Ps76
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Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 4:58 am

Was just wondering what the reason was for the higher windows in the Boeing 737. What would a pilot need to see from the perspective - Maybe for light/general visibilty? Traffic?
 
CanadianNorth
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 5:14 am

They are called "eyebrow windows" I believe.

The original nose design of the 737 is basically the same as the 727, which is basically the same as the 707. Back in the day when the 707 was brand new, these windows were useful for spotting traffic, and they also could potentially help with weather, and if things were really bad help with navigation.

However, with todays technology the 737NG can do all that via computer faster, easier and more reliable. Thus, they have been eliminated on 737s currently in production, and it is an option to remove them on 737s made with them.

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FredT
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 5:32 am

Good for keeping an eye on the runway during turns in a visual landing pattern, I'd say... until someone who has flown'em chips in and says otherwise.

Their main purpose seems to be storing newspapers though.  Wink
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aero145
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 7:18 am

Quoting CanadianNorth (Reply 1):
They are called "eyebrow windows" I believe.

That is true...

I find it however funny that the new 737s or old modified 737s which do not have the eyebrow windows don't get my attention, they look somehow normal without them.

What do you think, guys?
 
covert
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 11:33 am

It made it easier to navigate by the stars in the 707 and 727, now it just lets too much light in.
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mohavewolfpup
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 12:20 pm

how are they a maintenance issue? I think I saw a post in a thread they have maintenance issues. leaky? or just antiqued?

sadly, if I was a pilot I would mourn the loss of being able to see stars out them, but I am really cheesy and like stuff like that.

nothing beats being at 37,000 feet hauling 100+ people to their futures, destinations,marriages,family,vacations,hopes and dreams, etc and looking at stars wizzing by at 500 mph.

okay, i'll cut the sap :p

it also shows how much more reliant we are becoming on computers also to do the work of what pilots had to do in the past manually (finding the north star)
 
N231YE
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 12:58 pm

Quoting Mohavewolfpup (Reply 5):
how are they a maintenance issue? I think I saw a post in a thread they have maintenance issues. leaky? or just antiqued?

The eyebrow windows added "unnecessary" weight, and I believe the maintenance issues included lamination problems (?).
 
N243NW
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 1:43 pm

Quoting CanadianNorth (Reply 1):
Thus, they have been eliminated on 737s currently in production

 checkmark 

Quoting CanadianNorth (Reply 1):
and it is an option to remove them on 737s made with them

 checkmark 

Same story with the 717. Is there an option offered [yet] from Boeing to fill existing windows with this model as well? Or is the demand (fleet size) too small to make such a retrofit cost-effective?


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nonfirm
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 5:22 pm

Quoting Mohavewolfpup (Reply 5):
how are they a maintenance issue?

The removal of the eyebrow windows is very helpful for maintenance.First off there are four less windows that need to be attended to also they have a problem with delamination.If the delam is out of limits then they need to be replaced.I have found with our fleet of 737-400's that almost all of the eyebrow window's are on defferal for delam also with the hud's installed on the Capt's side they are almost useless.As stated most of the time they are blocked anyway with window shade's or paper.  airplane 
 
mohavewolfpup
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 08, 2007 11:33 pm

Quoting Nonfirm (Reply 8):

what's the worry with the delam? decompression issues, or just visual issues?

and how are they blocked off? just a metal plate welded in?
 
IAHFLYR
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 12:05 am

Quoting FredT (Reply 2):
Good for keeping an eye on the runway during turns in a visual landing pattern, I'd say

That would sure be a diving turn to keep the runway in sight out the eyebrow windows!  eek 

I like the no eyebrow look on the 73's.
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aero145
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 12:18 am

Quoting Mohavewolfpup (Reply 9):
just a metal plate welded in?

Probably...


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pilotaydin
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 5:37 am

Quoting FredT (Reply 2):
Their main purpose seems to be storing newspapers though.

bingo, a klenex box fits RIGHT into the damn thing, and i can pull one out during meal times and i love it LOL

it's so annoying though when the sun is high up, it really bakes you sometimes
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nonfirm
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 11:25 am

Quoting Mohavewolfpup (Reply 9):
what's the worry with the delam? decompression issues, or just visual issues?

and how are they blocked off? just a metal plate welded in?

The problem with the delam is when it grows beyond the limit from the corners of the window and the sides you are only allowed a few inches if it's beyond then you need to replace the window.Here is the link of the mod.
RE: 737 Eyebrow Mod (by ZANL188 Nov 26 2006 in Tech Ops)?searchid=174667&s=737+eyebrow+window#ID174667  airplane 
 
EssentialPowr
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 1:59 pm

This all may have been mentioned to some degree, but I will condense it:

- Eyebrow windows were originally installed so a sextant could be used...

- The maintenance bonus comes from the elimination of a heated piece of glass...

