Engineering Timelines - The equations of flight

The simplicity of flight
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Weight & Velocity

For a jumbo jet with a wing area of 511m² flying at 900kph (250m/sec) at an altitude of 12km, where the air is one quarter the density of that at ground level, we can calculate its weight like this:

w = 0.3 x 1.25÷4 x 250² x 511m²

= 2,990,000 newtons (300 tonnes)

This is roughly its weight at level flight. Its maximum take-off weight is 394 tonnes.

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Alternatively, we could look at an albatross that weighs 87 newtons and has a wing area of 0.62m² ... Here's how to calculate its velocity:

v² = w ÷ (s x 0.3 x d)
= 87 ÷ (0.62 x 0.3 x 1.25)

= 19.2m/sec (43mph)