It is because of the carbon fibre. This is the same reason that the 787 has bigger passenger windows. Here you can find a link explaining the polarized windows on the 787. Because of its higher tensile strength, you can have bigger windows. Windows are considered weak points in the fuselage where there is no structural reinforcement. This means that the windows have to be supported by the fuselage and structural components around the window. Boeing Pilots do not fly with their elbow out the window during flight, so Boeing removes that feature. They added bigger windows because they could. There is there separation for the six windows because there is support needed.
Hope this helps, Charlie
The rules on visibility from the cockpit have been updated.
There are rules and regulations imposed on the view from the cockpit, for very good reasons - collision avoidance for instance. During approach, the pilots must be able to see the runway while on the glide slope, at any COG location. From Torenbeek:
The angle of view forward and downward must be sufficient to allow the pilot to see the approach and/or touchdown zone lights over a distance equal to the distance covered in 3 seconds at the landing speed when the aircraft is
- on a glide slope,
- at a decision height which places the lowest part of the aircraft at a height of 100 feet above the touchdown zone (see Fig. 3-25) ,
- yawing ± 10°,
- making an approach with 1,200 feet Runway Visual Range, and
- loaded to the most critical weight and center of gravity location.
Some additional requirements from British regulations were:
- When taxiing, the pilot should be able to see the ground at a maximum of 130 ft trom the airplane, but preferably this distance should be 50 ft or less.
- When climbing, the pilot should be able to see at least 10° below the horizon and preferably 15-20° below it.
- When landing, the pilot should be able to see below the horizontal when the airplane is in the tail-down attitude .
- Another desirable feature is that during taxiing the pilot should be able to see the wingtip on his side of the airplane.
The FAA made a proposed regulation on improved visibility from the cockpit in 1971. However, according to the aerospace industry, this would impose structural limitations on cockpit design with high weight and drag penalties. From FAA AC 25.773-1, published in 1993:
A majority of the commenters responding to Notice 71-2 objected to the proposed amendments. In general, the airplane manufacturers believed the proposed requirements were too stringent and exceeded the state-of-the-art, particularly with respect to the size of transparent panels, considering weight and structural strength necessary to provide clear vision in the specified areas.
The B777 was designed before 1993 and followed older regulations. The view from the cockpit for aircraft designed after 1993 (the 787 for instance) complies with the Advisory Circular 25.773-1, allowing a smaller field of view compared with earlier regulations.
The windows are curved because current technology allows for double curved surfaces that are strong enough for bird impact, although the B787 has had some problems with cracked windshields.. As @PeterKämpf points out, the flat panels of the past required using more of them to keep reasonable aerodynamics, drag and noise: if the panels must be flat, many small panels make for better aerodynamics than a few big panels.
Having many cockpit windows is a relic of past times, where most of the work was VFR and there were no such things as a TCAS.
Let's take a look at the Boeing 707 for example:
As you can see, there are many big windows, even additional small ones at the top to make it easy to spot traffic.
However, IFR and systems like TCAS have made it unnecessary to use many big windows. Today, windows in the cockpit are only needed for take-off, landing and taxi. The rest works automatically.
And if you think: "Why bother, just let those windows in there, the better view is always better". Glass is significantly heavier than the other materials used on aircraft. And as you know, every pound counts in aviation.
This change happens slowly as you can see. That's why the 777 has still got quite big windows and the 787, the current Boeing flagship, smaller and less.
This trend will, of course, continue in the future, until the minimum for above-stated purposes is found.