Why dont planes have filters or grills over the engines?

Question

the hudson river crash was caused by a bird flying into the engine and the story of the man who got sucked in the military planes engine. would a big filter work to prevent objects from flying into the engines?And why hasnt it been done yet?

Answer 1

I used to be stationed on the USS Constellation. We had to walk the flight deck between flight ops. Every little spec of debry had to be removed, to protect the jet engines. We called it FOD (foregin object damage).



Miltary personel's jobs often require them to get very close to jet intake of running engines while doing there jobs, make this kind of accident a risk, when all saftey regulations are not followed.



http://www.brooksidepress.org/Products/OperationalMedicine/DATA/operationalmed/OperationalSettings/Naval%20Aviation%20Medicine/FlightDeckSafety.htm



Here is the guy getting sucked into the A6. It is low resultion black and white flight deck video. Not very graphic, but scarry.

http://www.youtube.com/watch?v=5jxcSY1AwrM







Jet engines need unrestricted air intake. The engines would not get enough air with air grill. The problem get worse at lower speeds and higher altitudes.



At very low speed you would just have a flock of brids, held to the grill by suction, stalling the engine. At flight speed, your grill or mesh be more junk being sucked in the engine. If the grill did not break, you would have bird mush destroying the engine.



The grill would never be strong enough, and would cause a lot of turbulance.





Here is some info on turbofan jet engines.

http://science.howstuffworks.com/turbine6.htm

Answer 2

First, the hudson river incident was not "a crash". It was a controlled ditching into water, because the pilot made the assessment that he could not reach any other safe landing area.



Second, was not caused by "a bird flying into the engine", it was caused by a large flock of birds and several birds flew into both engines at the same time and caused both of them to shut down. All jet engines are designed and tested to survive bird strikes, though the engine may shut down if the bird is large enough. In the Hudson crash that happened exactly as it should have done. Obviously a plane with no engine power can only fly for a limited distance before landing. The plane remained completely under control at all times, so there were no safety issues caused by the engines not behaving as they were designed to behave.



There is no way you could make a grille strong enough to stand the force of say a 10-pound bird hitting it at several hundred miles an hour. The best it could do would be chop the bird into slices like a vegetable slicer. The fan blades in the engine do that already when the bird hits them, so having a grille would make no difference.



In any case, you would need a grille that covered the entire aircraft, not just the engines. Bird strikes on the wings or the pilot's cockpit window could also do a lot of damage, except that those parts are also designed and tested to withstand such impacts.



I don't know the particular military incident you mentioned, but most likely either the person sucked into the engine or the plane's flight crew were not following the proper procedures. The best way to fix that problem is for the military not to recruit stupid people.

Answer 3

Remarkably enough, the Navy person who was sucked into the engine, survived.

Modern jet engines are built specifically to minimise damage from a bird strike.

The Hudson River incident was multiple Canada geese. Even if the engines had been restartable, there was no time to go through the restart procedures. The pilot made the "best choice" decision, and felt he would cause less fatalities either in the aircraft, or on the ground, by pancaking into the river. He very soon realised he would never make a landing field, and trying anything else other than the river would certainly have been worse.

He did a remarkably fine, cool- headed approach and execution. He followed all the rules.

A similar attempt to land into a rough ocean would most probably have been much more serious.

Filters are NOT practical, and would make no difference.

You have probably read or seen the story of the British Airways 747 that lost all 4 engines after flying into the pumice dust cloud from a volcano. They followed all the rules. After some considerable time and multiple tries to restart the engines, the crew managed to get all 4 running again, in time to gain height and reach the nearest airport. One engine did fail again when they flew back into the dust cloud, but they landed safely, even with poor visibility through the front due to the abrasiveness of the dust. They also had NO approach height help, they were flying by directional beacon, speed and altimeter only, right to touchdown!

What they DID have was good altitude when the failures occurred.

The aircraft was stripped of most of its paint as well.