Fuel Flow Discussion, Moved from Float Mounting

[Bcone1381]

Yes.......

[zkelley2]

Just an fyi, not all fuel sector's "off" will prevent cross flow. For example on a maule you have to put the selector in r or L to prevent cross flow. Off just blocks the port going forward but is just as open to both tanks as the both position is.

[AKKen07]

Would putting the crossover vent attachments at the top outside corners of the tanks help with fuel inadvertently transferring?

[AKKen07]

Thanks for that!

[Archer39J]

More like their pressures need to be equalized, which you can do in ways other than a cross vent.

[svyolo]

I read about someone that had a valve on the crossover. I can't remember if it was certified or EAB. I think I might do the same.

[yateselden]

I am considering install of the crossover vent from top of sight glass connections, with a small Parker shut off valve for parking unlevel. Crossover may not be needed, but shouldn't hurt anything either. I'll add it to check list. I do return more fuel to the right tank maybe a crossover will help with that.

[Gerhard Rieger]

Thanks Bob/Mark,

[Archer39J]

Or they follow the installation instructions without an understanding of the design and how different platforms will affect it's performance.

[Mark Goldberg]

Bob has made some suggestions for flying your planes:

OPERATION OF BEARHAWK FUEL SYSTEM

Take off and land on Both at fuel valve selector.. Be sure
both tanks have fuel in them.

Cruise can be on left or right to insure both tanks have fuel in them.
Both can be used if flow is about even.

In rough air on landing stay high, do not drag it in if fuel is low.

Bob has no problem with any of us adding a vent tube between the two tanks. With a gravity flow system, he does not think it needed. But no harm for sure except the following point. If you do add a cross vent tube, you will have fuel coming out of the gas caps if you park the plane on a slope. Without the cross vent, you can just turn the selector valve to off.

Bob understands that having any fuel pump, especially the higher pressure pumps used with fuel injected engines - will suck air and not fuel if given the opportunity. He thinks the Continental fuel injection system might be a little worse in this regard than the Bendix system used on Lycomings.

He feels with low fuel level in the tanks, slipping or skidding (or even rough air) while on approach to landing can cause an interruption of fuel flow. If you think about being in a bank and slipping or skidding so the fuel in the upper wing tank sloshes outboard could un port the fuel outlets. Mark

[zkelley2]

A lot of efi systems do not get installed correctly leading to loss of power. We can't really say here but it's quite common.

[AKKen07]

Not to keep beating the poor horse but I was just browsing my Bingelis Firewall Forward book when I ran into a paragraph stating that any fuel system with tanks that feed simultaneously MUST have a cross vent to feed equally. I think I’m pretty well convinced at this point.

[Gerhard Rieger]

If you do not have both, then a header tank makes sense. the exact reason I am using a two Gallon header tank. I will not have a problem slipping my aircraft and un porting will not influence it. Having larger vent lines will make sure that the header tank stays filled at all times. put an opened beer can to your mouth upside down. then stab a hole in the bottom which is now on top. hope you can swallow fast. it will be down your throat before you know it. Make sure you vent the header tank well, I have two 1/2 inch vent lines, one to each wing tank. One will always be higher than the other because one is in the front left corner and the other rear right corner. any bubbles from air entering the fuel system because of un-porting the main tank will go up and out the highest vent line and breath back to the main tank, it will also make sure that the header tank stay full as you resume normal flight, if you crash and your aircraft's belly is ripped open ripping of your fuel selector, you will have your two main tanks spilling their fuel out at an alarming rate below the floor and have exactly the same problem I have using the header tank. this is a very interesting read, lots to consider.

[svyolo]

I read the NTSB report a couple of times before. It doesn't seem like the Feds want to spend much time analyzing EAB accidents. Not much useful information. I am pretty sure their description of the "Emergency Power Switch" is way off.

N22GM probably had a complete dual EFII system. It is very redundant (more than I actually require) Other than an electrical feed or fuel problem, the only single failure that makes the engine go quiet is the Crank trigger (Hall Effect Sensor).

Just not enough info in the NTSB report. Too bad. Thats what those reports are for. So the rest of us can learn something.

[yateselden]

As I keep reading posts, this cross vent would be a good safty feature if you should happened to plug a vent with bugs or whatever. And that also reminds me of them damn mud dobbers!