Because you don't actually care about the weight on the landing gear, you care about the mass of the aircraft. A scale in the landing gear would measure the weight, which is force that is currently applied to the scale. However, this is not only composed of the aircraft mass, but it is influenced...
Weight of an object is not the same of mass (en.wikipedia.org/wiki/Mass_versus_weight). For the performance calculation you need to use the mass of the aircraft (even if often we say "weight"), but a scale can only measure the weight, which is, however, influenced by external factors (like wind).
I think most people here understand the different of mass and weight, but 1- do it matter so much on a scale? 2- are you sure mass is more useful e.g. to calculate lift? 3- and id doesn't matter on your conclusion? Do you think anybody will measure mass of each cargo unit? (Standard passenger are weighted). -- unnecessary and wrong pedantry.
1) It does! The wind can really makes the measurement wrong by pushing on the wings. This is why when the aircarft performs the periodic weight schedule this must be done in a controlled environment (inside an hangar). 2) Yes, in the sense that you use the mass (Kg) and you multiply it by 9.81 to get the force (N). 3) You can use a scale to measure a cargo (the wind does not affect it) and the same for standard passengers (unless they wear a wingsuit :)). Also scales are often larger than the object you want to measure, while the landing gear is smaller. This has strong impact on the accuracy.
Yes, of course you need a scale to measure the weight and then compute the mass. But you can accurately do that only in a controlled environment, not on the ramp where wind, surface irregularities, etc. are present. This is why you compute the mass and not measure the weight with the landing gear. I improved the answer, even if it is a bit useless because the quesiton is closed.
How the pilots do normally, the pallet has been scaled (not on the aircraft), you compute the total mass by adding it to the empty mass of the airplane you know.
But I don't know the mass of the airplane, I only know the weight. And the forklift driver brings me a ticket with the weight printed on it, not the mass...
Let me re-explain: to know the mass of the aircraft you obviously must use a scale to get the weight and then convert it to the mass. However, this works accurately only if you do the weight mesurement in a controlled environment, so that the weight is a good representative of the mass and not falsified by other forces (wind, weight shits, etc.).
You're not taking the bait... Okay, so I'm not used to converting so I looked it up and to convert weight to mass you divide the weight by the force of gravity which would be 1 G. Is that the formula you would use? Does that yield a different answer than the weight? My point is you're not getting downvoted because you're technically wrong, you're being downvoted because you're being pedantic.
"Does that yield a different answer than the weight?": if you measure it in the gear, yes. I've already explain why. Keep downvoting a correct answer then, what else I have to say...
No, you really haven't explained anything You simply keep insisting that mass is correct. And I'm trying to explain to you that nobody gives a rip about mass, we all talk in terms of weight. Every pilot, every loadmaster, I've been doing this for a few decades now... Nobody uses mass. Nobody.
You know that pounds and kgs are unit of measurement for mass, and that weight is measured in Newton, right? So, what we call 'weight" in everyday life is actually the mass. But this is not the important part, you are focusing on the difference on that terms and you forgot to read the rest of the answer. If you don't like my answer, then read the other one that i linked above, which point out the same thing (including mass!=weight...).
Discussion on answer by ocirocir: Why…
Discussion on answer by ocirocir: Why…