whee wrote:I don't like both...maybe it's more that I prefer L/R/off valves because that's mostly what I have experience with.

On my way to High Sierra 2013 I was cruising along at 10k MSL when the engine quite. I was running on both but when I checked the tanks the right was almost empty and the left was about half full; I really wasn't exactly sure how much fuel was in each thank. I switched to the left tank and turned toward the road that was behind me. After maybe a minute I switched to right tank and still got nothing. I ended up switching back to the left tank and left it there. After descending 5k feet the engine caught and we continued our trip. Obviously something was not right with that fuel system but the rest of the time I flew it I didn't use both and never had any more trouble.

I don't know what you were flying, but my '64 172 has a warning that the fuel selector should be placed in either left or right positions for operations above 5,000 has something to do with venting.

Husky's have an on off valve like the scout.

C206...at least the old ones...are right, left, or off. There is no both. One is to operate the boost pump while switching tanks as you have to move the selector through the off position to get to the other side. Never had any hiccups with it.

Agree with courierguy on the simplicity of the S7S Rans system, it's on or off. MTV is also correct in that parking on any incline will yield a puddle. I avoid beach operations with full tanks as fuel will squirt out of the vent immediately.

I think you will get along fine with either. Only advice is to not reinvent the wheel. Use a proven system for your BH. Fuel issues are the #1 cause of experimental aircraft accidents.

206 uses a IO-550 or IO-520, right? If so that would make sense with the return line routing via duplex valve to only the selected supply tank.

My C150TD had an on-off fuel selector. Worked great. I never ran a tank dry. The only issue was that even in off, the tans would cross-feed if parked out of level. It had 40 gallon tanks so I usually started off with about 30 for just local flying, but with full tanks if I parked left wing low the vent would dribble gas.

Both my old C170 & my current C180 have left-both-right-off selectors. I generally just use the both setting. Even if one tank feeds a bit faster than the other, it only amounts to a few gallons. Let's see, even 5 gallons @ 6# per gallon only equals 30 pounds, and only a couple feet out on the wing. Seems like that makes no more difference than whether the right seat is empty or has a 200# pax in it. And unless something is mechanically wrong, you'll never run a tank dry on "both" unless you're really really low on fuel. But I do know several people who've run a tank dry in flight (with fuel in the other tank), causing at best an "oh shit" moment and at worse a forced landing. I know of two of these "fuel mismanagement" incidents that ended up on the ground, luckily no bent metal in either case.

I think I'd prefer a "both" position, and would probably use it 99% of the time. Don't a lot of the factory fuel injected systems use a header tank for the return line? Why not just go that route?

Referencing the Maule fuel systems, only the 210 Continental and Allison turboprop models have header tanks.
Lycoming powered Maules do not have header tanks so one is dependent on fuel arriving from both or either wing.
The original fuel selector was Left Right and Off.
Because of a mishap where someone took of with low fuel and had to dogleg around brush, the selected tank unported in the skid and all got quiet except for crunching of brush.
At this time Maule elected to change to Left Right Both and Off selectors and the POH indicates use of Both if low on fuel for takeoff or landing.
Both and Off selection allows for crossfeed of the main tanks.
The Aux tanks in wing tips feed into the adjacent mains upon pilots application of panel switches.
The system allows for easy fuel management, a close knowledge of how much fuel one has used and what remains, and the ability to have the aiplane in lateral balance.
Always fuel up with selector on Left, so no crossfeed thus Full tanks.
Always leave aircraft parked on either Left or Right.
Run on left main for 15 gal duration of the Aux tank, 11.5, 13, 15, or 21, (dependant on which system one has) then switch to Right main.
At 12gph this would be 1 1/4 hrs for the most common 15 gal aux.
After 45mins, switch both of the aux transfer pump on so the left main fills up and right main more gradually fills up.
No lateral instability as both tip aux tanks are transferring inboard to the mains.

Zzz wrote:206 uses a IO-550 or IO-520, right? If so that would make sense with the return line routing via duplex valve to only the selected supply tank.

Tripple Z.....check this out, page 2-2

http://www.mennen.org/airplanes/Logs46Q ... Manual.pdf

Like gbflyer pointed out, there were "optional" systems in those years. My 185 has the Left, right, both setup with a fuel shut off button. Good diagrams of both systems in the POH. My POH in the plane actually has a set of "expanded instructions" that made it in as a supplement at some time. There also seems to be an evolution of the fuel pump rocker switches through the years as well.

Bill

Thanks for that find, 59SC. I see that the 185 configuration uses a header tank downstream of the selector valve. This is something others (Pusher) have suggested to me, the problem is that the minimum size of the header tank is 5 gallons. Pusher said he uses a 3/4 gallon header tank mounted on his firewall cabin-side (correct me if I'm wrong, Pusher) to play this role, but his application is for a different aircraft and different engine.

