Airframe and systems
The 777's wings feature a supercritical airfoil design that is swept back at 31.6 degrees and optimized for cruising at Mach 0.83 (revised upward after flight tests to Mach 0.84).[120] The wings are designed with increased thickness and a longer span than previous airliners, resulting in greater payload and range, improved takeoff performance, and a higher cruising altitude.[47] Folding wingtips were offered when the aircraft was launched, to appeal to airlines who might use gates made to accommodate smaller aircraft, but no airline purchased this option.[121] The wings also serve as fuel storage, with longer-range models able to carry up to 47,890 US gallons (181,300 l; 39,880 imp gal) of fuel.[87] This capacity allows the 777-200LR to operate ultra-long-distance, trans-polar routes such as Toronto to Hong Kong, for which the amount of fuel carried would theoretically allow a Honda Civic to circle the equator approximately 84 times.[122]
The airframe incorporates the use of composite materials, which comprise nine percent of its original structural weight.[123] Elements made from composite material include the cabin floor and rudder. The main fuselage cross-section is circular[124] and tapers rearward into a blade-shaped tail cone with a port-facing auxiliary power unit.[5] The aircraft also features the largest landing gear and the biggest tires ever used in a commercial jetliner.[125] Each tire of a 777-300ER six-wheel main landing gear can carry a load of 59,490 lb (26,980 kg), heavier than other wide-bodies such as the 747-400.[126] The aircraft has triple redundant hydraulic systems with only one system required for landing.[127] A ram air turbine –a small retractable propeller which can provide emergency power– is also fitted in the wing root fairing.[128]
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