Birdstrike, Why Such A Threat? Options

[countryguitar]

As a new (non technical) member I've been itching to know more about the following:
How come, with all the technology on aircraft today, birdstrike is still such a danger?
As someone who knows little about aircraft engines, how come the bird entering the engine is not like a tomato in a blender? Why does the bird not just enter the engine, get chopped up into a million pieces and then afterwards the engine gets cleaned? Yet it's an immediate emergency landing type scenario. Be gentle with me.

[chris_pilot]

Aircraft fly at very high speeds, so a bird strike is like being hit by a feathery missile mid-air... not so good. As for engine related bird strikes, the result can be catastrophic. The blades of a jet fan spin at a very high speed, if a bird flies into the engine it can bend one of the blades, which then bends the next, and that one bends the next blade; causing a cascading failure. This upsets the finely tuned mechanics of the aicraft and can lead to a complete failure.

Welcome to the forums!
Chris

[ChillSpiller]

A birdstrike can be critical to either the structure or the engines but it doesn't have to. I'd say it heavily depends on airspeed, the size and ammount of birds as well as the flight situation eg. take off or leveled flight.
The entire aircraft is a light built structure with a very slim outer shell and so a bird can go right threw it at high speeds or even at 150kts. At those speeds they get hard as rocks. At low speeds a damaged hull isn't that much of a problem but at higher speeds it can turn into a big one if it isn't noticed as the airflow might tear apart more of it. Even windshields aren't always "birdresistant". Just some examples of what a bird can do to the fuselage:´
Damage to horizontal stabilizer, damage to wing, radar cowling, radar cowling2, this birdy desperately wanted to get out
Engines are usually tested to resist birdstrikes but this doesn't mean it won't harm them. Again it depends on size and speed. Small birds usually aren't a big problem as they fly right threw but it will still need thorough inspections as the blades might be deformed and the performance of the engine will go down as well as unbalance will go up which causes a quicker wearout. Heavy unbalance can even rip the entire engine apart. Bigger birds and depending on how far they enter the engine can even loosen blades and destroy the compressor and turbine. If they get stuck in the bypass they might cause a fire. As you see it can be harmless, cause a flameout and powerloss or even destroy the entire turbine section. FOD is something you don't want in an engine as it is precisely built and balanced and even a little disturbance can cause heavy damage at such high rpm. Some examples of how an engine can look like afterwards: Low pressure turbine, fan blade damage, totaled engine, totaled, burnt engine, prop damage

edit: Some further information on birdstrikes
birdstrike research, Certification standards, more research, Video Canada Air Force CT-155 Hawk, accident report CT-155

[Aspiring Boeing ...]

Well simply because the engine has so mush energy being transferred in such a short amount of time and the engines are spinning really quickly (45 spins per second for some engines for a take off rpm at 2,700). Even though the blades are made of titanium they are extremely weak when spinning at this speed, so when throwing something into the engine that is fairly big it can cause a very lot of damage, it would thar some blades off and they obliterate the bird, aswell as the fragments that are broken off from the engines. That is what I am aware of anyway. Some engines spin at 3,000rpm, that makes them even more brittle. If you think about one of the fans being smacked by a heron the blade would come off and damage loads more blades, causing a similar thing to ocur like in a blade off test, see this:http://uk.youtube.com/watch?v=Ek6adm4iV4Y

Seems Chill spiller has beeten me to it -with the vid, but anyway you get the idea.

Regards,
Chris

[ChillSpiller]

[...] if a bird flies into the engine it can bend one of the blades, which then bends the next, and that one bends the next blade; causing a cascading failure. [...]

It's not the blades bending each other but the high rpm that causes a handfull of blades to hit one and the same bird. They deform on impact. The blades usually can't touch each other unless they come apart. A cascading failure can occur from one turbine stage to another though if parts come loose or the bird isn't chicken mcnuggets yet.

[Piltdown Man]

The basic problem is the energy that has to be absorbed by the aircraft plus the residue left behind. Look at an aircraft from the front. Anything that you can see can be hit by a bird. Also many of the air intakes, which may of may not be visible, are capable of ingesting a bird. The heavier the bird, the greater the damage. I have known of nosewheel steering being taken out, birds entering the flight deck via a side window in kit form, pitot head blockages, engine sensors blocked, air-co packs knocked out, wheel brake lines severed, windshields broken and obscured, wiper blades removed, weather radar reduced to components, major avionic malfunctions and sheer fright at the "BANG". Aircraft are pretty fault tolerant devices, but when systems and/or the people operating them are degraded, you are one step closer to something unpleasant happening.

PM

[Aspiring Boeing ...]

It's not the blades bending each other but the high rpm that causes a handfull of blades to hit one and the same bird. They deform on impact. The blades usually can't touch each other unless they come apart. A cascading failure can occur from one turbine stage to another though if parts come loose or the bird isn't chicken mcnuggets yet.

Until they have been through the engine. Just not that salty really, a bit flamable too.

Regards,
Chris