User:Mtvssf/sandbox/Morphing Winglets

Morphing winglets are aircraft wingtips which dynamically actuate in response to changes in flight conditions. In line with the concept of the morphing aircraft, morphing winglets allow aircraft to actively alter shape to improve performance, efficiency, and controllability. Additional benefits of these devices include reductions in fuel use, aircraft noise, and aircraft wingspan at the airport.

Although not implemented on a broad scale so far, efforts led by aircraft manufacturer Airbus, along with its affiliates, hope to commercialize morphing winglets in the near future.

Conventional Winglets

Conventional canted winglets extend up and away from the end of an aircraft wing, arch 30 to 60 degrees, and compose around 5% of an aircraft's total wingspan. These winglets are typically composed of aluminum composites used in airframe construction and weigh around 130 pounds each on airliners like the Boeing 737. Newer aircraft as the Boeing 787 have adopted carbon composite constructed winglets in lieu of the traditional aluminum ones. This has the effect of considerably reducing winglet weight.

Although various advances in winglet technology have been made in recent times (including the construction of blended winglets, split-tip winglets, and raked winglets), none of these designs incorporate a wingtip with in-flight actuation capabilities.

Morphing Winglet Geometry

As no standard design for morphing winglets exists, many different designs and systems for actuation are currently being probed. The main parameters which research looks at to base such technologies and exact shape of the morphing winglet are:

1. Winglet Cant Angle
   • This parameter refers to the angle the winglet makes with the rest of the wing. For reference, a cant angle of zero would entail the winglet being flush with the rest of the wing. Having a variable cant angle is expected to greatly increase aircraft efficiency and increase the load an aircraft can carry.
2. Winglet Span
   • This value is the length each winglet adds to the overall aircraft wingspan. It is expected to range from 1 to 5 meters on most aircraft and increase the ratio of wingspan to wing area—aspect ratio—to significantly boost efficiency.
3. Winglet Sweep Angle
   • This refers to the tilt of the winglet forwards and backwards. Sweep angle will likely vary from 0 to 70 degrees and allow for the optimization of aircraft lift to drag ratio. This parameter is difficult to engineer in that it greatly complicates the mechanical design of the wingtip for what is only a marginal increase in efficiency.
4. Winglet Toe Angle
   • This is the angle the base of the wing is rotated to, to counteract changes in the distribution of wing weight caused by installation of the morphing wingtip. Toe angle has little overall effect on efficiency as the increase in lift force caused by modifying it is accompanied by an increase in drag.
5. Winglet Twist Angle
   • This parameter is the angle the tip of the wing is twisted to. It is designed to offset the drag increases expected to be caused by changing a winglet's toe angle.

Aerodynamic Implications

Morphing Winglets improve the aerodynamic efficiency of an aircraft in multiple ways:

1. Canted winglets' design are optimized to manage lift-induced drag and span-wise aerodynamic loads for one specific point in an aircraft's flight. This theoretically determined point refers to one specific altitude, wind direction and wind speed combination, among other factors. Hence, the actual time an aircraft may spend at this theoretically determined point in flight will never equal its total flight time. This results in an aircraft experiencing a reduction in aircraft wing performance and uptake in induced drag the further it deviates from this ideal flight point. When aircraft winglets are made to actuate, they readjust the shape of an aircraft wing in real-time, bringing an aircraft aerodynamically closer to the conditions it is flying through.
2. In flight, an aircraft wing encounters a flurry of forces (including inertial, aerodynamic and thrust) which cause slight alterations in its shape. These forces can cause an aircraft to deviate from its most efficient shape while passing through a specific set of conditions at a certain point, causing an increase in overall drag force. Morphing winglets, by virtue of their ability to adjust to minimize the torques and flexions the wing may face from these forces, help maintain ideal wing shape and increase efficiency.
3. Due to manufacturing inconsistencies and general wear and tear as an aircraft ages, an aircraft will tend to roll to one side or another during flight. Currently, aircraft wing devices as ailerons and flaperons work to minimize these deviations and ensure that an aircraft does not roll about its roll axis. Morphing winglets are designed to work in conjugation with these devices, deflecting to ensure that the aircraft does not unintentionally roll.

Additional Impacts

Implications of morphing winglets beyond those pertaining to aircraft performance include:

1. An estimated 2.5% increase in fuel efficiency as compared to that offered by conventional winglets
2. A 4.2% to 6.6% increase in overall aircraft range, depending on flight length.
3. An approximate 3.1% increase in lift to drag ratio during the climb phase of flight.
4. A 2 decibel drop in overall aircraft noise emissions. This is significant when considering the strict noise abatement programs airports around major cities have began to implement in recent decades.
5. A decrease in overall aircraft wingspan at the airport. Morphing winglets ability to go entirely vertical (normal to the surface of the wing) greatly increases the possibilities of larger aircraft to go to smaller aircraft gates which they may ordinarily have been too wide for.

Current Status

While multiple patents for morphing winglets have been filed, the concept has had extremely little implementation on aircraft in the real world. The only recorded case of an aircraft implementing morphing winglets was on the North American XB-70 Valkyrie, which could position its winglets downward in order to attain Mach 3 flight using wave-riding.

A more recent development in morphing winglet technology was in 2015, when FACC AG (Fischer Advanced Composite Components) came up with a working prototype for a morphing winglet. This prototype was comprehensively tested by the company in a wind tunnel. The results of these tests are still actively being probed by aircraft manufacturer Airbus. FACC AG expects their morphing winglet product to be market-ready by the end of 2018. FACC AG has also worked in parallel with the Dutch National Aerospace Laboratory (NLR), Institute for Manufacturing Technology and Advanced Materials (Fraunhofer IFAM), and the Spanish Research Center for Composite Materials (FIDAMC) to further their product's development.

See Also

• Richard T. Whitcomb
• Wingtip device
• Noise abatement
• Fuel efficiency