Beauty of Future Airplanes is More than Skin Deep

An 18-month NASA research effort to visualize the passenger airplanes of the future has produced some ideas that at first glance may appear to be old fashioned. Instead of exotic new designs seemingly borrowed from science fiction, familiar shapes dominate the pages of advanced concept studies which four industry teams completed for NASA's Fundamental Aeronautics Program in April 2010. Look more closely at these concepts for airplanes that may enter service 20 to 25 years from now and you'll see things that are quite different from the aircraft of today. Just beneath the skin of these concepts lie breakthrough airframe and propulsion technologies designed to help the commercial aircraft of tomorrow fly significantly quieter, cleaner, and more fuel-efficiently, with more passenger comfort, and to more of America's airports. You may see ultramodern shape memory alloys, ceramic or fiber composites, carbon nanotube or fiber optic cabling, self-healing skin, hybrid electric engines, folding wings, double fuselages and virtual reality windows. "Standing next to the airplane, you may not be able to tell the difference, but the improvements will be revolutionary," said Richard Wahls, project scientist for the Fundamental Aeronautics Program's Subsonic Fixed Wing Project at NASA's Langley Research Center in Hampton, Va. "Technological beauty is more than skin deep." In October 2008, NASA asked industry and academia to imagine what the future might bring and develop advanced concepts for aircraft that can satisfy anticipated commercial air transportation needs while meeting specific energy efficiency, environmental and operational goals in 2030 and beyond. The studies were intended to identify key technology development needs to enable the envisioned advanced airframes and propulsion systems. NASA's goals for a 2030-era aircraft, compared with an aircraft entering service today, are:
A 71-decibel reduction below current Federal Aviation Administration noise standards, which aim to contain objectionable noise within airport boundaries.
A greater than 75 percent reduction on the International Civil Aviation Organization's Committee on Aviation Environmental Protection Sixth Meeting, or CAEP/6, standard for nitrogen oxide emissions, which aims to improve air quality around airports.
A greater than 70 percent reduction in fuel burn performance, which could reduce greenhouse gas emissions and the cost of air travel.
The ability to exploit metroplex concepts that enable optimal use of runways at multiple airports within metropolitan areas, as a means of reducing air traffic congestion and delays. The teams were led by General Electric, Massachusetts Institute of Technology, Northrop Grumman and The Boeing Company. Here are some highlights from their final reports:
The GE Aviation team conceptualizes a 20-passenger aircraft that could reduce congestion at major metropolitan hubs by using community airports for point-to-point travel. The aircraft has an oval-shaped fuselage that seats four across in full-sized seats. Other features include an aircraft shape that smoothes the flow of air over all surfaces, and electricity-generating fuel cells to power advanced electrical systems. The aircraft's advanced turboprop engines sport low-noise propellers and further mitigate noise by providing thrust sufficient for short takeoffs and quick climbs.
With its 180-passenger D8 "double bubble" configuration, the Massachusetts Institute of Technology team strays farthest from the familiar, fusing two aircraft bodies together lengthwise and mounting three turbofan jet engines on the tail. Important components of the MIT concept are the use of composite materials for lower weight and turbofan engines with an ultra high bypass ratio (meaning air flow through the core of the engine is even smaller, while air flow through the duct surrounding the core is substantially larger, than in a conventional engine) for more efficient thrust. In a reversal of current design trends the MIT concept increases the bypass ratio by minimizing expansion of the overall diameter of the engine and shrinking the diameter of the jet exhaust instead. The team said it designed the D8 to do the same work as a Boeing 737-800. The D8's unusual shape gives it a roomier coach cabin than the 737.
The Northrop Grumman team foresees the greatest need for a smaller 120-passenger aircraft that is tailored for shorter runways in order to help expand capacity and reduce delays. The team describes its Silent Efficient Low Emissions Commercial Transport, or SELECT, concept as "revolutionary in its performance, if not in its appearance." Ceramic composites, nanotechnology and shape memory alloys figure prominently in the airframe and ultra high bypass ratio propulsion system construction. The aircraft delivers on environmental and operational goals in large part by using smaller airports, with runways as short as 5,000 feet, for a wider geographic distribution of air traffic.
