Flying Wings & Winglets
Our professor at Stanford University, Barry Katz, challenged us to apply the Modernist mantra “Form follows function” to a mass-produced object of our choice. I decided to explore the efficiency of flying wings and winglets, starting with the impact of the flying wing design in our American history.
Flying Wings
The flying wing first emerged in the 1930s when the Horten brothers designed it for the new Nazi regime in Germany. By the 1940s, German designer Alexander Lippisch had also created a flying wing, the Me 163, which reached a speed of 600 mph. The Horten brothers went even further, creating the Ho 229, a 61-feet wingspan aircraft that was the fastest aircraft in WWII, reaching speeds of 620 mph due to the efficiency of the flying wing design.
While the Germans were busy building their own flying wings, merican aircraft designer Jack Northrop was working on designing his own flying wing in California, with the goal of minimizing the tail and fuselage. His first flying wing, the N-1M, took off in December 1942 and he continued to develop the concept for the next three decades. In 1946, he built the YB-35, a flying wing powered by four turboprop engines that flew at a speed of 400 mph, but had a slow speed on long-range cruise. In 1947, he introduced his new YP-49 flying wing, which was powered by eight Allison jet engines and was capable of flying at 400 mph at a ceiling of 40,000 feet. It functioned not only as a bomber, but also as a passenger aircraft, carrying 80 passengers with an observation lounge and crossing America in just 4 hours. However, the YP-49 had difficulties flying with a lot of computer controls, which the US Air Force found to be unstable and dangerous. In 1949, the US government ordered all YP-49s to be destroyed.
At that time, the world was ushering in a new era of nuclear power, while the Soviet Union was busy developing a massive arsenal of weapons. The US sought to fly at high altitudes to evade the advanced radar systems of the Soviet air defense, but this proved too high to accurately target their intended objectives. To gain a tactical advantage, the US needed a new, innovative approach that would render their aircraft invisible to the enemy radar, effectively denying them any information about their movements.
In 1970, 30 years after the destruction of Northrop’s flying wings, the US government chose the Northrop flying wing team to design a new aircraft in a top-secret project known as the Black Program. The project took 18 years and was shrouded in secrecy, with even Congress unaware of the amount of money being spent. Finally, in 1988, Northrop revealed the B-2 Stealth Bomber in Palmdale, California to a stunned audience. The whole nation and the world were amazed by the new aircraft, which made the US Air Force the dominant global power. As Dr. Aryeh Nusbacher of the Royal Military Academy Sandhurst put it, “by God, it is American!”
The B-2 had over 130 onboard computers that controlled every aspect of the aircraft. Its smooth, curved shape made it invisible to radar, as its shape continually changed, confusing enemy radar. It was also coated in radar-absorbent secret materials (RAM) that reduced its detection further. The B-2 had a 172 ft. wingspan, weighed 154,000 lbs. empty, and 375,000 lbs. loaded. Its structure was mostly made of carbon fiber, which was lighter than aluminum and stronger than steel. The B-2 also had special exhaust vents on its wings that, when mixed with cool air, allowed it to exceed the speed of sound. It had a top speed of 680 mph at a service ceiling of 50,000 ft and could fly 6,000 miles without refueling. The B-2 could carry up to 40,000 lbs. of laser-guided nuclear bombs and missiles. By the time the B-2 was ready for use, the Soviet Union had already collapsed, and there was no need to use it for bombing missions. However, the B-2 made its combat debut in 1999 during the conflict in the former Yugoslavia. Its effectiveness in carrying out airstrikes was unparalleled in history. Former President Bill Clinton noted that the B-2 flew less than 1% of the total missions, but was responsible for dropping 11% of the bombs.
Winglets
While the B-2 continues to improve its efficiency, there’s an interesting development happening on the edge of the wing. Winglets, which are wingtip devices, improve aircraft wing performance. There are two types of winglets: blended and split scimitar.
The vortex pressure on the wings creates high drag, which means more fuel is burned. Aerodynamicists designed blended winglets as an extension on the wingtips to reduce vortex pressure, resulting in less drag and less fuel burned. The story interestingly goes beyond that, it does not only reduces fuel consumption but also reduces noise on takeoff by 6.5% and lowers emissions by 6% reduction in CO2 and 8% reduction in NOx.
For example, winglets on Boeing 737 reduce 1,163 tons of CO2 per year per plane, saving up to $11,000 per plane annually. Winglets increase aircraft payload and allow the plane to achieve a 1,200 ft higher optimal altitude than non-winglet equipped planes. Additionally, blended winglets reduce maintenance by up to 3% at takeoff thrust and 4% at cruise thrust, which increases the age of the wing.
Richard Whitcomb, an American aeronautical engineer, first proposed the concept of winglets (vertical or near vertical) in the 1970s. It took three decades for the aircraft industry to adopt his concept, and in 2011, Boeing introduced the Boeing 737 MAX 200, which featured Split Scimitar Winglets. The new winglet design replaced the aluminum winglet tip cap with a Scimitar Winglet tip cap, resulting in a 2% reduction in drag. This improvement can save up to 45,000 lbs of fuel per year, increase payload up to 2,500 lbs, or increase range by up to 75 nautical miles. Furthermore, it can carry over 12 more passengers than its competitor, with a 14% reduction in fuel and much less noise.
The growth of low fare airlines on Boeing 737 MAX in 2013, resulting in more people being able to travel by air, reflects the philosophical principle of Louis Sullivan: “form must ever follow function.” The form of winglets and flying wings not only serves a functional purpose but also undergoes continuous improvement to increase efficiency. As Jeff Smisek, CEO of United Continental Holdings, notes “These airplanes are not only fuel efficient but they are operationally more reliable, they are environmentally more responsible, and they are very customer pleasing.”
My nostalgia for aircraft wings affirms that they are not only aesthetically pleasing but also contribute to improving our lives in various ways.
