He entered the pitch-dark hangar and stared into its inky emptiness. Suddenly, two brilliant shafts of blue light cut downward through the murk, focused on a pair of vertical blades taller than a person, curved outward, seemingly suspended a dozen feet above the floor and 25 paces apart. The sight was dramatic and compelling. Yes, he thought, these are the capstones that might help to achieve my hopeful goal of 50.
Ultimately, they did that—and much, much more.
That epiphany had its beginnings in 1991 when a friend told Joe Clark he wished for better performance from his Gulfstream II. An aviation business whiz, Clark was a Seattle-based Learjet dealer and co-founder of regional carrier Horizon Air.
- Cuts drag by some 7%
- Performance silenced skeptics
- Adopted for the BBJ, 737NG and more
Ever eager to advance aviation, Clark accepted the G-II performance challenge. He and Dennis Washington, the aircraft’s owner, formed Aviation Partners Inc. (API) with the goal of adapting evolving winglet technology to boost the Gulfstream’s numbers. They assembled an elite team of aerodynamicists who then designed an airfoil featuring a large radius and smooth chord rather than the more common vertical end blade. This all-new “blended winglet” reduced drag, increasing fuel efficiency and improving climb performance.
The modification’s results were so impressive that API adapted the design to the Hawker 800 family and the Dassault Falcon 50, 900 and 2000 models. The blended winglets proved so popular with Falcon operators that Dassault installed them on Falcon 2000LX, 2000LXS, 2000S and 900LX models in production.
A major development in API history occurred in the late 1990s involving Borge Boeskov, another friend of Clark’s. Then head of product strategy at Boeing, Boeskov had been tasked with increasing the Boeing 737’s range, which he did by mating the 737-800’s wings and undercarriage with a 737-700 fuselage and adding extra fuel tanks.
Impressed with that design’s potential, Boeskov pitched the idea of marketing it to corporations, governments and individuals as a business jet. Management liked the idea and named Boeskov president of Boeing Business Jets, a new entity.
While Boeskov was aware of API’s curved winglets, some within Boeing, were skeptical of their true effectiveness. Meanwhile, Clark pushed back, telling Boeskov, “If that’s a business jet, it needs winglets,” and that API’s could improve performance by 4-5%. Clark later invited his friend to a special presentation in a nearby hangar; Boeskov accepted.
That was the event where Boeskov first saw the blended winglets that API envisioned for the Boeing Business Jet (BBJ). When the hangar lights came on, he saw the pair of fiberglass winglets perched on tall black posts positioned where the wingtips of an actual aircraft would be. He regarded the winglets as visually appealing and distinctive, and when Clark said API would finance the design if Boeskov would test-fly the resulting prototype, a deal was struck.
The results of the flight tests were better than Clark had predicted, showing a drag reduction of nearly 7%. Thus did API’s tall, curved winglets become integral to the BBJ’s visual impact and performance. They also helped to surpass Boeskov’s 50-aircraft goal for the BBJ easily. According to Aviation Week Network’s Fleet Discovery database, Boeing has produced 159 BBJs.
Even more significant, the model’s efficiency so impressed the leadership at Boeing’s commercial division that Boeing and API created a joint venture company, Aviation Partners Boeing (APB), in 1999. Its purpose was to make API’s winglet technology available for in-production or in-service Boeing aircraft, including the 737 Classic, 737NG and BBJ, as well as the 757-200 and -300 and the 767-300ER and -300F.
In 2012, APB began developing the “split scimitar”—essentially a curved ventral fin to complement the blended winglets above on 737NG models. That mod reduced drag by as much as another 2%.
Both Clark and Boeskov have since flown west, but their aerodynamic legacy will have a positive impact for decades to come. Today, more than 9,500 Boeing airliners are fitted with blended winglets; 1,700 of those sport split scimitars. Those are in addition to the approximately 2,000 business jets operating with the API winglets.
Although the original purpose of blended winglets was to increase business jet range, the efficient design has collectively reduced fuel consumption in excess of 16.5 billion gal., thereby preventing the emission of some 150 million tons of carbon dioxide.
Gary Dunn, a well-known API veteran who succeeded Clark as president, says thousands more Boeing aircraft and business jets remain candidates for some proven and well-blended improvement.
William Garvey was editor-in-chief of Business & Commercial Aviation from 2000 to 2020.
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