Bird vs. jet engine

By Phil Plait | February 17, 2009 12:14 pm

[Update: A bunch of people have commented that this was not actually a bird getting chucked into the engine, but an explosive charge that dislodged a blade inside the engine. That gives you a more dramatic piece of footage than otherwise, but the results are similar.]

When a bird got swept into the engine of Flight 1549 out of NYC in January, the plane went down. How could a bird do that to a plane engine, you might ask? Well, watch this video to find out:

Remember, the fans inside a jet spin very rapidly, and are under a fantastic amount of stress. Poke them hard enough, and kablam.

My first thought was, "Why this doesn’t happen more often?" but then I realized that birds actually don’t take up a lot of space compared to the volume of space a plane uses, and probably stay away from airports because of noise. I suspect that’s a good thing. [Update: BABloggee "Grey Wolf" informs me it is indeed a problem. The FAA spends as much as half a billion dollars per year on this! Wow.]

CATEGORIZED UNDER: Cool stuff

Comments (77)

  1. calamarain

    It’s not a bird, one of the blades is blown of with an explosive charge as a test.

  2. IVAN3MAN

    Turboprop (propeller) engines are less prone to bird strikes.

  3. OrochiDP

    If I recall correctly, that’s not a birdstrike. What you see is a explosive charge on the blade simulating a blade shattering due to stress. It’s a test designed to make sure the engine contains the shattered blades in the case of a failure.

    A jet engine can suck down many a bird, but bombs they can’t do much with.

  4. Tim G

    The engine goes out but fortunately, the damage is contained within the cowling. We don’t want hydraulic lines severed.

  5. Flip

    Was the bird invisible in this video?

  6. Cheyenne

    That video is going to be turning up in one of my midflight nightmares sometime soon I’m sure!

    I occasionally fly into small regional airport that has a problem with migratory geese landing around the runway at certain times of the year. They have a border collie that goes out to chase them off. It’s pretty cool to see. I like that some multi-million dollar plane and its passengers are being protected by a dog!

  7. Sir Eccles

    @Flip

    No bird was used in that clip. They use an explosive charge inside a hollowed out turbine blade to create a worst case scenario of a blade actually breaking if it had been damaged by a bird strike. Most bird strikes merely make a fine red mist rather than do any actual damage. Problems occur when you hit a flock of many birds or larger birds like geese as in the case of the crash.

  8. DustPuppyOI

    I remember a teaching assistant in my first year’s physics class mentioning how we would stress test turbines by catapulting frozen chickens at the blades.

  9. foolfodder

    Sorry for off-topic post, but I thought people might like to know that Brian Cox is on TV tonight on BBC2 at 9:00. http://www.bbc.co.uk/programmes/b00hr6bk

  10. Sir Eccles

    @DustPuppyOI

    Different test and not what is shown in the video above. Also they defrost the chickens.

  11. Jim C

    Phil,
    I’m a mechanical engineer, and I’d like to point out that this video is not a bird ingestion test. This video is a of blade-out test, where a fan blade is separated (via an explosive charge) from its hub. The lucky blade in your video is the one that is colored differently. A blade-out test is significantly more violent than a bird strike test, as instead of a 4 pound bird, the jet engine is ingesting a fan blade. These blades are quite large and heavy, and of course, are made of of extremely strong metal. What you are witnessing in this video is actually a successful test of the blade containment system, a Kevlar wrap that is designed to force the blade through the engine instead of letting rip through the aircraft’s cabin.

    For an actual bird ingestion test, check out this link (http://www.youtube.com/watch?v=rSafRuLB0c0). While the engine is certainly being damaged, it’s not nearly as violent as the blade-out test. I may not be remembering correctly, but I believe that the FAA requires an engine to run for 20 minutes or so after a bird strike, but only for birds of a limited size (and number). There’s not much you can do if you ingest a flock of geese.

    -Jim

  12. @Sir Eccles
    Egads, imagine what the requirements for aircraft if they had to withstand frozen bird strikes. Good thing we don’t see frozen geese flying around :) :) :)

  13. pjb

    That”s a blade off test. See 4:45 here : http://www.youtube.com/watch?v=j973645y5AA It looks like the same test facility.

