Weight and balance

 

Original post below, video is new. Enjoy!

 

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It is important to load the aircraft within limits. A too heavy aircraft, or one with a too far forward of aft centre of gravity, may not fly very well.

The Piper 28 is build in America, unfortunately for Europeans, all the data is in gallons, pounds and inches. The easiest way is to do all the calculations in the US units and only convert to a metric value whenever it is necessary.

Make a weight and balance and fuel calculation for the planned flight. Your aircraft manual will contain a weight and balance chapter with specific numbers and a graph containing the loading ‘envelope’. You can calculate with pen and paper, or like my example, with a spreadsheet program on a computer.

Note! Always refer to the specific manual of your aircraft as slight differences may apply.

Loading

In short, if you add up the weight of the aircraft, everything in it and the fuel, you have the take-off weight, which should be less than the maximum take off weight.

Not only the weight, but also the location of the load makes a difference. The position of the load is measured in inches aft of a reference point called the datum line. The further aft, the longer the ‘arm’.

Multiply all the weights with their respective arm, the result is the moment. Then add all the moments together and then divide the total moment by the total weight to find the new arm.

Let’s have a look at that in practice.

With the aircraft loaded at zero fuel we have: 1649 lbs and 86.35 inch.
The moment is 1649×86.35 = 142368

Now add 48 USG. At 6 lbs per gallon this is 288 lbs. The arm for fuel is 95.00 inch so the moment is 288×95 = 27360

Added together is the takeoff weight, 1649+288 = 1937 lbs

For the arm, add the moments together, and devide by the weight. (142368+27360) / 1937 = 87.62 inch.

Draw this point in the graph and if it is within the envelope, you are save to fly!

Draw the various weight and arm values for take-off, landing and zero fuel in the graph. When the points are all within the ‘envelope’ it is safe to fly.

It’s easier than it looks on the excel sheet, but the sheet makes conversion of units, Lbs to kg to USG to litres easier, as well as last minute changes.

1 thought on “Weight and balance

  1. Pingback: Exercise 2: Preparation for and action after flight | flightinstructoronline

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