Zzz wrote:It's probably not germane to the core philosophy of tank selection, but I will have 73 gallons aboard. The mains are 25 gal each, and the aux tanks are 11.5 each. The design intends no pump for the aux tanks like a Maule, at least as I understand it. Honestly I need to study that more.

Personally, I can't say I often miss the 20lbs (per side? I forget what Bob said) which the aux tanks add, 50 Gal is a lot of fuel already!

There are occasional times when I wish I had more fuel, but I do mean occasional - maybe twice a year, just to save descending from 11,000 to refuel, when my buns of steel are up to the challenge.

I never really thought about the possibility of having no fuel pumps with Aux tanks. Very interesting.
I guess that would work, but you would at least need a really good check valve in each line, so the mains don't drain outboard.

The one thing with Aux tanks with pumps, more weight in the wing tips when landing means the aircraft has a sort of yaw-pendulum effect. My uncle-in-law owned a Maule for many years and complained about that effect, apparently they get a little ground-loopy with empty mains and full aux. I haven't experienced it myself.

Battson wrote:

Zzz wrote:It's probably not germane to the core philosophy of tank selection, but I will have 73 gallons aboard. The mains are 25 gal each, and the aux tanks are 11.5 each. The design intends no pump for the aux tanks like a Maule, at least as I understand it. Honestly I need to study that more.

Personally, I can't say I often miss the 20lbs (per side? I forget what Bob said) which the aux tanks add, 50 Gal is a lot of fuel already!

There are occasional times when I wish I had more fuel, but I do mean occasional - maybe twice a year, just to save descending from 11,000 to refuel, when my buns of steel are up to the challenge.

I never really thought about the possibility of having no fuel pumps with Aux tanks. Very interesting.
I guess that would work, but you would at least need a really good check valve in each line, so the mains don't drain outboard.

The one thing with Aux tanks with pumps, more weight in the wing tips when landing means the aircraft has a sort of yaw-pendulum effect. My uncle-in-law owned a Maule for many years and complained about that effect, apparently they get a little ground-loopy with empty mains and full aux. I haven't experienced it myself.

The main appeal of the aux tanks is having enough fuel to play once you've reached a real out-there backcountry destination, where it's 2 hours to the next fuel. There's no way my butt could match the endurance of 73 gallons. LOL.

Akgreg and I made use of his Flint tip tanks when in the Wrangells, and it was nice to not worry about whether we had gone beyond the point of no return fuel-wise. Well, we did worry, but we didn't have to cross it.

How to plumb them, and how to isolate them properly is worthy of study, but I haven't looked too deeply into it yet. I don't like the idea of adding more weight either but with a 540 up front I think it's the smart thing to do.

Battson wrote:

Zzz wrote:It's probably not germane to the core philosophy of tank selection, but I will have 73 gallons aboard. The mains are 25 gal each, and the aux tanks are 11.5 each. The design intends no pump for the aux tanks like a Maule, at least as I understand it. Honestly I need to study that more.

Personally, I can't say I often miss the 20lbs (per side? I forget what Bob said) which the aux tanks add, 50 Gal is a lot of fuel already!

There are occasional times when I wish I had more fuel, but I do mean occasional - maybe twice a year, just to save descending from 11,000 to refuel, when my buns of steel are up to the challenge.

I never really thought about the possibility of having no fuel pumps with Aux tanks. Very interesting.
I guess that would work, but you would at least need a really good check valve in each line, so the mains don't drain outboard.

The one thing with Aux tanks with pumps, more weight in the wing tips when landing means the aircraft has a sort of yaw-pendulum effect. My uncle-in-law owned a Maule for many years and complained about that effect, apparently they get a little ground-loopy with empty mains and full aux. I haven't experienced it myself.

I wore out an M6 with tip tanks, not sure if I ever had empty mains and full tips?? Not sure what the situation would be!

fly wrote:Zane,

Obviously it's your airplane, build it the way you want. Saying that, EFII adds a lot of complexity. Now you will need redundant electrical systems, two electric fuel pumps, return lines, duplex fuel selector, ect.

Personally, I'd prefer a less complex system for a backcountry airplane. I'd likely use a Bendix fuel injection system with magnetos and a wobble pump. Light and simple. No battery, no problem.

Making the decision is the hard part. No matter what you decide, building it will be easy!

You should talk to somebody who's had an engine fuel pump fail and had to get to a flat spot using the Christen Wobble pump. Granted most of these went in airplanes with lousy L/D numbers but the two cases I know of the wobble pump went away to be replaced by an electric fuel pump.