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5 Answers

Empty Weight Calculation with full fuel

Asked by: 4013 views Student Pilot

Hello,

I'd like to calculate Empty Weight CG with full fuel. TCDS indicates total fuel of 50 gal. (300 lbs.) at +95 and unusable fuel of 12 lbs at +112. Should I subtract -300 lbs at +95 and then add 12 lbs. at +112?

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5 Answers



  1. John Scarry on Apr 18, 2017

    Probably not. It depends on how the manufacturer defined empty weight. Most define it to include unusable fuel. To get a definitive answer you need to refer to your Airplane Flight Manual.

    My Cherokee 140 AFM says that the AIRPLANE EMPTY WEIGHT includes 3 pints of unusable fuel weighting 2.2 pounds at an ARM of +103. In my case to get the full-fuel (50 gallons) CG I would add 47.8 gallons (286.8 lbs) at an ARM of +95 to whatever the current W&B says is the CG.

    If your plane is like mine, then to get the full-fuel CG you would add 288 lbs at +95.

    If the manufacturer defined empty weight to be zero fuel (unlikely) then your method is correct.

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  2. JohnFlyby on Apr 18, 2017

    Thank you for your answer, Empty weight always includes unusable fuel. So, is it correct to subtract -300 lbs. at +95 of full fuel and then add 12 lbs. at +112 of unusable fuel to get correct Empty Weight CG?

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  3. John D Collins on Apr 19, 2017

    Some people will calculate the empty weight using the method you describe, but it is not optimum. The fuel weight will vary with temperature and most fuel tanks will hold more fuel than the stated capacity. These errors are eliminated if you weigh the airplane when it is empty and all fuel is drained except for the unusable fuel. Then it is a good idea to add the fuel back in and see how much is actually stored in the tanks.

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  4. Mark Kolber on Apr 19, 2017

    You’ve lost me. It might be me, not you.

    Don’t you have an official weight and balance document that gives you the aircraft empty weight, arm and CG moment? Why do you need to calculate that?

    Or perhaps you are over complicating something simple? The full fuel empty weight is just the empty weight plus total usable fuel when full.

    If your empty weight is 1500 and your total usable fuel is 60 gallons, it just 1500 + (60X6) and however that comes out using your weight X arm calculations.

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  5. JohnFlyby on Apr 19, 2017

    Thank you all for taking time to respond. This is actually a question in my exam. It’s just a basic knowledge test about weight and balance.

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