SAA-SAL
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Why B747-400D Doesn't Have Winglets

Sat Nov 25, 2000 5:24 am

I was wondering why a B747-400D (high capacity, shorter range) doens't have winglets. Winglets reduce drag so they should also do this on short haul flights?
SAA B747 SP, Luxavia B747 SP
 
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RE: Why B747-400D Doesn't Have Winglets

Sat Nov 25, 2000 5:36 am

Winglets only really make a difference on supper long haul flights. Winglets reduce drag but they also create weight which only balance out on long haul flights!
Iain
 
JSchultz
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RE: Why B747-400D Doesn't Have Winglets

Sat Nov 25, 2000 6:48 am

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?

Jim
 
Tarantine
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RE: Why B747-400D Doesn't Have Winglets

Sat Nov 25, 2000 11:17 am

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.
 
galaxy5
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RE: Why B747-400D Doesn't Have Winglets

Sat Nov 25, 2000 11:08 pm

winglets really dont help out at all. they may add a few km in range after a 12-16hr flt but they cost extra weight and money to put on. but they do look cool. 
"damn, I didnt know prince could Ball like that" - Charlie Murphy
 
flight152
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RE: Why B747-400D Doesn't Have Winglets

Wed Nov 29, 2000 11:16 am

They reduse drag which increases range which is not neaded.
 
Guest

RE: Why B747-400D Doesn't Have Winglets

Wed Nov 29, 2000 1:52 pm

Hey, Airbus may think that they invented all the high tech stuff, but they did not! Where was airbus when the 707 was created? I agree, if winglets are so great, why are they not on the high tech 777?
 
Guest

RE: Why B747-400D Doesn't Have Winglets

Thu Nov 30, 2000 12:42 am

Where on earth do you guys get your ideas from??

Have you seen the BBJ and the B747-200 with WINGLETS? They make a huge difference to the fuel flow. Try doing some research on wingtip vortices and induced drag.

As for why they are not on the 777, remember that the 777 was a new design, the concept of NOT INVENTED HERE was applied.......

I'm sure that APN of Seattle will prove the winglets make an improvement on the 777... just give them time.

PS, to answer the question of where was airbus when the 707 was invented.... well i guess that it was busy flying the COMET!

Boeing and Douglas actually learned lessons from the design of the COMET such as not to use square windows.

PPS, where is the USA SST? Remember that Concorde is based on 1960s technology.
 
Guest

RE: Why B747-400D Doesn't Have Winglets

Thu Nov 30, 2000 6:20 am

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
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RE: Why B747-400D Doesn't Have Winglets

Thu Nov 30, 2000 8:12 am

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
 
AFa340-300E
Posts: 2115
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Why The 777 Has No Winglets.

Sun Dec 03, 2000 4:31 am

Hello,

There are two major means to decrease drag on wings: either put winglets or increase wingspan.

The A340 and 747-400 got a winglet, but that wasn't the ideal because those required a wing strengthening to hold the weight of the winglets (thus adding structural weight).

The 777 got a lengthened wingspan.

The newest aircraft get blended winglets, thanks to which a lesser structural reinforcement is required.

The 777LR will feature raked wingtips, already fitted on the 767-400ER.

And yes: the NASA invented the winglets on a US Army requirement. After making some tries they saw that winglets reduced drags (seen on DC-10's models).

Best regards,
Alain Mengus

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