Thursday, October 2, 2008

Myth busted? Pterosaurs 'too heavy to fly'

Sci. & Tech.
Myth busted? Pterosaurs 'too heavy to fly'

London (PTI): Pterosaurs, the ancient reptiles which could grow to the size of small aircraft, were too heavy to fly even with their massive wings, a new study has claimed.

Pterosaurs, which existed alongside the dinosaurs and vanished along with them around 65 million years ago after a possible asteroid impact, were often known as the terror of the prehistoric skies.

Now, scientists in Japan have found evidence that the pterosaurs struggled to get off the ground because they could not flap fast enough to create the thrust that's required to keep their enormous bulk airborne.

According to lead scientist Katsufumi Sato, the largest animal capable of soaring across the sky unaided could have weighed no more than 40 kg or the size of a labrador dog, 'The Daily Telegraph' reported.

They have based their findings on an analysis of data on the flight of 28 birds from five large species, including the world's biggest, the wandering albatross. They calculated that it was physically impossible for them to stay aloft.

In fact, Prof Soto and colleagues travelled to the Crozet Islands -- halfway between Madagascar and Antarctica -- and attached accelerometers, devices the size of AA batteries which measure thrust, to the wings of the birds.

Unlike turkeys or bustards, whose short wings are good for quick take-off but not for soaring, these larger birds fly long distances using dynamic soaring -- they ride changing wind currents without moving their wings.

But when the wind dies down, or blows at a constant speed, they have to flap or be pulled down by air resistance and gravity. The maximum speed a bird can flap is limited by its muscle strength and decreases for heavier species with longer wings.

Prof Sato concluded that animals heavier than 40 kg would not be able to flap fast enough to stay aloft. And, this would explain why the wandering albatross weighs only 22 kg.

"A bird weighing close to 40 kg would be incredible unstable and would not have a safety margin to fly in bad weather."

Story courtesy of The Hindu News@

Image courtesy of Flickr @

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