Weighing, every 5 years #72

Weighing, every 5 years
This year Rans S4 -FW became due for a reweigh check for its PFA Permit.

There was the chance to use borrowed BMAA's digital set of three scales which became an afternoon's two man task, attempted inside the hangar due to gusty conditions. The Rans was emptied of all loose items, then blocked up under the main wheels to bring the wings horizontal & tail raised on a 'work-mate' folding table bench to flying level position, using a spirit level

These scales required careful use with no side loads: after switching on unloaded they self zero, then the plane was lifted and lowered gently wheel by wheel as the scales were inserted. Don't forget, as I did, to reduce the total weight measured for fuel in the tank.

After many permutations we finally arrived at a total close to my own bathroom scale result of 2005, but we were unhappy with a loose wiring plug & unreliable readings.

A fortnight later we had another go, obtaining stable readings by rolling onto a borrowed triple set of calibrated "Dr.'s quality" scales for a final empty weight of 336 lb. That requires the other wheel to roll onto planks or blocks exactly the same height as the scales.

N.B. Tipping the plane sideways throws a lot more weigth onto the lower wheel & reduces the scale load so isn't acceptable.

Two sessions did Vince's own S4 5 yearly check. We used one bathroom scale first 'calibrated' by getting me accurately weighed first at his local Dr's surgery.  on The tail & fin was poked just outside the hangar doors so it could be lifted high enough to exactly level the fuselage top. Wind made for variable readings, but in between gusts we got similar totals to my Rans & settled for that. His inspector was happy with the new straightforward weight & balance sheet e-mailed to him.

RANS S-5 weight and balance sheet:Airplane's fuselage root tube should be level (horizontal), either block up under the scales under the mains or "dig a hole" for the nose wheel.
   Item              Weight         Arm         Moment.
1 Nose Gear ______ ________21.25"____________
2 Wing Fuel _______________ 66.5" ____________
3 Pilot ____________________66.5" ____________
4 Mains ______ ____________72.5"  ____________
Total Weight= ______          Total Moment= ______
Total Moment divided by Total Weight = C.G.
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Typical All up Weight C of G Calculation for Rans S4 G-MWFW
Item                    Lb. Weight         Arm Inches             Moment inchLb.
Empty plane           336.1                 56.05                      18840
Pilot                      194                    61                           11834
Wing Fuel              19.3                   61                             1177
Fuselage Fuel         30                      84                             2520
Pilot’s equipment     7.6                    61                               464
Total                    587                               Total Moment 34835

C of G  = 34835/587 = 59.35 inches Aft of Datum (limits 58.5 – 61 inches)