Mirage From Portugal, joined May 1999, 3125 posts, RR: 13
Reply 1, posted (15 years 11 months 3 weeks 5 days 8 hours ago) and read 2704 times:
Air has different pressures as it passes under or above the wing. At the edge of the wing the flow with higher pressure "wants" to mix with the flow with lower pressure causing some drag.
Winglets avoid this mixing of different pressures, so they avoid the drag.
Winglets are more efficient at long flights saving more fuel burning.
I'm sure you'll get better answers because I'm not a pilot.
Leo-ERJ From , joined Dec 1969, posts, RR:
Reply 2, posted (15 years 11 months 3 weeks 5 days 8 hours ago) and read 2700 times:
Reducing drag in for any flying object is very important in most situations. I won't be going into details because this can get pretty complicated. The winglets reduce drag by spreading of the vorticity in the wingtip region and keeps the air friction drag lower in the inner part of the lift generating system. Basically, it separates the airflow and breaks the lift resistance which was created at the wingtip.
There are many different types of winglets depending on its purpose. You can see that a MD-11 has also an additional downward winglet opposed to a A330 or B744 which hasn't got quite an extension. They rely on the stress boundaries presented by each aircraft and often vary. The shifting of airflow is affected and many factors will come into play. In many aircrafts performing is increased with the use of winglets and less fuel is burned during cruise.
L-188 From United States of America, joined Jul 1999, 30174 posts, RR: 58
Reply 5, posted (15 years 11 months 3 weeks 5 days 3 hours ago) and read 2667 times:
We had a big disscussion about winglets in my aerodynamics class. You will still get a vortex off the winglet the difference that it make is that the vortex is much smaller and tighter. This is where the drag reduction comes into play.
Also despite the fact the winglets are usually pointed just about straight up and down the winglet acts like it is a straight extention to the wing. So you can get the same benifit by simply extending the wingtip.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
JETPILOT From United States of America, joined May 1999, 3130 posts, RR: 27
Reply 6, posted (15 years 11 months 3 weeks 5 days 1 hour ago) and read 2664 times:
Winglets also have an angle of attack to the relative wind enabling them to produce lift in the forward vector increasing cruise speed approx 1-2% on the 747. Acting like sails on a boat they have also been given the nickname tipsails.
A wing with winglets has a larger effective span. It allows a smaller wing with winglets to act like a larger span wing without the weight of additional wing structure.
Ravi From Singapore, joined Oct 2005, 0 posts, RR: 0
Reply 8, posted (15 years 11 months 3 weeks 20 hours ago) and read 2636 times:
Boeing found, with the 747-400, that the comparable increase in efficiency with increased wingspan was greater than by having winglets. This led the company to do some serious research into wingtip devices. Boeing settled upon the raked wingtip design (not the sort used on the 767-400ER, but the 777 and 737NG) as it did not incorporate unnecessary structural strengthening required for winglets (they twist in flight and the wing must be made stronger).
In essence, instead of a winglet, Boeing just increased the wingspan to the weight of what it would have been with a winglet. More performance was generated in this area.
Then Boeing discovered the blended winglet, which does not require the same level of structural strengthening and older types. Boeing, ofcourse, has a patent pending on the 767-400ER raked wingtip, which is the best of both worlds - winglet and increased span, with significantly less weight.
Virgin747 From Canada, joined Oct 1999, 327 posts, RR: 0
Reply 9, posted (15 years 11 months 3 weeks 15 hours ago) and read 2628 times:
The winglets on the 747 400 were also added on as a result of the extra 6ft that was availble to them and they did'nt want an aircraft that was hard to manuvuere around crowded airports. And when the 747400 had the wing extension, it would provide more fuel space,but add more weight.