    This is a bird ingestion test: http://www.youtube.com/watch?v=rSafRuLB0c0

  14. DTdNav

    Birds are actually often attracted to airports because of the open space and plentiful food. Since the two most vulnerable phases of flight are takeoff and landing, this is a naturally bad combination. We probably don’t see more accidents of this nature because of the great effort that most airports make to keep birds away. They’ll use air cannons, air horns, falconers, weed/grass control, anything to make the area undesirable to birds. The USAF also has the BASH and BAM programs to try and mitigate this threat. (Not a joke. BAM = Bird Avoidance Model, and BASH = Bird Aircraft Strike Hazard).

    The one encounter I had with a duck on takeoff resulted in the loss of one engine. It turned out that the engine just flamed-out from air starvation. No permanent damage was found. They did have to clean out all the fat from around the turbines and fuel nozzles though.

  15. IVAN3MAN

    According to Wikipedia — Bird strike: The first recorded bird strike fatality was reported in 1912 when aero-pioneer Cal Rodgers collided with a gull which became jammed in his aircraft control cables. He crashed at Long Beach, California, was pinned under the wreckage and drowned.

  16. Dave Wiley

    Flight 1549 suffered from numerous bird strikes from geese. One bird strike may or may not take out an engine. I believe the fans are supposed to be able to survive a bird strike or two. This test was for containment. Making sure everything stays inside as the engine comes apart.

  17. Cool video Phil. I remember watching one of those MOST SHOCKING VIDEOS EVAR!!!1! type shows and they had a guy on an aircraft carrier get sucked into a fighter’s jet intake. Fortunately, he survived- his buddies signaled the pilot to cut power quickly (I would think the pilot probably knew something was up). Coupled with the comparatively small size of a fighter jet’s intake, his helmet probably saved his life- it flew off his head and broke the blades before his body got flew in there.

    -I liked watching this particular shocking video show because the people in the videos always survived with relatively minor injuries, it gave me the warm fuzzies.

  18. Angel

    Phil, you know, airports use hawks to keep birds out from planes.

    I read about the explosives used in this video, but can’t help remember the joke:

    -Joe, why didn’t unfreeze the chicken before throwing it?
    :P

  19. T.E.L.

    Let’s say that the relative speed between the plane and the goose is only 200 mph. That’s like dropping the bird from the Sears Tower Skydeck and having it smack into Wacker Drive. An adult Canada Goose can weigh around ten pounds. The collision is a lot of energy.

  20. Adrian Lopez

    That particular video depicts the use of a small explosive to take out one of the blades.

    Here’s a test with dead birds:

    http://www.youtube.com/watch?v=y2OS2pwrZTI

    And here’s an actual bird strike:

    http://www.youtube.com/watch?v=5jN0bqL9cM0

  21. Todd W.

    So, here’s a question: why not put some sort of screen over the intake so that birds can’t get in to muck things up?

  22. I took a whole flock of birds in a KC-135. Those big ole CFM56s just chewed them up and spit them out no problem. Heck, in the cockpit we couldn’t tell which engine(s) had taken birds. When we finally got on the ground, we found all 4 had taken birds. Some of them only needed to be washed out and were good to go.

  23. T.E.L. brings up a good point. Keep in mind that the Columbia was done in by a small piece of fiberglass insulation doing a relative 500 mph.

  24. kcocgib

    video no longer available. wth?

  25. conyx

    I once saw on YouTube a device for a table saw designed to stop the saw instantly. (http://www.youtube.com/watch?v=esnQwVZOrUU) I believe that such a mechanism should be applied too for jet engines, if we can find a way.

  26. Sarah

    “why not put some sort of screen over the intake so that birds can’t get in to muck things up?”

    Cost/benefit trade-off. A screen strong enough to stop a 25 lb bird would be heavy, restrict airflow affecting engine efficiency, collect ice and so need anti-ice … and what if the screen broke? That may be worse than a bird

  27. Elmar_M

    The russians had a pretty cool solution for problems like this on their Mig29 backfire bombers.
    Now russian military airports are messy (and I mean like chunk and rusting aircraft rotting away on runways, oil, animals, etc. The russian reasoning behind that is: In war you can not always expect to have a perfectly clean airport.
    So the Mig29 had air intakes opening towards the top for take offs and landings. The main air intakes are closed up for that time. Once the plane has gained hight, they open the vents. There is still a small risk, but that gets smaller the higher the plane flies.
    I am not sure how applicable that would be for conventional planes though, since their air intakes are much larger (for fuel efficiency reasons).

