Engineering Timelines - The equations of flight

The simplicity of flight
P A N E L F O U R

Human powered flight

Imagine you have a school project to build a human powered plane.

You test your best athlete
and discover that he can turn out
250 watts for a sustained period.
He weighs 60kg. You decide you can
build a plane weighing 40kg
with a finesse of 20.

So your total weight will be
100kg (1,000 newtons) and your
drag 50 newtons (1,000 ÷ 20).

If your drag is 50 newtons
and power is 250 watts,
your speed will be 250 ÷ 50
or 5m/sec.

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At 5m/sec, with a
weight of 1,000 newtons, how big do your wings need to be?

s = w ÷ (0.3 x 1.25 x v²)
= 1,000 ÷ (0.3 x 1.25 x 5²)

= 100m²