Reader Response Draft 2

 The article “What is a raked wingtip?” by Essential Pilot (2018) highlights the concept of the raked wingtip design used by Boeing’s B787 aircraft. Having entered service in 2011, the 787 is one of the newer aircraft in Boeing’s lineup. Its design was heavily conceptualised around efficiency which was achieved with its substantial use of composite materials and raked wingtip design. One of the primary aerodynamic challenges for aircraft is drag, with vortex drag amounting to nearly 40% of the total drag during cruise (Kim, 2015). Wingtip vortices are formed when high-pressure air meets lower-pressure air at the wingtip during lift generation. This induces drag as a downwash is generated which alters the angle of attack of the aerofoil (Essential Pilot, 2018).  To address this, aircraft manufacturers employ wingtip devices such as winglets and raked wingtips. Wingtip devices increase the aspect ratio of the wing, reducing the tip vortices and induced drag (Tamayo, 2018). Boeing’s success with raked wingtips in the 787 resulted in the newer generation of B747 and B777-X employing the use of these wingtips. The 787's wingtip is a revolutionary advancement in aerodynamic efficiency and fuel consumption and thus should be an industry standard moving forward. 

By having a greater sweep angle on the wingtips, Boeing was able to increase the wingspan on the 787 of 60.12 metres. This increases the aspect ratio of the aerofoil and distributes lift more evenly throughout the wing causing less turbulence at the wingtips and a decrease in vortex drag. Consequently, this design leads to an increase in fuel efficiency and an overall reduction in noise during flight. The improvement in fuel efficiency from using raked wingtips also resulted in several additional benefits, namely an increased range and lower emissions. The Boeing 787-9 variant has the longest range at 7565 nautical miles (Boeing, n.d.). This is a 25% increase over the B767-400ER, the aircraft it replaced (Flugzeuginfo.net, 2019). This increased range can be attributed to both the weight savings from the use of composites as well as the aerodynamic efficiency achieved by the raked wingtips.

The 787’s enhanced fuel efficiency has also contributed to lower carbon emissions. In reference to a case study done by the International Bureau of Aviation (IBA), “the Boeing 787-9 is the most efficient widebody aircraft in the Qatar Airways fleet” (IBA, 2021). In a comparison between the airline’s Boeing 777-200LR and 787-9 aircraft, the 787 had an output of 115 grams per seat, which is 34% less than the 777s. This case study quantifies the reduction in carbon emissions that the 787 is able to achieve with greater fuel efficiency.

Next, with the reduction of wingtip vortices, the airflow over the wing is smoother which leads to fewer vibrations during flight and in turn less noise produced. According to a study conducted by the Civil Authority of Aviation (CAA) on the noise monitoring of aircraft at London Heathrow Airport, the 787 was quieter by 7 decibels on average when compared with the older 767 type during departure. On arrival, noise levels were measured to be 3 decibels lower on average (CAA, 2014). This further adds to the benefits that the raked wingtips bring to the efficiency of Boeing’s 787 aircraft.

The predecessor to raked wingtips was the blended winglet, which Boeing installed on their 737NG (Next Generation), 757 and 767, its newer aircraft at the time. As its name suggests, this device was able to reduce drag experienced by the aircraft by blending the wing and winglet reducing fuel costs from 4 to 6 percent (Teschner, 2012). While the winglet is less efficient compared to the newer raked wingtip, it still offers certain advantages over its replacement. Since the winglet is blended upwards, the wingspan of the aircraft stays relatively unchanged making it more compatible with airports. Next, the winglets have a simpler design since they involve the same shape as the existing aerofoil making it easier to manufacture compared to the raked wingtips. This design also allows winglets to be retrofitted to older aircraft without requiring a wing redesign, improving their aerodynamic efficiency without much certification having to be done for new designs. This allows for the aerospace industry to progress in terms of efficiency and sustainability.

In conclusion, despite the minute shortcomings of the raked wingtips with its lower compatibility with airports and more complicated design, the raked wingtip is still regarded as an innovation in the aerospace industry due to its superb aerodynamic efficiency and should be adopted as an industry standard moving forward.

References

Essential Pilot. (2018). What is a raked wingtip? Essential Pilot. http://essentialpilot.co.za/2018/08/25/what-is-a-raked-wingtip/

Kim, U. (2015). Numerical analysis and optimization of wing-tip designs [Master’s thesis, San Jose State University]. San Jose State University. https://www.sjsu.edu/ae/docs/project-thesis/Uram.Kim-S15.pdf

Tamayo Ibáñez, A. (2018). Numerical study of current wing-tip devices for commercial aircraft [Bachelor’s thesis, University of Barcelona]. UPC Universitat Politècnica de Catalunya. https://upcommons.upc.edu/handle/2117/174536

Teschner, T.-R. (2012). A comparative study between winglet and raked wingtip wing configurations [Bachelor’s thesis, Hamburg University of Applied Sciences]. HAW Hamburg Reposit. https://reposit.haw-hamburg.de/handle/20.500.12738/6042

IBA. (2021). Aviation carbon emissions case study: Qatar Airways. https://www.iba.aero/resources/articles/aviation-carbon-emissions-case-study-qatar-airways/

Boeing. (n.d.). Boeing: 787 family. https://www.boeing.com/commercial/787#family

Flugzeuginfo.net. (2019). Boeing 767-400ER technical data. https://www.flugzeuginfo.net/acdata_php/acdata_7674_en.php

Civil Aviation Authority. (2014). CAP 14924: Review of aircraft noise metrics and measurements. https://www.caa.co.uk/publication/download/14924