AR1300
Topic Author
Posts: 1686
Joined: Mon Feb 07, 2005 1:22 pm

Why The Forehead On Some A/c?

Tue Apr 12, 2005 3:23 pm



Why is that in some airplanes like in the 757, A320,Md-80's the nose has kind of a ''forhead'', beeing the ''line'' that we could draw from the nose to the rear of the ac ''low'' in the fuselage, and in some ac like the 767, A340, 737, 777 is more ''centered'' to the middle of the plane?
Does it make a difference in the aerodynamics?The A380 and the 787 are like the ''low'' models, so I assume that there is something.Anyone?Some help?

Mike.

P.S:I'm not the best of the artists, so I'm sorry for the graphic if you don't like it.  Smile
You are now free to move about the cabin
 
EMBQA
Posts: 7797
Joined: Sat Oct 25, 2003 3:52 am

RE: Why The Forehead On Some A/c?

Tue Apr 12, 2005 9:30 pm

Because the 757, A320 and MD-80 are narrow body aircraft, carry less people and need smaller baggage areas.....767, A340 and 777 are wide body aircraft, carry more people and need larger baggage areas.
"It's not the size of the dog in the fight, but the size of the fight in the dog"
 
SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

RE: Why The Forehead On Some A/c?

Tue Apr 12, 2005 11:35 pm

Not so sure that I'd agree with that answer.
Here are two similar size narrow-body aircraft:

View Large View Medium
Click here for bigger photo!

Photo © Daniel Wojdylo
View Large View Medium
Click here for bigger photo!

Photo © An Jing


On the Douglas designs, the nose was well below centerline, and rounded. On the Boeings it was only slightly below centerline and more pointed. These shapes were also seen on the DC-8 or the B-707, 727 Note that the actual deck level, as shown by the bottom of the 1L and 1R doors is slightly below the cheatline on the DC-9 shown, and slightly above the cheatline on the Boeing.

The below-deck space was very similar, but the flight decks were different. On the 737, you would find that the main cabin floor continued all the way forward to the rudder pedals. In the DC-9 there was a step up at the pilot seats.

I'd expect that the reasons for the forward fuselage shapes were very esoteric engineering decisions.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
aeroweanie
Posts: 1577
Joined: Fri Dec 03, 2004 9:33 pm

RE: Why The Forehead On Some A/c?

Wed Apr 13, 2005 5:43 am

The 757 gained the "forehead" when they stuffed the 767 cockpit into it at a late stage of the design. Originally, it had a 707/727/737 nose.
 
SlamClick
Posts: 9576
Joined: Sun Nov 23, 2003 7:09 am

RE: Why The Forehead On Some A/c?

Wed Apr 13, 2005 7:04 am

Quoting AeroWeanie (Reply 3):
The 757 gained the "forehead" when they stuffed the 767 cockpit into it at a late stage of the design. Originally, it had a 707/727/737 nose.

That would explain the major syllabus item in 757/767 differences training. In one you step UP onto the flight deck, on the other you step DOWN. If I could only remember which was which I'd avoid embarassing myself when I jumpseat.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
aeroweanie
Posts: 1577
Joined: Fri Dec 03, 2004 9:33 pm

RE: Why The Forehead On Some A/c?

Wed Apr 13, 2005 8:43 am

According to the .dxf CAD files on the Boeing website, on the 757 you step down, while on the 767, you step up.
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Why The Forehead On Some A/c?

Wed Apr 13, 2005 5:30 pm

Quoting AeroWeanie (Reply 3):
The 757 gained the "forehead" when they stuffed the 767 cockpit into it at a late stage of the design. Originally, it had a 707/727/737 nose.

Any Pics of the Older version.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
aeroweanie
Posts: 1577
Joined: Fri Dec 03, 2004 9:33 pm

RE: Why The Forehead On Some A/c?

Thu Apr 14, 2005 1:05 am

After the T tail dissapeared, but before the 707/727/737 nose dissapeared:

 
mdsh00
Posts: 3968
Joined: Mon May 17, 2004 11:28 am

RE: Why The Forehead On Some A/c?

Thu Apr 14, 2005 9:06 am

If you look at it, the 777 has quite a noticeable forehead.


View Large View Medium
Click here for bigger photo!

Photo © H. Meier



Does this have anything to do with its cockpit looking like the 767?
"Look Lois, the two symbols of the Republican Party: an elephant, and a big fat white guy who is threatened by change."
 
RedDragon
Posts: 1096
Joined: Sat Jul 03, 2004 2:24 am

RE: Why The Forehead On Some A/c?

Thu Apr 14, 2005 8:13 pm

Quoting Mdsh00 (Reply 8):
Does this have anything to do with its cockpit looking like the 767?

After having done forum and Google searches and found nothing (despite remembering at least some vague mention a few months ago)... I believe that the 777 shared the 767's crown, this being effectively the "forehead" area above the cockpit windows. Can someone who knows more definitively confirm this?

Rich
 
aeroweanie
Posts: 1577
Joined: Fri Dec 03, 2004 9:33 pm

RE: Why The Forehead On Some A/c?

Fri Apr 15, 2005 12:55 am

The 777 started life as the 767X, which grafted the 767 cockpit onto a new, larger diameter fuselage. I just did some overlays and yes, the 767 and 777 nose lines match up to a point aft of the windshields.
 
phollingsworth
Posts: 635
Joined: Sat Mar 06, 2004 6:05 am

RE: Why The Forehead On Some A/c?

Fri Apr 15, 2005 2:28 am

Quoting AeroWeanie (Reply 10):
The 777 started life as the 767X, which grafted the 767 cockpit onto a new, larger diameter fuselage. I just did some overlays and yes, the 767 and 777 nose lines match up to a point aft of the windshields.

If you look closely at a 777 and a 767 you will see a circumferential butt splice just aft of the cockpit. In the picture above it is just aft of the Star Alliance logo. Forward of this splice the two aircraft share identical outer mold-lines. Boeing did this to maximize commonality between the original 767X and the remainder of the 767 fleet. Then they decided to install an upgraded 747-400 set of displays. It wasn't until the 764 came out that the cockpits if some 777s and some 767s returned to a high cockpit similarity

Who is online

Users browsing this forum: Bing [Bot], tb727 and 20 guests