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)
The Equations of Flight
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