Upskill / Regulation & business / Safety assessment for aircraft systems: FHA, PSSA, SSA, fault trees and FMEA (ARP4761A)
Safety assessment for aircraft systems: FHA, PSSA, SSA, fault trees and FMEA (ARP4761A)
How aircraft systems are shown to be safe enough: failure condition classifications and probability targets, functional hazard assessment, fault trees with latent failures, FMEA and the system safety assessment, and common cause analysis, following one brake-by-wire system. Part 2 of the Systems engineering and safety series.
By Aerospace Garage Desk · Managing it · 45 minutes · 24 narrated pages
What you will be able to do
✓ Explain the 1309 rule, the five failure condition classifications and their probability targets per flight hour in FAA AC 25.1309-1B and EASA AMC 25.1309.
✓ Carry out a functional hazard assessment: classify failure conditions by phase, conditions and crew response, and turn them into safety requirements.
✓ Build and quantify a fault tree with minimal cut sets, exposure times and latent failures, and apply the 2024 latent-failure criteria.
✓ Use FMEA and FMES data to feed fault trees correctly, and describe how the system safety assessment closes the loop.
✓ Apply zonal safety, particular risk and common mode analyses to show independence, and link classifications to development assurance levels.
✓ Draw safety assessment lessons from an official investigation in which one event defeated redundancy.
Course content
Session 1 · Why safety assessment: the 1309 rule and its numbers
1.1
One rule behind every system · free preview
Five classes of failure condition
The inverse relation: the worse the effect, the rarer it must be
Worked example: what the targets mean for a fleet
Session 2 · Functional hazard assessment on the brake system
1.2
Functional hazard assessment: start from functions, not parts
Classifying with care: phase, conditions and the crew
From hazard list to safety requirements
Worked example: Halny's system FHA for 'decelerate on ground'
Session 3 · PSSA and fault tree analysis
1.3
The preliminary system safety assessment: testing the architecture on paper
Fault trees: gates, cut sets and the shape of failure
Exposure time and hidden failures
Worked example: putting numbers on Halny's fault tree
Session 4 · FMEA, FMES and the system safety assessment
1.4
FMEA: from each part upwards
FMES: grouping failure modes by effect
The system safety assessment: closing the loop
Worked example: the supplier's FMEA arrives
Session 5 · Common cause analysis: zonal, particular risks and common mode
1.5
Common cause: when two become one
Zonal safety and particular risks
Common mode analysis and the pointer to assurance levels
Worked example: a zonal walk in the main wheel well
Session 6 · Lessons from service and the road to Part 3
1.6
Assumptions: where safety arguments quietly break
After certification: keeping the assessment true
Where the numbers stop: errors, assurance and the road to Part three
From the investigation file: American Airlines Flight 191, Chicago, 1979
Who this course is for
Safety, systems and avionics engineers at airframers and suppliers who write FHAs, fault trees and FMEAs
Certification and airworthiness engineers who review 25.1309 compliance against FAA AC 25.1309-1B and EASA AMC 25.1309
Engineering, reliability and continuing-airworthiness managers who own failure-rate data, CMRs and design changes
You need: Part 1 of this series (systems engineering, requirements and the V-model) or equivalent experience; basic probability (multiplying and adding small numbers).
Upskill courses are for professional development and are not approved by any aviation authority. Learner Terms