Birdstrike Capability Cockpit Windows 737

[aviatic737]

Hi everyone,
Does anyone have reliable information on the tolerance of the cockpit windows regarding birdstrikes?
I've had a lot of discussions with some colleges about whether or not to fly high speed at low altitudes. As some people don't seem to be worried about a bird hitting the screen at 335 kts, I am!
I've heard something about that Boeing states 280kts to be the maximum speed for which they assume to be safe but I couldn't find anything in the books...

Cheers

[john_tullamarine]

Think I'd be worried also .. the 737 is an old certification so one should really research the TC basis .. however, for the purposes of your question, the current requirements are probably a good place to start .. check
25.631 and 25.775

Unfortunately, the PC I'm on at the moment has a high security setting so I can't download the TCDS ... but you might check out TCDS A16WE at the FAA site

[Canuckbirdstrike]

The B737 was certified to FAR 25 standards for bird strikes - a 4 lb bird at Vc (design cruise speed). That being said, high speed flight below 10,000 feet is a high risk activity with respect to bird strikes. The certification standard assumes only a single bird impact and the standard does not require that there is "no damage". While the probability of bird strikes does reduce with altitude the problem is that as altitude increases the bird species struck are large - waterfowl or raptors - many of which exceed four pounds weight. Further to this the certfied standard produces an impact force; that force increases as the SQUARE of the speed increase and as a direct function of the bird weight. It is also important to remember that when climbing at a constant IAS the TAS increases with altitude. The last piece of the equation is that during the acceleration phase rate of climb is reduced - right in the middle of the bird rich altitudes. So add up the risks; bigger birds, more exposure and probability during acceleration and increased severity. I did a detailed risk analysis on this for Transport Canada and the results are very sobering.

As for what Vc for the B737 is, I don't have that information, but in my mind it doesn't matter. For more information I suggest you read sections of the Transport Canada book Sharing the Skies, available online at:

http://www.tc.gc.ca/CivilAviation/Ae...13549/menu.htm

The last point is that not only do you need to consider the windshield you need to consider the aircraft structure....

I have lots of pictures, but I need to figure out how to post them.

So those who are not worried about hitting a bird at 335 knots need to rethink their position.

Remember if you operate in North America or Europe that currently there are millions of bird migrating north over the next few weeks.....

[Centaurus]

In Australia, fearless 737 pilots happily accept ATC requests for "high speed below 10" and bugger the risk of a bird in the face Funny sort of risk management.

[TopBunk]

In the good old days of the Berlin corridors, we were restricted to cruise at 3000ft and latterly at FL85/95 depending on direction. The length of time in the corridors was 15-20 minutes. If we had cruised at 250kts the schedules would never have worked. We used to fly the 737-200's at 320kts all the time, don't recall having any birdstrikes, so I guess we were lucky!

[Canuckbirdstrike]

Topbunk, you were lucky!

Further to the risk equation recent studies of North American bird species with an average weight greater than 4 lbs has shown that thier populations are increasing. The Canada Goose population went from 2 million in 1991 to 6 million in 1999 and there is no indication that the ecosystem has reache its maximum carrying capacity. The same population trends are also occurring in europe and other parts of the globe.

[aviatic737]

Thanks everyone for your posts!
Some very interesting informations most of which strengthened my point of view. The problem here is that the risks of really hitting a bird seems so remote that one tends to rather accept high speed below FL100 than "creeping down" with 250. Very subjective indeed. Nevertheless I ask again: Has anyone found anything in an official (Boeing?) documentation?

[Jetavia]

Well you have the NNC 3.2 (window overheat) saying if window heat off, not to fly faster than 250 kts below FL100, so you can say it can be used at a guide eventhough heated windows will be able so support an impact at a higher speed.

[Centaurus]

It takes very little effort to read about the dangers of a bird strike during high speed flight, but I would hazard a guess and say that few pilots or air traffic controllers bother to research the subject even though the internet is available. "It will never happen to me" comes to mind.

[Capt. Greaseon]

Might be a bit off topic but always wanted to ask this question.

Is there any evidence that using the weather radar can reduce the chance of a bird strike ??? (Not that the radar can show birds, but more from the point of view that birds somehow sense the signals generated from the antenna and tend to avoid it.)

[Canuckbirdstrike]

Once again the urban myth of birds sensing radar signals is dragged out... I can state categorically that birds are incapable of detecting the signal propagated by an aircraft weather radar. Remember the signal strength is low to start with and decreases as the square of the distance. So don't waste your time with turning on the radar with the objective of reducing the likelihood of a bird strike.

[Dehavillanddriver]

What is the dirdstrike worldwide for aircraft below 10000 but not in the circuit or on approach?

I would venture that it is not huge.

[rubik101]

Having taken a hit straight in front of my face at FL130, decending and about 300 kts, I can tell you that the noise is very loud, the screams almost as loud, the mess on the window indescribable and the smell in the cockpit unpleasant. The window, cracked, crazed and unusable to see through, but with an intact inner pane and no loss of pressure!
Once in 35 years of flying so why not say, it won't happen to me?