Fuel Transfer Calculator

[PhantomPholly]

Several experimental aircraft have fuel tanks which first transfer into a header tank.

How difficult would it be to add a feature (which would require additional fuel flow sensor/s) to calculate fuel transfer (e.g. removing quantity from tank 2 and adding it to tank 1)?

While I know this probably isn't at the top of the list, it seems like it would be pretty simple to engineer.  Too, it might eliminate the need for watching a clear plastic tube for bubbles to determine if the tank was empty...

 

[dynonsupport]

We don't have hardware to support more than one fuel flow sender, so this isn't really possible in the current systems.

Can't you just watch the fuel level in tank 1?

 

[PhantomPholly]

Tank 1 is a header.   Yes, I have a sight gage.  However, I had a bad experience with fuel in the cockpit and really don't want to reinstall plastic lines between the transfer pumps and the header just so I can "watch for bubbles" while transferring.  Too, with that method I really don't know how much I've transferred from either wing.

Anyway, I'd forgotten the fuel flow takes a special input - too bad.  There is a third-party gizmo which will flash at you when the fuel stops transferring (essentially telling you it is seeing bubbles in the line), but it is not as nice as knowing positively how much is in each wing, and the price is as high or higher than another fuel flow sensor.

Well, thanks anyway...    

 

[dynonsupport]

Well, if you're looking for a project, you could use a 555 one-shot timer hooked to the output of a fuel flow sender, and then hook the output to the contact input of an EMS. This would give you an indication if fuel was flowing, but not how much.

Sorry that I assumed you had electronic fuel level senders in your tanks.

 

[PhantomPholly]

Well, if you're looking for a project, you could use a 555 one-shot timer hooked to the output of a fuel flow sender, and then hook the output to the contact input of an EMS. This would give you an indication if fuel was flowing, but not how much.

Sorry that I assumed you had electronic fuel level senders in your tanks.

Another thought would be individual countdown timers which started counting down when either power or ground was detected. The transfer pumps are extremely predictable, although no one transfers at quite the same speed as another. Fill a tank once and time how long it takes to transfer all of the fuel out, add one minute, and set that as your countdown timer. Each time the pump is activated, it starts counting down; each time the pump is turned off, the timer stops. As a for-instance, one of my pumps takes 35 minutes to transfer 16 gallons while the other takes 40.

I also had in mind removable ferry tanks with my proposed solution. For example, someone might want to install soft fuel bladders (in a 2 seater you could easily add an extra 50 gallons of fuel between right seat and baggage area). If such a solution hooked in with a tee just before the transfer pump(s), all you would have to do is to initialize the "tank #2 total fuel" before flight and you would always know exactly how much you had transferred and how much was left. This would be useful for trips across the pond if the pilot didn't want to stop in Iceland (although, having lived there, there is much to recommend Iceland!).