[ccsmith51]

I am going to reweigh my plane on Wednesday. I was telling a fellow RV owner, and another fellow that is an A&P, that I was going to go through the trouble of draining fuel from the tanks so that I could get an empty weight W&B.

The RV guy says why? He says that draining is a PITA and he just fills the tanks, then reduces the total weight buy the fuel weight, and the total moment arm by the fuel moment, to get the empty weight and moment.

I said that kinda makes sense, but then he would not know the empty weight on each wheel. He said so what. What is important is to know what the empty weight is and the empty weight moment arm. He says that knowing the weight on each wheel is unimportant.

As an example, he asked me right then what the weights were on each wheel. I said I didn't know since I didn't know the exact weight in each fuel tank. My A&P buddy says "What is on each wheel if you are the pilot and your friend is the passenger?" I said I have no idea.

But, they said, I could calculate whether the CG was in range, without knowing what was on each wheel...

I guess it all makes sense, but since I have always weighed without fuel and gotten the empty weight on each wheel, it just seems wrong.

What say the VAF brotherhood? Is there a downside to not knowing the empty weight on each wheel?

It sure is a heck of a lot easier to put gas in the tanks than to drain it out....

 

[BobTurner]

May not be "by the book" but I weighed mine with full fuel, and calculated the empty weight and balance.

My logic was that I usually fly with full tanks or close to it; I never fly with empty tanks. So this method minimizes calculation errors (exact arm of fuel; unusable fuel weight) for the configurations where it is most important to me.

My guess is that either way is limited by the accuracy of the scales, and the measurements of the arms to the tires, more than if you do it empty or full.

 

[Walt]

I always weight them empty.

According to the Bible (43-13, chapt 10-14)...
.
Drain the fuel system until the quantity
indicator reads zero or until the tanks are
empty with the aircraft in level flight attitude,
unless otherwise noted in the TCDS or Aircraft
Specifications. The amount of fuel remaining in
the tank, lines, and engine is termed residual fuel
and is to be included in the empty weight. In special
cases, the aircraft may be weighed with
full fuel in tanks provided a definite means of
determining the exact weight of the fuel is
available.