40 years of airliner technology

When the Beatles arrived in New York in February 1964, they stepped off Pan Am's 707-320 Clipper Defiance, a first-generation pure-jet aircraft that was less than five years old. The classic 707-the longer-range, turbofan-powered 707-320B-was then quite new. A week before the Fab Four's US debut, Hawker Siddeley handed over a brand-new Comet 4 to Kuwait Airways. A brand-new Comet, by gad.

That can seem a long time ago, but 1964 was also the year that Boeing's Jack Steiner and Joe Sutter started the design of the 737. Only two years later, Boeing and Pan Am would launch the 747.

No sensible person in 1964 believed that the future belonged to short, fat 120-seaters or 490-seat giants. Britain and France had signed the Concorde agreement in blood in 1962 and Boeing, Lockheed and North American were competing for a government contract to build a US supersonic transport that naturally would be bigger and faster. Since Lockheed and North American had built supersonic-cruise airplanes, FAA, which the best-and-brightest in the White House had nominated to run the project, eliminated them and awarded the contract to Boeing.

That was not a pretty story, but we can pass over it because the SST not only failed commercially but proved largely outside the mainstream of airliner technology. Concorde was a technical marvel because it was done at all, but it just squeaked through to transatlantic range with 100 passengers, with its takeoff weight screwed up to the absolute limit and after long and expensive redesign on its inlets.

Many people in 1964 thought that the 707's configuration with its underwing engines was also old hat. Had the Beatles flown over a few months later, they would have traveled on a rear-engine BAC VC.10, as trendy as Mary Quant and Carnaby Street and one of a troika of aft-engine airplanes that British industry expected to conquer the world. It was not to be.

One reason that the British invasion fizzled was that the 1960s were the heyday of the "stretched" airplane. Boeing followed the 727-100 very rapidly with the dash 200, the DC-9-30 came quickly on the heels of the DC-9-10 and Douglas produced the stretched and refined Super 60 series of DC-8s, many of which still are hauling cargo today. The stretched airplanes sold better and lasted longer than the original designs. The UK's aircraft had been designed without the same development potential; it was a mistake that Europe would not make again.

The most important technical development of the 1960s resulted from the US Air Force's CX-HLS project for an ultra-large long-range transport, a 700,000-lb.-plus airplane with four engines. Pratt & Whitney and GE submitted designs for the new engines in April 1964. Delivering 40,000 lb. thrust they had large front fans and bypass ratios above 6:1, much greater than any earlier model.

Defeated by GE in the competition to power the USAF transport, which became the C-5A, Pratt & Whitney joined forces with Boeing and developed the JT9D for the huge 747, no less than two-and-a-half times the size of the 707. A bold and successful design, the 747 featured an efficient, high-speed wing with sophisticated high-lift devices so that it could use normal runways. After looking at a two-deck model, Boeing settled on a single main deck with a large, container-loaded lower deck for baggage and cargo. Too large to be flown manually, the 747 had quadruple hydraulic systems.

The Concorde did have one major effect on the 747. Convinced that the future belonged to SSTs, Pan Am founder Juan Trippe insisted that the 747 should be designed so that it could be converted into a cargo airplane, with a nose door for straight-in loading. The result was an upper-deck cockpit, which had to be extended into an aft fairing to reduce drag-a fairing that was large enough to accommodate a lounge and eventually a cabin.

Coming two years after the 747, the L-1011 and DC-10-10-Tweedledum and Tweedledee, their wingspans identical to the inch-seemed less risky. American Airlines' chief engineer, Frank Kolk, who drafted the first specification for a domestic widebody jet, had a twin-engine airplane in mind; what stood in the way of that concept was United Airlines' "Denver requirement." United needed an airplane that could take off from mile-high Denver on a hot day and fly to either coast, which meant a heavy fuel load for Boston or a high one-engine-inoperative ceiling if the destination was LAX. Consequently, the TriStar and DC-10 turned out to be the first and only large three-engine airplanes.

Of the two, the L-1011 was more of a technical showpiece. Its Rolls-Royce RB211 engines had aerodynamically refined fans made from the new wonder material carbon fiber-epoxy composite. That was the downfall of Rolls, which went bankrupt after prototype fans were damaged in heavy rain, and nearly the downfall of Lockheed. The TriStar went into service with titanium-alloy fan blades, but Rolls could not match the thrust growth that GE provided for the DC-10 and the production line dribbled to a halt by 1984.

