RR#3
The article “What is a ‘Raked’ Wingtip?” by Trifly (2018) discusses the groundbreaking design of the Boeing 787's wings. Unlike traditional aircraft designs, the wing engineers did something different from the typical formula, opting for a unique wing structure. Typically, airplane wingtips are upswept, a design that has been effective for many years. However, in the 787, these were replaced with a raked wingtip, which sweeps backward (Onemonroe, 2023). The primary function of any wingtip is to reduce drag, which results from the pressure differences between the upper and lower wing surfaces. The most compelling reason for using a raked wingtip is its enhanced fuel efficiency. According to Kim (2015), Boeing and NASA collaborated on wind tunnel tests to validate the theory that improved wingtips could reduce drag and increase fuel efficiency. The results show that the raked wingtip reduced drag by 5.5% compared to other wingtips, which showed a reduction of only 3.5% to 4.5%. However, as Trifly (2018) suggests, this technology is a relatively new innovation and requires more space than conventional winglets, leaving it uncertain whether raked wingtips will fully replace the older designs.
Despite some drawbacks, the raked wingtips of the Boeing 787 show how having an unconventional swept-back design is beneficial in several ways, which are improving fuel efficiency and enhancing passenger comfort.
The raked wingtips of the Boeing 787 are beneficial as the fuel efficiency of the aircraft is greatly improved. Vortices that are generated by the wingtips from the airflow through the wings are undesirable. This poses some issues when the aircraft is in flight, as it reduces the aircraft's efficiency. In fact, almost 40% of the drag produced by the aircraft stems from the wings, decreasing lift (Zaccara, 2022). There is a clear linear relationship between wingtip vortices and induced drag: the greater the vortices, the more drag the aircraft experiences. Raked wingtips help to minimise this issue by reducing vortices. As the raked wingtips are swept back, they effectively channel and diminish vortices away from the main wing, minimizing drag. As a result, less fuel is burned, as the engines don’t have to overcome the extra resistance caused by drag. This leads to a significant improvement in fuel efficiency, with the Boeing 787 achieving a 20% gain in this area, offering substantial cost savings for operators. According to Greenworldwide (2023), the Boeing 787 ranks second among the five most fuel-efficient airplanes globally. Furthermore, the raked wingtips provide an additional advantage over winglets during takeoff. Not only do they reduce drag, but they also increase lift. This is especially important and a huge contributing factor to achieving fuel efficiency, as the takeoff and climb stages are when the aircraft consumes the most fuel rate.
Raked wingtips also contribute to a smoother and more comfortable flight experience for passengers. Airflow from the main wing to the wingtips plays a significant role in generating drag (NASA Glenn Research Centre, 2023). With raked wingtips, this drag is reduced through the increased wingspan of the sweepback, allowing for less turbulence and a more stable flight.
The raked wings on the Boeing 787 also have the ability to bend more than conventional wings. While this flexibility might appear alarming to passengers, it offers several advantages. For example, when the aircraft is going through turbulence, the wings would bend and flex, reducing the effect of turbulence in the cabin. This feature enhances passenger comfort, especially for those sensitive to motion sickness, as the effects of turbulence are mitigated. Given that long-haul flights often encounter turbulence, the reduction in these effects makes the 787 an attractive option for operators focused on passenger comfort. The Boeing 787’s raked wingtips provide an edge over other aircraft that rely on more conventional designs. The smoother, less turbulent flights result in a more comfortable experience for passengers, making the Dreamliner a preferred choice for many airlines.
Despite the many significant advantages, there are some factors worth considering. The swept-back configuration of the raked wingtip differs from the more compact, upswept design seen in conventional aircraft. The longer design can create challenges in terms of maneuverability on the ground. For instance, the 787 requires more space while taxiing and parking, as its wingtips extend further than traditional designs (Gudmundsson, 2022). As a result, airports may need to upgrade their taxiways and gates to accommodate and handle the 787.
Despite being a relatively new technology, the raked wingtips of the Boeing 787 have demonstrated great benefits for operators. Emirates, the national airline of the United Arab Emirates, had expressed a preference for the Boeing 787, indicating that it will likely replace the aging fleets of Airbus A380s and Boeing 777s (Fehrm, 2017). The introduction of raked wingtips in newer aircraft models, such as the latest Boeing 747s and 777Xs, further justifies the use of the raked wingtip technology. The raked wingtip has the potential to save fuel, increase passenger comfort, and improve flying efficiency, making it a crucial component for the development of aviation's future.
References
Fehrm. (2017, November 15). Why did Emirates choose Boeing’s 787-10? Leeham News and Analysis.
Gudmundsson (2022). General Aviation Aircraft Design: Applied Methods and Procedures (2nd ed.). Elsevier Science.
Guo, He, Wang, Wang (2021). Chinese Journal of Aeronautics. Chinese Society of Aeronautics and Astronautics.
https://www.sciencedirect.com/science/article/pii/S1000936121000480
Hepher et al. (2024, May 22). Singapore airlines: What is aircraft turbulence and how common is it?| reuters. https://www.reuters.com/business/aerospace-defense/what-is-aircraft-turbulence-how-common-is-it-2024-05-21/#:~:text=Long%20planes%20can%20feel%20most,handling%20turbulence%2C%20according%20to%20Turbli.
Kim (2015). Numerical Analysis and Optimization of Wing-tip Designs. San Jose State University.
https://pdp.sjsu.edu/ae/docs/project-thesis/Uram.Kim-S15.pdf
Lyakhovetskaya (2024, March 12). Top 5 most fuel-efficient airplanes in the world. Green Worldwide Shipping. https://www.greenworldwide.com/top-5-most-fuel-efficient-airplanes-in-the-world/#:~:text=The%20787%20Dreamliner%20is%20another,20%25%20better%20than%20comparable%20planes.
National Research Council (2007). Assessment of Wingtip Modifications to Increase the Fuel Efficiency of Air Force Aircraft. The National Academies Press. https://nap.nationalacademies.org/read/11839/chapter/5#37
NASA Glenn Research Center (2023, November 2). Winglets. NASA Glenn ResearchCenter
https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/winglets/
Trifly (2018, August 25). What is a “raked” wingtip? Essential Pilot. http://essentialpilot.co.za/2018/08/25/what-is-a-raked-wingtip/
Winglets vs raked wingtips: What’s the difference? Blog Monroe Aerospace. (2023, July). https://monroeaerospace.com/blog/winglets-vs-raked-wingtips-whats-the-difference/?srsltid=AfmBOorhHwjT5SD9-ztzPg32jJgiiQ5TIV4LQ1wWFWaSk6fHt191fuQx
Zaccara et al., (2021, July 22). Flow control of wingtip vortices through Synthetic Jets.ScienceDirect
https://www.sciencedirect.com/science/article/pii/S0894177721001345.
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