That's great to solve the problem of combining supply and preventing sucking air, however there is another element to the equation: fuel cooling. 3/4 gallon with a minimum run is not enough to adequately cool the fuel according to what I've read. 5 gallons is recommended, and makes for a pretty big tank to be mounted inside the cabin. There isn't adequate space in the floor. Maybe under the pilot's seat, but still...

The full return with duplex valve seems simpler to me, save for this tank selection business.

Zzz wrote:The full return with duplex valve seems simpler to me, save for this tank selection business.

That's my thought.

I plan to install a SPRL V4 valve with L/R/Both/OFF. I only had 12.5gal in each wing in the Luscombe where the Bearhawk will have 26gal in each wing. I never notice a wing get heavy with one take full and the other empty and I never wished for a "Both" position on the selector valve. My reasoning for installing a valve with "Both" on the Bearhawk is so that it is there encase I ever wish I had it.

I'm a "Both-er." Seems to me that the simpler the better when it comes to your fuel system. Gravity hasn't failed on me yet!

It seems that a carburetor solves a whole bunch of problems....

Take your simple solutions elsewhere! Z's high tech! I mean, the guy rebuilt a gopro!

Personal preference here, I like the FI route as well. I'd personally lean more towards mechanical FI and an advanced ignition. I see your goals too, though.

Total thread drift

Ran a Callair out (L or R wing tank) at six inches AGL. Really prefer Pawnee's nose tank with selector frozen in ON.

My 170 has the XP Mods Continental IO-360 STC.

fuel flows from each tank to and thru the stock tank selector valve to a Maule header tank (2-3 quarts or so) attached on the forward cabin wall by my left knee. Fuel flows from the header tank to the gascolator to the engine. Fuel return from engine comes back to the header tank and vents upward into the wing to a tee fitting that goes back to both tanks. Tank vents are behind the struts like a 182. I don' t think any of the return fuel ever makes it back up the vent line to the tanks and have never in 1000 hours or so seen any evidence of that such as one tank filling while the other is selected or any real difference in left/right fuel consumption while both are selected.

I don't think you need a duplex valve with a header tank like this. The Hawk XP is rigged like this though the header tank is under the floor. Happy to send you some pics of the setup and/or the fuel system drawings when I get home Friday.

Pete

Zzz wrote:But for fuel system design considerations, I'm looking more closely at whether there are advantages to utilizing separate tanks independently in flight.

Is it a big deal to not have a BOTH selection?

Thoughts?

Ahhh I am always late on the uptake these days!

We spent three days flying backcountry in perfect weather last weekend, no wind to worry about.

We learned this, I favour a left our of balance condition and right-hand circuits (heavy right foot). My good buddy / co-captain for the weekend favours the left-hand side (he's a lefty, perhaps unsurprisingly!).

We each ended up 20L difference across the tanks, because of the above. The draw will favour the highest pressure tank.

We each used the L-R-BOTH selector and fuel pump to switch tanks and drain back to level pegging. I installed the SPRL V4 valve.

We actually got a little air bubble in the process too, which caused an engine stutter - it happened while crossing the ranges at high altitude, instead of powering out of a short gravel bar!
I'll post a video of the weekend in Bearhawk in the Backcountry.

CamTom12 wrote:Take your simple solutions elsewhere! Z's high tech! I mean, the guy rebuilt a gopro!

Ha! You got that straight. Stripped it to all the individual components and put 'er back together. Colossal waste of time.

c170pete wrote:My 170 has the XP Mods Continental IO-360 STC.

Thanks for sharing Pete. I've been wondering how XP Mods did their fuel system.

You hi-tech guys are in the driver's seat. They will eventually put us old, low tech out on the ice. Immediate action? Reboot.

Zzz wrote:

CamTom12 wrote:Take your simple solutions elsewhere! Z's high tech! I mean, the guy rebuilt a gopro!

Ha! You got that straight. Stripped it to all the individual components and put 'er back together. Colossal waste of time.

Might be true. Hell, probably true.

But I bet you learned a bit and enjoyed the process.

I think we've got something in common in this, Z.


Just my opinion, but drive on with your high tech FI plans. The journey will make you happy and you'll make it redundant enough to be no issue. And if it ever is an issue you'll have enough means of communication to make it a non-issue.

I've found with my 172 that the left tank will drain faster than the right tank when I have it set to both so I'm diligent about switching from both to one tank... unless I'm over hostile terrain and above 5000' in blatant disregard for the placard not to do so.

So... If there were no issues with flying on Both (which is debatable even in the 172 if there really are issues), then it does seem to be a nice redundancy. It's part of my checklist on pattern entry to make sure the tanks are on both.

73 gallon tanks?!!?!!! Are you flying non-stop to Hawaii?!!!!