Ex. of W&B w/wo rear seat in C172

[Gucci Pilot]

It's why you can't use the rear passenger arm from the W&B sheet instead of the actual arm of the seat itself from the equipment list.

I never said anything about using the rear passenger arm...

You need the arm from the equipment list. Measuring isn't an option.

I never said anything about pulling out a tape measure either...

The arm of the back seat is located at 70 inches, see page 3 of TCDS No 3A12.
http://rgl.faa.gov/Regulatory_and_G...754258e86257acc0077095f/$FILE/3A12_Rev_83.pdf


Weigh the seat

multiply seat weight by 70 inches to get seat moment.

Subtract seat moment from airplane empty moment.

Subtract seat weight from airplane empty weight

Divide new airplane empty moment by new empty weight to get new empty arm.

Have a nice day.

Boom! Case closed

 

[bnt83]

I never said anything about using the rear passenger arm...

Sometimes they show up the same, just depends on the manufacturer. At most an inch or so different.

 

[Jaybird180]

So, I guess by extrapolation...

When I fold the back of my rear seat down to haul long stuff, I should carry a third weight and balance and be remeasuring the arm to reflect that the back of the seat (a whopping 12# or so) is no longer the same distance from datum line?

This could go on infinitely.

The airlines get around this requirement by making each passenger bring their seats to the full upright position during takeoff and landing. Any passenger that doesn't comply gets a taser to the groin.