Winglets
 

After a few red's a question has come up.

Are winglets there primarily to-
A.Increase lift.
B.Decrease drag.

I could also put in-
C.Looks good
D.Somewhere to put the company logo.

mainwheel,
I'm thinking it must be primarily to reduce drag.
It is possible to dispatch a 747-400 with 1 winglet removed if the fuel uplift is increased. I cant remember the amount of fuel but if this is the case then no winglet must mean more drag so more fuel burn.

They are there to reduce vortex generating swirl over the tips from the high pressure underside to the low pressure underside. This effectively increases the aspect ratio of the wing, and so should reduce induced drag.

Designed right, the increase in profile drag should be rather less than the reduction in induced drag.

G

Now I'm confused!;)

My fault, try high pressure underside to low pressure upper surface.

G

..another important concern with the big birds is the existing airport apron infrastructure.... I have no doubt that Mr Boeing would have far preferred to go for an increased wingspan .. but the bird then wouldn't fit into the gates without a major (read super expensive worldwide) rework ... so the only effective way to get a reduction in induced drag is to go for something more brutal ....

I suspect that, for many of the smaller aircraft, marketing has had a say in the way drag reduction is approached .....

Ghenghis is right. They reduce the flow of air outward over the wing tip which causes drag.
Didn't Mc Donnel Douglas have to fit them on the MD11 to get the fuel burn and range quotes on the aircraft they sold to Swissair.
:)

Saw a new B737-800 with wingets. They're huge! Nearly as big as the fin!

TRUE FAITH
I dont think that there is a performance penalty on the 747-400 with one winglet missing. Could be wrong...again!

For Winglet Off ops, I think the fuel load is increased on the wing with the missing winglet to make up for the weight difference. will check MEL next time at work. Air Canada operated a B744 for a few days minus a winglet.

boeing put them for airlines to put their logos on...just to remind their pax who they are flying on(also so they know who to blame for delays due to atc/weather/security etc etc:D :D
but i will check the mel and let you know unless denzel gets there first

ok th e mel says (for major us airline)but is prob a boeing std
1 may be missing
reduced performance limited weights by
20,800 lbs from the t/o runway,climb limit,and approach limit weight and
10,000 lbs from the etp/terrian clearance weight


also surprising is there is no time limit
but i expect with those restrictions any long flt will not happen
hope this helps

screwdriver,
BA's CDL states that aswell as some performance limitations the planned trip fuel should be increased by 2.5%. I didn't notice anything about where the fuel should be put on the aircraft as Denzil mentioned.

Winglets why?
 

It is said down under that Qantas have gone for winglets on their new 737's because the CEO thought they looked sexy. Now there is a sound business practice.

Thank you all.Sounds like drag reduction is the correct answer.
As to Qantas's thinking-maybe it might be better looking out the cabin window if your not flying VirginBlue.

I guess the size of the vortex is proportional to induced drag.




http://www.b737.org.uk/737winglets.jpg




More info here.




BTW I saw a VirginBlue -800 a couple of weeks ago.

TRUE FAITH
Thanks for putting me right on this.

Winglets are there primarily for induced drag reduction.

However,

By increasing the efficiency of the wing outer section they also increase lift by making the wing "virtually" longer and also therefore increasing the aspect ratio.

Also, I read an article when I was an apprentice about wing "sails", these were described as long thin winglets which reduced drag on smaller slower a/c and were more efficent than winglets over short distances. Somewhat like the B737-800 BBJ.

All MD11s had the winglets btw. Believe they were tested on a Finnair DC10.