Van's RV-9A in Aurora

The Big Picture

The Big Picture
Flying! 8/28/2011

Saturday, July 30, 2011

Weight and Balance

6 hrs
Did the Weight and Balance today.
Drove to Georgetown and picked up the EAA 187 scales.

Got a race car you need to weigh?

Made up a set of tare boards for leveling
First leveled the plane. Here it is with the boards arranged to get the plane level.

Then I checked the calibration of the scales. I used 101 pounds of weight plus my own weight. The bar bell is supposed to be 25, but I got a bargain because 5 scales think it weighs 26. The plates are all right on 25. All four scales had the same numbers as each weight plus my own were added. I think that's accurate enough, although that isn't quite the range needed for the main gear load.

Calibration - 101 is the correct number

Then I rolled the plane up the ramps. I didn't have enough traction to pull it up, so I got three chocks and moved each wheel up by hand about a centimeter at a time. I have blisters and sore legs from making dozens of laps around the plane, and getting up and down 3 times per lap.

Then started taking measurements, remembering to close the canopy. Measured with bare airframe, 1056 lbs, 6 lbs over my guess. Then added seats, seat belts, and wheel fairings. The total for all this is 1072, quite a respectable number. The usefull load is then 678 pounds, which allows for full fuel, 100 lbs baggage, and two standard weight people.

This is weight without wheel fairings.

Later I came back and measured gear leg stations from the datum, which is 70" from the wing leading edge. First I had to accurately lay out the datum line, then measuring from that was straight forward.

Heres the data:
Nose Wheel 242 lbs @ 33.25"
Right Main 415 lbs @ 91.0"
Left Main 415 lbs @ 91.0"

I've borrowed spreadsheets from this search on VAF and modified them for N207LT.
Here is one calculator, and here is a scenario calculator.
The result is a perfect situation. By myself I am usually flying in utility category, and with a standard weight pax I can't load it out of CG!