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Comment by tacticus | Hacker News Reader

Landing weights are usually a bit lower than take off weights due to the extra shock on landing.

for example the a340-600 has a MTOW of 380 tons but a Max landing weight of 265 tons. Just a bit of a difference.

That's the fuel the plane takes off with. I don't know how much this beast uses, but those six engines must be burning quite a lot of it. Also, the landing gears seem to be very robust.

The A340-600 has four engines, not six. But the point is still true with, say, a Boeing 787. Here are the figures for the 787-9: maximum takeoff weight: 560,000 lb; maximum landing weight: 425,000 lb [1]. In case of an emergency the pilot has to get rid of fuel before landing if the airliner is above maximum landing weight.

[1] Figures given in pounds on wikipedia, the kg version looks like a "dumb" conversion: https://en.wikipedia.org/wiki/Boeing_787_Dreamliner#Specific...

We don't know Roc's maximum landing weight but abort is possible if the maximum landing weight is more than weight of the whole craft plus its cargo minus the fuel. I assume it takes of with a lot of fuel because it has potentially 1.5x time fuel consumption of an old 747.

Fundamentally, landing speeds are lower than takeoff speeds. To travel at the same (low) speed and rate of descent with more weight means getting more lift at the same speed. That is done by increasing angle of attack or adding flaps. There is a limit to both.

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