Friday, Oct 24, 2014
The housefly will laugh. “You call that flying? Watch me!” Some other time surely! The housefly will laugh. “You call that flying? Watch me!” Some other time surely!
Written by Ranjit Lal | Posted: April 6, 2014 1:36 am

Even now, I can happily spend the whole day watching planes land and take off. It really is astonishing how 500 tons of shiny, roaring metal races down the runway, and then finds itself rising into the sky, lifted by nothing more than air. And those heart-stopping landing moments as it drops lower and lower, the puff of smoke and squeal of rubber as it touches down with those flimsy looking wheels. And all that noise and drama — it’s a spectacle every time.

And then there are birds… We don’t blink when 500 pigeons do a mass vertical take-off (in stupid panic), or when a black kite dives down between a mess of high-voltage wires to snatch up a dead rat from the middle of a road. We are, of course, still deeply envious of their ability to fly, which is why we keep them cooped up in claustrophobic cages as “pets”.

But we observed what was going on, and down the eons, the heavy brains got to work — Archimedes, Aristotle, Galileo, Leonardo Da Vinci, Isaac Newton, Daniel Bernouilli, et al. We know about lift and drag and thrust and angles of attack and aerodynamics and aerofoils.

It’s all very complex physics that gets more intricate as you delve deeper. But there’s a simple experiment I never tire of doing, which will bring a smile to your face and a lift to your heart, and that explains some part of it. Hold a flight feather absolutely horizontally (a zero angle of attack as they would technically say), its curved, convex surface facing upwards.

Then whisk it swiftly forward… What happens? Yes, the feather wants to fly — it rises! You can understand this happening if the feather was held at a slight angle — as pressure would build up under it due to resistance — but with a flatly held feather? Nothing like this happens with a flat piece of paper. Ah, but the feather has a convex surface and what’s happening was explained by the good Dr Bernouilli. Because the topside of the feather is curved, the air rushing over it has a longer distance to cover and must speed up and, in doing so, exerts less pressure than the underside, thus resulting in lift. It’s called the Bernouilli principle and is why aircraft wings are so shaped, and is responsible for providing 2/3 of the lift experienced by a wing. The rest is provided by the angle of attack — the angle at which the wing is slanted.

We gawp at air shows as fighter jets perform breathtaking stunts, but we’re still top-gunned by birds. Jet engines gulp vast quantities of aviation fuel, produce shattering noise, and most planes need runways and elaborate navigation systems and gigantic backup. Birds tank up continued…

comments powered by Disqus
Featured ad: Discount Shopping