Why do aircraft wings turn up at the ends?

Wow a whole boat load of bad answers:

* Wingtips * are simply the ends of the wings and nothing more.

Wingtip devices (which is what I think you mean) come in many flavors:

*Winglets*

Blended winglets

Wingtip fence (airbuss others)

Raked wingtip

non-planner wingtips

Actuated wingtips (XB-70 compression lift)

Wingtip devices are generally used to increase the lift generated at the wingtip plus reduce the lift-induced drag caused by end vortices's thus improving lift-to-drag ratio. This increases fuel efficiency and performance. They also decrease wake-turbulence for aircraft flying behind them.

Winglets

Are the most common on newer aircraft and function very simply with a toed out angle to them. This toed out angle not only accomplishes all of the above general functions but also adds a thrust vector.

More on the other types of wingtip devices:

http://www.answers.com/topic/wingtip-device

Ok. The teacher has graded all of the quizzes and here are the results. Charles has the correct answer yet again along with gailforce and nevit. I won't repeat what he said about winglets but I will add a little about how and why they work. As mentioned, wing tip vorticies are generated off the tips of any wing. These vorticies are simply another form of drag like all turbulent air coming off a wing so reducing the severity of the vortices results in a reduction in drag. The reason the vorticies form in the first place is due to the spanwise flow of air from the root to the wingtip. That's rignt, air not only flows from leading edge to trailing edge, along the cord, there is also a component that flows along the span especially in a swept wing jet. As the low pressure air flowing spanwise over the top of the wing meets the high pressure air flowing out from the bottom at the tip, a little tornado, or vortex, forms and that's not good as far as drag goes. Now here is where almost every answer above is wrong. WINGLET DIVICES PERFORM ONLY ONE FUNTION. THEY REDUCE SPANWISE FLOW OVER THE UPPER SURFACE OF THE FRIGGIN WING. It doesn't matter whether or not they are swept out or angled or anything else. If they are angled outboard they are less effective at reducing spanwise flow but that angle does have the effect of increasing the aspect ratio and therefore lift so in some designs this can be a good trade off. They used to use wing fences to control spanwise flow but winglets do a better job with the added advantage of a slight increas in lift. Now, everybody but the three that did their homework will be staying after school to write "reduce spanwise flow" a hundred times on the blackboard. And I don't like apples.

The rudder has a negligible effect on turning the plane anyway. To turn, you roll the plane with the ailerons, so the lift from the wings has a sideways component which accelerates the plane in a horizontal circle. At a large bank angle like 45 degrees, you have a force equal to the whole weight of the plane making it turn, which is far more than you would get from a "small" thruster at the wing tips. In fact it can be much bigger than the force from the main engines. All the rudder does is help to keep the nose of the plane pointing in the right direction, since unlike helicopters, planes are not very good at flying sideways or backwards. If you did try to turn using just the rudder (or your thrusters) the only result would be that the plane would fly sightly sideways (yawing). If it did turn, it would only turn very slowly and not in a controlled manner. No "clever" plane designer would replace a simple metal plate on a hinge with a more complicated and expensive set of wing thrusters to achieve the same thing.

A lot of wrong answers here, but some are right. The up-turned parts at the tips of the wings are called winglets. Simply enough, they help the wing produce more lift by not letting air "slide" off the tips, and they reduce the drag by not allowing wingtip vortices to form. So overall, they make the aircraft more efficient.

In addition to the correct answers above (Spanwise flow etc)it is also suggested (And proved a little) that a correctly designed Winglet will save 6% fuel on a long haul flight.

Also, as modern Aircraft are being built with them as standard or retrofitted, it makes the "Winglet free" wing look out-dated.......for this reason, a lot of Business Jets are having Winglets put on just to look good (They do perform a little of course but not enough to assist the wallet of a Biz jet owner).

We call these "Blinglets".

Back in the 70's, the wig tip device that caught everyones eye was a mimick of the Hawk/Eagle wingtip feathers. 4 or 5 "Fingers" stuck out of the wingtip. It was tried on a light A/c, and it probably caused more drag.

not all do but now in day most airlines use them

their called wing lets. or Wingtip devices.their intended to improve the efficiency of fixed-wing aircraft. it makes it so friction cant build up at the end of the wings and it saves the airline more money in engine repairs gas etc. and the plane goes faster using less power.

some planes that have them include....all airbuses

737`s 747`s 757`s

crj700 and a lot more!

planes that Boeing plans to put wing lets on includes

Boeing 767-400ER

Boeing 777-200LR/-300ER/Freighter

Boeing 787-8/-9/-10

Boeing P-8 Poseidon

I assume you are talking about the dihedral or winglits.

I'll discuss both.

The Wingtips are there because of the way the wing works. Low pressure exists above and high pressure below. This difference in pressure is always trying to equalize. When air flows from the bottom surface to the top, it forms a vortice, increasing drag. Wingtips help stop these vortices's and increase fuel efficiency. They also help minimize the formation of wake turbulence, which can be deadly to other aircraft.

The dihedral help increase stability on the longitudinal axis( from nose to tail). This occurs because when the plane starts to turn, the relative wind strikes the wing at an angle. Because it's angled upwards, the wing will tend to level off again.

Here is an example of a wingtip http://www.airliners.net/open.file/1167199/L/

and of a dihedral( you can notice the wings angle upwards)

http://www.airliners.net/open.file/1152973/L/

Also if it interests you, a downward angle is called an anahedral. It does the opposite of the dihedral. It increases the aircraft's response to a roll command, and because of this it's mainly found on fighters, like this one.

http://www.airliners.net/open.file/1242791/L/

It is to do with the flow of air over the wings and what happens to the flow at the tips. Apparantly there is a lot of air 'spilt' at the wing tips and so that the wings dont have to be made longer (more size and weight) the turn up section greatly reduces the amount of lost air thus giving the plane more lift.

Some do and some don't. Engineers discovered that the slight upturn on the end of the wings of airplanes reduces the drag enough to actually improve the "mileage" they get. So it is a fuel saving thing.

The winglets reduce the vortices created by the wingtips as they move through the air reducing drag and improving performance, both fuel efficiency and low speed performance as there is less induced drag on the plane.