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Unusable fuel

That's something that you should measure or should have been determined as part of the Phase 1 for your aircraft. For my aircraft it was a bit less than 1/2 gallon per side in level flight.
 
Tom,
Here is how I did it:
Before my tanks had ever had any fuel in them, I leveled the airplane and put a measured 5 gallons in each tank. I then disconnected the fuel line at the carb and used the electric pump to empty each tank. I noted the time 'til the last fuel came out. I then measured how much fuel came out. I did some math and found out how many gallons-per-hour the Facet pump was capable of putting out, and how much "unusable" fuel was in the tank. On my RV-6, the unusable fuel was .5 gal per side. Since this fuel should always be on board I weighed the aircraft that way.
If you have fuel injection I think you could disconnect the line to the fuel servo.
Oh, and don't forget to ground the aircraft and fuel containers.
 
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I had a flight instructor that was passionate about letting students know most people confuse unusable fuel as undrainable fuel which is not the case.
 
In my testing it is about a pint on either side. It is very low.

I agree, about the same for me.

That's something that you should measure or should have been determined as part of the Phase 1 for your aircraft. For my aircraft it was a bit less than 1/2 gallon per side in level flight.

Agree as well.
Probably best to use no less than 1/2 Gallon per tank as your unusable fuel
for any practical flying applications and planning.
In a nose up attitude you'll get more fuel out of the tank than in a nose down attitude because of the rear location of the fuel pick up fitting.
For planning, I consider 1 gallon a minimum and in reality I've never gone much below 5 gallons in anyone tank except for phase 1 testing.
 
Tom,
Here is how I did it:
Before my tanks had ever had any fuel in them, I leveled the airplane and put a measured 5 gallons in each tank. I then disconnected the fuel line at the carb and used the electric pump to empty each tank. I noted the time 'til the last fuel came out. I then measured how much fuel came out. I did some math and found out how many gallons-per-hour the Facet pump was capable of putting out, and how much "unusable" fuel was in the tank. On my RV-6, the unusable fuel was .5 gal per side. Since this fuel should always be on board I weighed the aircraft that way.
If wesyou have fuel injection I think you could disconnect the line to the fuel servo.
Oh, and don't forget to ground the aircraft and fuel containers.


Thanks Mike. As usual Steinair has The and
 
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