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When referring to mass and balance calculations, is it better to refer to mass or weight and balance. Or does it even matter? Are both okay?

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It is largely semantics. I have never heard of someone using the phrase 'mass and balance' when referring to calculations about an aircraft.

At the same time, an important role in developing an aircraft is that of 'Mass Properties Engineer'. Their professional society is SAWE, the Society of Allied Weight Engineers (historically, they were the Society of Aeronautical Weight Engineers). From their website:

The Society of Allied Weight Engineers (SAWE) is an international, non-profit organization of mass properties engineers dedicated to promoting the mass properties discipline. Our members work in civil and military aircraft, space and missile systems, marine and land vehicles, on-shore and off-shore platforms, and other industries that support our efforts. If you are looking for help predicting, controlling, and verifying the weight and balance of your products, you've come to the right place!

The SAWE website links to a presentation explaining their role in the world, they switch between both terms depending on context.

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Mass and balance is more accurate, it is used e.g. by SKYbrary (Eurocontrol). However the most common wording is weight and balance, it is used e.g. by Airbus.

ATPL schools use mass and balance, e.g. Jeppesen or Mermoz Institute.

The center of mass is the barycenter of masses, the center of gravity is the barycenter of weights. When gravity is uniform across the body volume these two centers are coincident. Thus centering the masses or the weights is equivalent.

When performing the centering, we manipulate mass values expressed in kg or lb, not weight values in N.

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(Source).

A mass (kg) under the effect of gravity creates a weight force (N), which associated with an arm (m) creates a moment/torque (Nm) acting on the center of mass. Mass and balance is the check of both the total mass and how these moments cancel each other. However this centering is also valid when the masses are subject to additional accelerations due to turbulence or maneuvers, so the centering is not limited to moments created by gravity, this is a good reason for not talking about weight and balance.

Likewise when we says the maximum takeoff weight of the A320 is 68000 kg, we are actually using a mass unit and expressing a mass, not a weight.

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It's somewhat of a false dichotomy. You are balancing weight, but you're balancing it by shifting mass.

If Earth had 0 gravity, you'd still be balancing mass, to perform and survive high-g maneuvers. But if a large spacecraft had to fly so close to a black hole that gravity varied across the fuselage, you'd definitely be balancing weight.

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    $\begingroup$ What is a high-g maneuver with 0 gravity? Infinite acceleration? ;) $\endgroup$
    – Chris
    Commented Jun 22 at 17:32
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    $\begingroup$ @Chris Earth's gravity has no effect on the g-force you get in sharp turns. Fighters would still have to hit 7-9g to stay competitive, although they wouldn't call it "g". $\endgroup$
    – Therac
    Commented Jun 22 at 17:34
  • $\begingroup$ @Therac I think what Chris meant is that if g is 0, you would need infinite acceleration to reach 7-9g's. Because 'g' is a measure for how many times you experience earth's gravitation. So from that perspective, earth's gravity definitely does have an effect on the math. (But indeed not on what the fighter would experience) $\endgroup$
    – Opifex
    Commented Jun 24 at 7:33
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    $\begingroup$ @Opifex I get the joke now. Though a "high-g maneuver" is essentially a single term by now. $\endgroup$
    – Therac
    Commented Jun 24 at 14:15

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