1. Structural Health Monitoring Systems in Airbus Military
Javier Gómez-Escalonilla
Fatigue & Fracture Mechanics Dept.
Briefing to Aerodays 2011
Parallel session 1G
Technologies in the European Research Area. Advanced Structures

2. • Why Structural Health Monitoring Systems?
• Structural Health Monitoring System
 Architecture
 Artificial Neural Networks
 Capabilities (Usage-Based Maintenance,
Usage+Condition-Based Maintenance)
Contents
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

3. • Problem #1: Common increasing requirements to keep the
ageing fleets in service even beyond initially established
service lives.
Why Structural Health Monitoring Systems?
Source: Defence Industry Daily
Fighter/Attack
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011
Tanker
Bomber
Airlift
Average
fleet
age
(USAF)

4. Why Structural Health Monitoring Systems?
Age
Workload
• Problem #2: Frequency of maintenance actions and time to
complete drive the operating and support cost of the
airframe.
New Early Mature Late Mature Final Life
Aircraft Stage Stage Stage
Fatigue inspection is a
minor issue.
Limited depot work.
Fatigue inspection
increasing.
Periodic depot visits.
Fatigue inspections are
major labour cost
drivers.
Periodic depot visits
with increasingly severe
emergent repairs.
Total workload
Unscheduled workload
Scheduled workload
Depots deal with major
structural issues.
Major Structural Life
Assessment Program
required to fly due to
structural fatigue
issues.
Problems fielding
deployable units due to
smaller population of
available airframes.
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

5. • Problem #3: Real usage of military aircraft shows a
significant dispersion:
Need of more frequent
May have less frequent
 More severe usage than designed
inspections (safety issue)
 Less severe usage than designed
inspections (economic opportunity)
Why Structural Health Monitoring Systems?
Safety issue
Economic opportunity
Fatigue
damage
Aircraft life
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

6. • Current solutions:
Why Structural Health Monitoring Systems?
No aircraft installation
needed
Simple aircraft
installation
Takes advantage of
aircraft flight data
High accuracy for
fatigue damage
estimates
Manual collection of data.
Subjective information
CREW
FORMS
PARAMETRIC
Applicable to wing root
mainly
Limited accuracy
High installation and
maintenance costs
ADVANTAGES TECHNOLOGY DISADVANTAGES
STRAIN
GAUGES
FATIGUE
METERS
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

7. • Airbus Military models can be fitted with two structural
monitoring systems:
 Aircraft Condition Monitoring System Short-term structural
integrity management (22 aircraft)
 Structural Health Monitoring System Mid and Long-term
structural integrity management (50 aircraft)
Structural Health Monitoring System (SHMS)
Aircraft Condition
Monitoring System
Structural Health
Monitoring System
Hard landing detection
Load exceedance detection
Fatigue damage accrual
Unscheduled inspections
Customized scheduled
inspections
Aircraft
Structural
Maintenance
Program
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

8. Structural Health Monitoring System (SHMS)
Maintenance
Database
Aircraft
virtual sensors
• Combination of sensors, data acquisition technology and
algorithms with the goals of improving flight safety and
reducing life-cycle costs.
Flight recorded
data
Scheduled
Signal fault
detection
Sensor error
correction
Crack initiation
analyses
Crack growth
analyses
SHMS
System self-
validation
Structural assessment
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

9. Structural Health Monitoring System (SHMS)
Scheduled
Maintenance
Database
Aircraft
virtual sensors
• Two main functionalities: Usage Monitoring Function (UMF),
Operational Loads Monitoring Function (OLMF).
Flight recorded
data
Fleet management support
information
Individual aircraft maintenance
program evolution
USAGE
MONITORING
FUNCTION
Assessment of usage patterns
of each individual unit of the
fleet
OPERA
TIONAL
LOADS
MONITORING
FUNCTION
Estimation of accumulated
damage of the airframe.
Prediction of cracks in the
future (quantitative review
of the condition of
the airframe)
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

10. • OLMF based on a dense network of virtual sensors distributed
throughout the airframe:
 Minimum installation and maintenance costs
 Minimum weight
 Maximum reliability
Structural Health Monitoring System (SHMS)
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

11. Structural Health Monitoring System (SHMS)
• Additional advantages:
 High flexibility
 Adaptation to future needs (new maintenance tasks, repairs)
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

12. • Virtual sensors are based on Artificial Neural Networks
(ANNs), algorithms that can learn the underlying mathematical
relationship between flight parameters and strains at virtual
sensor locations.
• ANNs are trained using information from physical sensors
installed in some aircraft of the fleet.
Artificial Neural Networks
Flight parameters
(time histories)
• Speed
• Altitude
• Weight
• CoG accelerations
• etc
Strains at virtual
sensor
(time history)
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

13. • Once trained, the Artificial Neural Networks can reproduce the
strains with similar accuracy as a physical sensor.
Artificial Neural Networks
Physical sensor
(strain gauge)
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011
Virtual sensor
(ANN)

14. • The combination of diagnostic and prognostic capabilities of
the SHMS enables the Usage-Based Maintenance (UBM)
concept.
Capabilities
Diagnosis Prognosis
Usage-Based
Maintenance (UBM)
Impact: Customized Scheduled Maintenance
Benefit: Tailored Maintenance Time and SystemAvailability
Impact: Usage assessment
Benefit: Improved usage understanding
Impact: Minimization of incipient failures
Benefit: Improved mission reliability
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011

15. Usage-Based Maintenance
Same inspections for
all aircraft
Conventional maintenance
More severe usage Less severe usage
More frequent
inspections
(safety)
More severe usage Less severe usage
Less frequent
inspections
(economy)
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011
Usage-based maintenance

16. • Future developments: addition of physical inspection sensors
and link to logistic support systems to enable the
Usage+Condition Based maintenance (U+CBM) concept.
Virtual
sensors
Usage+Condition Based Maintenance
Flight data
Have cracks have been detected?
How are they going to evolve?
Why have they appeared?
Could new cracks appear?
Physical inspection
sensors
Direct link to
Logistic Support
Management
System (LSMS)
SHMS
Could critical locations generate
cracks?
How are they going to evolve?
Why have they appeared?
UBM
Structural Health Monitoring Systems in Airbus Military – Aerodays 2011
U+CBM
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Structural Health Monitoring Systems in Airbus Military – Aerodays 2011