The Future of Aerospace (1993)

ALBERTUS D. WELLIVER

There is a misconception today about what technology really is. Technology has now come to mean specific things: fault-tolerant computers, portable satellite phones, featherweight composite materials. But these individual items, however important they may be, are not examples of the true meaning of the word technology. Instead, these are examples of technical excellence.

Are they important? Yes. But there is a higher form of technology at work behind these specific pieces of equipment—behind the benefits they produce. The ultimate technology is not based on microchips, alloys, or composites. Instead, higher-order technology is based on human experience, wisdom, and judgment. Higher-order technology is knowing how, where, and when to apply individual instances of technical excellence. In short, the development of technical excellence is essential, but it does not mean much unless it finds its way into a product and produces a benefit.

In aviation, the ultimate technology means listening to the customer and adding value to the airplane. In Boeing's design process, every new technology development must earn its way onto an airplane by adding value in one of three ways: in-

creased safety, improved operational efficiency and economic utility, and greater customer satisfaction.

Aviation history is full of examples of technologies that looked like winners but fell far short of expectations. Some of the examples are tragic mistakes; others are only humorous oddities, like Howard Hughes's Spruce Goose. Still the biggest aircraft ever to fly, it now sits in an amusement park in Long Beach, California. But the "Goose" was a true technical pioneer. Its compression-molded birch construction is one of the earliest examples of composite materials. Unfortunately, even with eight engines it was grossly underpowered. A single mile-long hop was all it could manage. It is a classic case of technical excellence in one area, the use of new material, but a lack of true technology in how to use it.

Higher-order technology, the technology of knowing how to apply examples of technical excellence, is now shaping the development of two exciting classes of airplane. One is the development of large subsonic transports, including the potential for new airplanes larger then any current commercial transports. The other is the prospect of a high-speed civil transport (HSCT).

Although these two categories of airplane are very different, they do have one thing in common: A successful design will depend on how technical excellence is applied to the satisfaction of the customer. By themselves, individual examples of technical excellence will not produce a winning design. A good airplane is the result of good decisions, not just good components.

When the 747 was first under development in the mid-1960s, Boeing engineers studied a number of different concepts. Some were simply stretched 707s. Others were all-new designs, including double-deck and single-deck airplanes ranging from 250 to 500 passengers in size.

The stretched 707 was quickly ruled out. It was too small to serve a rapidly expanding travel market. The decision was made to build a brand new airplane that was much bigger. The question came down to whether to build a double-deck or single-deck airplane. The choice was tough. Both had advan-

tages and disadvantages, and both configurations featured the latest in technical excellence. This included such innovations as the first high-bypass turbofans, the most advanced high-lift flap and slat combinations, and what was then a new concept in avionics, the inertial navigation system.

But it was not any of these individual examples of technical excellence that made the 747 a success. Instead, it was how this technical excellence was applied to the airplane. If we had built a double-deck, single-aisle airplane, it would not be able to carry the 8-foot-square containers that were beginning to dominate the cargo market, and our customers told us we had to have container-carrying ability to meet varying passenger and freight demand. The double-deck layout became one wide, single deck with twin aisles. This configuration was wonderful for passengers, and it produced the finest freighter in existence.

Wisdom, judgment, and experience produced a winning design that applied the latest in technical excellence. But is was the human beings who decided how to apply it that made the difference, not the hardware itself.

Today it is hard to imagine that the 747 could ever have looked any different than it does, with its distinctive hump and graceful lines. Just picture how the airplane would look if it had been built with the original decks, single-aisles, and no hump. And just think about whether this airplane would have been successful without its wide, twin-aisle layout.

Despite the many changes in configuration, the design process for the 747 was not unique. The decisions involved in applying technical excellence are always complex. In any airplane program, many concepts must be explored before the best solution is found.

The development of the 777 is an example of how this exploration process continues to shape every design. The first 777s will enter service in 1995, becoming the largest commercial twin-jet transports. The 777 is intended to meet the market needs better than any other airplane in its class. It does this by providing new levels of passenger comfort, unsurpassed operation economics, and simplified maintenance procedures, to name just a few of the design objectives.

As with the 747, the 777 incorporates many examples of technical excellence. Included are fly-by-wire flight controls,

lightweight composite materials, an advanced airplane information management system, and state-of-the-art avionics. For instance, the air data inertial reference system has 50 percent fewer parts, which improves reliability and eases maintenance.

The fundamental question, though, is how to apply these and other examples of technical excellence. When Boeing began thinking about the airplane that would become the 777, many concepts centered on modifying the 767. As surprising as it may seem now, Boeing thought about stretching the 767 and even adding a double-deck section to the rear fuselage. The airplane would have had one full-length deck and a second, half-length upper deck. Obviously, Boeing did neither of those things but instead decided that a new airplane was the best way to meet market needs.

The same decision-making process applies to all other commercial transport studies, including the potential future development of large commercial transports. Air travel is currently growing at rates that will cause passenger traffic to double by the year 2005. As a result, Boeing and others have begun preliminary studies of airplanes that could potentially be larger than the 747.

If an airplane that size is ever built, it would certainly include more than a few examples of technical excellence—things like digitally controlled high-bypass engines, extensive use of composite materials, computer-modeled aerodynamics, and advanced, integrated electronic systems. In addition, everything we have ever learned about safety, operational efficiency, performance, and customer satisfaction would be in that airplane.

As with the 747 and 777, however, success will depend not only on individual examples of technical excellence but on the higher-order process of applying it. And what will the final result be? Simply speaking, it is too early to tell. It is certain, however, what factors will shape this process. Principal among them is listening to the customer's needs and developing a keen understanding of the marketplace, including, for example, the several city pairs throughout the world where individual airlines fly back-to-back 747s within three hours of each other.

