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 For safe life components it would also be possible to detect early failures and withdraw
them from service ahead of their expected life, or for healthy components continue to
use them beyond the design life and only withdraw them when their health indicates a
requirement to do so.
 Potential to both improve airworthiness and gain economic benefits was originally
conceived within the context of a rotorcraft Health and Usage Monitoring System (HUMS)
but is applicable to any health or usage monitoring system.
CBM Approach – SHM Potential
T. Ewbank, Cranfield University,
Application Of Condition Based Maintenance On Aerospace Structures
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• Difficult to access inspections
• Hot spot monitoring
SHM Applications
18
• Impact damage in composite
• Wireless/passive sensing
• Appropriate for in-situ embedded or attached
robust sensors during component manufacture
• Cost effective, lightweight sensors (optical,
acoustic, electromagnetic, etc.)
Acoustic Emission
Acellent Technologies
Desirable SHM Attributes
19
 Physics-based material properties measurements to
 determine material state throughout life cycle – allow design
conservativeness to be minimized
 Intelligent structures (self-diagnostic, self-healing, health
monitoring & diagnostics, manufacturability w/sensors, etc.)
Leading to design optimization, weight saving, less fuel
consumption & environmental impact
SHM Outcomes
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 Develop and demonstrate SHM technologies that can be
used to monitor structural integrity in service conditions
with high reliability & durability.
 As in conventional NDT, a single technology will not be
suited for the entire range of applications, based on
different materials, component geometries and damage
scenarios.
 Diagnosis must have high reliability over the aircraft
lifetime, since un-justified maintenance actions are quite
costly to the operator and spurious warnings degrades
confidence in the system.
 Accuracy and reliability may even be more stringent, since
further optimization of structural design will rely on SHM
with better knowledge of actual flight loads & condition.
Challenges to SHM
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 Components shall qualified, as part of aircraft certification, meaning they
shall perform the specified function while withstanding the specified
environmental conditions.
 Include large variations of temperature, vibrations, impacts, Electro-
Magnetic Hazards, chemical fluids, etc… as per RTCA DO 160 and aircraft
integrator directives.
 Components qualification shall demonstrate that the system performs
reliably in the specified environmental conditions, in all the aircraft
operational conditions over it’s lifetime.
 Specific issues need to be considered particularly:
 Easy installation and application on surfaces
 Accuracy and reliability when used on painted surfaces
 No corrosive damage to surfaces where applied
 No delaminating between sensor and monitored structure
 Suitable for metal, composite, sandwich structures
 Suitable for various damage: cracks, corrosion, delamination, de-bonding…
 Clearly different requirements will apply onto the system components:
sensors, processors, computers, wiring, power supply, … depending on the
technologies, architecture and installation location retained.
 Micro-Nano-Technologies have the potential for supporting qualification
requirements and the SHM business case.
System Qualification
H. Speckmann, Materials & Processes - Testing Technology, Airbus
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Implementing SHM
 SHM is not a new concept - it is already implemented on military aircraft,
with a different rationale but some converging features.
 Still the constraints of airworthiness certification and the existing
cost/benefit have limited its introduction in commercial aviation
 There is currently no specific FAA or EASA policy on CBM for civil aircraft. However,
some guidance is provided in FAR-29 (FAA, 2003) on achieving maintenance or
airworthiness credits with HUMS that could be developed.
 US DoD stated the requirement to transition to a CBM program by the end of 2015.
 Confidence needs to be built that SHM will bring the expected benefits, while
maintaining or improving the safety and efficiency of modern aircraft – by
progressive introduction and proving the reliability & benefits.
　
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