New trend in Design of Nose of Aircraft

[Denti]

As far as i know the original 707 had a periscopic sextant through a hole in the crown of the fuselage. The eyebrow windows were there to increase the field of view as pilots were used to larger windows from pre-jet aircraft.

[Groundloop]

The eyebrow windows were there to increase the field of view as pilots were used to larger windows from pre-jet aircraft.

Are you sure. Have you looked at the size of windows on the Constellation series?

The eyebrow windows were brought in to provide a better view up - after the TWA Super Constellation climbed up into the underside of the United DC-7 over the Grand Canyon. Similarly side windows began to have that distinctive downward V so that crews had a better view down.

The advent of TCAS WAS the reason for deletion of eyebrow windows - which also resulted in quite a significant reduction in mass (an alumunium panel is a lot lighter than a window and frame) which is why retrofitting became very popular.

[inducedrag]

Wiper Blades position are also changed from horizontal to vertical

[Spanner Turner]

280KG EACH for the 747 front windows ?

No, they don't weigh THAT much !! About 150lbs (68kgs)
I'm not that strong and I've moved plenty of 'em over the years, -200's, -300's, SP's and -400's. (Mostly with a helping hand though)
Personally, one of my favourite components of the 747. Beautifully designed, constructed and very reliable. Of course originally designed and built in the '60's by draftsman without CAD or any computers- fantastic curved glass !
Below is copied from the Maintenance Manual.


FLIGHT COMPARTMENT WINDOWS - DESCRIPTION AND OPERATION

1. General
A. Six windows are symmetrically located around the forward end of the flight compartment. The windows are designated right side and left side windows No. 1, 2, and 3, as shown on Fig. 1. The corresponding left and right windows are identically opposite assemblies.
B. All flight compartment windows are of laminated construction. The No. 1 windows, which are the pilots' windshields, consist of a greater number of laminations to withstand bird impact.
C. Pressure sealing is accomplished with a gasket or rubber-beaded seal molded to the windshield frame and the No. 2 and 3 window step cuts. An aerodynamic seal is accomplished by filling the gap between window edge and fuselage skin flush with aerodynamic smoother. This also serves as a weather seal for keeping out moisture.

2. No. 1 Windows
A. The left No. 1 window is the captain's windshield. The right No. 1 window is the first officer's windshield. The left and right windshields are opposite assemblies and installations.
B. Each windshield weighs approximately 150 pounds and consists of transparent layers secured between a Z-frame and mounting ring. The layer construction allows for thermal differentials and prevent crack propagation between the structural layers. The Z-frame and mounting ring attach to the fuselage structure surrounding the windshields.
C. Two types of No. 1 windows can be installed: a five-layer soda-lime glass laminate or a five-layer tempered glass and soda-lime glass laminate. Windows with a P prefix serial number are constructed of five basic layers: a glass outer layer, an interlayer, a glass structural ply, an interlayer and a glass crew shield. Windows with a T prefix serial number are constructed of five basic layers: an outer tempered glass layer, an interlayer, a glass structural ply, an interlayer and a glass crew shield, which is a structural ply. New and replacement T prefix No. 1 windows have outer glass ply with greater thickness for added strength.
D. The inner face of the face ply is covered with a conductive coating, which is part of the antifogging and anti-icing systems. Bus bars, embedded in the windshield layers, contact the conductive surface near the top and bottom of the windshield. Two temperature control sensors are laminated into the windshield adjacent to the conductive coating. Only one control sensor is used; one is a spare that is used only if the other fails. Wires from the bus bars and sensors extend through the windshield laminations to the terminals on the inner face.


Confusion can occur when the wrong part of the manual is referenced - my job is to make sure that this doesn't happen!! 2 quotes below from the removal/installation task.
One relates to the equipment required (generic in nature), the other to the window itself.

" Equipment and Materials Required
A. Crane equipped with 40-foot boom and capable of lifting 500 pounds or equivalent
B. Mobil mechanical lift (capable of extending to a height of 35 feet) or overhead crane capable of lifting 500 pounds (i.e 227kgs) "


" CAUTION: USE CARE WHEN HANDLING THE WINDSHIELD ASSEMBLY. IT WEIGHS APPROXIMATELY 150 POUNDS AND IS A HIGH COST ITEM. "

[stilton]

Yes, I can see you wouldn't want to drop one.


Apart from birdstrike damage etc would these front windshields ever need to be replaced or would they last the life of the Airframe ?

[Volume]

they last the life of the Airframe ?

That is the dream of all maintenance staff...
No. They do not last very long, on some reginal jets you may have to replace them as frequent as every 2 years. They consist of several bonded layers of glass and/or trasparent plastics, as they are subjected to UV and huge temperature changes, the adhesive ages and you get delaminations. The seals do also age and you get water ingress (no good idea if you freeze it or have an electric heating as part of thze design...). Additionally they sometimes crack, if they are installed with build in stress due to typical tolerances not accounted for in the design.
Industry is still waiting for a company which designs long lasting cockpit windows.

[CallmeJB]

Huh, I stand corrected. I checked and our AMM says the same (obviously).

I was referencing the Weight and Balance Control and Loading Manual, which has a diagram and the below table on one of the later pages:

ITEM WEIGHT B.A.
NO. BODY COMPONENTS LB/EA KG/EA IN.

1 Door 5 Main Entry Door (Left) 440 200 2261

2 Side Cargo Door 1952 885 1850

3 Door 1 Main Entry Door (Left) 452 205 464

4 Upper Deck Door 211 96 405

5 Emergency Exit Left Side (Not Shown) 22 10 370

6 No. 3 Windshield (Left & Right) 60 27 326

7 No. 2 Windshield (Left & Right) 45 20 306

8 No. 1 Windshield (Left & Right) 620 281 299

9 APU Exhaust Cone 100 45 2760

10 APU Access Door (2) 80 36 2699

11 Bulk Cargo Door 147 67 2006

12 Aft Cargo Door 742 337 1865

13 Aft Outbd Main Body Gear Doors (2) 18 8 1465

14 Aft Inbd Main Body Gear Doors (2) 103 47 1441

That's "No. 1 Windshield (Left & Right) 620 LB/each 281 KG/each 299 inches CG"

Perhaps I misread it and it's 281 KG for both the Left and Right together, but that's still a significant difference from the AMM. I wonder why.

Sorry for the formatting. I don't have enough posts yet to be able to post pictures from an album.