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long hydraulic lines (and possible leaks) and avoids
the need for both main hydraulic circuits (one for
stand-by) to power systems such as brakes. Some
A380 systems have a main circuit providing hydraulic
power in normal mode with alternate mode provided
by a LEHGS.
Airbus says that at a structures level, significant
maintenance savings were achieved through use
of new advanced materials because "scheduled
corrosion and fatigue inspections [are] eliminated
or threshold and repeat inspection [intervals are
extended]". Overall, carbon-, glass- and quartz-
fibre reinforced plastics (CFRP/GFRP/QFRP) and
glass-laminate aluminium-reinforced epoxy (GLARE)
materials account for 25% of A380 weight.
Apart from their application in secondary structure,
CFRP/GFRP/QFRP materials are used in primary
areas. For example, CFRP is used in the A380 centre
wing box, rear pressure bulkhead, upper-deck floor
beams, tailplane and tailfin.
"[Aircraft parts] made of these composite
materials do not require [inspection for] corrosion
or fatigue, [which] has contributed to a greatly
reduced structures maintenance programme," says
Airbus. Compared with standard aluminium alloys,
GLARE offers lower crack growth (which leads to
longer fatigue-inspection intervals), better resistance
to corrosion (which will stop at the first glassfibre
layer) and better impact resistance while enjoying
the same repair techniques.
Accordingly, use of GLARE has increased initial (and
repeat) corrosion- and fatigue-inspection intervals.
GLARE is used for upper and lateral fuselage, shells,
and tailplane and tailfin leading edges.
Titanium, which does not corrode, is used for
landing gear, engine pylons, tailplane centre joint,
torsion box fittings, passenger- and cargo-door
"scuff" plates, seat tracks in "wet" areas, and engine-
nacelle attachments, plugs and nozzles.
Airbus says that a new production technique --
laser-beam welding -- is used for lower-fuselage skin
and stringer joints to improve corrosion resistance
and fatigue behaviour. "Elimination of rivet-holes in
panels and stringers [removes] potential water-traps,
and [reduces] corrosion [and] potential starting-
points of fatigue-cracks."
The A380's alternative General Electric/Pratt &
Whitney Engine Alliance GP7200 and Rolls-Royce
Trent 900 engines bring significant scheduled-
maintenance advantages, says Airbus. Three-
dimensional aerodynamics, and "state-of-the-art"
cooling techniques, coatings and materials, lead to
more-efficient compressors and turbines, enhanced
by the Trent 900's contra-rotating high-pressure
spool and the GP7200's blisks.
Engine performance retention is increased, as is
on-wing time -- thus reducing shop visits over the life
of the aircraft. Having fewer engine parts reduces
shop-visit material costs and dis- and re-assembly
times and costs. Many more engine trend-monitoring
measurements leads to "significantly improved
'predictive' maintenance, avoidance of engine failures
and reduced unnecessary maintenance", says Airbus.
Airbus says that important reductions in
unscheduled maintenance have been accomplished
through "design changes, material selections,
reliability improvements and technology injections". For
example, the A380 sports a new electro-pneumatic
system developed from that on the A340-500 and
-600. "The system is electrically monitored [which
means many] failure causes [such as contamination
of pneumatic lines] could be excluded."
All pneumatic-system valves are switchless, being
much more reliable than traditional switched units, and
the A380 bleed system uses overheat-detection loops
to locate leaks. Light-emitting diode and high-intensity
discharge lights offer life times of more than 100 and
20-40 times, respectively, those of standard bulbs.
The A380's duplicated aircraft-environment
surveillance system units (AESSUs) integrate four
functions previously performed by discrete systems
-- weather-radar, terrain-awareness and warning
(TAWS) and traffic-alert and collision-avoidance
(TCAS) systems; computing functions; and the
Mode S transponder. This results in reduced wiring
and fewer installed parts and interfaces between
avionics-boxes, says Airbus, while increased
reliability reduces troubleshooting and unscheduled
Where previously, failure of any of the above
functions meant that the corresponding system was
lost, the A380's integrated design tolerates failure of
an AESSU without loss of any function. The master
minimum equipment list (MMEL) allows aircraft
despatch with a non-operative AESSU.
The manufacturer claims the A380's integrated
modular avionics (IMA) represents an avionics
design-philosophy revolution, significantly reducing
the number of avionics boxes.
Before, most systems had separate computer(s)
and controllers with each function performed by a
line-replaceable box with a hardware part-number
-- often combined with a dedicated software part-
number that meant spares were held for each
hardware/software part-number combination. Now,
classic line-replaceable units have become avionics
applications hosted on one (or more) IMA-modules
(or core-processing input/output modules).
"Avionics functions are no longer split by hardware
boxes, but by multiple different applications software
on the IMA-modules" that can host several avionics
Airbus says that at a structures level, significant maintenance savings were
achieved through use of new advanced materials
Titanium, which does not corrode is used for the engine pylons
and engine-nacelle attachments, plugs and nozzles.
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