Archives

August 2012

Sun Mon Tue Wed Thu Fri Sat
      1 2 3 4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31  

Recently in Aerodynamics Category



Movie Monday subjects are sometimes tough to decide. This week, for instance. Do we go with the Collier Trophy homage, in honour of the 2012 award that is being presented on Thursday to the Boeing 787? Or do we make it about the winglet, a la the vortex-reducing airframe accessory unveiled last Wednesday for the 737 Max? Alas, nobody ever won the Collier Trophy for inventing a wingtip device.

But we have the next best thing. Richard Whitcomb developed the methodology for applying winglets. He also claimed the Collier Trophy in 1954 for inventing the area rule, which adds a pinch in the fuselage aft of the wing leading edge to minimise drag at transonic speeds. In yet another revelatory moment, Whitcomb also came up with the supercritical wing, which can hold more fuel with no drag penalty compared to a thinner wing at the same cruise speed. 

The video above unfortunately cuts off just before Whitcomb discusses winglets. But this video released shortly after Whitcomb's death provides a few more details.

MIAMI -- I'm here in Florida for the next two days for an Airbus simulator training that will explore the European airframer's digital fly-by-wire philosophy, which has oft been a point of discussion about the role of computers and the role of pilots in flying. 
For Airbus, fly-by-wire has resulted in hard limits on the aircraft flight envelope, preventing over-speeding, stalling, and over-banking of the aircraft. The maximum bank allowed is 67-deg, with nose-down pitch not exceeding 15-deg and a 2.5g limit. An auto-thrust system complements the A-floor protection by automatically spooling up the engines, limiting nose up pitch (angle of attack) to prevent the aircraft from stalling and providing best climb performance.
Those philosophical discussions, both of which diverge and converge amongst commercial aircraft manufacturers, have guided aircraft development for three decades now, with some implementation of fly-by-wire included on every single new aircraft in development. The systems have evolved from simply providing a flight control input all the way to being the basis for structural design through limiting loads on an airframe.

The video above shows the technology in action aboard an A320 family aircraft operating around South America in routine operation and presented in rather dramatic fashion. 

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 wring 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. 

joeclark.jpg
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. 

Photo Credit Billypix

UPDATE: Additional photos below the fold
"Boe 03" B787-8 N787BX

"Boe 03" B787-8 N787BX

After spending an extended layup in maintenance at Boeing Field, ZA003 emerged with what at first glance looked to be a repair to the composite skin or maybe it was a change to the 787's HF antenna system? It was neither. The black, green and silver arrangement on the 787's vertical stabilizer is the first test of hybrid laminar flow control (HLFC) technology being evaluated for use on the 787-9. 

HLFC is designed to reduce the drag on the leading edges of the horizontal and vertical stabilizers by sucking in the surface airflow through small holes, allowing the boundary layer to remain attached, moving the onset from smooth laminar to turbulent flow further back along the surface. 

The test patch is installed in a limited area on the leading edge of the vertical stabilizer - which is built by Boeing - one-quarter to one-half of the way up the fin, estimated to be positioned on the adjacent forward panels between ribs 3 and 7, just below the HF antenna. Boeing declined to comment on the tests.

The system, as Aviation Week's Guy Norris describes, is unlike previous testing by NASA, and the 787's system is "essentially passive":
This is important because passive systems are less complex, and lighter. Active systems, by contrast, require a turbocompressor, or other mechanical device, to suck the air into the wing.
It is believed Boeing aims to cut drag on the horizontal and vertical stabilizers by 1% for the 787-9, due for entry into service with Air New Zealand in late 2013.

The system underwent flight testing in early June at San Bernardino Airport in California and was spotted up close while on its visit. Those familiar with the system say the Boeing test includes a primer-colored perforated leading edge, pressure sensors, boundary layer rakes, the suction port at its base.

Photos Credit SBD Photo
Legacy 450_Cockpit_560.jpg
Listen to an Embraer technical briefing on the Legacy 500/450 fly-by-wire system with Fabrício Caldeira, flight control laws manager (first speaker), and chief project pilot Eduardo Camelier:

For as long as there has been fly-by-wire on aircraft, there's been a debate about how to best utilize the electronic flight control system and where to draw the line between pilot freedom and hard and fast boundaries protecting the aircraft and its occupants. This debate is far from settled with the most famous dispute between Boeing and Airbus charting different courses through computer driven flight control actuation.