  28. Nithin Surendran

    Phil, I have the same question as Todd. Why cant we have a protective “metal net” or something to keep the birds out?

  29. JGK

    Why in the world don’t they have some sort of metal screen on the front that would allow airflow but stop birds??? I am trying to think of how that wouldn’t work scientifically but can’t.

  30. Mike D

    You can’t put a screen over the intake because that will build up ice and ice is much worse on an engine than a bird is. By the way, one of our engineers actually forgot to thaw the bird. Needless to say the test was repeated. He made VP before he left for greener pastures.

  31. Todd W.

    @Sarah

    Makes sense. Does anyone know what kind of research, if any, is going into new generation engines that, due to a different design, would not have this problem? Any avionics specialists here?

  32. Al

    Um, the MiG-29 is a fighter: NATO reporting name “Fulcrum”…

    “Backfire” was a much larger Tupolev design, without the intake system described…

  33. Ian

    That is not a bird strike test. That is a blde out test which employes an explosive charge to disconnect a blade. Different. It takes a lot of birds to stop a large engine.

  34. Murff

    Bird strikes are not generally dangerous, as mentioned before, only large birds or flocks are dangerous. There is really no way to “bird proof” an engine. Jet engines are quite resilient as well. There are many engines flying today with damaged compressor blades as well as some with missing blades. Further back in the compressor the blades are actually quite small. The engine I currently work has 9th stage blades that are less than an inch tall (not including the root). There are limits when inspecting and we are allowed 3 blades to be missing at that stage as long as the are not in a row and the hub is not damaged.

    I like jet engines :)

    @Chemist – in that Navy video, the intake had a splitter near the fan, the guy caught the splitter with his shoulder. A flashlight and possibly his helmet came off and went through the engine, you can see the sparks fly out the exhaust. The risk those guys take doing night ops on a carrier deck are amazing.

  35. Sir Eccles

    Hmm, perhaps someone could design a bird powered engine. A couple of circuits of the airport to suck up some fuel then off you go.

  36. Todd, avionics refers to the instrumentation used in aviation (radars, radios, TCAS, etc.). Perhaps you were looking for Aerospace engine experts? Engine design is ALWAYS something the folks at GE, P&W, RR, etc. are looking at. But as Sarah said, it’s all a cost analysis going on there. Having TWO engines is really the best safety device we’ve come up with. Heck, even in the 4 engine monstrosity of the KC-135, I’ve done a “single engine” approach (in quotes because it was simulated with three in idle).

    The chance that BOTH get taken out by birds is very small, and most aircraft can fly with just one engine. The recent example is so special not because he landed it safely on the Hudson (which was quite a feat, due credit), but that both engines were taken out.

    Of course, engineers and designers are always looking at better and more efficient solutions. Don’t worry Todd, they are looking at making airtravel almost as safe as a General Products Hull. ;)

  37. Good call Ian!

    The engines are under huge stresses, but it does take a lot for an engine that large.

    When I was in the Coast Guard there was a story going around the airstation that when one of the Chiefs was younger he pointed the stream from a fire hose directly at a T-58 turboshaft engine (pretty small engine; intake was about a foot or so) when the compressor was turning (just for washing, no ignition) and the compressor latched onto the water stream and screwed itself out of the engine.

    We never found out if it was true, but, man, that would have been something to see.

  38. Todd W.

    @Larian

    Thanks for the correction and the added info. Clearly, I know nothing in this field.

