What made Dassault a winglet convert?

 - September 21, 2007, 6:35 AM

For years, Dassault’s marketing executives maintained the position that Falcon business jets flew perfectly well without the aerodynamic benefits of winglets. But then something strange happened. People started seeing winglet-equipped Falcons being test flown in the skies above Seattle, and rumors began swirling that Dassault might be about to change its stance on winglets.

Now, the Falcon 7X and the Falcon 2000LX are fitted with winglets and soon the Falcon 900 series will be. So what made the French business jet manufacturer change its mind?

It all comes down to basic aerodynamics. Increasing a wing’s aspect ratio cuts the induced drag, thus reducing fuel burn. Adding winglets is a nifty way of increasing aspect ratio without adding to the wingspan. “It is always interesting to add wingspan, but it increases strains on wing gearboxes. Winglets add less strain than a straightforward wingspan increase,” Dassault senior vice president for civil aircraft Olivier Villa explained to NBAA Convention News.

In the past adding winglets would have exceeded the wing’s strain limits, Villa said. But on the 7X, Dassault designers began considering winglets as soon as the wind tunnel test phase began as a way to squeeze extra range out of the design. “We studied them as adjustment variables,” Villa said. When Dassault officially decided to boost the 7X’s range from 5,700 nm to almost 6,000 nm, winglets contributed greatly to achieving that goal.

On the 2000LX, the range increase could have been achieved by adding an extra fuel tank, “but this would have significantly increased the maximum takeoff weight, which we did not want to do,” Villa said. So Dassault again opted for winglets. This time, it partnered with Seattle-based Aviation Partners, rather than use its own design. “They are retrofit specialists, and part of the market on the 2000 series is retrofit,” Villa explained.

The wingbox reinforcement included with the winglets was deemed “significant but retrofitable.” The winglets add 275 pounds to the empty weight while Mtow remains the same.

On the Falcon 900 series Dassault is trying to fit the same kind of winglets as those of the Falcon 2000LX. “Although the wing is the same, the wing load is spread differently,” Villa noted. The Falcon 900 study is still preliminary, he added.

Asked whether the still-under-wraps super-midsize Falcon will have winglets, Villa said it’s too early to say.