Engineering Timelines

The simplicity of flight
P A N E L T H R E E

Finesse & Power

For the horizontal flight of
a plane, the thrust of the engines
is equal to the drag, while the lift
is equal to the weight. The ratio of lift to drag is known as the finesse.

For a jumbo jet the finesse
is 15 at cruising speed.

If the engines were to run out of fuel
at a height of 12km, a jumbo jet
could rely on its finesse to
glide 180km to a landing.

v = velocity
w = weight (lift)

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How powerful do the engines need to be?

Power is the energy expended in an action.
We calculate the power required to achieve flight like this: velocity by drag

drag = w ÷ finesse
= 300 tonnes ÷ 15

= 20 tonnes
(200,000 newtons)

So, the power required
= v x drag
= 250 x 200,000 newtons

This represents
50,000 kilowatts