Health and Usage Monitoring System (HUMS) Flashcards
What is the HUMS?
Health and Usage Monitoring SYstem is the continuous monitoring of key structural, envronmental and flight parameters by means of permanently attached or embedded sensor systems, in order to ensure the structural integrity.
Why is there the need of the HUMS?
- Design uncertainties
- Manufacturing uncertainties
- Material variations
- Envrionmental effects
- Aging
What are the problems of conventional structures?
- Designed to achieve a set of intended functions under pre-selected loads and forces
- Large safety factors are employed to account for the uncertainty in the external loads
- Unable to adapt to structural changes and to varying usage patterns & loading conditions
What are the purposes of HUMS?
The purposes are the improvement of:
1) Maintenance & Operability
- Reduction of inspection time
- Reduction of maintenance efforts (deferred maintenance/repair, maintenance of demand)
- Increased availability
2) Design guidelines
- Extended life of structures
- Improved safety
- Optimized structural effiency
- New design philosophies
- Weight saving ( safety factor reduction)
These two improvements lead to more efficient and economically attractive aircraft (reduced life cycle costs)
What are the maintenance strategies and which apply to HUMS?
1) Corrective
Once failure occurs, maintenance is done.
-Low cost
-High risk
- Expensive repair
- High downtime
- Not acceptable in aerospace
2) Preventive
Periodic maintenance is done. We substitute the components after the scheduled time.
- High cost
- Low risk
- Repair is done on component still working (we don’t use its residual life)
- Maintenance well scheduled
3) On condition
We inspect the components when there is an indication that the component has some issues. (additional minor inspections). We monitor some parameters related to the status of the component.
- Additional cost
- Additional safety
- Required special skills
4) Predictive
Onset detection of damage and propagation monitoring. (ability to predict the residual life).
- Low cost
- Additional safety
- Reduction of inspections
- In-service monitoring
HUMS is used on: On condition and predictive maintenance. For on condition maintenance it monitors some parameters since sensors are required. For predictive maintenance sensors + a predictive system/algorithm are needed.
What is the HUMS goals?
The purpose of HUMS is to increase safety, reliability and availability, as well as to reduce operating costs, by providing diagnosis and prognosis of critical components.
What is the evolution of Monitoring Systems and what are the advantages of HUMS wrt to others?
- Visual Inspection (VI)
- Non-destructive Testing (NDT). The main tool to check health of component.
- Health and Usage Monitoring System (HUMS).
The advantages of HUMS are:
- HUMS = innovative Non Destructive Testing (NDT) method
- Peculiarity: Sensors remain attached/embedded in the structure
- Advantage vs NDT: Availability of information on structural events or states at any arbitrary time (real time monitoring).
How are the HUMS principles and its set-up?
To set up the HUMS, there is a need of:
1) Physical Probes (acoustic, electro-magnetic, optic) installation + Material/Structure. The probes can be installed on the surface, can be embedded or be positioned between two components (integral sensor).
2) Interaction
We need connection with an interrogation unit. The data collected by sensors can be analyzed in order to give the diagnosis (identification of the damage, flaw, origin of a problem). The structural health monitoring system (SHM) checks the structure and evaluates the follow up actions for maintenance. After the diagnosis the system has to detect which are the characteristic parameters (flaws, stress/strain) to be monitored to follow the evolution of the prboelm discovered in the previous steps. Then there is the prognosis: The prediction of the evolution of damage, flaw, and residual life and definition of the maintenance procedures.
Therefore, the main steps of Diagnosis and Prognosis are:
Diagnosis:
1) Detection of whether damage is present in the structure
2) Identification of the location of the damage
3) Quantification of the severity of the damage
Prognosis:
4) Evaluation of remaining structural integrity and risk assessment
- Diagnosis and Prognosis start from the collection of significant data, which are then used to mofity the maintenance procedures
- HUMS is based on a variety of sensors (including accelerometers for vibration data) and a data acquisition system
- Data can be processed on board (real-time) the aircraft itself or from a ground station
- HUMS specifically dedicated to monitor structures integrity are called SHM (Structural Health Monitoring) systems
What are the HUMS overall benefits?
- More efficient and effective maintenance procedures with substantially reduced downtime (therefore availability). Also reduced inspections and increased safety.
- Substantial time savings to inspect structures or parts of structures which are difficult to access or located in remote positions (therefore availability).
- Occuplaztional health and safety benefits in accessing structures located in hazardous positions/environments (therefore safety).
- Early diagnosis of a defect/damage (therefore availability, safety).
- Improved design efficiencies through the avialability of continuous monitoring, which lead to the increase of its safety and reliability (therefore safety).
What are the HUMS safety benefits?
- Accuracte identifications of faults prior to catastrophic failures
- Informed decision-making
- Risk mitigation and avoidance
- Lower risk of failure in flight
- Lower risk of emergency landings
What are the HUMS maintenance benefits?
- More efficient maintenance, as unscheduled events can be pushed to align with scheduled actions so the aircraft is making money instead of waiting for parts shipiment
- Elimination of the need for portable equipment installation and reduction of the need for additional maintenance flights due to onboard rotor track and balance capability
- Troubleshooting and diagnosis of potential faults through proper use of the system
- Deferment or elimination of certain maintenance inspection intervals as HUMS matures
- Diagnosis of problems before they cause collateral damage
What are the HUMS readiness benefits?
- Demonstrable reudction in downtime for unscheduled maintenance events
- Proactive maintenance, allowing aircraft downtime to be a scheduled and anticipated event rather than an unexpected inconvenience
- Immediate recognition of a seemingly insignificant problem, before it turns into a significant one, allowing for better planning for the operation of an aircraft
What are the HUMS operations and support cost benefits?
Repair costs can be reduced by identifying a faulted component and performing maintenance before collateral damage is inflicted. Futher, the ability to replace or repair a part before it breaks will result in increased operational time and consequently increased revenue.
- Increased useful life and efficiency by reccomending changes to system components. Frequently, one damaged part will go unnoticed, eventually resulting in a sever malfunction.
- Identification of certain problems that warrant grounding of the AC immediately, thereby preventing further damage and resulting in a cost savings through averting damage to components other than the root cause
- Extensions of the life of an aicraft’s avionics and airframe by reducing overall vibrations on the aicraft.
Describe the diagram that defines HUMS
In a life consumption - time in operation graph, there is the Design life of the component on the y axis and the Time based service without diagnostics/prognostics on the x axis. This two points give the design line of the component.
With HUMS, we can know if usage is less (service life extended) or more ( safety increased) than predicted.
What HUMS events can be monitored?
- Damages
- Loads/Displacements
- Stresses/Strains
- Flight parameters
- Environmental conditions
