The effects of winglets on transport jet aircraft
History of airplane design includes many attempts to significantly reduce INDUCED DRAG.
Unfortunately induced drag is omni present like death and taxes!So all can be achieved is anadesign of winglets to optimize induced drag(vortex drag) by increasing effective aspect ratio and thus reduce induced drag by permitting significant lift to extend al the way to the wing tips.
The initial types of winglets developed were end plates or wing tip fins which airbus has favoured in its designs and still feature on their A380s. Boeing/MDC on the other hand have favoured the more modern blended winglets.
In principle, winglets do the following:-
1) reduce induced drag for a given weight
2)the amount of Induced drag reduction is equivalent to extending the original wing span by half of the winglet height(aproximately).
3)the expected advantages of winglets is less wing bending moments and resultant wing weight increase than with a spanwise increase(albeit of the order of around 2%) .The decision on whether to use winglets in the design process is likely to be dominated by special circumstances. Among these is a non optimum span loading on the original wing,minimum practical skin gauges already used on the outer panel so that the bending moment of the winglet attachment does not require more material, the desire to avoid a span increase for reasons associated with airport gate/ramp facilities limitations or hangar space, and the possibility of flow separation at the winglet root at high lift coiefficient because of flow interference.
A last non- technical factor to incorporate winglets is the desire to look modern ("sexy").
The main benefits of winglets to Aviation are:
Reduced wake vortex for aircraft following a winglet incorporaed aircraft
A more comfortable ride for passengers in turbulence
Less effort from the pilot during the flare to land
Perhaps( please verify this) smoother upset recovery
Improved low speed assymetric flight characteristics(especially within ground effect)
Due to increased directional stability...slight reduction in crosswind handling limitation as mentioned in previous threads (about -3kts)
Slightly improved fuel economy during cruise (about 2.5% savings for a 1500nm stage length)
It would be interesting to review why Boeing cancelled the original 767-400 programe (which incorporated blended winglets) and whether the lack of winglets on 777s is purely due to gate limitations or not cost benefit due to the already supercritical nature of its wing.
Am not sure whether incorporation of winglets. Can result in improved service ceiling as well as improved glide range with both engines flamed out?
Most corporate jets with their quests for pushing the speed/ range envelope have featured blended winglet technolgy and some thing might be learnt from these jet toys of today too. Incidently, the mid air collision between 737(classic??) And Embraer Lineage corporate jet over Brazil a few years back...which saw the loss of the Boeing and succefful landing of the Embraer with a partially torn winglet...might attest to the handling advantaages of incorporating winglets in improving directional stability??(just wrth researching whether their presence played a role at al in the ulimate recovery of that flight..according to the CVR the cockpit crew did well but did not deviate majorly from SOPs.
I hope this general commentary is helpful to your thesis on effects of winglets on handling characteristics of B767. Given the choice to add or not to add winglets..will depend on the residual airframe life and have to be balanced against re-certification obstacles and the resultant cost benefits but in general I expect a god rather than detrimental effect especially for those operators stuck with the old airplane that still has mileage in its airframe when weighed against the capital costs of acquiring a newer airplane with a similar payload range capability!
Improved fuel consumption
Last edited by Vc10Tail; 7th Jun 2013 at 11:17.
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