The 747, DC-10 and L-1011 put three companies into the business of big engines, and many of the engines in production today are direct descendants of those original big-fan powerplants. The focus in the early 1970s was on reliability, maintainability and durability. Higher temperatures and pressures boosted performance and efficiency but played merry hell with critical components such as turbine blades and seals. Wear and erosion robbed the engines of performance as they aged. Hydromechanical engine controls-essentially, analog computers running on fluid pressure rather than voltage reached awesome levels of complexity.

Delivered to Air France in 1974, the A300 was technically quite conservative-a conscious decision on Airbus's part because any TriStar-like problems would have been terminal. But it did introduce some important innovations. Despite the commercial performance of its aircraft, the UK took second place to nobody in wing aerodynamics: The A300 wing had a so-called "rooftop" section that spread the lift more efficiently. The hardworking wing allowed the A300, initially designed for short European flights, to stretch to US transcontinental missions and Asian regional services. Another important feature was the way the airplane was made: The major sections were delivered to the final assembly line in as complete a form as possible. Originally devised as a way to share the work among Airbus's partners without the expense of two assembly lines, it turned out to be a more efficient way of building airplanes.

The A300 was the first twin-engine, twin-aisle airplane, a formula that has turned out to be the industry's equivalent of the minivan. By the end of the 1970s, Boeing was developing the 767 and Airbus the refined A310 and both infused new technology into their designs. After a pitched battle among airlines, manufacturers, pilot unions and regulators, they entered service with automated glass cockpits and two pilots. Digital engine controls and better materials-for example, single-crystal high-pressure turbine alloys and powder-metal disks-helped achieve a massive improvement in engine reliability, to the point where regulators allowed the new twins to fly the Atlantic and, eventually, the Pacific. The first 777 was a three-engine version of the 767 designed for overwater routes; extended-range twin-engine operations made it unnecessary.

In 1979, about a week before GE and Snecma intended to pull the plug on an engine project that was going nowhere fast, former Douglas salesman Jackson McGowan sewed up a deal to convert the world's DC-8 Super 60s to CFM56 power. In the following year as

Boeing's blue-eyed boys were working on the 757 and 767, the company authorized a low-key effort to look at ways to protect the 737 from being wiped out by the stretched, re-engined DC-9 Super 80, later designated the MD-80.

Many people assumed there was no way to hang the CFM56 on the short-legged 737, but CFM trimmed a few inches off the fan and Boeing engineers used newly developed computational fluid dynamics tools-a "virtual wind tunnel"-to tuck the engine closer to the wing and design a flattened inlet. Combined, these measures raised the lower inlet lip by a few crucial inches so that it would not act as a Shop-Vac. Launch customer Southwest

Airlines, combined with the bulletproof reliability of the CFM56, helped turn the 737-300 into a bestseller.

Airbus was looking at a single-aisle jet and the 737-300's success moved the goalposts. Chief Engineer Roger Beteille was the principal advocate for a gutsy decision: The new A320, launched in 1984, would be a fly-by-wire design featuring a new level of cockpit automation, sidestick controls, no control "feel" and "envelope protection," a robust set of limiters that would prevent the airplane from leaving controlled flight.

Boeing's initial response was, in effect, we'll see your FBW and raise you. It promised a radical new 150-seater that would use 50% less fuel than the A320. The 7J7 was powered by high-speed propeller or prop-fan engines with a twin-aisle, six-abreast cabin. Boeing will tell you that the 7J7 was scuppered because real fuel prices took a dive; Airbus maintains that the project was never much more than a diversion, intended to make airlines hesitate before committing to the A320 and allowing Boeing to sell them more 737s. After Airbus sold A320s to United and Northwest, in 1986-87, the 7J7 quietly disappeared.

Meanwhile, Airbus notched up two more firsts. ETOPS had wrong-footed the Europeans, who had designed the A310 for minimum costs on medium-range flights and found themselves out-ranged by the 767. In efforts to get more range out of the A310 and A300, Airbus introduced lighter tail surfaces made of carbon fiber, the first use of the material in primary structure on a commercial airplane, and wingtip fences, the first such devices to appear on a production airliner.

