why does the airplane pilot change the shape of the wing during takeoff and landing?

Question

why does the airplane pilot change the shape of the wing during takeoff and landing?

Answer 1

The fundamental reason is to lower the stall speed to allow for lower speed touchdown or liftoff and reduce the need for runway length. People will often state this effect as "increasing lift" which is not exactly getting to the heart of the matter. The amount of lift is not really changed since lift is essentially equal to weight (during flight) regardless of flap setting. The needed lift can be generated at a lower speed with flaps deployed.



The secondary reason is to increase drag, which is helpful during approach to landing because the descent tends to accelerate the airplane. They also provide aerodynamic braking during landing roll out to assist with wheel braking or other slowing measures. Obviously drag is undesirable during take off, so a lesser flap setting may be selected which has most/all of the stall speed lowering effect, but less of the drag effect.



The third effect they have is on attitude and trim. With flaps deployed, an airplane flies with a more level deck which improves the pilot's forward view and passenger comfort, but must be compensated for with trim during the transition between no-flaps and flaps-deployed.

Answer 2

Airliners are equipped with trailing edge flaps and leading edge devices -

These items increase lift of a wing and also increase drag -



Increase lift is nice factor for takeoff -

Increase lift and drag is good factor for speed reduction and landing -



With more lift for takeoff, airplanes can use a shorter runway -

But by using increased flaps, the airplane will not be able to climb as well -

Reduced speed on landing (more flap setting) reduces runway length required -



One thing - use of spoilers in conjunction with flaps in flight is often prohibited -

Spoilers "kill lift" but with flaps, would increase drag beyond safe limit -

After landing, ok to deploy spoilers - which then become "speed brakes" -



If you want to study wings, and flaps - study the wing of a 727 -

When I was an instructor, it was my favorite subject for lift discussions -



The 727 has triple slotted trailing edge flaps -

On the leading edge side, it has both Kruger flaps and slats -

When the outboard flaps are UP, the outboard ailerons are locked -

So, in cruise, it is only inboard ailerons and spoilers for roll control -



Boeing engineers who designed 727 wing deserve a Nobel Prize of Aerodynamics -

And it is the inspiration for all the later Boeing planes -

Answer 3

The plane's wing has to generate lift equal to the planes weight for the plane to fly.



Planes are designed to have the wing operate as efficently as possible at the speed and altitude the plane will be expected to cruise at, while still providing good climb performance. That allows them to use as little fuel as possible while crusiing, which is where a plane spends most of it's time.



But you don't want to have to take off and land at cruise speed (or even normal climb speed) - If it takes you 2 minutes to accelerate to 140 MPH, it may take another 2 minutes to accelerate to 200 MPH - but for that next 2 minutes, you are traveling much faster and using more and more runway. You'd end up needing runways 10 miles long. Plus, the tires, landing gear and brakes would have to be able to handle those speeds. The other problem is that airliners are pretty good gliders- it's pretty hard to get them to descend without gaining even more speed.



To allow planes to take off and land at lower speeds, planes (except for the smallest and simplest) have one or more devices that allow them to alter the shape of the wing to produce the needed lift at a lower speed.



Trailing edge flaps are the most common, and are found on every airliner and most small planes. These do several things that allow for lift at lower speeds: they increase the curve, or "camber" of the airfoil, they increase the angle of attack of the wing, and on airliners and some small planes they actually make the wing bigger by moving backwards before angling downward.



You may notice that on take off the flaps are only deployed part way. That's because most of the extra lift is taken care of in the first part of the flap movement. Deploying them all the way does create some additional lift, but it also creates much more drag, or wind resistance. That helps the plane slow down and allows it to descend more quickly without picking up speed.

Answer 4

The fundamental reason is to have a wider speed range. Flaps and slats allow an aircraft to fly more slowly while creating sufficient lift to stay aloft. A slower takeoff and landing speed gives a greater safety factor and also means that shorter runways may be used.

Answer 5

They are called Flaps. Flaps are devices used to alter the lift characteristics of a wing and are mounted on the trailing edges of the wings of a fixed-wing aircraft to reduce the speed at which the aircraft can be safely flown and to increase the angle of descent for landing. They shorten takeoff and landing distances. Flaps do this by lowering the stall speed and increasing the drag.



Extending flaps increases the camber or curvature of the wing, raising the maximum lift coefficient — the lift a wing can generate. This allows the aircraft to generate as much lift, but at a lower speed, reducing the stalling speed of the aircraft, or the minimum speed at which the aircraft will maintain flight. In other words, they allow the plane to take off, and slow the plane while landing.

Answer 6

The truest answer is he's not a speed demon on the ground. Otherwise he wouldn't care how fast he must move to keep in the air. But with high lift devices engaged he's able to travel slower with adequate lift, so he can land at a more reasonable speed or take off at a more reasonable speed. This saves wear and tear on parts and he keeps his job.

Answer 7

One doesn't actually "change the shape of the wing". BUT most modern aircraft have additional flight surfaces that can be extended or retracted to change the airflow over the wing. Slats (in front of the wing), and flaps (in the rear of the wing) can be extended to force the air to flow differently over the wing's surface, thus improving lift for slow flight. When these surfaces are retracted, they reduce drag and allow the airplane to go faster.

Answer 8

During take off and landing, speed of the aircraft is low. That means air going above and under the wing is slow. That means there is little lift. During take off, that means aircraft may not lift up. During landing, that means pilot either has to keep the speed high or drop suddenly.



To avoid this, pilot uses flaps to increase the drag. That in turn create greater difference between the speed of air above the wing and below the wing - which creates more lift. So during take off, it can lift up easier. During landing, pilot can slow the plane without dropping too suddenly.



Fighter aircrafts and ultra-high-performance aircrafts have an ability to change the shape of the wing, which most of them are triangular. Remember I used the word "drag" earlier? That drag slows down the plane. During high speed maneuvers, this is negative effect. So pilot stream lines the wing to reduce the drag. He has enough speed, so the lift isn't a problem. He can go faster and turn faster. When he lands and takes off, he has to do the reverse.



Does that help?



Does that help?

Answer 9

You'll notice birds do the same thing when landing, they change their wings to be more efficient at low speeds by spreading out the feathers.

Answer 10

Flaps are used for takeoff and SLATS are used for landing. It changes the amount of air passing over and underneath the wings causing it to ascend or descend with stability

Answer 11

Takeoff and landing aren't the same action.

Therefore, the wings respond differently to taking off = accelerating, and landing = decelerating.

Answer 12

To help with lift!