The Boeing Company's Subsonic Ultra Green Aircraft Research, or SUGAR, team examined five concepts. The team's preferred concept, the SUGAR Volt, is a twin-engine aircraft with hybrid propulsion technology, a tube-shaped body and a truss-braced wing mounted to the top. Compared to the typical wing used today, the SUGAR Volt wing is longer from tip to tip, shorter from leading edge to trailing edge, and has less sweep. It also may include hinges to fold the wings while parked close together at airport gates. Projected advances in battery technology enable a unique, hybrid turbo-electric propulsion system. The aircraft's engines could use both fuel to burn in the engine's core, and electricity to turn the turbofan when the core is powered down. NASA did not specify future commercial air transportation needs as domestic or global. All four teams focused on aircraft sized for travel within a single continent because their business cases showed that small- and medium-sized planes will continue to account for the largest percentage of the overall fleet in the future. One team, however, did present a large hybrid wing concept for intercontinental transport. All of the teams provided "clear paths" for future technology research and development, said Ruben Del Rosario, principal investigator for the Subsonic Fixed Wing Project at NASA's Glenn Research Center in Cleveland. "Their reports will make a difference in planning our research portfolio. We will identify the common themes in these studies and use them to build a more effective strategy for the future," Del Rosario said. These are some of the common themes from the four reports:
Slower cruising -- at about Mach 0.7, or seven-tenths the speed of sound, which is 5 percent to 10 percent slower than today's aircraft -- and at higher altitudes, to save fuel.
Engines that require less power on takeoff, for quieter flight.
Shorter runways -- about 5,000 feet long, on average -- to increase operating capacity and efficiency.
Smaller aircraft – in the medium-size class of a Boeing 737, with cabin accommodations for no more than 180 passengers – flying shorter and more direct routes, for cost-efficiency.
Reliance on promised advancements in air traffic management such as the use of automated decision-making tools for merging and spacing enroute and during departure climbs and arrival descents. The teams recommended a variety of improvements in lightweight composite structures, heat- and stress-tolerant engine materials, and aerodynamic modeling that can help bring their ideas to reality. NASA is weighing the recommendations against its objective of developing aeronautics technologies that can be applied to a broad range of aircraft and operating scenarios for the greatest public benefit. "This input from our customers has provided us with well thought-out scenarios for our vision of the future, and it will help us place our research investment decisions squarely in the mainstream," said Jaiwon Shin, associate administrator for aeronautics research at NASA Headquarters in Washington. "Identifying those necessary technologies will help us establish a research roadmap to follow in bringing these innovations to life during the coming years," Shin said. The next step in NASA's effort to design the aircraft of 2030 is a second phase of studies to begin developing the new technologies that will be necessary to meet the national goals related to an improved air transportation system with increased energy efficiency and reduced environmental impact. The agency received proposals from the four teams in late April and expects to award one or two research contracts for work starting in 2011. NASA managers also will reassess the goals for 2030 aircraft to determine whether some of the crucial technologies will need additional time to move from laboratory and field testing into operational use. The four teams managed to meet either the fuel burn or the noise goal with their concepts, not both. A companion research effort looked at concepts for a new generation of supersonic transport aircraft capable of meeting NASA's noise, emissions and fuel efficiency goals for 2030. NASA envisions a broader market for supersonic travel, with aircraft carrying more passengers to improve economic viability while meeting increasingly stringent environmental requirements. Teams lead by The Boeing Company and Lockheed Martin evaluated market conditions, design goals and constraints, conventional and unconventional configurations, and enabling technologies to create proposed roadmaps for research and development activities. Both teams produced concepts for aircraft that can carry more than 100 passengers at cruise speeds of more than 1.6 Mach and a range of up to 5,000 miles.