- The new structure keeps the cockpit cooler (huge for glass tube a/c), is lighter, stiffer, more fatigue resistant, and completely eliminates a part number.

Good deal all around!

(And if you are a manufacturing guy, the last thing you do is cut out a piece and then weld in a blank...you just eliminate the stamp that cuts out the window in the first place!!!)

[Edited 2007-01-09 06:07:38]
 
2H4
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 2:15 pm




Quoting EssentialPowr (Reply 14):
- Eyebrow windows were originally installed so a sextant could be used...

Are you sure about that? If that is indeed the case, why would the VC-137C have had an entirely separate sextant port installed?

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EssentialPowr
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 2:57 pm

B/c a VC 137C uses celestial as a secondary nav to this day... not so the 737, and a dedicated port is not nec in the first place if you've ever used a sexant...an eyebrow window will work, but even from the 707 days Boeing projected that electronic, ground based nav eliminated celestial nav. Old habits die hard in the mil and the Nav in particular...
 
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HAWK21M
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 8:03 pm

Quoting N231YE (Reply 6):
The eyebrow windows added "unnecessary" weight, and I believe the maintenance issues included lamination problems (?).

Don't forget cockpit noise reduction.
regds
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BAE146QT
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 8:35 pm

Quoting HAWK21M:
Don't forget cockpit noise reduction.

Forgive me if this has been asked before, but it strikes me that a thick piece of glass would be a better sound insulator than a few mm of sheet metal and a plastic facade.

So does the noise reduction come from that fact that you're losing four panel lines and a row of rivets/bolts?
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HAWK21M
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 09, 2007 9:58 pm

Quoting BAe146QT (Reply 18):
So does the noise reduction come from that fact that you're losing four panel lines and a row of rivets/bolts?

Addition of Vortex generators too.
regds
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EssentialPowr
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RE: Reason For The 737 Higher Front Windows?

Wed Jan 10, 2007 5:50 am

Quoting BAe146QT (Reply 18):

So does the noise reduction come from that fact that you're losing four panel lines and a row of rivets/bolts?

Absolutely; removal of the window results in a more continuous piece of metal. Any seal b/t a window and the frame will eventually leak somewhat, and therefore hiss, over time...
 
KELPkid
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RE: Reason For The 737 Higher Front Windows?

Wed Jan 10, 2007 6:28 am

Quoting Mohavewolfpup (Reply 9):
and how are they blocked off? just a metal plate welded in?

Although it is now possible to weld aluminum (TIG and MIG), I'd put money on the mod being a sheet of aircraft-grade aluminum large enough to cover the hole and then some, placed inside the pressure vessel, and then rivited from the outside. Any mechanics want to comment on this? Also, do the interior panels receive an update at the same time to a part without the window cutouts?
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zanl188
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RE: Reason For The 737 Higher Front Windows?

Wed Jan 10, 2007 6:46 am

Quoting EssentialPowr (Reply 16):
B/c a VC 137C uses celestial as a secondary nav to this day... not so the 737, and a dedicated port is not nec in the first place if you've ever used a sexant...an eyebrow window will work, but even from the 707 days Boeing projected that electronic, ground based nav eliminated celestial nav. Old habits die hard in the mil and the Nav in particular...

The VC-137Cs are all in museums, modded to another type, or scrapped now so they are certainly not using celestial nav to this day.

So if somebody were to use the eyebrow window with a sextant how would that work exactly? If the pilot stood on the floor the yoke would be poking him in the groin -- I guess he could stand on the seat and do it that way. Just seems awkward to me.


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[Edited 2007-01-09 22:50:22]
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N231YE
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RE: Reason For The 737 Higher Front Windows?

Wed Jan 10, 2007 9:00 am

Quoting EssentialPowr (Reply 20):
Absolutely; removal of the window results in a more continuous piece of metal. Any seal b/t a window and the frame will eventually leak somewhat, and therefore hiss, over time...

Since the noise seems to be caused by some sort of disturbance in the airflow, would the removal of the window provide some sort of performance benefit?
 
EssentialPowr
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RE: Reason For The 737 Higher Front Windows?

Wed Jan 10, 2007 11:09 am

Quoting ZANL188 (Reply 22):
The VC-137Cs are all in museums, modded to another type, or scrapped now so they are certainly not using celestial nav to this day.

The point is that a lot of mil a/c had them, to include P3s which are still on active service w/ the NAV.

Quoting ZANL188 (Reply 22):
So if somebody were to use the eyebrow window with a sextant how would that work exactly? If the pilot stood on the floor the yoke would be poking him in the groin -- I guess he could stand on the seat and do it that way. Just seems awkward to me.

Uhh... remaining seated?

Quoting N231YE (Reply 23):
Since the noise seems to be caused by some sort of disturbance in the airflow, would the removal of the window provide some sort of performance benefit?

