Monroy Long Range Tanks Upflow?

[Matt Ward]

I’ve got the LR 17g aux tanks on my M20E and am noticing fueling flowing from the mains to the aux. Last Saturday I filled the mains to 26g while the aux appeared empty. I went out today and about 2 gallons moved “up” from the mains into the aux. I guess it’s normal but I don’t understand how that’s working. What is forcing fuel out of the mains? Anything to be concerned about? Thanks!

[M20F-1968]

The mains and the aux tanks are connected.  There is some resistance in the connection, and when the mains are filled to a level that allows flow into the aux tanks, that occurs.  However the flow rate from the main tank to the aux tank is slower than the max rate you can fill the main tank.  Thus, you fill the main tank and close your hangar door.  The fuel runs from the main to aux tank over the next 15 minutes or longer.  Thus you think fuel ran uphill.  It was really running downhill slowly.

John Breda

[carusoam]

Matt,

you want to review the tanks and how they are organized...

The key thing is they are not separate or independent...

know how the interconnections work to minimize surprises.

Doc John (above) explained some of the finer details as well...

If you do additional reading... you will probably find that not all Monroys are set-up the same...

Mr. Monroy visits around here often...
 

PP thoughts only, not a mechanic...

Best regards,

-a-

[LANCECASPER]

@Gagarin

[Guest]

The interconnecting plumbing from the extended range tank to the main tank is normally 3/8” OD fittings and tubing, meaning that the hole  in the fitting is only 5/16.  Enough to cover transfer of fuel for engine operation, but too slow while filling the tanks through one filler port.

Clarence

[Yetti]

Water or in your case AVgas always seeks a level

[Airways]

A non-return valve between the external tank and the main would have been nice. The fuel gauge in the wing is pretty useless now...

[Yetti]

2 minutes ago, Airways said:

A non-return valve between the external tank and the main would have been nice. The fuel gauge in the wing is pretty useless now...

You must have never driven an old ford truck.  You kind of ignore the numbers and learn from experience how much is in the tank and how that relates to the gauge.  If you have a fancy digital display you can recalibrate it.   Or if you have a fuel stick.  You can draw new lines.

[GDGR]

37 minutes ago, Airways said:

A non-return valve between the external tank and the main would have been nice. The fuel gauge in the wing is pretty useless now...

Isn’t the fuel gauge only accurate when it’s empty or full anyhow? 

[Airways]

That’s sufficient for certification, but those optional gauges in the upper wing are much better than that.  Well, were...

[amillet]

Does the add on fuel bay have its own fill port? @Gagarin

[Guest]

7 hours ago, amillet said:

Does the add on fuel bay have its own fill port? @Gagarin

Yes, two filler ports per tank.

Clarence