Laminar Flow Research Aircraft

F-16XL Laminar Flow Research Aircraft F-16XL was used in the Cranked-Arrow Wing Aerodynamics Project (CAWAP) to test boundary layer pressures and distribution.
Two F-16XL aircraft were used by the Dryden Flight Research Center, Edwards, CA, in a NASA-wide program to improve laminar airflow on aircraft flying at sustained supersonic speeds. It was the first program to look at laminar flow on swept wings at speeds representative of those at which a high speed civil transport might fly.

Technological data from the program will be available for the development of future high-speed aircraft, including commercial transports. As such, it supported the NASA Office of Aero-Space Technology's goal of reducing travel time to Asia and Europe by 50 percent within 20 years.
The initial research phase of the program at Dryden was flown in a single-seat F-16XL-1. This aircraft was later used at Dryden in a sonic boom research project with the SR-71 and in a Cranked-Arrow Wing Aerodynamics Project (CAWAP) to test boundary layer pressures and distribution. In 1997 Dryden replaced the aircraft's analog flight control system with a digital system and planned to use the aircraft as a testbed for autonomous systems to be employed in spacecraft.

The aircraft at Dryden subsequently used for the supersonic laminar flow program was the two-seat F-16XL-2, identical to its sistership except for the cockpit configuration.
The two aircraft are the only F-16XL's built and were used by NASA because the unique delta wing design is representative of the type of wing that will probably be used on future supersonic cruise aircraft.

Project Background:

A certain amount of air turbulence occurs on the surface of most aircraft wings, regardless of the shape and sizeof the wing. As air moves across an airfoil, it is changed by the frictional force between it and the airfoil's surface from a laminar (smooth) flow at the forward area to a more turbulent flow toward the trailing edge. The 'perfect" wing would demonstrate laminar airflow across the entire surface of the wing, with no sign of turbulence. This turbulence affects flying performance by increasing aerodynamic drag and fuel consumption.
NASA's single-seat F-16XL presents a unique look to an observer from above as it flies over the snow-covered southern Sierra Nevada Mountains of California.

Research by NASA to improve laminar flow dates back to around 1930 when NASA's predecessor organization, the National Advisory Committee for Aeronautics (NACA), photographed airflow turbulence in the variable density tunnel at its Langley Research Center in Hampton, VA. Smoke was ejected into the air stream and photographed as it showed visual signs of turbulence (disturbed rather than streamlined flow) on the upper wing surfaces. Early research such as this led to the eventual elimination of protruding rivet heads and other construction and design features that could create turbulence on high-speed aircraft.
Much laminar flow research is carried out with two basic types of experimental devices — active and passive — that are attached to the research aircraft's wing. These devices are commonly called "gloves."

Active test sections contain tiny holes or slots through which most of the turbulent layer of air is siphoned off by an internal suction system built into the wing. This decreases drag and enhances aerodynamic lift by either eliminating the turbulent airflow or reducing its effect.
Passive experimental devices also attach to or become a part of the research aircraft's wing, but do not use a suction system to remove the turbulent air. Through careful contouring of the wing's surface, some laminar flow can be achieved naturally.

Both types of laminar flow devices obtain data from sensors and other instrumentation built into or attached to the wing to measure airflow characteristics (especially the region of transition from laminar to turbulent flow) and pressure distribution.

Dryden has conducted laminar flow studies in past years with F-104, F-14, F-15, and F-111 high-performance aircraft, and also with a JetStar business-type aircraft. The projects with the F-16XL, however, were the first that sought to achieve a significant percentage of laminar flow over wings comparable to those of a high speed civil transport. These flight tests were conducted under supersonic flight conditions similar to those such a transport would encounter.
Flight Research The F-16XL's unusual curved double delta wing platform is apparent in this photo.

