757 winglets.

[Ivan aromer]

How does the addition of winglets on the B757 improve the lifting ability off a runway. I am familiar with the reduction of induced drag resulting in a decreased fuel burn in the cruise, but for the life of me cant work out why winglets should result in the ability to lift alot more from a give runway than a nonwinglet 75!

[kwachon]

The wingspan is effectively extended by a length equal to the winglet height.

e.g. winglet is 8 feet tall, then wingspan is effectively increased by 16 feet.

More wing area = more lift

Just a simple answer, there are of course other complexities involved regarding drag etc.

KW

[Re-Heat]

I was going to cut and paste, but a direct link seems more appropriate:

Wingtip device - Wikipedia, the free encyclopedia

[porch monkey]

Often, it isn't actually about the runway, more about obstacle clearance. The increase is usually because of better aerodynamic performance in the climb out, especially 2nd segment, which is often the limiting part. The improved cruise performance is a nice side benefit.

[muduckace]

A wings effective lift at slower speeds is further out on the wing, at high speed the lift goes inboard.

Not sure but I suspect the above statement about wing area above may be a correct statement for slow lift and makes use of the lost lift slipping off the outer wing portion at high speed.

[tightcircuit]

Just looked at the figures in our computer take off programme. At max weight on a standard day 26L at LGW the wingletted 757 rotates 8kts slower and has a V2 9 kts slower.

[DAL2728]

8kt slower rotation speed is a very tangible benefit of winglets!

[BITE System]

If I remember correctly induced drag is more prominent at slower speeds, so if you are reducing induced drag with winglets, then you are also increasing the lift produced. So when comparing an aircraft without winglets to an aircraft with winglets the aircraft with winglets will get airborne earlier and have an increased payload.

[ClippedCub]

Winglets are just low drag wing endplates that control the mixing of high pressure air from the lower surface, with low pressure air on the upper surface. By making it harder for these two flows to meet, you end up with an increased, effective, aerodynamic aspect ratio, which equates to about 1/3 the height of the winglet. Hence, the total wingspan effectively increases by 2/3 the height of one winglet.

By controlling the spill over from lower to upper, the outer wing generates more lift resulting in an increase of CLmax. The CLmax increase shows up in reduced stall speed, which leads to reduced takeoff and landing speeds and distances.

Winglets work best in the high CL environment, e.g., takeoff, climb, high altitude cruise, and landing.

Most winglets on GA are for looks.

[tightcircuit]

I am a total pratt. Please ignore my post above. I had completely failed to notice that I had left the flap selection in auto in the t/o performance programme. The computer had automatically a different flap setting for the winglet version. Rubbish in rubbish out.

Sorry all

TC

[Gillegan]

Ability to climb (or Rate of Climb) can be considered as the difference between Thrust Available and Thrust Required. (Remember that in steady state flight, Thrust = Drag). If total drag is decreased (due to decreased induced drag), then the "Excess Thrust" is greater, yielding better climb performance which also translates into greater payload.