A Boeing 747-400 lands at sunset on
Runway 27R at London Heathrow Airport. Derived from the
earlier versions of the Boeing 747, the 747-400 retains the
four-engine wide-body layout of its predecessors, whilst
incorporating numerous technological and structural changes to
produce a more efficient airframe. Its most distinguishing
features versus preceding 747 models are 6-foot (1.8 m)
winglets mounted on 6-foot (1.8 m) wing tip extensions, which
are found on all 747-400s except for Japanese domestic market
versions. It is the best-selling model of the Boeing 747
family of jet airliners - the first 747-400 came into service
in 1989 with KLM.
A 747-400
typically takes off at 290km/h (180mph), cruises at 910km/h
(565mph) and lands at 260km/h (160mph). The 747-400's wingspan
was stretched by 17 feet (5.2 metres) over the Classic 747
through wingtip extensions. For reduced aerodynamic drag, the
wings were fitted with 6 feet (1.8 metres)-tall winglets.[13]
Despite the added length, the wings were 6,000 pounds (2,700
kg) lighter as a result of new aluminum alloys.
The
747-400's leasing, resale and salvage value has dropped
steeply because it is relatively expensive to operate. As many
747-400s are now more than 20 years old, airlines are
beginning to replace them. Airlines using the 747-400 have
accelerated its retirement (as of 2015) and are replacing the
model with more fuel efficient aircraft. The main appeal of
the 747-400 like its predecessors was its range rather than
its capacity, and in many cases it has been replaced by
wide-body twin-engine aircraft of similar range, such as the
Boeing 777 and Boeing 787 Dreamliner. |