The initial flight test phase of the Dryden Supersonic Laminar Flow Control project (SLFC) examined the performance of an active experimental wing section on the upper surface of the left wing of the single-seat F-16XL-1. The 1991-1992 tests showed that with active laminar flow control, the aircraft achieved laminar flow over a significant portion of the wing during supersonic flight, although it did not obtain laminar flow on the active glove at the design point of Mach 1.6 (1.6 times the speed of sound) at 44,000 ft. The experimental glove with active (perforated titanium) and passive sections was designed by Rockwell International's North American Aircraft Division, El Segundo, CA. (now a division of Boeing).

Dryden then used the two-seat F-16XL-2 to conduct a more comprehensive research effort, consisting of two phases. The first phase used a passive glove on the right wing to obtain baseline configuration data that served in the design of the active glove, which was installed over a portion of the left wing. This effort was far more comprehensive than the initial flight phase, and explored regions of transition and the maximum extent of laminar flow obtained over a wider range of supersonic Mach numbers.

The glove covered about 75 percent of the upper wing surface and 60 percent of the wing's leading edge. It was designed by a NASA and contractor team which included the Langley Research Center, Dryden, Rockwell International, Boeing, and McDonnell Douglas. It featured a titanium suction panel and a foam-and-fiberglass passive fairing. The device was instrumented to measure laminar flow and other variables such as surface imperfections and the acoustic environment that may affect laminar flow at various flight conditions.

The metal surface of the experimental wing panel was perforated with about 10 million nearly microscopic laser-cut holes. Through the tiny holes, a suction system embedded in the wing (and mechanized by a turbocompressor in the fuselage) drew off a very small portion of the boundary layer of air just above the wing's surface, thereby expanding the laminar flow across the wing. The flight engineer used a control panel located in the aft cockpit of the airplane to fine-tune the amount of airflow sucked through the holes. This procedure permitted investigation of the effect of suction volume on the area distribution of laminar flow. Researchers believe that laminar flow conditions can reduce aerodynamic drag (friction) and help reduce operating costs by reducing fuel consumption.

The project flew the F-16XL-2 45 times between Oct.13, 1995, and Nov. 26, 1996, obtaining significant amounts of valuable flight research data. NASA research pilot Dana Purifoy flew 38 of the missions, with NASA research pilot Mark Stucky flying the other 7. During the flights, there were few problems with the experimental suction hardware. Because all laminar-flow-related data are restricted, however, the results of the flight research cannot be reported publicly at this time.

Project Management
The F-16XL flight project office was located at the NASA Dryden Flight Research Center, Edwards, CA. The NASA Langley Research Center, developed and coordinated F-16XL experiments. Project managers at Dryden were Marta Bohn-Meyer and Carol Reukauf.

BOEING 757-300 NARROW BODY:
The stretched, 240 seat Boeing 757-300 is the first significant development of the basic 757-200 and is aimed primarily at the European vacation charter market.
Although design work on the original 757 began in the late 1970s and its entry into service was in 1983, it wasn't until over a decade later in the mid 1990s that Boeing began to study a stretched development of its popular narrowbody twin. This new 757 stretch was covered by the 757-300X designation until its launch at the Farnborough Airshow in England in September 1996.
The most obvious change over the 757-200 is the 300's 54.43m (178ft 7in) long fuselage, which is 7.11m (23ft 4in) longer than the standard aircraft (and only fractionally shorter than the 767-300). This fuselage stretch allows a 20% increase in seating to 225 to 279 passengers, depending on the interior configuration. Lower hold freight capacity is also increased by 40% over the 757-200 by virtue of the longer fuselage.
Another feature of the 757-300 is its new interior which is based on that developed for the Next Generation 737 models. Features include a new sculptured ceiling, larger overhead bins, indirect overhead lighting and vacuum toilets.
The 757-300 shares the 200's cockpit, wing, tail and powerplant options, although the 300 will feature strengthened structure and landing gear to cope with the increased weights, new wheels, tyres and brakes and a tailskid.
The 757-300 first flew on August 2 1998, with certification in January 1999, and entry into service (with launch customer Condor - the charter arm of German flag carrier Lufthansa) in March 1999. The -300's 27 month development program from final configuration to planned first delivery is the fastest for any Boeing airliner (the 777-300 took 31 months for example). Other early customers are Icelandair, Arkia, Northwest, American Trans Air, Continental, and JMC Air.

