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Birdstrike Jet/prop/research/opinions?

Thu Nov 07, 2002 7:46 am

Is there any research, or what is your opinion, on the vulnerability of jets/props to the affects of birdstrikes in terms of engine failure? This post is prompted by the recent tragic crash of the Luxair Fokker 50 were a birdstrike has been proposed as a possible cause of the accident.
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RE: Birdstrike Jet/prop/research/opinions?

Tue Nov 12, 2002 3:25 pm

I have heard of engineering companies that fire dead turkeys from an air-cannon into running engines. I am not sure if it is to see if the engine will continue running, or testing the fan-blades resistance.

Remember when sex was safe and flying was dangerous?
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RE: Birdstrike Jet/prop/research/opinions?

Sat Nov 16, 2002 1:13 pm

Well, just yesterday, I killed a poor bird...

I was taxiing on the active for takeoff at the command of a Let 410 (turboprop commuter, plenty of pics in on some caribean island, when a flock of birds that rested on the runway took off (without being cleared!!!) in front of us. All of them (beautiful long necked white birds, about 3 feet long in all and weighting about 7 to 10 lbs, I guess) flew to the right to avoid the plane except one poor sleepy animal that went left, right into the left propeller as the plane moved forward. All I saw and heard was a small explosion with a muffled "poof" and white feathers flying everywhere. The prop was in the beta range at 1500 RPM. The poor thing didn't stand much of a chance... The prop was absolutely intact.

I have hit other birds before, the worst case being a big crow (about 20 lbs) that hit the wing leading edge at about 120 kts, right after take off. It left it pretty bent up, but it flew back just fine, unlike the bird...

I suppose the real danger isn't your isolated "one bird" collision. Now if your ran into a whole flock of them, that could be some real trouble. Turboprop engines' air intake are usually protected by the prop "milkshaking" the bird before it could enter, but I've been told the shock can sometimes trigger the autofeather (ironic term, in that case). Imagine that happening to both your engine at the same time, right after take off...

I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
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RE: Birdstrike Jet/prop/research/opinions?

Mon Nov 18, 2002 12:41 pm

An Eastern Air Lines Lockheed Electra in Boston many years ago ran into a large flock of starlings just after takeoff....and three engines failed.
Crash and burn was the result.
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RE: Birdstrike Jet/prop/research/opinions?

Mon Nov 18, 2002 1:05 pm

I hit a bird (or actually the bird hit me) in a Cessna 152. My fear was that it actually broke the prop but nothing was broken except for the bird. What was scary is that I never even saw it at all, just heard the big THUMP it made hitting the plane.

RE: Birdstrike Jet/prop/research/opinions?

Mon Nov 18, 2002 1:18 pm

Dear Ukair -
Here are some facts, and opinions about birds... first of all they belong in my pot on my stove, not in MY engine - sorry, ornithologists and bird watchers...
Birds love airports - they assume the runways are for them as well, and all these wind socks, and lights to sleep at night, its nice.
But they have nasty habits of taking off at the same time as airplanes... What I heard is to use the weather radar to "scare them away" during the takeoff roll... ok, fine - but a question - will they takeoff because they are scared by the radar... maybe would they stay quietly on the ground next to the runway if not scared by radar transmissions...
Further, I was told all birds takeoff against the wind (they know that better than some of our friends here)... so a plane scares them, with radar or not, they get scared, and if the wind comes from across the runway, a crosswind for our airplane, but - "kwack kwack VR V2" for birdies, will be called right at the time they cross the path of the metal bird... and visit the compressor...
I had a 747 engine failure - # 4 - I think was a pterodactyl (call sign -heavy), that entered the engine right at rotation... engine failed within seconds, we heard compressor stall, engine fire light ON, we took care of check lists. The place we were had no maintenance, so we decide to go some 400 NM away, 1 hour flight... There was a problem there as well, does not go exactly like in simulators... with a few fan blades busted... N1 rotating fast although we were flying at speed just slightly above flaps retraction, the engine nacelle was shaking badly (and the outer wing part as well) - so we did reduce our speed to reduce the vibration and N1 rotation... flew with some flaps until we reached our airport...
When an engine fan windmills fast (bird strike damage, a few blades missing) this creates quite an unbalanced rotation... the reason the nacelle was shaking like that...
I hate chicken anyway  Smile
(s) Skipper
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RE: Birdstrike Jet/prop/research/opinions?

