If winglets are used to reduce the induce drag, why are some widebody airliner don't have winglets?

Question

Why do they don't put winglets to all types of fixed wing aircraft in order to reduce drag?

Answer 1

It is possible to design very efficient wings (or wings with the same gains as the ones with winglets) with no winglets. For example the Boeing 777 and the 787 doesnt have winglets (However 787-3 would have winglets, the intention being weight and span reduction and is meant for shorter hauls). As a matter of fact an increase in wingspan is generally more effective than a winglet of the same length.

The winglets usually comes as a compromise, when you cannot redesign a wing, or fancied by the operator or where a shorter wingspan is practical. Besides they increase parasite drag and require enhanced wing strengths for safe assembly.

Large winglets are of benefit in short distance flights, where it enhances climb performance. Raked wingtips is the buzzword now, preferred over winglets for long distance flights where cruise performance is more important.

Answer 2

Winglets are not used to reduce drag, in fact they add drag.. They are used to increase lift. With some aircraft designs, the lift to be gained by winglets would not be enough to offset the increased drag produced by winglets. Anytime you attach something to an airplane in addition to its conventional structure you necessarily increase drag.

Answer 3

There were many Aircraft including wide bodied that were built before winglets were recognized. You've probably seen older Aircraft whose owner or operator hasn't bothered to upgrade.

Economic factors are different for owners and and some operators.

Answer 4

Wingtip vortices sort beacuse there is low tension on the proper of the wing and extreme tension below. Air flows from below the wing upward. on the the perfect option wing this varieties a Counter clockwise spiral and on the left a clockwise spiral. including a winglet provides a barrier no longer allowing the air to rotate from the extreme to the low. additionally by skill of reducing spanwise pass winglets enhance effincency. raise triggered drag is a by skill of-fabricated from raise. once you're producing raise you're additionally producing drag. extra raise=extra drag so a miles better attitude of attack and a miles better velocity propose extra triggered drag as a results of fact extra raise is being produced. Now that spiraling vortex is springing up drag. If we get rid of or cut back that's length we cut back drag.