History of airbus A380


The 555 seat, double deck Airbus A380 is the most ambitious civil aircraft program yet. When it enters service in March 2006, the A380 will be the world's largest airliner, easily eclipsing Boeing's 747.
Airbus first began studies on a very large 500 seat airliner in the early 1990s. The European manufacturer saw developing a competitor and successor to the Boeing 747 as a strategic play to end Boeing's dominance of the very large airliner market and round out Airbus' product line-up.
Airbus began engineering development work on such an aircraft, then designated the A3XX, in June 1994. Airbus studied numerous design configurations for the A3XX and gave serious consideration to a single deck aircraft which would have seated 12 abreast and twin vertical tails. However Airbus settled upon a twin deck configuration, largely because of the significantly lighter structure required.
Key design aims include the ability to use existing airport infrastructure with little modifications to the airports, and direct operating costs per seat 15-20% less than those for the 747-400. With 49% more floor space and only 35% more seating than the previous largest aircraft, Airbus is ensuring wider seats and aisles for more passenger comfort. Using the most advanced technologies, the A380 is also designed to have 10-15% more range, lower fuel burn and emissions, and less noise.
The A380 features an advanced version of the Airbus common two crew cockpit, with pull-out keyboards for the pilots, extensive use of composite materials such as GLARE (an aluminium/glass fibre composite), and four 302 to 374kN (68,000 to 84,000lb) class Rolls-Royce Trent 900 or Engine Alliance (General Electric/Pratt & Whitney) GP7200 turbofans now under development.
Several A380 models are planned: the basic aircraft is the 555 seat A380-800 (launch customer Emirates). The 590 ton MTOW 10,410km (5620nm) A380-800F freighter will be able to carry a 150 tonne payload and is due to enter service in 2008 (launch customer FedEx). Potential future models will include the shortened, 480 seat A380-700, and the stretched, 656 seat, A380-900.
On receipt of the required 50th launch order commitment, the Airbus A3XX was renamed A380 and officially launched on December 19, 2000. In early 2001 the general configuration design was frozen, and metal cutting for the first A380 component occurred on January 23, 2002, at Nantes in France. In 2002 more than 6000 people were working on A380 development.
On January 18, 2005, the first Airbus A380 was officially revealed in a lavish ceremony, attended by 5000 invited guests including the French, German, British and Spanish president and prime ministers, representing the countries that invested heavily in the 10-year, €10 billion+ ($13 billion+) aircraft program, and the CEOs of the 14 A380 customers, who had placed firm orders for 149 aircraft by then.
The out of sequence A380 designation was chosen as the "8" represents the cross-section of the twin decks. The first flight is scheduled for March 2005, and the entry into commercial service, with Singapore Airlines, is scheduled for March 2006.
Apart from the prime contractors in France, Germany, the United Kingdom and Spain, components for the A380 airframe are also manufactured by industral partners in Australia, Austria, Belgium, Canada, Finland, Italy, Japan, South Korea, Malaysia, Netherlands, Sweden, Switzerland and the United States. A380 final assembly is taking place in Toulouse, France, with interior fitment in Hamburg, Germany. Major A380 assemblies are transported to Toulouse by ship, barge and road.
On July 24, 2000, Emirates became the first customer making a firm order commitment, followed by Air France, International Lease Finance Corporation (ILFC), Singapore Airlines, Qantas and Virgin Atlantic. Together these companies completed the 50 orders needed to launch the programme.
Later, the following companies also ordered the A380: FedEx (the launch customer for the A380-800F freighter), Qatar Airways, Lufthansa, Korean Air, Malaysia Airlines, Etihad Airways, Thai Airways and UPS. Four prototypes will be used in a 2200 hours flight test programme lasting 15 months.