Tue Nov 19, 2002 3:09 am

On the Eastern Electra accident at Boston. The airplane hit a flock of starlings and ingested them into 3 engines. The engines did not fail; what happened is that the engine RPM decayed to a point where the generators dropped off line, power was lost to the hydraulic pumps, and they didn't go to manual operation in time to save the airplane. At the base of the pedestal are 3 panels in the floor, you have to open these panels and pull the handles which disengages the boost packages and allows you to fly manually. It's awfully heavy on the controls, but do-able. Now, on take-off those panels, are left open until at a safe altitude and then closed to allow for a quick access. Pulling the deboosters and operating the airplane was part of my training as an FE on the L-188.
Capital Airlines lost a Viscount over Maryland after an inflight hit by at least 2 geese on one horizontal stabilizer, which caused it to fail. That occurred in the late '50's.
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RE: Birdstrike Jet/prop/research/opinions?

Tue Nov 19, 2002 8:38 am

I think there were more bird accidents with the Electra. An extensive investigaton carried out lately showed that the sound spectrum of the Electra's engines in some way seemed to attract starlings. If I am right, there were some changes on the engine intake to alter the noise and make it "non-attractive" after these accidents.
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RE: Birdstrike Jet/prop/research/opinions?

Sun Nov 24, 2002 1:07 am

To answer the original question, there are tests carried out where chickens are thrown into engines to ensure birdstrike resistance. This is also true for other susceptable parts of the aircraft structure (leading edges, canopies, nacelles etc,..). I had the pleasure of firing the 'canon on a few occasions at British Aerospace at Brough (E Yorks) where they have a 30 foot canon which can fire a 1 lb chicken (or simulated chicken) at over 500 knts.

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RE: Birdstrike Jet/prop/research/opinions?

Sun Nov 24, 2002 3:20 am

I will always remember our birdstrike at Manchester in Summer 2000 (757-200). Departing r/w 24R and at about 120 knots I spotted a large flock of birds heading towards the runway. The Captain (flying pilot) called continue, despite the very high risk we would collide with them.

And that we did, the birds hit the forward left fuselage obscuring the view from some passenger windows and damaging the left pitot system. Miraculously, no birds (that we know of) entered the engine. We returned for an immediate landing and the damage was quite spectacular with several bird remains down the left fuselage!
I used to love the smell of Jet-A in the morning...
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RE: Birdstrike Jet/prop/research/opinions?

Sun Nov 24, 2002 6:05 am


I discussed this subject with the USDA's new airports coordinator recently. The fact is that the criteria which aircraft must meet to pass birdstrike tests are pathetic.

FAA regulations are effectively based on single-bird strikes. An engine must withstand a hit by a SINGLE bird weighing just 4lbs.

In North America there are 36 species of bird weighing more than 4lbs...and 14 of them weigh more than 8lbs (exceeding even the slightly stricter criteria for 777 engine strikes).

The largest of these bird species is the mute swan, which typically weighs almost 60lbs.

Another couple of worrying points:

About 90% of strikes occur below 3,000ft (thereby affecting the most critical phases of flight).

Around 30% of strikes are multiple hits - almost all of the 36 species mentioned above display flocking characteristics. In addition most of these species are rapidly increasing in population.

There are proposals on the table to increase the birdstrike design criteria - perhaps to ensure engines can keep running for at least 20mins after a strike (at present they don't have to keep running at all, merely contain the impact). But these proposals won't affect the aircraft already flying.

Hope this helps,

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RE: Birdstrike Jet/prop/research/opinions?

Sun Nov 24, 2002 6:16 am

I believe bird strike tests on engines aren't to test for survivability so much as to check that the engine and prop will stay intact so as not to FOD out the aircraft.
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RE: Birdstrike Jet/prop/research/opinions?

Sun Nov 24, 2002 6:57 pm

Chief is correct. An engine passes a birdstrike test if it contains the damage and remains capable of being shut down.

But it's a lot easier to contain damage when it's only being hit by one small bird (as occurs in the testing phase). In reality there's a strong possibility of the engine being hit by multiple, large birds. An MD80 hit 400 birds on takeoff from DFW back in '97.

This is increasingly worrying because of the proliferation of twin-engined aircraft which are more vulnerable in the case of a multiple strike in the engine area.

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