The 777 Airfoil

Sun Sep 02, 2001 12:38 am

I was watching a show about the 777 on the Discovery channel, and they said that the 777 had a new, revolutionary airfoil design and makeup that allowed it to have fast climbout rates and could enable it to takeoff in virtually any environment. So I was wondering what made this airfoil so efficient and remarkable?
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RE: The 777 Airfoil

Sun Sep 02, 2001 2:06 am

Like the 757 and the 767 wings, the 777 airfoil is supercritical. These are generally "fat" or relatively deep in cross-section and generate lift across their entire upper surface rather than a concentrated area close behind the leading edge. In the case of the 777, the wing generates a lot of lift toward the trailing edge and is said to be "aft loaded". This is reflected in the scooped-out appearance of the underside of the wing near the trailing edge and is described as inverse, or aft, camber.

A critical design element of the wing is the flaps. These play the biggest part in giving the 777 an exceptionally short takeoff and landing capability for such a large aircraft. A set of double-slotted flaps are positioned on the inboard trailing edge between the engine and the fuselage. The outer wing trailing edge supports a large, but simple, single-slotted flap section. The flaps can be moved to six positions. Extra help for takeoff and landing is provided by a high speed aileron, which converts to a slotted flap for slow flight. A cove lip door seals the hinge gap when the "flaperon" (a combination of aileron and flap), is used as an aileron. This door opens to provide a smooth air flow when it is used as a flap, at which time it can be "drooped" down to 36 degrees. A set of seven spoilers and seven leading edge slats on each wing complete the slow flight ensemble.

A super advanced airfoil, designed to be ultra efficent over both long and short hauls.
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RE: The 777 Airfoil

Mon Sep 03, 2001 8:59 am

The so called "super-critical" and "aft-loaded" airfoil was developed by NASA in the mid 70'es, and hardly any new airliner design has come of the drawing board since 1980 without taking advantage of that development.

It is one of the mojor differences between the Classic 737 and the 737NG.

One great advantage of the super-critical airfoil is that it can be made thicker without too much drag increase. That helps greatly to reduce weight of the wing structure. It also leaves more room for fuel in the wing, which makes it possible to design the best fuel weight distribution over the wing, which further reduces structure weight.

Especially the B777 has taken advantage of that extra strength in having an exceptionally long wing span. And as the modern airliner it is, it is of course equipped with all the most efficient high lift devices, leading edge slats, double slotted flaps and drooped ailerons (or flapperons).

Drooped ailerons were pioneered by the A320, but on the 320 family planes they are not slotted. As far as I know also the 330/340 family only uses unslotted drooped ailerons. And then I think that the MD-11 ends the list of planes which use drooped ailerons.

Regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs
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RE: The 777 Airfoil

Wed Sep 05, 2001 10:26 am

I have also noticed that the 777 has a very thick wing. Even on the outer reaches of the wingspan, it is not too thin. However, its rival, A330/A340 have very thin wings in comparison. What was the design concept for these planes? Their wingspan is almost a large as the 777; however, much thinner. Are they aft loaded as well?

Also, how aft loaded is a 747? I know there were some changes made to the 747 wing when the 400 series came along, but the overall thickness is about the same.

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