  39. Phil,
    See this:
    Why Birds Collide With Airplanes
    from the Boston Globe (Registration Required)
    While delivering a lecture at the University of Alaska, Fairbanks, years ago, I was asked to address a group of students who had recently lost their fathers in a military airplane crash at nearby Elmendorf Air Force Base. Their jet had been brought down because of a “bird strike” – birds flying into the aircraft’s engine. Twenty-four people died.
    … A student asked, “Why do birds collide with airplanes, and how can we prevent such collisions?” That is a question that the aviation world has tried to answer for years.
    …In the 1980s, before my trip to Alaska, I undertook a biological study of why birds cannot get out of the way of aircraft. My investigation took me from Logan International Airport to a sea gull nesting area on Monomoy Island.
    http://snipr.com/bzdnh

    Regards,
    Don O’Shea

  40. Calli Arcale

    I’ve been told (can’t remember where at the moment) that depending on the test, a frozen chicken may indeed be used. It produces different but still useful results when compared to the thawed chickens, which are different than the whole (not gutted, not de-feathered, etc) birds.

  41. Retrogarde

    I spent some time at friends living at the border of Schiphol airport, Amsterdam. My friends lived within a few hundred of meters of a runway. There were plenty of birds around that were very relaxed with the ongoing, deafening air traffic. There were birds sitting on the lamp posts while screaming jets came in. I guess the problem (most of the time) with birds and airports is flocks of birds.

  42. Conyx sez:
    I once saw on YouTube a device for a table saw designed to stop the saw instantly. I believe that such a mechanism should be applied too for jet engines, if we can find a way.

    That’s a terrible idea. “Let’s just instantly stop the engine in the middle of the air”. Sure, the engine stops turning, but at the rate it’s going the bird is already a red cloud. Basically, you’re saying that every bird strike should become an emergency of the scale of flight 1549.

  43. Elmar_M

    @Al
    Yes, the Mig29 was called Fulcrum and not backfire. That is not what I meant though. What I meant was, that it was designed as a backfire “fighter- bomber” (heavy fighter aircraft). It made very limited use of electronics and relyed on tube technology where possible. That way it would still fly after an EMP. The air- intake design also helped, since it would have allowed it to take off from a partially damaged runway in case of a US first strike.
    So yes, it was not the NATO designation, but it was its intention by design. I hope I made myself more clear this time.

  44. MadScientist

    I like the other video with an actual (frozen?) bird test – the turbo fan’s blades sure flex – and then flex right back and keep on running. No shots of the actual turbines themselves though. :( Surely there must be some – these guys take the engine apart and inspect every little piece.

  45. justcorbly

    Once upon a time, I knew an Air Force officer assigned to a lab doing work on collisions with flying birds. He claimed it was part of his job to buy lots of frozen chickens for the tests.

  46. Guysmiley

    That’s a terrible idea. “Let’s just instantly stop the engine in the middle of the air”. Sure, the engine stops turning, but at the rate it’s going the bird is already a red cloud. Basically, you’re saying that every bird strike should become an emergency of the scale of flight 1549.

    Exactly. What he didn’t mention is that the tablesaw is junk after that safety mechanism kicks in, it’s an explosively fired brake.

    There’s no such thing as a “bird-strike proof” engine, period. Honestly the best protection is having engines that are widely separated. This of course leads to problems with engine-out yawing force, but that can be handled by a sufficiently large rudder and limiting the max thrust of the remaining engine.

    The accident with flight 1549 was a total freak occurrence. And it didn’t happen right after takeoff, it was minutes and miles away from the airfield, so these people pimping anti-bird solutions around airports are totally full of it.

  47. pjb

    Several of the people suggesting a screen over the turbofan are severely underestimating the drag that a screen can produce at those airspeeds.

  48. alfaniner

    Memo: Don’t use frozen chickens.

  49. MadScientist

    Hmm … screen over the turbofan to keep birds out? Of course! All jet engine designers over the years must have been morons and never thought about such things. Duh. Restricting the air flow only leads to lower efficiency, which means bulkier engines, more fuel, fewer passengers. Think about it: the screen must be rigid enough and have a fine enough mesh that a bird hitting it at, say 250 knots doesn’t get julienned and go through anyway and the mesh of course shouldn’t buckle and damage the fan; I don’t know if such conditions are even physically possible. I don’t know how you’ll cool the jet engine either; at the moment the turbofan pushes air around the engine, which fits within the cowling which is that big cylinder that most people think is actually the engine. The air flowing around on the outside of the engine is the ‘bypass’ air – it gets warmed up by the incredibly hot engine and a portion is diverted into the aircraft to maintain the cabin pressure – so restricting the air flow has a lot of unhelpful knock-on effects. Thanks to all the work on engines over the years, bird strikes are really not much of a problem; they happen all the time and you only see examples of the worst cases on TV. A huge flock of birds taking out both engines at once – that’s so unusual it may very well be the only case on record.

