Tips on Flying

Gulfstream’s innovative “winglet” design ushered in a new era in business jet travel
history, aviation, g650, technology
Written By J. Mac McClellan

By the late 1970s, the Gulfstream II was the dominant business jet in the world—which stands to reason since Gulfstream introduced the world to purpose-built business aircraft in the form of the sleek Gulfstream I. Though the GII had no equal in cabin comfort, speed or range, consumers wanted more and Gulfstream knew it could deliver.

The GII had the range to cross the Atlantic nonstop, and to span the continental United States against the fiercest headwinds, but the world’s business environment was changing. Asia and the Middle East were rapidly becoming global markets and resource centers, but the distances were too great for the GII to link those areas with the business capitals of Europe and the United States. A particularly demanding, but necessary, city pair for business was Riyadh and London. No business jet could come close to making that trip nonstop, particularly westbound to London against the prevailing westerly winds.

The Rolls-Royce Spey jet engines that powered the GII were the best and most reliable engines available at the time, so there was no range improvement possible from more efficient engines. That meant the extended range (of what would ultimately become the GIII) could only come from reduced drag, allowing the airplane to fly farther on the same amount of fuel.

In the 1970s a new airfoil technology called “super critical” was in vogue. The name super critical refers to the wing’s ability to operate efficiently while flying at Mach 0.80 (80 percent of the speed of sound). As an airplane’s speed approaches Mach 1—the sound barrier—drag increases enormously. The super critical wing design helped control that drag increase.

Gulfstream engineers believed they needed to design an entirely new wing using super critical shapes to achieve the low drag and thus long range needed to make the GIII a success. But as the engineers conducted their testing, they discovered the GII wing was already very efficient and delivered essentially every performance advantage a newly designed wing could achieve.

The engineers deduced that instead of creating an entirely new wing, the drag of a GII wing could be effectively reduced if the wingspan was longer. In general, the longest possible wing creates the lowest drag. But lengthening a wing increases the load on the wing structure. To carry the loads of a longer wing, the internal structure of the wing must be beefed up and that adds weight. At some point the extra structural weight of a longer wing overwhelms its advantages in drag reduction delivered by the longer wingspan.

Nonetheless, Gulfstream engineers were able to increase the GIII wingspan by 6 feet/1.8 meters compared to the GII, and that extra span delivered significant drag reduction without adding meaningful weight to the structure. But the low drag and increased efficiency of the longer wingspan wasn’t quite enough to meet the GIII range targets. A new technological advancement was required, and it came in the shape of a winglet—a near vertical extension of the wing at the wingtip.

Experimentation proved that small winglets helped reduce drag. But the engineers understood that to really add range, a winglet needed to be tall. So they created 5-foot-high/1.5-meter-high vertical wingtips, and in 1980 the GIII became the first large-cabin business jet to sprout winglets.

A successfully designed winglet causes the wing to perform as though the wing has a much longer span, so drag is greatly reduced. However, because the winglet is vertical it does not create the same structural loads on the wing as would an increased wingspan. A winglet is not a proverbial engineering “silver bullet” in terms of drag reduction or increased structural weight, but is actually a very specific technology that optimizes the benefits and creates a balance between increasing wingspan and controlling structural loads.

Winglets actually capture some energy that is wasted by conventional wing designs. The goal for any wing is to keep air flowing smoothly front to back over both the upper and lower surfaces. However, at the wingtip some of the higher pressure air below the wing escapes and swirls upward. With Gulfstream’s winglet technology, that escaping high-pressure air flows over the winglet creating additional lift and reducing drag as it departs the airfoil, thereby increasing the total efficiency of the entire wing.

The winglet design for the GIII delivered as promised and the aircraft met its range goals.

While other business jet makers were initially slow to follow the technological path forged by Gulfstream engineers, the team of aerodynamicists in the flight sciences laboratories have continued to sculpt winglet design with the introduction of each new Gulfstream wing to deliver ever-increasing range, reduced drag, greater efficiency and legendary speed.

Experimentation proved that small winglets helped reduce drag. But the engineers understood that to really add range, a winglet needed to be tall.

The swooping winglets on the new ultrahigh-speed, ultralong-range G650 dwarf the original GIII winglets and curve gracefully and tilt outward compared to the near vertical position of the GIII winglet. Over the three decades between development of the GIII and G650, Gulfstream engineers have refined their wing and winglet technology so much that the G650 nearly doubles the nonstop range of the GIII. The range and high altitude cruise of the GIII simply wasn’t possible without Gulfstream’s breakthrough winglet technology. And the same can be said for the amazing performance of the G650.

Today winglets are ubiquitous on newly designed business jets from all manufacturers, but more than 30 years ago that wasn’t the case. Winglet technology is just one more example of what makes Gulfstream synonymous with “The World’s Most Advanced Business Aircraft.”

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