Fuel efficiency is directly affected by the magnitudes of drag airliners experience during flight. Apart from the parasite drag (form, interference, and skin friction), a large portion of the aerodynamic drag results from the airflow rolling from the higher-pressure side of the wing to the lower-pressure side, causing wingtip vortices.
Wingtip devices improve the aircraft’s performance by managing the pressure distribution as the high-pressure flow wraps around the wingtips. The lift-induced drag on aircraft is reduced by partial recovery of the tip vortex energy through winglets. Depending on the type of device and flight conditions, wingtip devices can improve fuel efficiency by 2-5%.
Narrowbody Boeing wingtip devices
Blended wingtips provide a smoother transition from the wing to the wingtip device. These are seen on many variants of the Boeing 737, 757, and 767 aircraft. Such wingtip devices are approximately 8 ft (2.4 m) long and 4 ft (1.2 m) in width at the base.
Each wingtip device on a Boeing 737 weighs about 132 lbs (60 kg). Once fitted, the winglets add about 375-500 lbs (170-225 kg) to the aircraft weight, depending on whether installed during production or as a retrofit.
Split Scimitar Winglets (SSWs) have been installed on most new Boeing 737-800 and 737-900ER models since 2014. These are also offered as a retrofit for existing blended winglet aircraft. Each SSW device weighs approximately 148 lbs (67 kg). Once fitted, the SSWs add about 400-550 lbs (180-250 kg) to the aircraft weight, depending on whether installed during production or as a retrofit. SSW provides up to 2.2% fuel savings depending on the flight sector.
The upgrade from a regular blended wing to an SSW on a Boeing 737 costs just under $1 Million. The modification requires a trailing edge wedge, strengthened stringers, and ballast weight to the wing. While the upgrades to SSW are costly, United Airlines states that the new winglet design demonstrates significant aircraft drag reduction over the basic blended winglet configuration.
The Advanced Technology (AT) Winglets on the Boeing 737 MAX are similar in size and weight to the SSWs. With over 8.2 ft (2.5 m) of the top portion and 4.5 ft (1.4 m) of the bottom part, these winglets are claimed (by Boeing) to provide a 1.5% fuel burn improvement over current technology winglets.
Airbus’ wingtip fences and sharklets
Airbus implemented wingtip fences on older A320 models and the superjumbo A380s. Wingtip fences were first installed to address the wingtip vortices and provide a physical barrier below and above the wing. As such, the iconic wingtip fences differentiate narrowbody Airbus aircraft from those of Boeing.
Each Airbus A380 wingtip fence weighs approximately 90 lbs (40 kg). On the much smaller Airbus A320, each wingtip fence weighs about 55 lbs (25 kg). It is noteworthy that the newer Airbus A320 family aircraft use blended winglets, similar to the winglets on the Boeing 737.
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Despite Airbus’ unique term “sharklets,” these are about the same size and shape as the blended winglets on Boeing 737s. The 8-ft (2.4 m) tall sharklets replace the A320 wingtip fences and are offered as an option on newly built aircraft. Sharklets reduce fuel burn by up to 3.5%, depending on the flight sector.
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