Boeing 777

The Boeing 777 is a family of long-range wide-body twin-engine jet airliners developed and manufactured by Boeing Commercial Airplanes. It is the world's largest twinjet and has a typical seating capacity for 314 to 451 passengers, with a range of 5,235 to 9,380 nautical miles(9,695 to 17,372 km). Commonly referred to as the "Triple Seven", its distinguishing features include the largest-diameter turbofanengines of any aircraft, six wheels on each main landing gear, a circular fuselage cross-section, and a blade-shaped tail cone.Developed in consultation with eight major airlines, the 777 was designed to replace older wide-body airliners and bridge the capacity difference between the 767 and 747. As Boeing's first fly-by-wire airliner, it has computer-mediated controls; it is also the first entirelycomputer-designed commercial aircraft.

The 777 is produced in two fuselage lengths as of 2014. The original 777-200 variant entered commercial service in 1995, followed by the extended-range 777-200ER in 1997. The stretched 777-300, which is 33.3 ft (10.1 m) longer, entered service in 1998. The longer-range 777-300ER and 777-200LR variants entered service in 2004 and 2006 respectively, while a freighter version, the 777F, debuted in February 2009. Both longer-range versions and the freighter feature General Electric GE90 engines and extended raked wingtips. The earlier 777-200, -200ER and -300 versions are equipped with GE90, Pratt & Whitney PW4000 or Rolls-Royce Trent 800 engines. The 777-200LR is the world's longest-range airliner and can fly more than halfway around the globe; it holds the record for the longest distance flown non-stop by a commercial aircraft. In November 2013, Boeing announced the development of upgraded 777-8X and 777-9X models featuring composite wings and GE9X engines.

United Airlines first placed the 777 into commercial airline service on June 7, 1995. As of February 2014, 60 customers had placed orders for 1,548 aircraft of all variants, with 1,178 delivered; the most common and successful variant is the 777-300ER with 464 delivered and over 700 orders. Emirates operates the largest 777 fleet, with 127 passenger and freighter aircraft as of June 2013. The airliner is rated as one of the safest aircraft based on its accident safety record and high number of flight hours. The 777 has been involved in three confirmed hull-loss accidents as of March 2014; the Asiana Airlines Flight 214 accident in July 2013 was the first fatal crash of the aircraft in 18 years of commercial service.

The 777 ranks as one of Boeing's best-selling models. Because of rising fuel costs, airlines have acquired the type as a comparatively fuel-efficient alternative to other wide-body jets and have increasingly deployed the aircraft on long-haul transoceanic routes. Direct market competitors include the Airbus A330-300, upcoming Airbus A350 XWB, and the out-of-production A340 and McDonnell Douglas MD-11. The 787 Dreamliner, which entered service in 2011, shares design features with the 777. The updated 777X, currently in development, further includes technologies used on the 787.

Background

In the early 1970s, the Boeing 747, McDonnell Douglas DC-10, and the Lockheed L-1011 TriStar became the first generation of wide-body passenger airliners to enter service. In 1978, Boeingunveiled three new models: the twin-engine Boeing 757 to replace its venerable 727, the twin-engine 767 to challenge the Airbus A300, and a trijet 777 concept to compete with the DC-10 and L-1011. The mid-size 757 and 767 launched to market success, due in part to 1980s extended-range twin-engine operational performance standards (ETOPS) regulations governing transoceanic twinjet operations. These regulations allowed twin-engine airliners to make ocean crossings at up to three hours' distance from emergency diversionary airports. Under ETOPS rules, airlines began operating the 767 on long-distance overseas routes that did not require the capacity of larger airliners.The trijet 777 was later dropped, following marketing studies that favored the 757 and 767 variants. Boeing was left with a size and range gap in its product line between the 767-300ER and the 747-400.

By the late 1980s, DC-10 and L-1011 models were approaching retirement age, prompting manufacturers to develop replacement designs. McDonnell Douglas was working on the MD-11, a stretched and upgraded successor of the DC-10,while Airbus was developing their A330 and A340. In 1986, Boeing unveiled proposals for an enlarged 767, tentatively named 767-X, to target the replacement market for first-generation wide-bodies like the DC-10, and to complement existing 767 and 747 models in the company lineup. The initial proposal featured a longer fuselage and larger wings than the existing 767,along with winglets. Later plans expanded the fuselage cross-section but retained the existing 767 flight deck, nose, and other elements.