  50. Luke

    You can’t use a screen for the same reason why you can’t cover the grill of your car. Engine overheating and a poor air/fuel mixture are major problems and the last thing you need is the engine to choke out at 30,000 feet. Also most planes can operate on one engine if they have to declare and emergency, this strike took out both engines which is even rarer.

    For the screen issue again, the mounting assembly would have to be very very tough to take a strike of a 10+lb bird at speeds up to and over 200MPH, also the screen would act like blades and just send small chunks into the engine which could gum it up even more.

  51. Murff

    As a general number, 80% of the thrust off a high-bypass engine (used on airliners) comes from the fan. Most birds strike the fan and centrifugal force shoots the remains to the outside and out the back of the fan. Only a small opening near the axial shaft leads to the core compressor. This is why smaller birds really don’t cause a problem, and even a single large bird is not catastrophic. The fan blades are generally a titanium – nickel alloy and can shred any bird pretty easily, it’s the bones and beaks that get into the core that tend to “shell out” the engine.

    Need to get a sensor system that can pick up the birds within a 100 yards radius, track them, and if any get close have some lasers take them out. Hmmm, what’s the name of that guy that comes up with over complicated solutions? :)

  52. Robbak

    Re: the finger-protecting table saw
    While the saw is not junk after the system fires, it does need repair.

    The system uses a spring-powered brake – basically, a spring clamp held off by a thin fuse wire. The system detects the change in impedance on the blade when it touches something moist (a finger, or, in the demonstrations, a sausage), and dumps a spike of current through the fuse wire, melting it, allowing the clamp to close. I believe the rotational force is used to wedge the brake on further.
    Resetting consists of replacing the fuse wire.

    The system does have one flaw: It needs to be disabled if you are cutting damp timber or metal. That means it needs to be disableable, which is a problem for any safety system: The user will, or course, forget to rearm it.

  53. @Murff do mean Rube Goldberg, click my name for a wiki link.

  54. Chris

    When I was a kid I read one of my dad’s books: “Grand Old Lady” by Mosely and Glines (hey, I found it on Amazon, but not including the link to avoid moderation), written in 1959.

    It is the story of the DC-3/C-47, a very successful aircraft design.

    One of the most striking pictures in that book was of a the head and long neck of a goose sticking out between the foot pedals. That much had made it through the fuselage. It is a very impressive illustration of bird strike.

    (by the way, there is a joke somewhere about someone using frozen chickens for bird strike tests, I have since forgotten it)

  55. Alan

    New Scientist this month has an anecdote in Feedback on the number of airplane strikes on animals in the USA 1990 to 2008.
    see “Danger: airborne turtles”
    http://tinyurl.com/dmbeyf

    Keep the interesting blog going, Phil.

  56. Belgarath

    Hi Phil,

    Bird strikes happen quite regularly, the thing that caused this problem was the DOUBLE ENGINE strike. While bird strikes happen probably daily in the US, a double bird strike with the birds spaced such that they hit both engines simultaneously is incredibly unlikely.

    Additionally, in this case, the birds were apparently of the very large variety (Canadian Geese)

    In this case, there were two factors that turned the ‘fairly common’ bird strike into a very uncommon accident. First, the double engine strike and second, the size of the birds. The combination of these two things are apparently what caused the accident. Of course, we will have to wait until the NTSB report comes out to know the cause of the accident.

    I fly the exact same aircraft as this one, but for a different airline. (I’m in and out of LaGuardia 10 times or more per month) I suspect that when we hear from the NTSB it will turn out that they hit more than one bird in each engine.

