selector valve is the low point in that system.

The RV does both different, the fuel is in the wing root and the selector valve mounts to the top of the spar (at least in the 6 and 7, not sure about 10,12,14), not the bottom skin. I should have been more specific in my original post. I stated "low wings" should not have a both, but there are some low wings that have done the design correctly to support "both". The RVs don't support that option.
 
Yes

How did the Air Tractor and Agwagon keep fuel in the header tank? Were the fuel tanks still high enough to gravity feed the header?

Yes. Both airplanes had a belly below the level of the wings, so gravity ALWAYS kept the header tank full.

In the ag business, you’re so transfixed with avoiding obstacles at 130 + MPH that you don’t need the extra distraction of managing fuel, other than having enough.

Regards,
 
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