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Anyone know the Arm for the Rv9A instrument panel

Mdragon

Active Member
Recalculating weight and balance after changing some avionics, need to know what the ARM is for the panel. Not at the plane so can't measure. By diagram appears it is roughly 80 inches aft of datum, but wondering if anyone knows the exact number.
 
Recalculating weight and balance after changing some avionics, need to know what the ARM is for the panel. Not at the plane so can't measure. By diagram appears it is roughly 80 inches aft of datum, but wondering if anyone knows the exact number.
The wing LEADING edge is 70 inch aft of datum as shown in Section 7 of builder manual. Measure from there. 80 inches sounds too far aft just looking at the sketch in builder manual, but measuring from leading edge of wing should be easy with a level and tape measure. Make sure plane is level.

Assume you have accurate weight and CG of the avionics / instruments / wires and tubes you added? if it's only a pound or two, I personally small weight changes I add to empty weight, CG will not change much if weight is near aircraft CG. The panel is near aircraft CG. A few lbs in the tail of course is a bigger change to CG and should not be ignored.

If you made extensive changes may I suggest you consider scales, weigh again. It is always a good sanity check and double check on your original measurement. Every couple of years it's good to do a W&B weight and balance again. If you did not do original weight and balance it may be a very good idea. I have weighed a few RV's after other folks and surprised a few times.
 
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On a RV9A slider, I measure 67.1 to the F1105 radio subpanel and 75.6 to the F7105 instrument panel bottom.
 
Remember,…. Panels are like people

Doesn’t stand straight up,…Some things hang out the front,….some things hang out the back,…. And some items are further than others,….

Depending on what you have,…you may need to add or subtract “arm” to get the correct moments,…..

(don’t ignore the wiring)

And weighing, if done correctly, should confirm your numbers…… or cause you to rethink what you assumed/included. ( be sure plane is level)
 
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