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Boeing 777 Family Background

 

 

 

Market demand has sized, shaped and launched the newest member of the Boeing widebody family, the 777. The airplane design offers features, innovations and approaches to aircraft development that set the standard for delivering value to airlines. The 777 -- the world's largest twinjet -- is available in three models: an initial 777-200 model, a 777-200ER (extended range) model and a larger 777-300 model.

On Feb. 15, 1996, the 777 was named winner of the prestigious Robert J. Collier Trophy by the U.S. National Aeronautic Association. The award honored the 777 as top aeronautical achievement of 1995.

Initially, United Airlines, All Nippon Airways, British Airways, Japan Airlines and Cathay Pacific were among a number of carriers with whom Boeing held intensive discussions, including many group sessions, to define and develop the new airplane's configuration. The participating airlines represented a full range of operations in terms of route structure, traffic loads and service frequency. Their input to the design process helped ensure that the final product has the broadest possible application to the needs of the world's airlines.

In every respect, the 777 design responds to market needs and customer preferences. The result is an airplane offering cabin spaciousness and flexibility found in no other jetliner and many features to enhance reliability and productivity -- all with lower operating costs. The 777 provides the most payload and range capability and growth potential in the medium-size aircraft category.

Another benefit of the intensive customer dialogue was a consensus that many items traditionally offered as optional, or special request, features on other airplanes should be standard (or basic) equipment on the 777 because they are so frequently specified by most airlines. About 80 such items -- including satellite communication and global positioning systems -- are basic to the airplane. This reduces variability during design and production, while providing the airlines with a more economical equipment package.

Wing Design
The 777 wing uses the most aerodynamically efficient airfoil ever developed for subsonic commercial aviation. In a further refinement of designs introduced on the Boeing 757 and 767, the 777 wing features a long span with increased thickness while achieving higher cruise speeds. This advanced wing enhances the airplane's ability to climb quickly and cruise at higher altitudes than competing airplanes. It also allows the airplane to carry full passenger payloads out of many high-elevation, high-temperature airfields.

Fuel volume requirements for the 777 are accommodated entirely within the wing and its structural center section. For the initial airplane, fuel capacity is 31,000 gallons (117,335 L), while the longer-range model and the 777-300 model can carry up to 45,220 gallons (171,155 L).

Airlines helping to design the 777 encouraged Boeing to commit to the performance capabilities of an optimum wing, which has a span of 199 feet 11 inches (60.9 m).

Propulsion
The three leading engine manufacturers have developed more efficient and quieter turbofans to power the 777, and all three have been selected by 777 customers. Engine selection by the airlines is split by roughly one-third for each of the engine manufacturers.

For the initial airplane, these engines are rated in the 73,400- to 77,000-pound thrust class. For the extended-range model and the 777-300, these engines will be capable of thrust ratings in the 83,600-to-98,000-pound category. The engines could be developed to even higher thrust ratings, depending on future payload and range requirements.

All three engines offer excellent fuel efficiency, while allowing the 777 to be as quiet as a 767, even though the 777 engines provide 40 percent more power. Key factors in this performance are new, larger-diameter fans with wide-chord fan blade designs and bypass ratios ranging from 6-to-1 to as high as 9-to-1. This compares to the typical 5-to-1 ratio for the engines of previous twin-aisle jets.

Pratt & Whitney is offering the PW4000 series of engines, General Electric is offering its all-new GE90 series, and Rolls-Royce is offering the Trent 800 series of engines.

Materials
New, lightweight, cost-effective structural materials are used in several 777 applications. For example, an improved aluminum alloy is used in the upper wing skin and stringers. Known as 7055, this alloy offers greater compression strength than current alloys, enabling designers to save weight and also improve corrosion and fatigue resistance.

Progress in the development and fabrication of weight-saving advanced composite materials is evident in the 777. Carbon fibers embedded in recently available toughened resins are found in the vertical and horizontal tails. The floor beams of the passenger cabin also are made of these advanced composite materials.

Other composite applications include those on secondary structures such as aerodynamic fairings. Composites, including resins and adhesives, account for 9 percent of the 777's structural weight, compared to about 3 percent on other Boeing jets.

