April 1999 - American Bonanza Society

"Figure 2V35B and F33A Bonanzas plus one forthe B55 Baron.Completing a W &B using this vectormethod (line segments) is a simple 20-40-second operation after a very shortlearning curve. Simply begin by findingyour basic empty aircraft weight and CGinches in the POH data for you r aircraftand plot this point on the graph. You willuse this same point for all futu re calculations.Next, plot your people, baggageand fuel load in connecting lines to reachthe total weight and CG inches. One ofthe advantages of the vector system is thatyou can see graphica lly where the CG ismovi ng relative to the forward and aftlimits as you add payload. See Figure 2.for a sample 3,400-pound gross weightBonanza W&B and Figure 3. for the5, I OO-pound B55 Baron. Both examplesuse identical people and ba ggageweights. The Baron, being able to utilizeits full I 36-gallon main tank usable fuelcapacity, has an additional 516 poundsof fuel on board.Just as a chain is only as strong as itsweakest link, a W &B calculation is onlyas accurate as its least accurate data.The Basic Empty Weight (BEW) providedin your POH should be accuratewithin I percent, provi ded it is correctedfor additional items normally carried inthe aircraft but not in it during weighing.This includes chans and case, headsets,flashli ghts, cabin covers, tool s, emergencykit, etc.In the real world. assumi ng "standardI 70-pound FAA" passengers in light aircraftis dangerous and can introduce anerror of as much as 40 percent. A goodestimate is preferable, (error 10 percent),but a discreet inqu iry is best (add 5pounds in summer and 10 pounds in winter).This will yield an error ge nerally lessthan 5 percent. Weighing passengers, althoughbest, is usually impossible. Baggageshou ld be weighed since mostpeople, using estimates. introduce at least10 percent erro r. Finally, fuel est imatesare accurate only if the aircraft tanks areful l or empty, unless we have an accuratepartial tank tab to reference, or weFigure 3are absolutely sure our electronic fueltotalizer is displaying the correct fuel remainingon board. Between full andempty, non-capac itance type fuel gaugesmay not be within 10 percent. Capacitancefu el gauges, properly calibrated, aregood for around 2 percent error at best.The bottom line is this: If everything isdone right, the best accuracy our data canhave is approxi mately 2 percent error.So, whatever method we choose, it'snow eas ier than ever to work a W&B.And by the way, if you ever decide toupgrade to your new "big Boeing,"American Aeronautics makes plotters forthem as well.For further injO/1llOtiol1 call AlllericanAerol1olllics at, 1-800 FLY IN CG (359-4624) or e-mail thelll at order@j1yil1cg. CO III or visit their website at Ilttp:!/www.jlyincg.colll.Ron Vickrey, ABS past president and currentABS and BPPP director. flies N55RV, a B55President II Baron. I-Ie holds a commercia llicense SMEL - CFI, MEL/SEt, Airplanes andInstruments, Advanced Ground InstructorABS April 1999Page 5653