Absolutely. Aside from the fact that the window is heavier than the blank aluminum that was there in the first place, any time a discontinuity in the a/c's skin is eliminated, the result is smoother airlflow. In short, eliminating the window enhances perfromance by:

1. reducing weight
2. " complexity, as those windows are heated and share a temp controller as well as have requisite wiring/circuit breakers/etc
3. reducing/removing spare parts from the inventory
4. reducing the build cost
5. smoother airflow over the nose section
 
N231YE
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RE: Reason For The 737 Higher Front Windows?

Wed Jan 10, 2007 12:17 pm

Quoting EssentialPowr (Reply 24):

I see...I knew about the weight issues for the window itself, but did not realize the associated systems/items and parts inventory. Since nobody uses these windows anymore...then logic says to remove them, and as stated, the benefit is great.

Thanks
 
rsbj
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RE: Reason For The 737 Higher Front Windows?

Fri Jan 12, 2007 12:40 pm

I fly a 707 (KC-135) and 737's and I have to say I have never once in thousands of hours used the eyebrow windows; even in tight visual patters or for traffic. To me and a lot of other pilots I fly with, they only serve as a nusance by letting in too much heat/light.

Also on the subject of noise reduction, I have found that it is the material itself that provides the quantity of noise reduction, not the thickness. For example a 2X4 (1.5") attenuates the sound by -30.5 dba, while 3/4" wood attenuates -29 dba; at least according to my trusty spectrum analyzer. Sound is insulated better usually with more dense materials, so Aluminum wins out over glass almost regardless of thickness.

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HAWK21M
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RE: Reason For The 737 Higher Front Windows?

Fri Jan 12, 2007 6:52 pm

Quoting RSBJ (Reply 26):
I fly a 707 (KC-135) and 737's and I have to say I have never once in thousands of hours used the eyebrow windows; even in tight visual patters or for traffic

You sure do.When you use the Newspaper to blank out the light.  Smile

Amazing how these Windows are always Blanked out with Paper to stop the light.
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JBo
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RE: Reason For The 737 Higher Front Windows?

Sat Jan 13, 2007 1:46 am

Quoting N243NW (Reply 7):
Same story with the 717. Is there an option offered [yet] from Boeing to fill existing windows with this model as well? Or is the demand (fleet size) too small to make such a retrofit cost-effective?

I'm not sure if Boeing would offer an eyebrow-removal program for the 717 as well. It appears the window design on the 717 (and DC-9, MD-80, et al) is different in that the eyebrow frame appears continuous with the rest of the windows.

So a removal of the eyebrow from a DC-9-based aircraft would probably be more espensive due to more parts potentially being involved.
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Gr8Circle
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RE: Reason For The 737 Higher Front Windows?

Sat Jan 13, 2007 3:02 am

Quoting Covert (Reply 4):
It made it easier to navigate by the stars in the 707 and 727, now it just lets too much light in.



Quoting Mohavewolfpup (Reply 5):
nothing beats being at 37,000 feet hauling 100+ people to their futures, destinations,marriages,family,vacations,hopes and dreams, etc and looking at stars wizzing by at 500 mph.



Quoting 2H4 (Reply 15):
Quoting EssentialPowr (Reply 14):
- Eyebrow windows were originally installed so a sextant could be used...

Are you sure about that? If that is indeed the case, why would the VC-137C have had an entirely separate sextant port installed?

The old 707's used to have a sextant in the same position as shown in the pic of the VC-137C abvove...I have personally seen them being used during flight, way back.....I agree that the eyebrow windows were probably useful to the navigators in those days.....
 
KELPkid
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RE: Reason For The 737 Higher Front Windows?

Sat Jan 13, 2007 3:20 am

Quoting Gr8Circle (Reply 29):
The old 707's used to have a sextant in the same position as shown in the pic of the VC-137C abvove...I have personally seen them being used during flight, way back.....I agree that the eyebrow windows were probably useful to the navigators in those days.....

I'm familiar with the Mark III Sextant, and it's usage in flight would depend upon a clear shot of the horizon and the aircraft's eyebrow would have to be pointed pretty much at the star you were shooting (or sun if you're doing a sun shot  cool  ), not to mention that the large gap between the windshield and the eyebrow could become a problem rather quickly...the only way I could see this possibly being of use is underneath a plexiglass dome  Sad Although I'm not familiar with the Boeing's cockpit, having only been there a few times in my life (and only once in flight, on a military T-43 as an observer  Wink ), it seems like it might be awfully cramped quarters to use a traditional sextant in...BTW the T-43, being a navigation trainer (amongst other uses), has several sextant ports, although I think the Air Force must have used something radically different from the Mark III, because it sure doesn't look like I could use a Mark III up there. The T-43's sextant ports look very similar to the VC-137's shown above.
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zanl188
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RE: Reason For The 737 Higher Front Windows?