Flight Deck and Airplane Systems
In response to airline preference expressed during the prelaunch definition phase, the layout of the 777 flight deck is in a horizontal format similar to that of the 747-400. Principal flight, navigation and engine information is presented on six large display screens.

Although these displays resemble conventional cathode ray tube (CRT) screens, they incorporate advanced liquid-crystal display technology. The depth of the new "flat-panel displays" is about half that of CRTs. In addition to saving space, the new displays weigh less and require less power. They also generate less heat, which contributes to greater reliability and a longer service life. The displays do not require the heavy, complex air conditioning apparatus needed to cool equipment on current flight decks. Pilots appreciate that flat panel displays remain clearly visible in all conditions, even direct sunlight.

Three multipurpose control display units (CDU), installed in the center aisle stand, provide data display and entry capabilities for flight management functions and are the primary interface with an integrated Airplane Information Management System (AIMS). The CDUs have color displays, again in response to market preferences. Adding color allows pilots to assimilate the information more quickly.

AIMS provides flight and maintenance crews all pertinent information concerning the overall condition of the airplane, its maintenance requirements and its key operating functions, including flight, thrust and communications management.

The flight crew transmits control and maneuvering commands through electrical wires, augmented by computers, directly to hydraulic actuators for the elevators, rudder, ailerons and other control surfaces. This three-axis "fly-by-wire" flight-control system saves weight, simplifies factory assembly compared to conventional mechanical systems relying on steel cables, and requires fewer spares and less maintenance in airline service.

A key part of the 777 systems is a Boeing-patented two-way digital data bus, which has been adopted as a new industry standard: ARINC 629. It permits airplane systems and their computers to communicate with one another through a common wire path (a twisted pair of wires) instead of through separate one-way wire connections. This further simplifies assembly and saves weight, while increasing reliability through a reduction in the amount of wires and connectors. There are 11 of these ARINC 629 pathways in the 777.

The 777 was the first Boeing model to be equipped with the Enhanced Ground Proximity Warning System (EGPWS) as standard equipment. The EGPWS displays potentially threatening terrain and gives an audible alert up to a minute in advance of possible terrain conflict, compared with 10 to 15 seconds for previous systems. It incorporates a proprietary digital terrain map, which it continuously compares to aircraft position data from the navigation system.

One new feature in the 777-300 flight deck is the addition of a Ground Maneuver Camera System (GMCS), designed to assist the pilot in ground maneuvering of the 777-300 with camera views of the nose gear and main gear areas. The cameras are on the leading edge of the left and right horizontal stabilizers and the underside of the fuselage and are used during ground maneuvering. The images are displayed at the Multi-Functional Display positions in the flight deck in a three-way split format.

In 1993, the 777 flight deck received accolades from the Industrial Designers Society of America. For the second year in a row, the 777 received the society's Industrial Design Excellence Award for its flight deck design..

Interior
In addition to being one of the most spacious passenger cabins ever developed, the 777 interior offers operators unsurpassed configuration flexibility. Flexibility zones have been designed into the cabin areas specified by the airlines, primarily at the airplane's doors. In 1-inch increments, galleys and lavatories can be positioned anywhere within these zones, which are pre-engineered to accommodate wiring, plumbing and attachment fixtures. Passenger service units and overhead stowage compartments are designed for quick removal without disturbing ceiling panels, air conditioning ducts or support structure. A typical 777 configuration change is expected to take as little as 72 hours, while such a change might take two to three weeks on existing aircraft.

Large overhead compartments provide passengers with increased stowage capacity. Outboard as well as center stowage units are designed to open downward for convenient loading. When closed, they fit neatly into the streamlined contours of the interior architecture and allow ample overhead clearance.

For improved, more efficient in-flight service, the 777 is equipped with an advanced cabin management system. Linked to a computerized control console, the cabin management system assists cabin crews with many tasks and allows airlines to provide new services for passengers, including a digital sound system comparable to the most state-of-the-art home stereo or compact disc players.

