Why to open cockpit window?

[kuobin]

Check B737 and ERJ ditching procedure ,they all require you to open cockpit slide window(No.2) before ditch, So why ?
Is this to guarantee complete depressurization before open cabin door?

[411A]

More than likely...to be sure it does not get jammed in the closed position, thereby precluding a rapid exit, if need be.

[A320Dreamer]

Just a guess, but it may be so you can get out? Since you can't open a door or window that slides out until the pressure is equal outside in the water and in the cockpit.. So, it would not be possible to open the cockpit windows in order to escape until the cockpit would be filled with water. That is, if the plane goes under...

[Spendid Cruiser]

Kuobin,

You are correct. Part of the ditching preparation is to close the pressurisation outflow valve, which means the cabin altitude may still be high enough above sea level to prevent the main doors from opening. Even cracking open one flight deck window will pressurise the aircraft.

[Capn Bloggs]

window that slides out
My cockpit window comes in. I think the 737's does too. Shouldn't be a problem opening it in. The water will be helping you.

which means the cabin altitude may still be high enough above sea level to prevent the main doors from opening. Even cracking open one flight deck window will pressurise the aircraft.
If you can't crack a main door because the aircraft is still pressurised, I doubt whether you'd be able to get your cockpit window open either.

[HPbleed]

If you can't open a door you won't be able to open the window, so the aircraft will already have to be depressurised. I imagine it's more to do with a rescue situation, the rear of the aircraft will sink first, so rescuers will have to access through the front. If the windows are already open it saves a person unfamiliar with how to open the cockpit window from struggling. It also enables a quick escape by the pilots!

[EW73]

Guys...
In the 737 procedures I've been associated with, the #2 windows are not opened until immediately after the ditching, the reason being to assist with the opening of either of the two front doors.
Having said that, I don't think, after the descent prior to the approach to ditch, when both packs are secured and then the outflow valve closed, there will be much of a problem with cabin pressure.
In any case, with any small residual pressure remaining following ditching, the initial opening selection of the main doors causes the top and bottom sections of the doors to pre-open, to equal that small difference, so opening either of those doors will not be problematic.
Additionally, both (or all four, depending on the model) of the overwing hatches will easily overcome any small pressure difference and spring open, thereby relieving any residual pressure in an instant!
I certainly wouldn't want to ditch with either of the #2 windows unlocked!

EW73

[onetrack]

It's important with any submersion, be it vehicular or aircraft, to have a window, or windows, opened quickly or early, to allow water in, to equalise the pressure between the cabin and the outside water.
It's virtually impossible to open windows and doors against even a metre or two of water pressure... we're talking a great deal of pressure here, with the weight of water.
If submerged, you let the water in (even though immediate thinking is, that's wrong - but it's not)... and the pressure equalises, and you can escape much more easily by swimming out... rather than desperately trying to force open a door or window, that is held firmly in place by water pressure measured in tonnes per square metre.
If you do wait until deep submersion before you try to open a door or window... and you do succeed ... the massive inrush of water will drive you back forcibly, and possibly injure you, and make it even more difficult to escape. Rapid equalisation of water pressure, immediately upon submerging, offers you the best chance of escape.
Once submerged, you're going to get wet anyway, the aim is to reach the surface quickly, and without unnecessary additional expenditure of energy and air supply.

Surviving ditching... http://amd.nbc.gov/library/handbooks/awds_92.pdf

[Spendid Cruiser]

If you can't crack a main door because the aircraft is still pressurised, I doubt whether you'd be able to get your cockpit window open either.
Obviously you have never flown a Classic and missed selecting GRD on the pressurisation panel. If you do the CC cannot open the cabin door, but a quick crack of the window and a bit of hissing later no problem.

[Capn Bloggs]

No I didn't Spendid, as I thought I indicated in my post.

From a recent copy of the 737 NG QRH for Ditching:

After Impact Procedure Review
...
Open flight deck windows. This ensures no cabin differential pressure prevents the opening of the doors or emergency exits.
...


That settles it. :ok: