What is the air-speed velocity of an unladen swallow?: the impact of birds on aircraft

The best coverage of the science behind the apparent "bird-strike" cause of yesterday's USAirways miracle on the Hudson can be found at Scientific American online:
It basically comes down to the physics equation for kinetic energy: Energy is proportional to mass times velocity squared. The velocity of the aircraft allows for the impact of this feathered bird to generate enough force to cause an engine to malfunction. [A 12-lb Canada goose struck by a 150-mph aircraft at lift-off generates the force of a 1,000-lb weight dropped from a height of 10 feet, according to birdstrike.org.]

Yes, this phenomenon is important enough to warrant a site called birdstrike.org and this past year's 10th meeting of Bird Strike Committee USA/Canada in Orlando.

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i HATE all Canadian Terrorist Geese!

Can we PLEASE take them off the endangered species List now/

All they do is poop all over my kids baseball fields. Oh, and fly into airplanes.

In ballistics terms, that goose is an 84,000 grain bullet at 220 ft/sc, giving kinetic energy of 9026 ft-lb and momentum of 82.06 lb-sc.

For comparison, a .50 BMG (Browning Machine Gun) at the muzzle might be an 800 grain bullet at 2895 ft/sc, giving energy of 14885 ft-lb and momentum of 10.28 lb-sc.

Yeah, you don't want to be in the way of either.

By Nelson Muntz (not verified) on 16 Jan 2009 #permalink

We have aerospace customers who simulate these things all the time. I think a bigger issue, is that one or more turbine blades are usually dislodged within the engine. The rotary energy in the turbine is much greater than the energy of the initial impact, and because the dislodged blades disrupt the smooth spinning will be quickly dissipated.

bigTom has the issue right. A bird striking an airplane is generally harmless to the airplane (though not to the bird) because the airplane is so much bigger and is designed to withstand such collisions. The exception is if the bird gets sucked into the engine, because it can dislodge a blade on a rapidly spinning fan. If that happens, the suddenly unbalanced turbine fan can be thrown off its axis in the attempt to conserve angular momentum. Worst case scenario: an uncontained engine failure (fortunately, that did not happen here). More likely result: engine shutdown. Having that happen to one of your engines (even an uncontained failure) is survivable, at least long enough to get to some kind of airport, and is a scenario that all commercial pilots train for. Having that happen to both engines means that you're basically a glider, which is why the pilots opted to ditch in the Hudson rather than risk a diversion to Teterboro (which they probably would have done if they still had one engine) and crashing into a populated area if that didn't work.

By Eric Lund (not verified) on 16 Jan 2009 #permalink

Re: Bird-strike kenetics: While I'm not a aeronautics expert, I believe the basic physics problem is not just the forces of the bird's mass X velocity vs that of the aircraft's... but rather vs the mass X velocity of the turbine fan blades (relatively light mass but extreme velocity) which would account for explosive forces.
Am I right?
Tony

Amen to the first post! Those buggers are threatened? I would have never deduced that from the flock of them hanging out outside my old office and pooping on the sidewalk and not being scared enough of people to move when one revs a car engine in front of them. I was starting to wonder what happened to the Victorian roast goose dinner! They're so plump, they've got to be tasty....maybe with a little Sichuan pepper and chilli oil?

By Foiegras4all (not verified) on 17 Jan 2009 #permalink

I think a bigger issue, is that one or more turbine blades are usually dislodged within the engine. The rotary energy in the turbine is much greater than the energy of the initial impact, and because the dislodged blades disrupt the smooth spinning will be quickly dissipated. basically comes down to the physics equation for kinetic energy: Energy is proportional to mass times velocity squared. The velocity of the aircraft allows for the impact of this feathered bird to generate enough force to cause an engine to malfunction.
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By neetugarg37 (not verified) on 21 Jan 2009 #permalink

Motion calculations for kinetic and potential energy lead to the total energy of an object, but if we wish to define that function for quantum mechanics and relativistic effects to achieve an exact answer there are several features to note. If a goose is equated to a photon, it's path and energy may be modeled to produce the impact's simulation for engineering design purposes of strict calibre.
That sort of analysis looks at energy in terms of ultramicro waveparticles with relationships to smaller force field particles. The collision's imaged reconstruction views the contact instant on a picoyoctotechnical scale to define how the feathers and fowl mass act to transfer momentum to the aircraft by exertion of force by energy fields. ( While crude symbolic kinetic energy transfer may be commonly talked about, it never actually occurs, except is superballistic events. ) That is true because the incursion of a material's energy and force fields into another object's matrix of fields will generate the repulsive reaction in a chain of events which depend upon the chemical composition of the objects.
Strict Lorenz-Einstein technicalities of kinetic bodies may be found at http://www.symmecon.com , along with views of the mathematical images of the h-bar and temperature particles.