On the one hand, Boeing leaves the pilot's judgment at the forefront, allowing overspeeding, stalling and over-banking within the flight envelope. The aircraft will let the pilot know, loudly, that they are approaching, or in, a potentially unsafe condition for the aircraft. Additionally, Boeing aircraft include an auto-throttle system resulting in the back-driven motion of the throttle quadrant providing a tactile cue to pilots without referring to the EICAS.

For Airbus, fly-by-wire has resulted in hard limits on the aircraft flight envelope, preventing over-speeding, stalling, and over-banking of the aircraft. The maximum bank allowed is 67-deg, with nose-down pitch not exceeding 15-deg and a 2.5g limit. An auto-thrust system complements the A-floor protection by automatically spooling up the engines, limiting nose up pitch (angle of attack) to prevent the aircraft from stalling and providing best climb performance.

While these have generally been two polar points on the augmented flight control spectrum, Embraer has charted its own path to full fly-by-wire for its first implementation on its all-new 10-passenger mid-size Legacy 500 business jet, due for entry into service in late 2012, followed by the smaller Legacy 450 in 2013. The aircraft were designed around their respective flight control systems allowing Embraer to optimize the structural sizing based upon the built-in protections.

As it fleshed out the elements of its fly-by-wire philosophy, Embraer drew on the lessons learned from notable accidents over the years that involved human factors resulting from improper aircraft handling.

What Embraer has created is its own course for implementing fly-by-wire technology and the Legacy 500 is its first platform. The path that Embraer has laid out for itself will undoubtedly become a hallmark of its flight control philosophy and will find its way the Brazilian airframer's next generation commercial aircraft.



Photo Credit Embraer
New Wing , originally uploaded by longbachnguyen.

If you look closely, all those red marks on the ZA001's wing, flaps and engine pylon are pieces of yarn. All the computer models running on all the super computers in the land are no match for seeing it with your own two eyes in flight.

When Mike Carriker discussed the new instrumentation added to ZA001 between first and second flight, the addition of yarn to the left wing was exactly what he was talking about.

The yarn will demonstrate how the airflow moves over the wing of the 787 and validate (or challenge) the computational fluid dynamics (CFD) models developed for the program.

AIRBUS UNDERTAKES BLENDED-WINGLET EVALUATION ON A320
Airbus has started flight-testing of Blended Winglet devices on an Airbus A320. The Blended Winglet technology, developed by Aviation Partners Inc. (API), has been specially adapted for these tests on the A320 Family.
Airbus A320 - MSN001 - F-WWBA
48289-224.jpg48289-241.jpg
More photos of the wingletted A320 taking flight after the jump.
I'll be the first to admit that there has been a distinct theme running through my posts this week. The newly flying 767-300ER with winglets just begs to be photographed. Here's the aircraft on its first flight in some very special air-to-air shots that really show off the new winglets. A very special thanks to Aviation Partners for the photos. (6 total, 3 after the jump)

a2a767_1.jpg a2a767_3.jpga2a767_2.jpg
The American Airlines 767-300ER, N389AA, outfitted with 11-foot tall Aviation Partners Boeing blended winglets, made its arrival at San Bernardino airport in sweltering Southern California, adorned with an experimental sticker below the one world logo. The aircraft will remain at San Bernardino for its two month FAA certification process.

767symetry.jpg
767landing.jpg
767tailwinglet.jpgMore photos below the fold.
Just broke:

Blended Winglets Make First Flight on Boeing 767-300ER

SEATTLE, July 21, 2008 /PRNewswire via COMTEX/ -- An American Airlines 767-300ER equipped with Aviation Partners Boeing Blended Winglets took to the skies for the first time at 1:50 p.m. central time Sunday July 20th. The newly modified aircraft flew a ferry flight from Kansas City, Missouri to San Bernardino, California where it will undergo two months of certification and winglet performance flight testing. The Blended Winglet installation, along with necessary wing and aircraft systems modifications, was performed by American Airlines employees at their Kansas City Maintenance Base.
AA767winglets-zoom.jpg Click for higher resolution expanded image

Cookies & Privacy