Un peu plus sur les splits / scimitar blended winglets...
http://www.flightglobal.com/blogs/flightblogger/2011/10/split-scimitar-winglet-next-on.html
Without the prospect of a clean-sheet design from Western manufacturers seating 150 to 210 passengers for at least a decade and a half, improving the current and future generations of 737s and A320s has put incremental improvement at the forefront of aircraft design. From in-flight entertainment and lightweight seats to wingtip treatments, the opportunities for suppliers to exploit the airframe status quo will mean big business for those trying to ring every ounce of performance from existing designs.
Joe Clark, CEO of Aviation Partners, redefined improvement in incremental efficiency a decade ago, transforming our visual expectations of what an efficient aircraft should look like, and now he's trying to do it again.
This time, Clark and his team of aerodynamicists have taken the blended winglet concept and turned it on its head. Literally. Seattle-based Aviation Partners unveiled for the first time at NBAA in Las Vegas last week its blended split winglet concept. Building on the blended winglet that is fitted more than 4,500 aircraft and nearly every Next Generation 737 that exits Boeing's Renton line, Aviation Partners has added a ventral strake and scimitar tips to the now-familiar design.
"The concept works for any airplane," says Clark, whose enthusiasm for his product is almost contagious. "It puts very little load increase into the wing, which is good. It's retrofittable on most winglets, both the scimitar tips and the ventral strake. We've done a lot of [computational fluid dynamics] work combining these all together to get us a performance of about 40% better than a normal winglet. So with winglets you'd get 5-7%, this you'll get 7-9.5%."
"For 2-3%, that's a huge number" for airlines whose biggest single cost is fuel, says Clark.
The retrofit package, he estimates, would see the skins removed from the airplane, installing a clevis fitting and some local beef up of the winglet, and would cost roughly $240,000 for operators, or about 40% more than the $600,000 for an existing set of winglets.
For airframers, the cost of developing a new aircraft, achieving a 20% improvement in fuel efficiency can run $7-10 billion, a conservative estimate as illustrated by the A380 and 787. To achieve an improvement of 2%, estimates Clark, runs at $30 to 40 million for a flight test and certification campaign, just 3% of the cost compared to an all-new clean sheet development program.
That exponential growth in the cost of an all-at-once leap in efficiency underscores the challenge of building all-new aircraft in the 21st century. Applying Red-Blue and London School of Economics academic Dr. Theodore Piepenbrock's Theory of the Evolution of Business Ecosystems, fewer options exist for major leaps in improvement. The mature "Red" environment of jetliner manufacturing likens steady incremental improvement to designing a better camel, a system built for long-term resilience not short-term speed, explains Piepenbrock's work.
"I've always told people that we're like what AMG is to Mercedes," says Clark of Aviation Partners' work. "They build fabulous cars, we just improve the performance of them. We're the refiners. As long as these big companies look at us that way, we can be very helpful to them."
Airbus plans to introduce its own "sharklet" winglet design on the A320 family next year, which will carry over to the A320neo, while Boeing will continue its current Aviation Partners Boeing winglet - a joint venture with Aviation Partners on the 737 MAX. Boeing, in the hunt for more efficiency improvement on the MAX, could find itself looking to the blended split winglet for its extra push.
The new patented scimitar tips, says Clark, are airfoils in themselves, contributing a half-percent to the overall drag improvement: "The scimitar adds quite a bit. Our CFD analysis shows the more careful you are with these tip vortexes, the better the performance is, so we've refined it to quite a good level in studying this area."
The company's experience developing and proving the efficiency gains with winglets has been significantly refined with its proprietary CFD models, each of which is tailored to a given airframe before they're even flown.
"When we did the 767 winglets, we never did a prototype and we hit the performance within one-tenth of one percent," said Clark, who also completed 75h of flight testing of a spiroid winglet design aboard his Falcon 50 earlier this year, validating an 11% improvement in drag.
Clark acknowledges that the new split design may not be right for all aircraft configurations: "Certain airplanes it's more difficult because their wings are lower, but we may use part of it, for example on a Falcon, we may use the scimitar tip and not have the ventral strake. You wouldn't get as much performance, but you'd get more. On a higher-wing airplane, one that's got a high wings, engine pods below like a Boeing or and Airbus, it's a lot easier."
No decision has been made about an aircraft as a platform for flight testing the blended split winglet concept, though Clark hopes to begin flight testing in the next six months.
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par aubla Ven 23 Oct 2009 - 9:09
