INSPECTION CHALLENGES
OF MODERN COMPOSITE AIRCRAFT
Airlines are turning to the latest ultrasonic testing equipment to help
check composite aircraft structures for damage from lightning strikes
// ROGERIO CARVALHO
Lightning strikes can affect airplane
operations and cause costly delays and
service disruptions. While lightning
strikes are common, aircraft have been
equipped with lightning protection
systems for decades, minimizing delays
and interruptions, as well as reducing the
significance of the strike. To maintain the
effectiveness of these systems, proper
inspection and repair procedures must
always be in place.
When aircraft are struck by lightning,
the outcome can vary from no damage to
serious damage that requires extensive
repairs and the aircraft taken out of
service, disrupting operations and causing
delays and high costs. With metal aircraft,
electricity can easily be conducted across
the skin to a wingtip or other edge from
which lightning can easily be dissipated.
However, composite aircraft are built
with metal foil, woven wire, or most
commonly an expanded metal mesh to
dissipate the impact of lightning strikes.
The two aircraft with more than 50%
composite material, the Boeing 787 and
Airbus A350, use different approaches to
lightning strike protection for their
composite fuselages. These new materials
pose an extra challenging for inspecting
the existence and extent of damage.
The frequency in which aircraft are
struck by lightning is dictated by many
factors, such as geographic areas and the
number of times the aircraft passes
through critical altitudes in the Landing/
Take off cycles. Due to its unpredictable
nature, having the ability and technical
means to perform these inspections
minimizes the impact these events cause
to the overall operation by enabling the
return of the equipment to service quicker
and safely.
INSPECTION PROCESSES
Aircraft manufacturers, such as Boeing,
already have extensive documentation and
procedures put in place for inspection that
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apply to analyzing lightning impact
evidence and evaluating the damage. Such
procedures highlight areas of interest, and
act as a guide for operators.
Inspection of composite aircraft poses a
challenge for operators. Whereas before,
aluminium damage could be rapidly
assessed and evaluated, composite
airframes add a new level of complexity to
this task, as the extent of the damage is
not as easily seen. In metal structures,
lightning damage usually shows as pits,
burn marks, or small circular holes, while
in composite aircraft, damage is often in
the form of burnt paint, damaged fibre,
and composite layer removal.
Composite structures are less
conductive than metal, causing higher
voltages. This is the type of damage that
can occur if a lightning protection finish is
not applied or is inadequate.
This has a direct impact on aircraft
availability and, in turn, puts great stress
on the timely release of aircraft for flights.
1 // The Dolphicam2
ultrasonic inspection
system is proving popular
with airlines because of its
flexibility and richness of
data it presents the user
Ultrasonic inspection
1
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