B747FAN From United States of America, joined Jul 2000, 82 posts, RR: 0 Posted (12 years 1 month 3 weeks 6 days ago) and read 6595 times:
Happy 100th anniversary to all aviation buffs.
Just wondering, if winglets reduce drag and increase fuel efficiency and range, how come the B777 does not have any. This may be a amateur question, but I have always wondered. Maybe some of you might give me some insight.
) He turns not back who is bound to a star. - Leonardo Da Vinci.
Cedarjet From United Kingdom, joined May 1999, 8558 posts, RR: 53
Reply 1, posted (12 years 1 month 3 weeks 6 days ago) and read 6518 times:
I think they meant to put some on (they look nice after all), but forgot. Either that, or after extensive windtunnel tests and scientific research, decided they weren't necessary. The most obvious answer is #1, but things have gotten awful strange in Seattle lately, so anything is possible.
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
Longhaulheavy From United States of America, joined Dec 2003, 402 posts, RR: 2
Reply 2, posted (12 years 1 month 3 weeks 6 days ago) and read 6400 times:
From something I found here: http://airtransportbiz.free.fr/Technique/Thewinglet.html
The A330 is equipped with a two metre tall, outwardly canted winglet at each tip aimed at reducing induced drag. However, although a newer airplane, the 777 was not designed with winglets. At the time Boeing chose to increase the span of the wing rather than add winglets. As increased span also increases wing aspect ratio [another measure of efficiency] Boeing outlined the addition of winglets did not overcome the weight penalty of carrying winglets. Sources have since shown that increasing the span of the wing by 4/5 of the height of the winglet will have a similar effect on induced drag as a winglet, though without the added complexities of extra outboard structure, extra weight and extra cost.
FoxBravo From United States of America, joined Nov 2003, 3067 posts, RR: 4
Reply 4, posted (12 years 1 month 3 weeks 5 days 23 hours ago) and read 6246 times:
The 777 wing is already very efficient, so any efficiency gains achieved by adding winglets would likely be offset by the additional weight and expense of the winglets themselves. Note that the 777 without winglets has the same range as, and a higher cruising speed than, its winglet-equipped rival, the A340-300. Different designs work well for different planes.
However, for the "Longer Range" 777s, Boeing evidently decided that the benefits produced by raked wingtips would offset the increased weight (as you may know, raked wingtips have a similar aerodynamic effect to winglets). So, in the design of any plane, it's a judgment call based on the balance of costs and benefits.
FYI, you might get somewhat better answers to questions like this on the Tech/Ops board, in part because there tend to be fewer Airbus v. Boeing arguments and less sarcasm in general over there, but I hope this helps a little bit.
And finally, don't be put off by the "already discussed before" police. The search function does not always work very well, and if you're new to the board it's inevitable that you'll occasionally ask something that has been discussed at some point in the past. There are people here who get their kicks out of pointing that out...just ignore them.