The International Cessna^® 170 Association

It's perfectly acceptable to fill the tanks and calculate out the useable fuel/oil etc. and it's associated CG. (It's just that method is more likely to err on the heavy side.)

I prefer weighing with the tanks FULL. That way you can just subtract out the weight of usable fuel ( by definition in a 170, 37.5 gallons, or 225lb, IIRC) and then you'll KNOW that your empty weight includes "unusable" fuel. It would be a tedious process to remove absolutely all of the fuel from the airplane, and if you don't you'll end up at some unknown point somewhere between zero fuel and unusable fuel.

as long as you also remove the total moment of all fuel, then add back the unuseable fuel and it's moment it would be close.... the undrainable fuel being one unknown.... that and the fact that the weight of fuel goes up and down...

av gas is 6.02 lbs per US gallon at "standard temperature" - defined as 15 degrees celsius (59 degrees Fahrenheit).
Its density increases to 6.4 lbs per US gallon at -40 F and 5.9 lbs per gallon 100 degrees

I know, pickin dirt out of the pepper, but there is no way to get the real, true, absolutely correct empty weight unless you drain it.... fact

BEEZERBOY wrote: but there is no way to get the real, true, absolutely correct empty weight unless you drain it.... fact

Just make sure you make fuel weight adjustments for temperature differences when doing your W&B computation prior to flight.

I remember the time in my wildly misspent youth that I had a date with a lovely young thing who, when asked what she'd like to do, told me she was dying to get "weighed". After dinner I made it a point to visit a drug store with a penny scale and got her weighed. I seriously kicked my butt somewhat later. After bidding her goodnight at her door I asked her if she had a good time and she allowed as how it had been "Wousey".

Oh boy.....

WOW

Waughed Out Woud

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