by Peter Degen-Portnoy

Created on: January 16, 2009

So just how does a bird weighing 12 lbs (5.4 kg) bring down a 160,000 lbs (72,575 kg) airliner and cause it to crash? What kind of match-up is this anyway?

Ladies and Gentlemen; may I have your attention please?! In the near corner we have the champion of modern mass transportation - the jet engine powered Airbus A320-200, weighing in at one hundred sixty thousand pounds! And in the far corner, representing the Class Aves (birds) and weighing in at twelve pounds, we have a Canada Goose!

The answer is actually pretty simple. The bird, or in some cases, many birds, get sucked into the engines, which break apart due to the presence of foreign objects. It's also called Foreign Object Damage, or FOD. Fortunately, modern aircraft are designed (and tested) to continue flying if an engine malfunctions. Break enough engines though and there just isn't any way to stay aloft. Our example aircraft, the Airbus A320, is a short to medium haul airplane and has two turbofan engines (all commercial jet aircraft use turbofans). Turbofans are seriously cool machines. Very simple and very powerful.

Just like the gas engine in your car, turbofans are internal combustion engines. They draw air in through a fan (that's the part you see when you look at the engine from the front) and feed the air into a compressor. The compressed air, which can be 23 times more dense than the air drawn in, feeds into a combustion chamber, where fuel is added and the mixture is ignited. That's the "combustion" part.

The combustion gases, which expand very rapidly, exit the only way they can - through the back - and enter a turbine, which is a windmill-like series of fans. The turbine is used to drive the compressor (the part near the front, just behind the intake fan). Although turning the turbine uses some of the energy of the combusted gases, there is still plenty to push out the back of the turbofan through a narrowing nozzle, which provides the thrust that pushes the airplane forward.

Not surprisingly, the blades in the fan and turbine are subject to high heat and a tremendous amount of stress. They are made with special manufacturing techniques, which essentially grow the blade from a single metallic crystal. During take off, these engines can hit temperatures of 2,840 degrees Fahrenheit (1560 degrees Celsius). As a means of comparison, water boils at 212 degrees F (100 degrees C), and paper burns at 451 degrees F (233 degrees C). We are talking seriously hot, here.

Time to complete the picture. 80

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