A historical look at how traffic has grown is another way to understand the market potential of an airplane bigger than the

747. The Pacific has truly become the 747 Ocean, as that airplane carries a majority of U.S.-to-Asia traffic. But on U.S.-to-Europe routes, and Europe-to-Asia routes, the evolution has been somewhat different. Although the 747 is popular, there has also been considerable growth in the use of intermediate-size airplanes.

With additional direct routes from the United States to Europe, twin-engine airplanes, especially the 757 and 767, are becoming increasingly popular. In fact, the majority of transatlantic flights are now made by twins, such as the 767. This means that any airplane larger than the 747 will have to meet Asian market needs, among others.

The second prospect for the future is a new generation of supersonic commercial airplanes. The task here is different, but the same principles of knowing how to apply technical excellence will guide the development process.

Environmental issues are a primary focus of this process. These issues include the need to control engine emissions and the need to control noise. The top priority is gaining a better understanding of the ozone layer. Boeing simply will not build an HSCT until it is known what the airplane will do to the atmosphere. The public will not have it any other way, and neither will Boeing.

At a cruising altitude of 60,000 feet, the HSCT will fly just below the highest concentration of ozone. Oxides of nitrogen from the engines are then exhausted directly into the lower half of the ozone layer. No one knows for sure what impact this would have.

Some earlier studies indicated that a fleet of HSCTs might deplete the ozone layer by several percent, but more recent studies, based on more complex models of atmospheric chemistry, indicate that the effect on the ozone layer would most likely be much less. In fact, ozone levels could even increase.

One way or another, we have to know before an HSCT is built. That is why the research being done right now is so vital. The efforts of the National Aeronautics and Space Administration (NASA), engine manufacturers, and others will

provide the information needed to design an environmentally acceptable HSCT.

The second environmental issue is noise. This includes noise from sonic booms as well as noise in a community during take-off and landing. Currently NASA is conducting human-response studies to establish criteria for sonic boom acceptability. Without those criteria it is impossible to know what configuration will result in an environmentally acceptable airplane.

Noise is also a major factor at low altitudes. The community noise standard is clear and tough. The HSCT must be no louder than current Stage 3 subsonic transports, but no suitable engine is yet available that meets that strict standard.

With engines built before 1972, engine noise could be reduced, but a heavy penalty was paid in efficiency. Today noise can be reduced without paying as great a price in lost thrust, but the target we need to reach is still beyond today's developments. Engine noise must be reduced by 15 to 20 decibels, with less than a 5 percent loss in thrust.

A number of promising designs now being tested may allow us to reach this goal. Most of these cut engine noise by mixing low-velocity outside air with the turbine exhaust. A number of factors, however, must be balanced to apply these new engine designs successfully to a commercial HSCT.

The engine must be quiet, but it cannot be too heavy. Many promising new nozzle and suppressor concepts unfortunately impose a serious weight penalty. An effective nozzle can easily weigh as much as the power plant itself. Engine location is another critical factor. The same engine may have much different noise characteristics, depending on where it is located on the plane.

High-lift systems are a second important part of reducing ground-level noise. Vortex fences can increase lift, allowing takeoff and landing at lower body attitudes and with shorter landing gear. This allows the airplane to fly at an improved lift-to-drag ratio for climb and approach.

Wake vortex image representation in computational fluid dynamics (CFD) allows for improved evaluation of the flow characteristics that lead to better performance. This performance includes benefits such as reduced noise on the ground

and less fuel consumption. This will be crucial if economic viability is to be achieved.

Many of the application judgments regarding technical developments will be made in view of the HSCT's economic constraints. Simply put, ticket prices cannot be at Concorde levels. Optimistic assessments show that if fare premiums for HSCT flights average 20 percent over the fares of subsonic flights, then nearly 65 percent of the potential HSCT market could be obtained. If fares averaged only 10 percent over, then nearly 85 percent of the market could be obtained.

The result is that for the HSCT to be economically viable, technical excellence must be achieved in two aerodynamic fields: computational fluid dynamics, or CFD; and hybrid laminar flow control (HLFC). With CFD analysis we are getting a better look at supersonic flight than we have ever had before. Computer-generated images give the clearest picture yet of supersonic flow, making possible the analysis of airflow both on the surface of the airplane as well as away from the vehicle. The result is much greater technical knowledge of shock waves produced by the wing, fuselage, and nacelles.

Hybrid laminar flow control is another area in which technical knowledge is growing rapidly. A 757 demonstrator, built as part of a Boeing/NASA project, recently became the first full-size commercial transport to fly with an HLFC system. The system is simple but effective. Air is drawn through microscopic holes in the leading edge by an engine-powered pump. The result is laminar flow over more than half the wing chord. In the spring of 1992, Boeing began working with NASA, Rockwell, and McDonnell-Douglas in testing a supersonic HLFC system. A NASA-owned F-16XL, with a cranked-arrow delta wing, will be fitted with a special HLFC glove.

If applied to an HSCT, the gains could be considerable. At Mach 2, skin friction accounts for 40 percent of drag, and an HLFC system could cut that figure substantially. At supersonic speeds, HLFC has the potential to be even more effective than at conventional speeds. Because of the greater amounts of fuel needed at Mach 2, even a small percentage reduction in drag could pay off economically.

By themselves, however, analytical tools like CFD, and new systems like HLFC, will not make the HSCT a success. It will

be up to engineers, to people, to make decisions on how to apply these and other technical developments. Their choices will be based on whether value is added to the airplane. They will listen closely to the customer to ensure that market needs are met.

Higher-order technology is more than simply having the tools to get the job done. It is having the wisdom, judgment, and experience to know how to apply those tools to produce a benefit for the customer.