SYSTEM SAFETYDefinitions:System Safety: The application of engineering andmanagement principles, criteria, and techniques to optimize allaspects of safety within the constraints or operationaleffectiveness, time, and cost throughout all phases of thesystem life cycle.Fail Safe: A design feature that ensures that the systemremains safe or in the event of a failure will cause the systemto revert to a state which will not cause a mishap.Hazard Probability: The aggregate probability of occurrenceof the individual events that create a specific hazard.Hazard Severity: An assessment of the consequences of theworst credible mishap that could be caused by a specifichazard.
Management: the act, manner, or practice of managing,supervising, or controlling.Hazard: existing or potential condition that can result in orcontribute to a mishap.Fault: a weakness or defect; mistake or errorFailure: inability of a system, subsystem, component, or part toperform its required function within specified limits.Emergency: unintended circumstance bearing clear and presentdanger to personnel or property which required immediateresponse.System: a group of interrelated, interacting, or interdependentconstituents forming a complex whole; a functionally related groupof elements.Risk: as applies to safety is the exposure to the chance of injury orloss.SYSTEM SAFETY
SYSTEM SAFETYSystem Safety made a significant contribution to the improvementof all types of aviation safety through engineering design processesand operational safety processes.Differences between basic system safety steps (methodology) andthat of Operational Risk Management steps are only in the degree ofgenerality. See below:System Safety Process:Define ObjectivesSystem DescriptionHazard IdentificationHazard AnalysisRisk EvaluationHazard Controls
LIFE CYCLE SAFETYThe portions of the life cycle of an air transportcategory aircraft that we will be concerned withare:Concept and Definition phasesDetailed design, fabrication and developmentDeployment and OperationsModifications
Failure Modes and Effects Analyses:FMEA/FMECA is performed on system components.There are several things that such analyses provide:Failure modes for the part / component.History of those failure modes expressed in failure rates λ,usually a function of time, failure mode frequencies, andseverity of the failure or what impact does it have on thefunctioning of the item.Cause of the failureAffect upon the next higher level of the system orsubsystem.Criticality which is simply the product of the failure rate,failure mode frequency, and the severity expressed as afraction.
THE SYSTEM SAFETY HIERARCHYSystem Safety Program:•System Safety Program Plan•System Safety Tasks•System Safety Engineering•Hazard Analyses•Design Requirements•Hazard Risk Assessments•Probability (Reliability Analyses)•Severity (Quantitative Analyses)•Risk indices•Safety Reporting•Contract Documents•Safety Recommendations(continued)
THE SYSTEM SAFETY HIERARCHY•System Safety Applications•Preliminary Analyses•Design Changes•Operational Analyses•Life Cycle Support•Verification of Controls•Risk Acceptance•Documentation•Reviews
OVERVIEW OF ORMOperational Risk Management Processes•Identify potential hazards•Access the risks•Analyze risk control measures•Make control decisions•Implement risk controls•Supervise and reviewOPERATIONAL RISKMANAGEMENT
OPERATIONAL RISKMANAGEMENTRules for making risk decisions:Accept no unnecessary riskMake risk decisions at the appropriate levelBenefits of taking risk must outweigh the costsIntegrate ORM into task planning and execution
OPERATIONAL RISKMANAGEMENTMore Risk Definitions:Identified Risk: Risk that has been determined throughvarious tools.Acceptable Risk: Identified risk that is allowed to persistwithout further controls.Unacceptable Risk: The risk than cannot be tolerated.Unidentified Risk: Risk that has not been determined.Residual Risk: Sum of acceptable and unidentified risk.
RISK ANALYSIS PROCESSESRISK = (f) of PROBABILITY & SEVERITY
Seminole Fuel System Schematic
AVIATION SAFETYOperational Aviation Safety:1.Airworthiness• Flight Safety• Ground Safety• Engineering• Quality Assurance• System Safety2.Medical Factors3.Operations and Maintenance
AVIATION SAFETYAviation Safety ContinuedAircraft Mishap Prevention:1.Safety Program Management• Risk Management• Safety Data• Material Factors2.Supervision3.Mishap InvestigationHuman Factors:1.Human Factors Design2.Human Psychology3.Human Physiology
SYSTEM SAFETY HIERARCHYSystem Safety Program:•System Safety Program Plan•System Safety Tasks•System Safety Engineering•Hazard Analyses•Design Requirements•Hazard Risk Assessments•Probability (reliability analyses)•Severity (quantitative analyses)•Risk indices
FUTURE TRENDS OF AVIATIONSAFETY1.Swing more towards automation in operations,maintenance, etc.• How do you determine the risk of upgrades tocomputers and the communication systems?• Where doe the pilot fit into the loop?• Where does the safety manager fit into the loop?
2. ORM begins to spend more time on reducingpilot error which drives more simulation andautomation.3.System Safety has become passé’ and is beingsuperseded by Software Safety Analyses.4. Human Factors have reached the point whereonly major design changes in aircraft willaccommodate the safest man-machine interfaceand that leads back to automation changes.FUTURE TRENDS OF AVIATIONSAFETY
5.Life Cycle of the aircraft get extended; esp. intimes of tight economics.6. Systems approaches to all safety are thetrend.FUTURE TRENDS OF AVIATIONSAFETYNASA Dryden Research Aircraft Photo CollectionNASA Dryden X-43A Photo CollectionNASA Dryden X-43A Photo Collection
5.Life Cycle of the aircraft get extended; esp.in times of tight economics.6. Systems approaches to all safety are thetrend.FUTURE TRENDS OF AVIATIONSAFETYNASA Dryden Research Aircraft Photo CollectionNASA Dryden X-43A Photo CollectionEclipse EM-0008-04: Eclipse QF-106 tethered flight#4
Eclipse EC97-44357-13: Eclipse project QF-106and C-141A climbs out under tow on first tetheredflight December 20, 1997NASA Dryden Research Aircraft Photo Collection