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Recently in NBAA 2011 Category


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


LAS VEGAS -- Citing change incorporation stemming from flight test, Boeing Business Jets president Steve Taylor says the first and only delivery of the 747-8I in 2011 will be "right at the end of the year".

"There's not a lot of margin", says Taylor of the 747-8I, which is expected to be certified late in the fourth quarter.

"We won't get three to five, the plan is to get one. And it's challenging," said Taylor today of the 2011 747-8I deliveries.

Almost exactly one year ago at NBAA 2010, Taylor said Boeing planned to begin 747-8I flight testing in March, which it achieved, and anticipated a four month flight test program.

At the time Boeing aimed to deliver the first five 747-8Is to VIP customers before the end of 2011.

"I lay awake at night trying to figure out how I'm going to deliver five of them in the compressed period we have," said Taylor in 2010.

Further putting pressure on flight test, weeks after that October 2010 estimate, Boeing suffered a fire aboard one of its 787 flight test aircraft, extending the majority-composite jetliner's certification effort by approximately seven months.

Boeing Commercial Airplanes CEO Jim Albaugh said in July the company planned to deliver its first green 747-8I to a completion center in early-December.

Boeing forecasts delivering 25 to 30 747-8 and 787 aircraft in 2011 and Taylor declined to discuss any potential impact on that estimate, citing the US Securities and Exchange Commission quiet period ahead of the company's quarterly earnings call on October 26.

Though, Taylor did say that the 25 to 30 estimate, which was revised downward in July, was developed when the company had already accepted that reality" of a single 747-8I delivery "before that plan came along".

Boeing reduced its overall 2011 forecast for its new program deliveries from 25 to 40 down to 25 to 30.

The airframer plans to deliver its first passenger configured 747-8I to Lufthansa in Spring 2012, and Taylor says the company has been in close communication with its customers about its delivery schedule.

"All of our customers are aware exactly where we are. We're talking directly with them, they know what's going on, there's no surprise that's happening behind the scenes here."

Ahead of the 2011 National Business Aviation Association conference in Las Vegas, which begins on Sunday, Pratt & Whitney Canada invited me to take a closer look at the Pacific Aerospace P-750 XSTOL and the engine that powers it, the PT6A.

The XSTOL, which stands for extreme short take off and landing, is a designation given by the New Zealand-based airframer when an aircraft can take-off with a payload in excess of its empty weight in under 800ft. At its core, the P-750's missions include a 4,000lb payload on short field takeoff capability on semi-prepared runways, aerial survey, crop dusting, fire fighting or carrying up to 17 skydivers to dump at altitude. We'll talk about that last mission a bit more later on.

That performance is due, in part, to the Cresco's thick wing and a span of 42ft (12.8m), 305sq ft (28.34 sq m) wing area and pronounced outboard dihedral. The design of the P-750 was derived by combining the engine and wings of the older Pacific Aerospace Cresco crop duster with a new large fuselage design and modified empennage. The type made its first flight in 2001 and was certified in 2004.

The other part is the 750hp (560kW) PT6A-34 engine selected by Pacific to power the P-750, which is significant for an aircraft whose empty weight is only 3,100lbs. 

Pratt & Whitney Canada started mass production of the PT6 in 1963, and is arguably aviation's most resilient turbine engine design, evolving incrementally over time with each new application. The P-750 is one of 130 different aircraft that have been powered by the PT6.

The engine's first application, the Beechcraft Model 18, first flew in May 1961 and was intended as a replacement of the P&W Wasp radial engine. To date, PWC has delivered 46,000 PT6 engines, 26,000 of which are still flying today having accumulated 350 million hours in service.

With its 1961 first flight, the PT6 architecture is only eight years shy of having as many years removed from its first flight, as its own first flight was from Orville & Wilbur at Kitty Hawk.

PT6 Modules.jpg
The engine, which can provide power from 500shp up to 2,000shp - depending on the application - and is principally made up of three major components, a gas generator comprising the compressor and combustor, the power section made up of the turbine which is spun by the combusted fuel and air, and a gearbox that connects directly to a propeller or rotor.

Those three elements have been scaled and customized over the years to create a modular system that can be tailored depending on the application.

"We can mix and match these to get better thermal ratings, better flat ratings, make the PT6 a sort of tailored engine to the aircraft these people are trying to make," said John Saabas, PWC President in a Friday interview. "When you're a small aircraft maker we can give you choice. We can give you a power range, thermal range, mechanical range.

"Socatas need lots of thermal power because they want to go fast at altitude, not so much mechanical power. King Airs want to take off with heavy loads and don't go quite as fast need more mechanical power. So a different gear box for those two even those it may be the same basic engine behind it. It just depends on how its rated."

"From a first-cost perspective, we also bring an advantage over some other technologies, some of the other choices that are out there," he says, citing higher SFC but a lower acquisition cost of the PT6 than the GE T700 that powers civilian and military rotorcraft. 

For Saabas the extended investment over decades and pressure to deliver another another major leap in fuel burn improvement is tempered by the cost competitiveness and market establishment of the existing engine. 

To look at the engine through Red-Blue, London School of Economics academic Dr. Theodore Piepenbrock's work on business evolution, the PT6 serves as a prime example of incremental, scalable development that has benefitted from continuous product evolution to drive out cost and improve efficiency and fuel performance over its extended lifetime.

Though even with its modular design, Saabas cautions that the PT6 is not focused as an off-the-shelf engine as it appears: "You don't want to get to a point where you're a commodity, we're always trying to decomoditize ourselves."

Though he acknowledges, the mix-and-match capability of the PT6 allows airframers small and large flexibility, but the scale of the complexity is the differentiator from project to project.

"There are some applications that some people want to take a [PT6A-42] and they want to adapt it, but we're developing for the Eurocopter, right now, the [PT6C-67E] which is a brand new version of the PT6 for the EC175, we're putting a FADEC on to that."

Overall, Saabas attributes the success of the platform to its overall reliability, achieving an in-flight shutdown rate of two per every million flight hours. Though, he also acknowledges market pressures by relative new-comers in the market, General Electric and its M601 and H-80 engine, which grew out of its 2008 Walter Aircraft Engines acquisition.

The engine, says PWC, has improved in line with the industry standard, delivering an extra percent of specific fuel consumption improvement every year, translating into a 20% improvement over the last two decades.

In a 2010 interview, Saabas said its plans for the introduction of new technologies into the PT6 remained a higher priority that its plans for a replacement, calling it an "advanced design study", though he says in Friday's interview that the PT6 replacement will evolve from the PT6 itself: "We're doing a couple of neat technologies to see if we can't improve the efficiency of the PT6 by double digits, and some of them use PT6 architectures, some don't. So let's call them a general aviation engine replacement if you will."

Yet Saabas, who has been PWC's president since 2009, says the company has stuck with the PT6 for as long as it has because there have been "a lot of generations of leaders at Pratt Canada who have been customer focused and out there trying to adapt the product to different marketplaces and aggressively looking for these applications for the engine and spending the money to develop it with the confidence that there was a marketplace."

Video Credit Pacific Aerospace
Cutaway Credit Pratt & Whitney Canada

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