FBW proved controversial when the A320 entered service. In the first five years of operations there were four fatal accidents. The key lesson: The fact that the airplane was highly automated did not mean that it would fly itself. Operators stiffened their training standards, with particular emphasis on older pilots transitioning from "classic" jets. Since then the A320's safety record has been excellent.

FBW did more than just distinguish the A320 from its competitors. Airbus moved into longer-range markets in 1987 with the launch of the twin-engine A330 and four-engine A340. The flightdecks of the new airplanes came from the A320 and the fuselage from the A300, while the A330 and A340 wings were basically similar.

Boeing's response was to introduce new technology of its own. The 777, a very effective counter to Airbus's big sisters, was the first large airplane to be created entirely on Dassault's CATIA computer-aided design software. Three-dimensional CFD produced a wing that would accommodate all the fuel the 777 and its derivatives should need over the product's lifetime but was nevertheless light and efficient. Robotics were used on the largest scale yet, including fiber-placement techniques to build the big composite tail skins. One crucial goal was achieving ETOPS from the first day of operations, and this was accomplished for the first time.

The big Boeing twin needed more power than any previous airplane. The new engines from Rolls-Royce, Pratt and GE were visibly different-they featured fewer, wider, more visibly twisted fan blades without mid-span shrouds, allowing them to handle more air within the same diameter. The first wide-chord blades had been seen on the RB211-535E4 for the 757; the key to making them work was to make them lighter yet stiffer. Rolls and Pratt developed proprietary, jealously guarded techniques for making hollow metal blades while GE made the jump to composite blades.

In 2000, GE and Boeing launched a pair of heavyweight 777s fitted with the new GE90-115B engine. Developing 115,000 lb. thrust, it not only is the most powerful airplane engine ever built but the biggest mobile power producer of any kind, delivering more push than even an aircraft carrier's nuclear reactor.

The new 777s and their Airbus counterparts, the A340-500/-600, exemplify what technology delivers to airlines and passengers today. Economical on medium-range flights, they are capable of flying routes well over 7,500 nm-50% farther than the long-range airplanes of the 1970s. Typifying the flexibility and versatility of the modern airliner is the A330-200. The 737s and A319s that once were considered short-range airplanes now carry business-class passengers from Europe to the US.

In 2004 Airbus' Super-jumbo and Boeing's all-composite 7E7 Dreamliner, now launched on an ANA order, are the first all-new airplanes since the 777.

Technical highlights of the A380 include the use of more sophisticated CFD codes to refine the design of crucial areas such as the nacelles and pylons and the wingtip fence, helping to yield a combination of wing and engine design that earns the giant airplane a superior QC2 noise rating at London Heathrow. Electrical power replaces two of the normal hydraulic systems-the A380 can survive a total hydraulic failure. The avionics are built on a highly redundant network, allowing an A380 to dispatch even with multiple failures.

Boeing's 7E7, if all goes to plan, will be built in massive sections, largely complete before delivery. Swing-tail 747s will fly the pieces into Everett, Wash., and assembly is expected to take no more than three days. The all-composite structure eventually will be wired with sensors to detect damage. The airplane should feature outstanding fuel economy thanks to high-bypass engines and will use electrical power to replace bleed air. Composites permit bigger windows, higher cabin pressure and higher humidity, which may be a necessity on 8,000-nm flights.

That much said, the basic layout of the A380 and the 7E7 is still that of Clipper Defiance: Swept, low-mounted, dihedral wing, engines on pylons, landing gear attached to the rear spar. The most recent attempt to do something different, Boeing's Sonic Cruiser, laid an egg in the market. There are Boeing people who think the future is the Blended Wing Body; the company is keeping them locked up in the basement until the 7E7 gets sold.

A series of Northrop Grumman flight tests in August 2003 and January 2004 suggest that it may be possible to suppress the sonic boom and fly supersonic overland, which would make the case for a new SST much stronger. Don't expect a 300-seat, 320-ft.-long monster very soon, however. The first step is likely to be a business jet, perhaps leading to a 50-passenger road warrior express. I for one will take little windows and Death Valley humidity if I can go at Mach 2.