Wing Fuel Sight Guage

[CoachTom]

Does anyone know if the wing fuel sight guage reads an absolute quantity (zero being a dry tank) or are they manufactured so they read zero above the unused fuel level?

So, in my 231 which has an unusable quantity of 4 gallons per tank, if the guage shows 14 gallons, only 10 is available for flight?

 

Thanks in advance!

 

[carusoam]

CoachTom,

The wing sight fuel gauges should be calibrated to read usable fuel while on the ground. 

As compared to, the gauges on the instrument panel that should be calibrated to read usable fuel while in flight.

I am reluctant to use the fuel gauges for flight planning without knowing its calibration status. 

[1] For fuel available for flight: The wing gauges are not that precise. I think they are marked in 5 gal increments.

[2] For weight and balance purposes.  You should add the unusable 4 gallons into your empty weight calculation, as you would for oil

Best regards,

-a-

[CoachTom]

I thought (and as I dont I know) if the wing guages are able to be calibrated or if they are the same for all wings?

They look like an old style lawn mower gas guage with the cork riding up and down a licorice twizzler.

The guages had to be replaced recently and there is no calibration except a detent which fits into a notch.

Reason for this whole thought or "thread" is I drained both wings when I had weighed the aircraft and the guages read eactly what I removed (10 gals on refill, 10 gals indicated)  so i was concerned I was including the 4 gallons when I looked at the wing guage and saw 10 gals and only had 6 available...

 

[peter]

We drained both tanks on our231 last year and created a graph showing indicated quantities on the wing guage, panel guage, and low fuel light vs useable fuel quantity in the tanks.  Before we did this we thought the wing guages were all wet, but afterwards we discovered they are probably the most accurate thing in the airplane (at least when sitting on the ground).  Below 10 gallons the wing guages will under read the fuel on board, but they were spot on above that amount. 

My SN is above 25-0447, which picked up a few extra gallons useable by relocating the fuel pick up.

I've emailed you a copy of the spreadsheet. If anyone else wants a copy, send me a pm with your email address and I'll be happy to oblige.

 

 

[carusoam]

pm sent...

Thanks Peter.

Best regards,

-a-