A 1992 Industrial Design Excellence Award was awarded to the passenger cabin of the new Boeing 777 jetliner, the first time the Industrial Designers Society of America honored an airplane interior.

A survey of nearly 6,000 passengers flying on long-range routes to and from Europe in first, business and economy classes revealed an overwhelming preference for the 777. The survey, conducted in 1999 by six airlines based in Europe and the Middle East, found that the Boeing 777 was preferred by more than three out of four passengers who had flown aboard both the 777 and the Airbus A330/340 airplanes.

Cargo Capacity
The fuselage cross-section of the 777 is circular and large enough to accommodate not only a spacious passenger cabin, but excellent capacity in the lower hold. The lower-hold mechanized cargo-handling system is compatible with all unit load devices (ULD) and pallets. One of the container arrangements utilizes LD-3s loaded side by side. The 777-200 can accommodate a maximum of 32 LD-3 containers plus 600 cubic feet (17 m3) of bulk-loaded cargo for total lower-hold volume of 5,656 cubic feet (160.17 m3). The 777-300 can accommodate a maximum of 44 LD-3 containers plus the same amount of bulk-loaded cargo as the -200 model for a total lower-hold volume of 7,552 cubic feet (213.8 m3).

Landing Gear
The main landing gear for the 777 is in a standard two-post arrangement but features six-wheel trucks, instead of the conventional four-wheel units. This provides the main landing gear with a total of 12 wheels for better weight distribution on runways and taxi areas and avoids the need for a supplemental two-wheel gear under the center of the fuselage. Another advantage is that the six-wheel trucks allow for a more economical brake design. The 777 landing gear is the largest ever incorporated into a commercial airplane.

High Reliability and Quality
New design and testing initiatives helped ensure the highest possible levels of reliability on the very first 777, compared to what had been possible on previous jetliner introductions.

Design/build teams, which bring together representatives of the diverse disciplines involved in airplane development, as well as suppliers and representatives of airline customers, allowed team members to work concurrently on the 777 structural and systems designs.

Continuing the "market-driven" approach, four 777 customers had on-site representatives working side by side with Boeing designers to ensure that the new airplane filled their needs. United Airlines, All Nippon Airways, British Airways and Japan Airlines had teams of between two to four engineers on site, who were actively involved in developing the 777.

For the first time, digital computers were used by Boeing engineers to design and electronically preassemble the entire airplane, increasing accuracy and improving quality. New laboratory facilities enabled the various airplane systems to be tested together as a single integrated entity in simulated flight conditions -- before the first jetliner took to the air. This allowed a smoother transition to flight testing and service introduction.

Among other initiatives, standard certification flight tests were supplemented with 1,000 flight cycles on each airframe-engine combination for the initial 777-200 model to demonstrate reliability in simulated airline operating environments. The Boeing-United Airlines 1,000-cycle flight tests for the Pratt & Whitney engine were completed on May 22, 1995. In addition, engine makers and the many suppliers of parts for the airplane intensified their own development and testing efforts to ensure that their products met airline requirements.

This thorough test program demonstrated the design features needed to obtain approval for extended-range twin-engine operations (ETOPS). All 777s are ETOPS-capable, as part of the basic design. To ensure reliability, the 777 with Pratt & Whitney engines was tested and flown under all appropriate conditions to prove it is capable of flying up to 180-minute ETOPS missions. On May 30, 1995, the 777 became the first airplane in aviation history to earn Federal Aviation Administration (FAA) approval to fly ETOPS at service entry. On May 4, 1998, the 777-300 achieved another historic milestone by becoming the first commercial airplane to receive type certification and 180-minute ETOPS the same day.

International Team
The skills and resources of a number of international aerospace companies contributed to the design and production of the 777. Firms in Europe, Canada, Asia/Pacific and the United States provided components and portions of the structure to Boeing.

The largest single overseas participant is the Japanese aerospace industry. Led by Mitsubishi Heavy Industries, Kawasaki Heavy Industries and Fuji Heavy Industries, this group of companies is continuing its long-standing business relationship with Boeing. Together, these firms helped design and build about 20 percent of the airframe structure.

 


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