Sat Jan 13, 2007 4:24 am

Quoting EssentialPowr (Reply 24):
Quoting ZANL188 (Reply 22):
So if somebody were to use the eyebrow window with a sextant how would that work exactly? If the pilot stood on the floor the yoke would be poking him in the groin -- I guess he could stand on the seat and do it that way. Just seems awkward to me.

Uhh... remaining seated?

Not particular what star you're shooting then are you?

Quoting KELPkid (Reply 30):
it seems like it might be awfully cramped quarters to use a traditional sextant in...

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N243NW
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RE: Reason For The 737 Higher Front Windows?

Sat Jan 13, 2007 4:24 am

Quoting JBo (Reply 28):
So a removal of the eyebrow from a DC-9-based aircraft would probably be more espensive due to more parts potentially being involved.

Thanks for the input. It makes perfect sense as far as costs are concerned.

-N243NW Big grin
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EssentialPowr
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 15, 2007 5:24 am

Quoting ZANL188 (Reply 31):
Not particular what star you're shooting then are you?

Out of an approx 6" x 10" window? Not a lot of field of view in the first place!
 
zanl188
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 15, 2007 5:28 am

Quoting EssentialPowr (Reply 33):
Out of an approx 6" x 10" window? Not a lot of field of view in the first place!

Hence my point that using the eyebrows for sextants is rather awkward and unlikely.....
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2H4
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 15, 2007 9:54 am




Quoting ZANL188 (Reply 34):
Quoting EssentialPowr (Reply 33):
Out of an approx 6" x 10" window? Not a lot of field of view in the first place!

Hence my point that using the eyebrows for sextants is rather awkward and unlikely....

That's what I was thinking....



So, forget about the reason for the installation of tiny eyebrow windows on the Boeings.....why the heck were tiny eyebrow windows installed on military Jetstreams?

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zanl188
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RE: Reason For The 737 Higher Front Windows?

Mon Jan 15, 2007 10:14 pm

Quoting 2H4 (Reply 35):
why the heck were tiny eyebrow windows installed on military Jetstreams?

Wasn't the JetStream originally a military design? In which case it would be easy to figure why they were removed for the commercial variants -- They look better without them

Quoting 2H4 (Reply 35):
So, forget about the reason for the installation of tiny eyebrow windows on the Boeings

Yeah I know you don't want to talk about Boeings but.. The 1st Boeing jet with the eyebrows was the B-52... I wonder if it didn't have something to do with the Buff being air refuelable -- judge closure rates, see the horror of the boom punching thru the eyebrow glass and all that  Smile
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longhauler
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 16, 2007 4:05 am

Canadi>n's arctic B737s were equipped with an Astro Compass, similar in use to a sextant. This was stored under the second jump seat behind the Captain, and mounted in a bracket on the First Officer's side (not eyebrow) window. In all the pictures I have of the B737 cockpit, I couldn't find even one with the Astro Compass in use!

It required a fairly large field of view, I can't imagine using an eyebrow window.
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2H4
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 16, 2007 4:24 am




Quoting LongHauler (Reply 37):
In all the pictures I have of the B737 cockpit, I couldn't find even one with the Astro Compass in use!

Here's one in a B-25 cockpit:




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jetmech
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RE: Reason For The 737 Higher Front Windows?

Tue Jan 16, 2007 10:41 am

Quoting KELPkid (Reply 21):
Although it is now possible to weld aluminum (TIG and MIG), I'd put money on the mod being a sheet of aircraft-grade aluminum large enough to cover the hole and then some, placed inside the pressure vessel, and then rivited from the outside.

The windows that I have seen blanked have always been on 747's. Most window cutouts in the pressurised skin will be re-inforced with a window forging (main entry and cargo doors seem to use "bearskin" doublers and triplers instead).

The blanks I have seen on 747's are usually pieces of aluminium plate about 4 or 5 mm thick. The edge of these plates is profiled to the same shape as the original primary window pane. The original window seal is fitted to the aluminium plate which is then installed into the window forging. The original retention clips are then used to retain the blank in the forging.

I am not too sure what happens with the 737 eyebrow windows, but I expect that it is a similar arrangement. I'm not too sure you would want to weld in these plates or go about drilling holes in the forging for rivets  Confused.

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HAWK21M
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RE: Reason For The 737 Higher Front Windows?

Thu Jan 18, 2007 12:24 am

Quoting JetMech (Reply 39):
I am not too sure what happens with the 737 eyebrow windows, but I expect that it is a similar arrangement. I'm not too sure you would want to weld in these plates or go about drilling holes in the forging for rivets

Anyone aware of the entire Job of this Mod kit.
regds
MEL
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