Airline customers were unimpressed with the 767-X proposals, and instead wanted an even wider fuselage cross-section, fully flexible interior configurations, short- to intercontinental-range capability, and an operating cost lower than any 767 stretch. Airline planners' requirements for larger aircraft had become increasingly specific, adding to the heightened competition among aircraft manufacturers. By 1988, Boeing realized that the only answer was a new design, which became the 777 twinjet. The company opted for the twin-engine configuration given past design successes, projected engine developments, and reduced-cost benefits. On December 8, 1989, Boeing began issuing offers to airlines for the 777.



Design


Boeing introduced a number of advanced technologies with the 777 design, including fully digital fly-by-wire controls, fully software-configurableavionics, Honeywell LCD glass cockpit flight displays, and the first use of a fiber optic avionics network on a commercial airliner. Boeing made use of work done on the cancelled Boeing 7J7 regional jet, which utilized similar versions of the chosen technologies. In 2003, Boeing began offering the option of cockpit electronic flight bag computer displays. In 2013, Boeing announced that the upgraded 777X models would incorporate airframe, systems, and interior technologies from the 787.

Fly-by-wire

In designing the 777 as its first fly-by-wire commercial aircraft, Boeing decided to retain conventional control yokes rather than change to sidestickcontrollers as used in many fly-by-wire fighter aircraft and in many Airbus airliners. Along with traditional yoke and rudder controls, the cockpit features a simplified layout that retains similarities to previous Boeing models. The fly-by-wire system also incorporates flight envelope protection, a system that guides pilot inputs within a computer-calculated framework of operating parameters, acting to prevent stalls and overly stressful maneuvers. This system can be overridden by the pilot in command if deemed necessary. The fly-by-wire system is supplemented by mechanical backup.



Incidents and accidents


As of March 2014, the 777 has been in 10 aviation accidents and incidents,including three confirmed hull-loss accidents,and threehijackings. Before 2013, the only fatality involving the twinjet occurred in a refueling fire at Denver International Airport on September 5, 2001, during which a ground worker sustained fatal burns. The aircraft, operated by British Airways, suffered fire damage to the lower wing panels and engine housing; it was later repaired and returned to service.

The type's first hull-loss occurred on January 17, 2008, when British Airways Flight 38, a 777-200ER with Rolls-Royce Trent 895 engines flying from Beijing to London, crash-landed approximately 1,000 feet (300 m) short of Heathrow Airport's runway 27L and slid onto the runway'sthreshold. There were 47 injuries and no fatalities. The impact damaged the landing gear, wing roots and engines. The aircraft was written off. Upon investigation, the accident was blamed on ice crystals from the fuel system clogging the fuel-oil heat exchanger (FOHE). In 2009, air accident investigators called for a redesign of this component on the Trent 800 series engine. Redesigned fuel oil heat exchangers were installed in British Airways' 777s by October 2009.

Two other minor momentary losses of thrust with Trent 895 engines occurred in February and November 2008. The National Transportation Safety Board (NTSB) investigators concluded that, just as on BA38, the loss of power was caused by ice in the fuel clogging the fuel-oil heat exchanger. As a result, the heat exchanger was redesigned.

The type's second hull-loss occurred on July 29, 2011, when an EgyptAir 777-200ER registered as SU-GBP suffered a cockpit fire while parked at the gate at Cairo International Airport. The plane was successfully evacuated with no injuries, and airport fire teams extinguished the fire. The aircraft sustained structural, heat and smoke damage. This aircraft was written off. Investigators focused on a possible electrical fault with a supply hose in the cockpit crew oxygen system.

The type's third hull loss and first involving fatalities occurred on July 6, 2013, when Asiana Airlines Flight 214, 777-200ER registered HL7742, crashed while landing at San Francisco International Airport after touching down short of the runway. Surviving passengers and crew evacuated before fire destroyed the aircraft. The crash led to the death of three of the 307 people on board. These were the first fatalities in a crash involving a 777. An accident investigation by the NTSB is underway; its initial focus is on the aircraft's low landing speed.

On March 8, 2014, Malaysia Airlines Flight 370, a 777-200ER carrying 227 passengers and 12 crew, was reported missing en route from Kuala Lumpur to Beijing. Air Traffic Control's last reported coordinates for the aircraft were in Vietnamese air space in the South China Sea at 6°55′15″N 103°34′43″E. The flight is presumed to have crashed into the sea, most likely due to catastrophic failure, as no 'mayday' type communication was reported.