On 23/01/14 21:33, Vir Campestris wrote:
On 23/01/2014 13:41, The Natural Philosopher wrote:
(there is a formula to do with drag and power and all sorts of stuff
that more or less says the best speed to fly a plane at is 1.5 - 2.5
times stall speed, so a 747 flying at 500mph has to take off at getting
on to 200mph plus. Even with all the flaps and stuff. A 300mph turboprop
need only take off at 120mph or so. And that means less runway: variable
pitch propellors are also very good at low speed thrust as well, so they
accelerate better from a standing start)

A 747 at cruising is alarmingly close to its stalling speed. The air is
thin up there - and that's why they go up there. Less drag.


It's not flying close top its stalling speed AT GROUND LEVEL where it
does its taking off.


Andy


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