Page 22 - July 2015 Volume 9, Number 7

Back to the fuel chart. If curiosity compelled me to know the Arm for that 200 gallons of fuel, the formula Arm = Moment/Weight would now be Arm = (2,437 X 100)/1,340 or 181.87 inches. No pilot cares where the Arm is to the nearest hundredth of an inch, so it is normally stated to the nearest whole inch: 182 inches.
For “fun” – satisfying that itch of curiosity – let’s calculate the Arm for the first 10 gallons put into the airplane and for the last 10 gallons added before the tanks are full.
The chart shows, for 10 gallons, a weight of 67 and a Moment/100 of 103. The Arm, calculated by us, is 154 inches. The 10 gallons that brings the chart from 530 to 540 gallons adds the same weight, 67 pounds, but increases the Moment/100 by 138 for an Arm of 206 inches. Wow, that fuel arm changed a lot! It moved aft by 52 inches, nearly a yard and a half!
This shift in Arm is not surprising when one understands the fuel system on the model 200. When the refueler pumps in the first ten gallons into an empty airplane – maybe the fuel had been drained for a re-weighing of the airplane – he uses the filler cap at the wingtip, fueling the main tank before the aux tank. The fuel he adds flows downhill, propelled by gravity, and ends up at the bottom of the nacelle tank – the lowest and most forward position of the
main complex of fuel tanks. As fuel continues to be added, it gradually begins to fill the other tanks in the main complex, some of which are forward of the main spar and some of which are located between the main and rear spars in the outboard wing. Only after the mains are topped, would the fueler now go to the aux tank cap between the nacelle and the fuselage to input fuel – a single bladder tank located between the spars of the center section. As you can see, the first fuel added sits more forward than the last fuel added.
In the Weight and Balance section of the POH, where we find the fuel chart we have been using, Beech also provides a “Weight and Balance Loading Form” chart. In fact, they even fill it in with actual numbers for both a forward and an aft loading example using the true Empty Weight figures for this exact Serial Number airplane as it was when it left the factory. How nice!
Line #11 on that form, labeled “Less Fuel to Destination,” has a column for “Weight” and another for “Mom/100.” I will wager that those who decide to use this form for their own W & B calculations make an error on this line more often than not. For example, let’s say they started the flight with 380 gallons – almost full mains – and landed with 100 gallons remaining, for a total consumption of 280 gallons. To find the numbers to enter into line 11, they refer to the fuel chart, go
20 • KING AIR MAGAZINE
JULY 2015