Tsufang@ci From Taiwan, joined Feb 2002, 39 posts, RR: 0 Posted (11 years 4 months 1 week 3 days 4 hours ago) and read 2558 times:
i've visit the boeing site to see the information about commercial airplane data
one interesting different between 744 and 744 domestic version that's no wing let on domestic version
why?as i know wing let is to reduce the effect of lift reduction cause by wing span too wide and large then the pressure under the wing large than the pressure on upper surface of the wing and on the most outboard position on the wing produce a down wash force let the lift reduce
and the wing let just like a wall to against this situation occur
so how do u think about no wing let on 744 domestic version?thanks
B747skipper From , joined Dec 1969, posts, RR:
Reply 2, posted (11 years 4 months 1 week 3 days 3 hours ago) and read 2539 times:
Dear Tsufang@ci -
PPGMD did mention it - for the 717, and I remember there had been about the same type of explanations about 747-400D a few months in the past as well...
The 747-446D (JAL) and 747-481D (ANA) are optimized for typical 90 to 120 minutes-long sectors, so they spend very little time in cruise, which is the only time winglets can be justified for economy...
I heard (or read) that - in addition, the 400D do not have the extra tank in the tail - and I also learned that if the airplane, at a later time, is used on longer sectors, the winglets can be installed... I think I read something about 2 of ANA's airplanes, retrofitted with winglets to operate on longer sectors.
Ybacpa From United States of America, joined Feb 2001, 1108 posts, RR: 1
Reply 3, posted (11 years 4 months 1 week 2 days 19 hours ago) and read 2488 times:
Without getting too technical, B747Skipper has it correct- the winglets only improve performance during extended cruise. By removing them they have slightly better takeoff performance.
And yes, this is retrofitable- either the addition of winglets, or, conversly, the removal of winglets to convert the plane to a -400D.
The fuel tank I understand is technically still possible to order with a 400D, but due to the short distances the airlines intend to operate them, this is not justified, and are therefore not ordered. I'm not sure what happens, though, if an airline converts a -400 to a -400D.
SkyTeam: The alliance for third rate airlines finally getting their act together!
CCA From Hong Kong, joined Oct 2002, 790 posts, RR: 14
Reply 4, posted (11 years 4 months 1 week 2 days 15 hours ago) and read 2466 times:
It costs fuel to have the additional weight of winglets but the reduction in drag from the winglet saves fuel, so there is a balance point at which the winglet starts saving fuel over the amount it costs to carry them and this point is about 2 hours into the flight so 400D's flights of less than 2 hours save fuel due to the fact of they aren't paying for the weight of the winglets.
Now I just checked the MEL and a missing winglet causes an increase of 2.5% in fuel burn now that isn't entirely the benefit of the winglet as the end of the wing is a little untidy without the winglet which will cause some drag.
Now the stabilizer is a normal 400 stabilizer except it has none of the plumbing for the fuel tank. As an example on this -400F you can see the two blank plates on the underside of the stabilizer towards the tip on the pick below. Freighters don't usually have the stabilizer fuel option like the 400Ds
SSTjumbo From , joined Dec 1969, posts, RR:
Reply 5, posted (11 years 4 months 1 week 5 hours ago) and read 2350 times:
I always thought this was why:
Basically, you have two winglets adding significant mass and not providing the aerodynamic benefits to rebuke the negative benefits of the winglets on short range flights, to put it in a nutshell for you. Please refer to the above picture for some sort of analogy .