HUMS Flashcards
(6 cards)
What is HUMS?
Health and Usage Monitoring System is the continuous monitoring of key structural, environmental and flight parameters by means of permanently attached or embedded sensor systems in order to ensure the structural integrity. If all structures are designed properly, do we need Structural Health Monitoring? Why do disasters happen? Design uncertainties (Loading conditions), manufacturing uncertainties, material variations, environmental effects, aging, etc. Conventional structures are dumb, they are not made to adapt, but rather to fit a very limited set of conditions with some wide margins for uncertainty.
Through HUMS, we increase the quality of maintenance and operability (shorter inspection times, reduction of maintenance efforts, and increased availability) and the quality of design guidelines (extended structure life, improved safety, new design philosophy, weight saving, and structural efficiency)
What are the types of maintenance strategies?
Corrective: failure occurs and thus maintenance is done. This is the lowest cost strategy implementation but the repair is expensive, and the strategy presents high risk. Unacceptable in aerospace.
Preventive: periodic maintenance is done. High cost as component may be working well but still get repairs. Low risk, highly scheduled strategy.
On condition: periodic minor inspections which determine whether the maintenance is performed or not. Additional cost but also additional safety. Requires additional skills to identify when to do repair or not.
Predictive: Onset detection and propagation monitoring. Reduces the number of inspections and allows in-service monitoring. Cheap whilst still giving additional safety. The ideal maintenance strategy for complex aerospace components.
On-condition and predictive strategies together form the basis of HUMS. HUMS aims to increase safety, reliability, availability, as well as reducing operating costs, via providing diagnosis and prognosis of critical components.
What are the principles and set-up for HUMS?
Physical probes must be inserted with the material/structure. It can either be a surface sensor, embedded sensor, or integral sensor.
Then there shall be an interaction, to be followed by analysis and diagnosis. Diagnosis is the identification of the damage, flaw, origin of a problem.
Following this, there is a detection and monitoring of characteristic parameters (flaws, stress/strain, etc), leading to a prognosis. Prognosis is the prediction of the evolution of damage, flaw, and residual life and definition of maintenance procedures.
See figures in doc. Keep in mind 2023 exam answer discrepancy.
What are the benefits of HUMS?
HUMS improve safety: accurate identification of faults prior to catastrophic failure, informed decision-making, risk mitigation and avoidance, lower risk of failure during flight, lower risk of emergency landings.
HUMS also has maintenance benefits: allows more efficient maintenance as unscheduled events can be pushed to align with scheduled actions so that there is less downtime, eliminated the need for portable equipment installation and maintenance flights, troubleshooting and diagnosis of potential faults through proper system use, deferment or elimination of inspection intervals, diagnosis of problems before collateral damage is caused.
HUMS causes increased readiness: reduction in downtime for unscheduled maintenance events, proactive maintenance, and immediate recognition of a seemingly insignificant problem before it escalates.
Economic benefits are also seen: more up-time and less downtime as well as prolonged lifetime creates more earning time, identification of problems before they damage components other than the root cause component, targeted and accurate maintenance and repairs.
See key figure in doc.
What events can HUMS monitor?
In metals, HUMS can detect cracks onset (localization and size), fatigue crack growth (localization and size), accidental damages (localization and intensity), corrosion (localization and severity), debonding (localization and size), loads/strains outliers (localization and intensity).
In composites, HUMS can detect impacts (localization and intensity), delaminations (localization and size), debonding of stiffened panels (localization and size), moisture and fluid absorption (localization and intensity), manufacturing defects, loads/strains outliers (localization and intensity).
