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Multiple bogies question

Started by Will, Sat, 4 Jun 2022 21:47

Will

As we know, the 747 can sit on two main bogies without collapsing. So I was curious about why the aircraft has both wing and body gear.

I understand that more than one purpose can be served by the same configuration, but what is the principle reason? Is it to distribute the weight so that the stress of landing and carrying the aircraft is borne by multiple struts? Or is it for braking -- because dividing the braking energy amongst 32 wheels is a better solution than concentrating the energy on only 16 wheels?
Will /Chicago /USA

Jeroen Hoppenbrouwers

This web resource says it is both:

QuoteSo, why such a large variation in the number of wheels? As I've stated before, the reason is twofold: to distribute weight and increase stopping power.

As airplanes grow in size, the weight they exert must be shouldered by the pavement they're riding on. For example, if a 747 were equipped with three large tires, it would cause the pavement to break and fail wherever it taxied. This immense weight focused on three points in the pavement is too much of a load. So the options are clear: Either increase the depth and strength of every taxiway and runway in the world, or add more tires to evenly distribute the weight. This is why the 747 has 18 wheels.

(... continues about brakes ...)

https://www.johnnyjet.com/ask-a-pilot-airplane-wheels-tires/

Will

Ah yes, not puncturing the pavement is another reason...!
Will /Chicago /USA

Avi

Don't forget, landing weight is one thing, takeoff weight is another thing. The difference can be by around 150t.
That's a lot.

Cheers,
Avi Adin
LLBG