Help required in development of load sheet [Archive]

pavil

18th Mar 2012, 23:30

as i dont know if you are trying to create a manual or computerised loadsheet, nor your level of understanding of weight and balance, ill explain the general idea to work out the index effect on anything on the aircraft.

Firstly, you will need to know a few things, ie the distance of the object on the H.arm, the H.ref, and the equation used by the manufacturer or airline to work out the index effect and the weight of the item at that position.

i dont know the boeing formulae or data for this so i will use an A330-200 as an example as i have these figures, but the basic formula should be the same. If you have a manual loadsheet, then you will be able to see the formula that your airline uses, normally above the trim chart.

A330-200; The tip of the nose is at H.arm = 6.3825m, and in our example row 1 starts at H.arm = 13.885m (ie 7.5m from tip of the nose). The H.ref is the distance where the aircraft is at a reference MAC of 25% (i think its the same on a 734, but if not then it should be where the C of G is), where on a 332, is at 33.1555m from H.0 (ie 26.773m from the tip of the nose).

to work out the index effect, we then use the equation;

index = (weight * (H.arm - H.ref)) / C

C = constant so that you have more workable figures (kg.m)

for the A332, C = 2500 so we can now work out the index effect of 1kg situated on row 1

index = ( 1kg * (13.885 - 33.1555)) / 2500 = -0.0077082 IU/kg

as i dont know what a row of your seats weigh, i will just use an example of 100kg for the row, which would give us an index effect of 100 * -0.0077082, which is -0.77082 IU for row 1. Just change the 13.885 above to whatever the figure is for row 2 to get that effect and so on.

If your airline has already incorporated the new seating configuration into your system, and you are only after the new passenger effect then you can do the folowing

As its too much work to figure out what passengers are sitting on each row to determine the weight, you can use a formula to work out a cabin average. In our example we will use 6 rows of 6 seats in bay A. We take the H.arm for each row and multiply it by the number of seats in that row, add the figures together then divide by the total number of seats, so;

h.arm bay a = ((H.arm row 1 * 6) + (h.arm row 2 *6).......(h.arm row 6 * 6)) / 36

or ((13.885 * 6) + (14.901 * 6).......(18.965 * 6)) / 36 = 16.425

you can now work out the total index effect for 1kg located anywhere in rows 1-6 (bay a) using the index formula above;

index bay a = (weight * (H.arm bay a - H.ref)) / C

which is (1kg * (16.425 - 33.1555)) / 2500

which equals -0.00669 IU/kg.

Once you work out each bay effect for 1kg, then its simply a case of working out your total passenger weight using whatever figures you use for males, females and children (or just adults), then divide that by number of passengers to give you a truer average, then use this new average weight to calculate the bay effect.

for example

male = 88kg, female = 70kg, child = 35kg

we have 100 males, 100 females and 40 children on board, spread through the cabin.

normal average weight total would be (100*88)+(100*70)+(35*40) = 17200 kg

as we dont know exactly how many of each are in each bay then we just divide the 17200 by the total number of passengers, so 17200/240 which gives us a new average passenger weight of 71.667kg.

If we have 30 pax in bay a, then the index would be

index bay a = (( (30 * 71.667) * (H.arm bay a - H.ref)) / C

so index bay a = ((2150.01 * (16.425 - 33.1555)) / 2500

total effect of passengers in bay a = -14.3883 Index Units.

You should be able to get all the figures you need from your manuals and just adapt the formulae to whatever you need to do but thats how you work it out anyway. Apologies for the long post but hope it helps