Fuel Flow Discussion, Moved from Float Mounting

[Archer39J]

Put it near the filler neck. Debating whether to even finish with a tube poking outside, but then this would also be subject to icing. Once I get one in hand and can do some testing I may decide to just have it terminate inside the wing with a weep hole in the skin, of course zero fuel/vapors dumping inside a wing bay would be the requirement.

[JJohnston]

What would you do with that (check valve)?

[Archer39J]

This is what I've been looking at, might be easier than a full cross vent and would work if both caps get clogged. https://www.mcmaster.com/5492k51

[Ray Strickland]

In my first homebuilt I had 1/4” vent tubes with a bulb of screen wire protecting the entrance from insects. No cross vent tube. Ran on both for 400 hrs w/o a problem. However, I have often thought that the small Bearhawk cap vents could be plugged by a direct strike from a fat, juicy bug. While it hasn’t happened in 200 hours (running on both), this discussion has convinced me to install a cross vent tube at the next annual—just to be safe.

[Nev]

This is a very good point you’ve made.

[patrickh99]

No fuel venting system is going to be perfectly symmetrical: different lengths, different bends, bugs, etc. The recommended fuel caps for the Bearhawk have the potential to aggravate the situation if they are not both machined exactly the same AND installed/aligned exactly the same. That is a small airfoil on the top of the cap; turn it slightly and you switch from pressure, to less pressure, to suction. Thank Bernoulli for that. All of the external venting components are affected by the relative wind angle & velocity, so you will never have equal pressure in tanks that do not have an internal cross-vent. Fuel pump presence or absence is irrelevant to this issue.

[schu]

Can someone give a list of planes that have;
1) A fuel system that allows for "BOTH"
AND
2) Does NOT have interconnecting tanks?
AND
3) Requires a fuel pump for normal operations.

I'm sure I could do the research, but without a floatplane I am traveling by speedboat which cuts into my free time!

www.amazonsaltandlight.org

I certainly can't. I doubt such an animal exists.

[whee]

I like the perspective Battson shared here. Recent experience has taught me how true it is that people are forgetful and prone to tunnel vision. Those two things can lead to very costly mistakes. A proficient pilot probably has sufficient excess brain power to easily manage fuel. A pilot that is minimally proficient might get task saturated just flying the airplane and can't handle managing fuel.

Adding a cross vent with a check valve like a Cessna is so easy I'm starting to think maybe I'll add one to my plane.

[whee]

I've been in that scenario many times, same as thousands of other pilots. It's up to the PIC to use their brain and not cause an engine out. When slipping to a landing always make sure to select the uphill tank. Or don't slip. Luscombes have no both position, no flaps, and glide forever; slips are a regular part of landings. With a measly 25gal of fuel it is common to land with little fuel on board while on a cross country.

However, with a carbureted engine at idle you have quite a while before the bowl is dry and and engine quits. If your on a 2 mile final in a hard slip to get down to the runway you might need a little refresher training😉

[Archer39J]

It doesn't seem to be a big deal for all those thousands of aircraft that don't have both selector.

[MattS]

Can someone give a list of planes that have;
1) A fuel system that allows for "BOTH"
AND
2) Does NOT have interconnecting tanks?
AND
3) Requires a fuel pump for normal operations.

I'm sure I could do the research, but without a floatplane I am traveling by speedboat which cuts into my free time!

https://www.amazonsaltandlight.org

[Collin Campbell]

This has been a long thread and I have been watching it with interest. Wow! There are certainly a lot of things to consider! I am thinking of a situation that has not been brought up. (or at least if someone did, I missed it) Here goes:

Suppose you are flying on a long trip, and coming in to land with low fuel. You have a fuel selector with only left/right positions. You have selected the LEFT tank...let's say there are only 5 gals in that tank. (pushing your luck...probably not recommended) As you are making your turn to final you notice that you are way too high with full flaps already extended. So you go to a full pedal forward slip to lose altitude...it's how it's done, right? Right rudder, left aileron...it's fun, right? You notice that the ball is way over to the left...what might not be realized is now the fuel in that LEFT tank is doing the same thing as the ball on your slip/skid indicator. it is moving to the far left side of the tank. How long before both of the fuel pickups in that left tank are unported and you start picking up air?? Who knows. Maybe you won't have to hold that slip for long and everything will be fine. Maybe not. This is one reason (a good one I believe) for having a fuel selector with BOTH positions. I think the uncoordination thing is a big deal.

[svyolo]

Lots of great info and experience. I got a lot out of this thread,

I only flew light GA for 80 hours in the early 80's. Almost all low wing. L or R only. I ran a tank dry once in 80 hours, nothing bad happened, luckily. I flew for a living for 31 years, and only had to manage fuel for 1 of those years as a flight engineer. 500 ish hours. In 500 hours I screwed up fuel management twice, which was about average. Again, nothing bad happened other than a bruised ego. The other 30 years it was all automatic. Never had a problem.

Apparently I am not smart enough to manage fuel. I prefer BOTH.

[Gerd Mannsperger]

The reason the both position was introduce was because some pilots are very bad at doing coordinated turns and say a Cessna 180 (without header tanks)
will simply have the engine stop if you do that (cross control a turn). I demonstrate this to any 180 guy I check out.
They learn to fly coordinated much easier after
You are correct People are not good with Checklists and procedure that is where annual training comes in. Do all the emergency training you can think of once a year. After a few years it is super easy and will stick with you so when you need it it comes naturally.
If you live and fly long enough you probably will have it happen to you so be prepared.( Cessna fuel systems are infamous for venting issues) The only person who can save the day is the pilot in command. Personally I have no issue with just having a right and left position. None of our aircraft have a both position. What ever you fly know your system and learn to use it safely. Extra venting and Balance tubes can help.
At the end of the day it is you as pilot in command that is between you and your beautiful homebuilt rolled up into a ball at some undesirable location.

[schu]

Makes sense. Both does make it easier to manage fuel, as long as it works.

Didn't someone test how long it took to get power back if you run a tank try? I think it was Bobby, and only a few seconds.