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HAWK21M
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#1 Windshield Mounting.

Sun Jun 03, 2012 9:28 am

The B737 mounts #1 Windshield from the Inside....The B757 mounts #1 windshieldfrom the outside.
Considering the Shell is pressurized,wouldn't the former installation be preffered.
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speedbird217
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RE: #1 Windshield Mounting.

Sun Jun 03, 2012 11:21 am

Quoting HAWK21M (Thread starter):
The B737 mounts #1 Windshield from the Inside....The B757 mounts #1 windshieldfrom the outside.
Considering the Shell is pressurized,wouldn't the former installation be preffered.

I'm no expert on this, but considering that the doors are usually constructed in a way that they have to be pulled inside first to avoid opening in-flight, I would think that a construction from the inside (like on the 737) makes more sense.
So things would "get sucked out" rather than being pushed in.
 
CM
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RE: #1 Windshield Mounting.

Sun Jun 03, 2012 2:50 pm

Quoting HAWK21M (Thread starter):
Considering the Shell is pressurized,wouldn't the former installation be preffered.

Perhaps.

When a window (or door) is larger than its opening in the fuselage, we call it a "plug" design. Essentially, it uses cabin differential pressure to seal itself into the fuselage opening, like pressure pushing on the large end of a cork. The 737 makes extensive use of plug designs, including the flight deck windows, cabin windows, passenger doors, and cargo doors. In the case of cargo doors, I believe the 737 is the only large jet from Boeing or Airbus using a plug design. Plug designs have many drawbacks, but one area where they excel is that plug designs are significantly lighter than the alternative.

Like any aspect of aircraft design, depending on where you put your priorities in the design process, design decisions come out differently from aircraft to aircraft. The 737 is designed to be a very lightweight aircraft, with many of its unique design choices being driven by an overriding philosophy to keep the airplane light (short landing gear, small right-hand side service doors, inward opening cargo doors, non FBW flight controls, etc). I believe if we could talk with the original designers of the 737 (or perhaps the 707, as the 737 cab design goes back even earlier), they would tell us it was weight which drove the decision to make the #1 window a plug design.
 
MD11Engineer
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RE: #1 Windshield Mounting.

Sun Jun 03, 2012 4:09 pm

Mel,

You probably have changed #1 windows on both the 737 and 757. Which one is easier and faster? The 757, where you just have to undo a load of bolts and then lift the window out from the outside or the 737, where you first have to dismantle half the cockpit to get access and then move the heavy and big window in the confines of the cockpit?

I think Boeing (like Airbus or Douglas) have decided that there is enough redundancy in the many bolts employed to hold the window in place and the it is more maintenance friendly (and therefore cheaper for operative reasons) to install the window from the outside.

I think, since the 737 shares the cockpit section with the 707, back then the engineers were not yet so sure about the loads, so that they wanted to play safe.

Jan
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CM
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RE: #1 Windshield Mounting.

Sun Jun 03, 2012 8:16 pm

Quoting MD11Engineer (Reply 3):
back then the engineers were not yet so sure about the loads, so that they wanted to play safe.

Could be true, but new aircraft designs I have worked on all have studied plug designs for the windows, enticed by the potential weight savings. As you note, the complexity of removal and replacement on the plug window is a powerful deterrent, generally outweighing the weight savings (pun not intended).
 
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HAWK21M
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RE: #1 Windshield Mounting.

Mon Jun 04, 2012 7:37 am

Quoting CM (Reply 2):
Plug designs have many drawbacks


pls list some...

Quoting MD11Engineer (Reply 3):
You probably have changed #1 windows on both the 737 and 757. Which one is easier and faster? The 757

Jan....Its true...The B757 Windshield is a faster replacement job than a B737,considering the access.But when one looks at the low frequency of the replacements,safety should get preference over an error that could occur.

[Edited 2012-06-04 00:39:02]
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AA737-823
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RE: #1 Windshield Mounting.

Mon Jun 04, 2012 9:03 am

Quoting HAWK21M (Thread starter):
The B737 mounts #1 Windshield from the Inside....

Which one are you referring to as #1? If you mean the forward-most (as some carriers label it), then no, actually, the 737 window mounts from outside.
If you mean the aft most, then I can't comment, as I haven't had to do one. We replace the forward most, and the sliders, fairly frequently at my carrier.
I'd prefer they mounted from the inside for two reasons, the first being pressurization concerns, and the second being that it's a pain in the neck to have someone outside catch the window and then hand it back in at you.
Nevermind the sealant cure time, which in a cold climate is a real downer. But then I guess there'd be sealant either way...
 
Tristarsteve
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RE: #1 Windshield Mounting.

Mon Jun 04, 2012 11:08 am

Quoting AA737-823 (Reply 6):

Which one are you referring to as #1? If you mean the forward-most (as some carriers label it), then no, actually, the 737 window mounts from outside.

Well in that case it has changed.
B737 200 up to 500 main windscreen mounts on the inside.Major job to change with removal of panels and then all the bolts are different.
At GF we had B737-200, and Tristar.
B732 windscreen change about 12 hours.
Tristar could be achieved on an one hour transit on the ramp. All bolts the same, nothing to move, no loose nuts, and fits from the outside.
 
CM
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RE: #1 Windshield Mounting.

Mon Jun 04, 2012 2:59 pm

Quoting HAWK21M (Reply 5):
pls list some...

If we were limiting our discussion to the windows on the 737 Classic / Jurassic, then certainly maintainability is a drawback of the plug design. The 737NG had a significant focus on manitainability & maintenance cost in its design, which I suspect was the reason the plug windows were eliminated.

In the case of cargo doors, using a plug design means the doors have to open inward. This design results in an area of unusable cargo volume just inside the door, but permits the doors to operate with a very simple latch mechanism and without powered door-opening actuators.

You can see this kind of thinking throughout the 737NG design, where a focus on maintaining very low weight and architectural simplicity in the design were powerful factors in design decisions.
 
yeelep
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RE: #1 Windshield Mounting.

Mon Jun 04, 2012 5:27 pm

The L1/R1 windows on all 737's are plug type, they have never changed. My background is on the -200, -400, -700, -800, -900. The NG's are somewhat quicker to change, due to improvements in the glareshield installation. The biggest improvement though has to be when they changed over to the nutplate strips with integral seals, sometime during classic production.
 
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HAWK21M
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RE: #1 Windshield Mounting.

Thu Jun 07, 2012 9:52 am

Quoting AA737-823 (Reply 6):
Which one are you referring to as #1? If you mean the forward-most (as some carriers label it), then no, actually, the 737 window mounts from outside.

Are you saying the #1L & #1R Windshield [Front most windows] are replaced from outside on the -NGs.When was this mod incorporated....any details.....
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