JSchultz From United States of America, joined Oct 2000, 9 posts, RR: 0
Reply 2, posted (14 years 5 months 1 week 9 hours ago) and read 3348 times:
There is also an issue with fatigue life of the wing that must be looked at. As far as the 747-400D goes.. those operators (JAL, ANA & KAL) must fly the 400D as a domestic for half of the a/c's fatigue life and them install the winglet/wing extension kit to fly the same aircraft as a long-hauler to use the entire fatigue life of the aircraft. Now the question is will the operators do that or sacrifice the shortened fatigue life?
Tarantine From United States of America, joined Sep 2000, 210 posts, RR: 0
Reply 3, posted (14 years 5 months 1 week 5 hours ago) and read 3318 times:
The main reason the 747-400 has winglets was to increase the overall wing area due to its 870,000lb Max t/o wgt.
The 747-400D has much less t/o wgt., but when the -400D gets high cycle time, it can be converted to a long range -400 model, then winglets will probably be attached.
I don't think winglets make much overall difference. If they really did, I am sure that the 777 would have them. I always thought of winglets as an airbus trademark.
N-156F From , joined Dec 1969, posts, RR:
Reply 8, posted (14 years 5 months 2 days 10 hours ago) and read 3216 times:
No Boeing/Airbus wars here, please. Airbus didn't invent the Comet, de Havilland did.
As far as winglets on the B747-400D, they really aren't needed. They add extra weight to an already underpowered design (B744D has 45,700 lbs. per engine, as opposed to 57,900 for B744). The reduced drag incentive only plays out on long-haul flights, which the B744D with a sub-2,000 mile range, does not do.
Now, once the jets reach the halfway point of their (perceived) design life, they'll likely be given extra fuel tanks, winglets, and bigger engines and used intercontinentally, or bought up by cargo operators then re-engined.
And, yes, I always have thought of winglets as an Airbus trademark myself- what planes they make don't have them? Just the A300 and A310-200, AFAIK. That's got to say something about their effectiveness.
Prebennorholm From Denmark, joined Mar 2000, 6699 posts, RR: 54
Reply 9, posted (14 years 5 months 2 days 8 hours ago) and read 3212 times:
Winglets were invented by NASA.
All details were published in a fully public NASA report some 25-30 years ago.
Winglets can reduce drag by up to around 3% on an ordinary airliner.
But their shape and profile is very complicated. And unfortunately they have to be optimised for one "Coefficient of lift" (Cl) of the wing. In laymen's terms it means that they must be optimised for one speed, one altitude and one aircraft weight. Therefore the actual gain will always be considerably less than 3%. For some flight regimes the effect can easily be negative.
There are different types of winglets. The small ones on most Airbus planes are considerably less effecttive - will never gain 3%, but then they have a wider speed/altitude/weight "window" in which their effect is positive.
From this information it is easily understood that their extra weight and supporting wing structure is hard to justify on short range planes.
It is quite natural that the first 737 with winglets was the BBJ, the only 737 long range version. And that on other 737s they are offered as an option only. Clever decision by Boeing.
The less effective, and also less harmful Airbus winglet version on ALL planes is probably an equally wise decision, Just different. Winglets will always be a compromise. Well, most things on airliners are compromises.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs, Preben Norholm