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9 Answers

Useful load vs. Payload

Asked by: 47307 views , ,
General Aviation

It is my understanding that basic empty weight is always used when calculating weight and balance.  Therefore, if I take my basic empty weight plus the weight of a full tank of gas and subtract that from max gross, I should be able to tell how much weight (passengers, baggage) I can bring aboard the aircraft.

Would this weight be considered useful load or payload?  What is the difference?

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9 Answers

  1. John D. Collins on Feb 11, 2011

    The empty weight is the weight of the airplane including anything that is permanently attached to it and includes any un-drainable fluids.  There is a maximum gross weight for takeoff and on larger aircraft there may be a maximum landing weight.  The useful load is the difference between the maximum gross weight and the empty weight.  To the empty weight, you have to add the fuel, oil, any other fluids, pilot and passengers, and baggage.  Sometimes there are sub limits such as a zero fuel weight, which restricts how much weight can be carried in the cabin. Some aircraft will have a higher maximum ramp weight that accounts for the fuel used prior to takeoff, it is usually an extra 6 to 15 pounds depending on the airplane.
    When you do a weight and balance, you have to add all the weights to the empty weight and make sure that any sub-limits are not exceeded.  In addition, you have to calculate and add the moments for all of the weights including the empty CG moment and make sure that the loaded CG is within the envelop allowed.  You should also calculate the weight and balance at the end of the flight to make sure you are still withing CG limits and below any landing weight limits.  You may satisfy the weight requirements, yet still have a problem satisfying the CG requirements.  Your only options are to reduce the weight, relocate the weight, or a combination to bring both the weight and balance into compliance with the limits.  Sometimes, but not always, reducing the fuel load will help.  In the case of my airplane it rarely will help if I have a CG issue due to the way the aft CG limit expands at lighter weights in combination with where the fuel moment arm is located.
    Payload usually refers to how much you can transport from one place to another.  Often in this regard, the pilot is added to the empty weight and considered part of a basic operating weight, then fuel is added, what is left over is the payload.  There are more possible ways of determining payload, such as maximum cabin load with full fuel and so on.  The important weights are the empty weights and the maximum weights along with any sub limits.

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  2. Plane Crazy on Feb 12, 2011

    In regards to weight and balance, please confirm that you are talking about using basic empty weight and not standard empty weight. 

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  3. Anyonymous on Feb 12, 2011

    Does fuel burn have a big effect on CG in regards to smaller (general aviation) aircraft?  I’m a student pilot and have only really flown the Cessna 172R
    However, based on calculations that I have done with a full tank and with an empty tank…and just me in the plane…the CG is still within limits.

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  4. John D. Collins on Feb 12, 2011

    It depends on the airplane and the fuel tank details.  In my Bonanza, the fuel moment arm is forward of the CG location, so as fuel is consumed, the CG shifts to the rear.  It turns out that on my model, a V35A with the V tail configuration, the CG envelope shifts to the rear at the same rate, so if I am inside of the CG at takeoff, I will remain in CG limits as fuel is consumed.  That works for about the first 400 lbs of fuel consumption, but as weights drop further, the CG remains fixed and any more reduction can cause the aft CG limit to be exceeded.  This doesn’t present an operational problem, because I have to be down to my last 44 pounds of fuel before this can occur.
    The conventional tail version of the Bonanza has more weight in the rear and the CG envelope is a constant value.  On that aircraft, if you are close to the aft CG limit and consume any fuel, it will put you outside the limit.  So off loading fuel to solve an aft CG issue doesn’t work for this model and the pilot has to be careful to calculate the CG as fuel is consumed to make sure it won’t end up outside of the CG envelope. The pilot has to use other options to keep the CG within the allowable limits.

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  5. Anyonymous on Feb 13, 2011

    Thanks, John!  I guess the hardest part would be calculating the maximum amount of fuel you can burn before the CG moves outside of acceptable limits.

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  6. Steve Pomroy on Feb 15, 2011

    QT:  “Would this weight be considered useful load or payload?  What is the difference?”
    Useful load is anything you can carry that is useful in some way.  Numerically, it is the difference between the maximum gross weight and the empty weight of the aircraft.
    Payload is the load you (if you are a commercial operator) could be paid to carry (i.e. – passengers and cargo).  So it doesn’t include operational necessities such as pilots or fuel.

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  7. Kent Shook on Feb 15, 2011

    I like Steve’s memory aid, but I would like to point out that in general, for smaller aircraft that aren’t generally used for part 135 and the like (the “pay” part), payload is generally considered to be basic empty weight + full fuel. So, if you see a “payload” number for a C172, it is probably not including the pilot.

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  8. Taralim on Jul 06, 2012

    DOM=38000kg, max. structural take off mass= 72000kg, MLW=65000kg, MZFM=61000kg, fuel burnt=8000kg, Take Off fuel= 10300kg. find Max allowesd take off massnad payload.  

    PS- as I understand burnt fiel is used flight fuel.
    reply ASAP by anyone will be great, m looking forward for exams to be in 3-4 weeks

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  9. Taralim on Jul 06, 2012

    Which is true of aeroplane Empty Mass?

    componenet of DOM
    DOM – fuel load?
    DOM – traffic load
    actual take off Mass ,less traffic.

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