pssa and saa framwwork 2014

8/10/2019 PSSA and SAA Framwwork 2014

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Unified Framework forPSSA and SAA withRelevant Safety

Requirements

Dr. Ahmed Bassyouni

Aerospace Consultant315 [email protected]

Dr. Ahmed BassyouniAerospace Consultant

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Preliminary System Safety Assessment (PSSA) is used to

evaluate planned architecture against the SFHA

requirements and allocate these and new derived safety

requirements to equipment and ITEMS (software, AEH,

hardware)

The difference between the PSSA and the SSA is that the

PSSA is a method to evaluate proposed architectures and

derive system safety requirements for each; whereas theSSA is a verification that the implemented design meets

both the qualitative and quantitative safety requirements

defined in the AFHA, SFHA and PSSA.

PSSA Structure and Function


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PSSA Structure and Function

PSSA Structure and contents should follow the Templatesof the Japanese JCAP and the Federal FAA Organizations of

Aircraft certifications.

The basic structure of the PSSA shall include the following contents:

1. Introduction

2. System description

3. System Boundary and Operations

4. Hazard Assessment

5. Safety Objectives6. Safety Assessment

7. Derived Safety Requirements


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PSSA

Safety Obje for FMEA

Define Mitg & Val

Faults impact Safety

FDAL & IDAL HW,SW

DSR Derived Safety Req

Define Severity Levels

Define Mitig Method

Define Val method

Support Certificate

FHA Func. Haz. Ana

FTA Fault Tree Ana

Failure Conditions

Failure Rates/detect

Prob. of Root Causes

Severity Levels

Safety Master Plan

CCM Com Cause Ana

Input & Output of PSSA

PSSA has to provide the DSR and techniques to Eliminate Hazard


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1. Identify the hazards and failure conditions for Aircraft

Systems components2. Assess the Severity and Establish Safety Objectives system

components

3. Overview the System Reliability Analysis

4. Develop FMEA, and FMES

5. Develop Mitigation Strategies to reduce risk6. Determine Effectiveness of Mitigation Strategies

[Acceptable Risk]

7. Develop DSR for LG components

8. Verify Implementation of Mitigation Strategies

Safety Validation and verification Tasks

1.Updating the PSSA/SSA Contents

2.Updating the PASA/ASA Contents


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Updating PSSA/SSA


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PSSA

DSR

Safety Plan for Developing PSSA and SSA


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Verify & Update

SHFA , FC tables

Update Equipment

Tech. Specs. FC

Tables

Verify & Update

FTA diagrams

CCA(CMA, PRA,ZSA)

FMEA

SSA

OCT

NOV

DEC

MAR

JAN

FEB

ATA-32 Landing Gear System


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In addition to PSSA/SSA it is recommendedto perform a PASA/ASA

PASA: Preliminary Aircraft Safety Assessment

ASA: Aircraft Safety Assessment

The PASA/ASA assesses the A/C level FC coming from aircraft level

FHA that combine failures of several systems that are not studied

or cannot be studied at system level.

It allows identification of the Development Assurance Levels

(DAL) for aircraft functions.

Updating PSSA/SSA, PASA/ASA


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Updating PSSA/SSA, PASA/ASA


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System Safety Assessment (SSA)

The SSAshall include quantitative analysis of critical failureconditions.

Failure rates from FMEA documents and risk times shall be

placed into FTAs to calculate the probability of failureconditions.

The mitigated RPNs shall be considered for Risk Assessment


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pssa and saa framwwork 2014

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