B777-Winglets?

[BMM389EC]

Noticing the trend in modern airliners all to be produced with winglets(B747-400,B737-800, A340,330,etc), does anyone have any ideas on why the B777 was never produced with winglets?

[747FOCAL]

The 777 is already optimized so much that the introduction of winglets will be very small on a percentage of SFC curve.

[john_tullamarine]

Might I be inflammatory and suggest that, on the bigger machines, the design preference would have been to increase the span but that airport infrastructure would then be compromised on the apron ?

I suspect that, for many of the smaller aircraft, fashion is involved.

[Bally Heck]

I seem to recall that the 777 was once envisioned with hinged wingtips to allow a greater span which could then be folded up approaching stand. I suppose if you forgot to lock them down before take-off then you might have winglets

Anyone else know about this?

[criticalmass]

Bally Heck,

I remember the folding wingtips (for ground clearance at airports) when the 777 was announced by Boeing but as far as I recall the "customer uptake" was so lacking that the idea was abandoned.

"Nothing quite impedes the progress of aerodynamics as a good idea at the wrong time!"

[Techman]

I think that Boeing is considering offering winglets as a retrofit option on all its models, past and present.

[126.9]

So, (to that smart, Standard Cathay Interview Reply) does that mean that the B747-400 wing is not optimized?

[BahrainLad]

Boeing initially offered folding wingtips to American Airlines so that the a/c could park at DC-10 and 767 gates.

Understandably, Boeing were pretty pissed off when AA decided to not order the 777, after the money that was spent on the design.

Then they were even more pissed off when AA decided to order the 777 3 years later, without folding wingtips.

[OneDotLow]

The B777 has what is known as a 'super critical wing'. The design is such that the Critical Mach Number (M-Crit is the speed at which supersonic airflow first occurs on the airframe), is higher.

As well as raising M-Crit, the wing is designed to give less drag at low speed.

I guess in the end they figured they had done a good enough job in designing the wing to no longer need winglets.

ODL

[Prof2MDA]

This has been covered here before, but the issue with winglets is that they are very effective, but the aircraft has to spend most of its time in a particular flight regime as they are idealized for just one phase of flight. The winglets on the MD-11 actually increase fuel burn during the climb and descent phases, for example. The airlines wanted the 777 to be efficient for both short and long haul, hence the wingspan was increased and they did everything they could short of winglets on it. A purely long range 777 would benefit from winglets, so far there aren't any!

[richard27]

I was told at a Boeing factory visit (by a performance engineer) when the first 777's were coming off the line that winglets are only as effective as adding half of their height to the length of the wingspan (per side). That is, if you put 6 ft winglets on, you would be better off increasing the total span by 6ft. The 777 wing was short enough to allow this without causing parking problems.