Winglets increase the fuel efficiency of aircraft that have them.
Winglets are not absolutely required but many planes have winglets added to improve the aerodymanic efficiency of the wing.
Winglets increase an aircraft's operating efficiency by reducing induced drag at the tips of the wings
to reduce drag
Usually control surfaces, like ailerons, flaps, slats, air breaks, on the wingtips you sometimes see winglets. On many airliners the engines are also attached to the wings. On military airplanes you can find external fuel tanks and weaponry.
They are called winglets, the main function of the winglets is to reduce drag. Reducing drag increases speed and decreases fuel consumption, thereby extending range and saving money.
Thrust vectoring. The winglets are there for stability - if they were to try placing ailerons on the winglets, they'd likely be unable to withstand the force exerted on them by the missile moving at speeds of over Mach 2.
What is a winglet? A plane normally has Wings along with tier control surfaces. The horizontal stabilisers with their control surfaces, they are the bits that look like wings on the tail. Then there is the one that points up into the air with its control surfaces which is the vertical stabiliser. If any one of these falls of you are in dire need of a parachute unless you are on the ground.
If this is in reference to winglets, they increase effective wing square area and thus add lift and can increase gliding or (Power off) range without materially adding drag.l That is the explanation I got from a museum official who is also a Glider Pilot, and winglets are common on advanced gliders.
I can't think of any cathedral-wing aircraft that DO use winglets. Spanwise flow on a cathedral wing would be flowing 'uphill' (inward) and would be interrupted by the fuselage.
The winglets work by reducing drag created by the vortices that are generated by a plane's wingtips. Aviation Partners Boeing estimates that its blended winglets for the 767-300ER will save up to 6.5 percent on fuel consumption, or a savings of roughly 500,000 gallons of jet fuel per aircraft per year for operators with the longest average sector lengths and highest aircraft utilization rates.
These are called winglets. They reduce drag therefore increase lift.
PUT THE WINGS UPWARD BEND THE ELEVATORS UP PUT SOME WINGLETS