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Severe-Archer-1673 t1_j4henwv wrote

Reply to comment by wj9eh in The Stratolaunch Roc, the largest aircraft ever flown, has just completed a 6-hour test flight. It aims to be a platform to launch reusable hypersonic craft from an altitude of 10 km by lughnasadh

I could be wrong, but I’ve always understood that they measure aircraft size, in terms of wingspan. I’ve never heard of takeoff weight being used as a ranking measure, in terms of size.

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Zakluor t1_j4hidss wrote

You're both right. Take-off weight is an important measure since cargo (passengers count in this context) is often measured that way.

Wingspan and, to a lesser degree, length, of the aircraft are often considered, too. Sometimes when they say 'largest' they talk about the width or diameter of the fuselage, as well, but that's usually in relation to an aircraft designed specifically to carry certain things. The Super Guppy and other cargo aircraft would fall into this category.

It really is context-dependent.

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wj9eh t1_j4hkktn wrote

Well as an aviation professional I can tell you that more or less everything is based on MTOW. If you're more interested in wingspan, that's of course absolutely fine. The only time that tends to come into play day-to-day is whether a plane can fit down a certain taxiway or a certain parking position or not.

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wooltab t1_j4ivsph wrote

Is the word "large" used in aviation to refer to takeoff weight?

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wj9eh t1_j4jwoaq wrote

Yes. A "large aircraft" for example is, in the regulations, anything over 5,700 kg MTOW. Any time anyone refers to size, it would be MTOW that one would think they're referring to. Otherwise we'd say "wingspan" or "length".

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Severe-Archer-1673 t1_j65mdel wrote

Using this logic, the space shuttle would be the largest aircraft, would it not? I get it, though, wingspan and takeoff weight are arbitrary methods of gauging an aircraft’s largeness.

I was a crew chief on C-5s, so I’m obviously biased toward wingspan. They’re all big, and it’s a small miracle they can fly in the air at all.

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wj9eh t1_j666xla wrote

Well I can speak for commercial aviation, where takeoff weight does have a few non-arbitrary consequences such as what sort of approaches and turns you can make and how much wake you produce. Also, wingspan has already reached its maximum in terms of what can fit in an airport, so now it's just about how heavy planes can get within that limit. But yes, it's as arbitrary as anything.

The space shuttle would be biggest but I'd argue it took off with a rocket, which isn't lifting off using the air but rather in spite of it. Then on the way down, it could only glide and not support itself straight and level. Again, as arbitrary as you like. It's all a miracle they can fly!

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