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rhinodriver
26th Oct 2005, 00:43
I was asked during an interview what the purpose of the winglets on the 744 were for. I gave the standard aerodynamic properties that winglets provide. The interviewer after saying that I was correct said that they were also for another reason on the 744. I was stumped. I fly fighters and had no idea what he was talking about. Anybody out there know what he could have been refering to? Thanks...

Intruder
26th Oct 2005, 00:45
They are also "FE deflectors" -- remind the Flight Engineer that he's preflighting the wrong airplane.

Dan Winterland
26th Oct 2005, 00:48
I was suprised that the MEL said you could fly with one missing, but not both!

Flight Safety
26th Oct 2005, 01:37
One reason I've heard is that Boeing wanted longer wings for the 744, but decided to use winglets on a shorter wing to get the same basic aerodynamic benefits of a longer wing, without the airport parking issues and the engineering issues of buillding a longer wing.

derekl
26th Oct 2005, 01:41
About five years ago I flew on a BA 744 SFO-LHR which had a missing winglet. Got a pleasant CC going when I told her she was short a winglet . . .

Carnage Matey!
26th Oct 2005, 02:01
As an aerodynamics engineer once said to me at a now defunct US aircraft manufacturer:

"We could have had a longer wing, but the winglets make it look more 'space age' so we went for that"

Perhaps aesthetics is the reason?

FlexibleResponse
26th Oct 2005, 14:42
At the time that the 400 model was conceived in the mid-late eighties, winglets and computers were becoming the must-have fashion items for new aircraft. To spruce up the 300 model, Boeing decided to add winglets to pretty much the same old wing design that they had since the introduction of the first 747 model.

As a result of the lack of aerodynamic optimization, the winglets only provided a modest improvement (reduction in drag) in fuel flow to compensate for the additional weight (approx 1200 lbs per winglet from memory) of the winglets over long sectors. But they looked good to the customers.

However, for short sectors the reduction in drag did not compensate for the increased fuel burn for the extra weight. For this reason, some Japanese domestic operators ordered their 747-400 models without winglets.

A-FLOOR
27th Oct 2005, 07:07
The basic -400 wing is a few feet longer than the classic 747 wing, even if you don't include the winglet. The -400D as used by JAL and ANA is a -400 with a classic wing without the tip antenna and with some other structural modifications to provide higher cycle life. :)

an3_bolt
28th Oct 2005, 01:12
In addition to the standard aerodynamic drag thingy depending on the original aerofoil pressure distibrution pattern and loading - think along the lines of sometimes increased directional stability eg Learjet or possibly increased lateral stability eg Lancair 360 homebuild and possibility of increased roll rate due to aileron flow pattern eg some sailplanes. The NASA website used to have a quick blurb on their early studies. I am sure the more enlightened out there can help think up some more groovy stuff.....
However, I believe (with no proof of any kind whatsoever) most importantantly a winglet is space for corporate advertising. Shareholder profits shall be held above all else. Long live the shareprice.:p::
By the way rhinodriver - did you get the job??

Dan Winterland
28th Oct 2005, 01:45
The 400 wing is different to the classic - it's not just had winglets added. The span of the 400 is 11' longer, the profiles are different, it has many carbon panels, different wing root fillets, diffrent tank volumes, different ailerons, different flap schedules and the flaps and spoilers are fly by wire. I've flown both and the handling is different.

The JAL ANA 400Ds do have 400 wings, the just don't have the winglets which are only beneficial in the cruise - a stage of flight the 400Ds rarely achieve.

rhinodriver
28th Oct 2005, 21:43
I managed to get a second interview that is coming up here is December! I sure hope I get the job!

Silverado
31st Oct 2005, 06:46
Sorry Dan the spoilers/speedbrakes are still cable driven and while the flaps are controled through the FCU'S on the 400, L/E flaps have always been controlled through wires, not cables, like the T/E flaps on the classics. The wing is 16' longer and I am not aware of any aileron differences.