  57. Sweet post! But of course I miss the aviation discussion by twelve hours. :(

    Lots of good responses here, so to quote Mr. James Carville I’ll say

    “Oh… It… We… have no response. That was perfect” :)

  58. CLM

    I saw what a turkey buzzard did to an A-7 jet engine in 1988. Luckily the pilot safely returned the plane to the airfield shortly after the strike. For those that aren’t familiar an A-7 is a single engine fighter with a large under nose air intake. Large enough for a person to get sucked into should they get to close on when one is running on the ground. Maintenance crew found a piece of broken fan blade a few inches away from a fuel line inside the fuselage. When the blade piece didn’t have enough energy to go all the way out of the plane it fell inside next to the fuel line. It could have easily torn through the housing and fuel line directly.

    I inspected the air intake and on the bottom lip was something. It was a smear of bird good with feather flecks in it. Along the inside of the long intake was a track where the bird had left as it slid into the engine. After the engine was removed you could see where several fan blades had been broken off by the bird. This actually protected the rest of the engine. When I looked at the exhaust end of the engine I saw a few white streaks around the cowling.

  59. One item not being mentioned in the saw-blade discussion is rotational inertia (angular momentum). Stopping a 1 lb (half Kg) blade spinning at 2,000 RPM isn’t too bad since it’s attached to a 100 lb (40 Kg) table saw. The transferred momentum might make the saw jump up a few inches, but then it’s over. Now try stopping a turbine/fan assembly weighing thousands of times more spinning ten to fifty times faster. Whatever that break mechanism is attached to will snap like a twig.

    In the video above the momentum from the spinning parts was distributed all over the housing in both space and time by the shattering parts. In the saw blade analogy it’s all together all at once.

    – Jack

  60. The thing I found fascinating is that the stroboscopic effect of the video makes the fan appear to be turning slowly in the opposite direction from its actual rotation. Bizarre.

  61. flynjack

    In combat flying there is the axiom “big sky little bullet”, the corallary in civilian aviation is “big sky little bird”. Despite these two axioms, I have been hit by both while flying, and most frequently by birds. We share the same airspace and sometimes the same piece of sky at the same instant in time. I have injested birds in my engine and had impacts on the wings and windscreen, though none have penetrated my cabin. Hard to see them at night and most of my strikes occured at night, usually I have been able to see and avoid during the day. A little hard to yank and bank a Airbus full of passengers though. Bottom line is it happens more frequently than most travelers are aware, and in the case of the Hudson incident it was just really really bad luck( and very good luck to have such a capable skipper to put it down so perfectly in the drink).

  62. Eric

    Doesn’t Professor Jones down a BF109 by startling a flock of seagulls in Indiana Jones and The Last Crusade? Who needs SAMs.

  63. Grump

    Now that everyone has had his/her say on this topic, let me make a late addition which no-one will ever see. :-)

    Frozen birds do more damage than thawed ones? Nonsense!* Haven’t you people ever seen the chicken gun? It has appeared in numerous Mythbusters episodes, but it was created to test this myth. As best as Jamie or Adam could tell, there was no difference at all. (At least in the case of a hit to the bodywork. They didn’t test the much-more complex and expensive case of turbine injection.)

    I like turbines. Partly because of their simplicity and elegance (at least in comparison to the horrifically ungainly internal-combustion piston-engine) and partly because of the impressive speeds and temperatures involved.

    One of the ironies of engine-making is that turbines are simpler and have far fewer moving parts than piston-engines, yet are more expensive than piston-engines, because those fewer parts have to be made with greater precision, and from much tougher (i.e. more expensive) materials, just to survive the stresses and temperatures.

    The first (semi-)successful jet engines, the German ones from WWII, could not survive bird-strikes. They could barely survive striking air! They had a mean running life-time of something like 10 hours! They had been made of inferior materials, simply because Germany didn’t have enough of the “good” metals and alloys to go around. The cheaper stuff either melted in the heat, or were stretched out by centrifugal force so much that they hit the sides of the engine and got stuck! Or the blades simply broke loose randomly.

  64. Grump

    “ingestion”, not “injection”! D’oh!

  65. Doug

    “The FAA spends as much as half a billion dollars per year on this! Wow.]”

    No, according to the article, that’s how much bird strikes cost aviation in terms of damage and repair time. The FAA (or separate airports) hire falconers and take other steps, but I doubt that costs more than a small fraction of the aforementioned half a billion per year.

  66. A question for animal lovers. Why are the guard dogs that are used to scare away geese trained to not only chase and not kill an occasional goose for food? Those dogs are presumably being fed some sort of animal protein; so training them not to kill the geese is simply relocating the animal killing to a different place, and it’s also resulting in greater net CO2 generation because of the processing and transport of their food.

    Also – won’t the geese eventually figure out that the dogs are toothless?

  67. Matt

    I think the youtube video posted by Phil should be viewed next to everyone’s favorite fight scene from the first Indiana Jones. We all remember how that ended.

  68. Caleb

    Many airports deploy various measures to repel local bird populations (sound beams, explosive flares, ground netting, etc.). Since birds generally (universally?) have their eyes positioned on opposite sides of their head, they lack stereoscopic vision that many other animals (like us) use to judge distance and thus rely on parallax to judge distance. In the right circumstances, birds can believe they may be farther away from a plane than they actually are.

  69. Due to the recent plane crash, there was a AMAZING article in Salon regarding the trouble with keeping birds away from airstrips. In specific, a Salon reporter spent a few hours talking to the guy who has this responsibility for San Francisco’s airport.

    I’m not even remotely surprised crows are his worst nightmare, they’re devilishly clever.

    http://www.salon.com/env/feature/2009/02/06/birdstrikes/

    Incidentally, this is one of the better birdstrike videos on youtube: http://www.youtube.com/watch?v=uYNpB-8_BSo

  70. Negatron

    Just two weeks ago we were on short final into SLC, I was flying pilot, left seat crj200. At about our 500 foot call, a flock of geese suddenly veered up out of the right and would have been in prime position to flow right through the right engine. i got to do a little fun low level evasive. Birds are everywhere around airports, especially the ones I fly mostly into in the west, with no pest control. I have been flying regionals for three years now and not a single birdstrike yet.

  71. Keith

    When I researched bird strike issues with wind turbines some time ago I learned something interesting. Unlike ourselves, birds see in a sort of frame by frame type vision. Similiar to the what you might expect from a 1920-30’s film. Their brains analyze each frame to the one before it and look for relative motion. In the case of the wind turbines they see what appears to them to be a open space between the blades and figure coast is clear. By the time they get to the blade, whack.

    I suspect that the same relative motion issue could be a problem with aircraft in general and if approaching straight on they may not perceive the motion until, at speeds of the aircraft, it’s way too late.

    Just a thought.

  72. ross w. cusimano

    as an Ex military fighter pilot our birds had intake engine screens. screens were in place at lower altitudes then lifted at higher alt. they never caused icing problems. Why are commercial airlines permitted to operate without engine intake protection. (cost consideration)

    Ross

  73. Tom E.

    Okay, please shoot this down! How about 4, 6, or 8 very strong(strong make of metal), very thin, rods attached to the rim of the engine and protruding out in front at some engineer determined length, and meeting directly in front of the center of the engine. Ice might be a problem but the air intake would prevent it once the engines started and so could be deiced or inspected before take-off. These bars would deflect most large birds or large multiple birds from entering the engine. Again, if ice was a problem they could be heated. I know it is a version of the screen idea but they make thin, metal rods out of some extremely strong materials now and much of the intake is by-passing the rods. The ultimate questions would be the optimal spacing which would determine the number of rods and at what length.

    It would not be 100% bird proof but would eliminate many decreasing the odds.

  74. USAF Safety

    @ Tom E.

    We’re still talking about a huge decreasing in efficiency. Nothing can be placed in front of the fans, so let’s consider that option dead. Many options have been discussed over the years, but none have turned out to be plausible. At this point the BASH programs have become the primary means for dealing with this problem. With the current engine design there is really no good way to engineer a solution. The FAA is looking at redesigning the engines to allow for an engineerable solution. If you do a patent search you’ll notice multiple patents for this idea, but nobody seems to be getting rich from it. At this point it’s not a realistic solution.

  75. HIAWATHA JOHNSON

    It seems so obvious that I am sure there has to be a good reason it would not work.

    But

    Why aren’t jet engines equipped with cattle guards?

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