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T he Conduct of Hazard Identification, Risk Assessment and the Production of Safety Cases TGO AGA 04 First Edition Aug 2008 Seychelles Civil Aviation Authority

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Table of Contents Foreword 1 Glossary 2 to 4 5 Cha p te r 1 S ystem Li fe cy cle In troduction 5 Planning for Saf e ty 5 F easibility an d Concept - Safety Activities Early in a Project 6 Design and De velopmen t 6 T ender and Co ntract 7 S yst em Rea lis atio n 7 Transition to Service 7 to 8 On-g oing Operation and Maintenance 8 Ch ange s 9 Re moving the System from Service /De comm issioning 9 10 Chapter 2 R isk Assessment and Mitigation In troduction 10 Requirement for Risk Assessmen t and Mitigation 10 S u mmary of the Seven Steps 11 to 12 13 Chapter 3 The Seven-Step Risk A ssessment and Mitigation Step 1 S ystem Description 13 to 14 S t ep 2 H azard and Conse quence Iden tification 14 to 17 S t ep 3 E stimation of the Se verity of the Hazard 17 to 18 C S t ep 4 E stimation/ Assessm ent of th e Likelihood of the Conseque nces Occurring 19 to 20 S t ep 5 E valu atio n of the Risk 20 to22 S t ep 6 R isk Mitigation and Safety Requirements 22 to 23 Step 7 C laims, Arguments and Evidence that the Safety Objectives and Safety Re quire ments Have Been and Docu menting this in a Safety Case 23 to 31 Appendix 1 Hazard Identifica tion using Brainstorming 32 1 In troduction Initial Pl ann ing 2 P reliminary Brainstorming (Scoping Brain s torm) 3

Preparation for Full Brainstorming 3 to 4 P r eparing a Brainstorm ing S ession 4 Co nduct of the Brainstorming Session 5 After the Brainstorming Session 5 to 6 38 Appendix 2 Failure Modes, Effe cts and Criticality Analysis 1 In troduction T he FME CA P rocess 1 to 2 Definin g the Syste m to be Analyse d 3 Block Diagrams 3 Narrative Text 3 Definin g Failure Modes 4 Performing the Analysis 4 to 5 Co mmon M ode Failures 5 T he FME CA Rep o rt 6 Upd a tin g the Hazard Log 6 to 7 45 Appendix 3 Hazard and Operability Studies 1 In troduction Initial Pl ann ing 1 P r eparation for the HAZOP Study 2 to 3 P l an ning a HAZOP Session 3 to 4 Bre akd own of the HAZOP process 4 to 6 Afte r the HAZOP Sessio n 6 Example of a HAZOP record sheet 7 52 Appendix 4 U sing Event Trees 1 In troduction E xample use o f an E v ent Tree 1 I dentifyin g Barriers and Miti gations Using Event Tree s 2 P rocedure for E v ent Tree Analysis 3 to 6

58 Appendix 5 D iagrammati c Representation of Safety Arguments 1 In troduction Goal Structured Notation - GSN 1 to 3 E xample of Goal Structured Notation 4 63 Appendix 6 Hazard Logs 1 In troduction Developing a Hazard Log 1 to 3 66 Appendix 7 R equired Level of Confidence in Evidence 1 In troduction Dete rmining the Required Level of Confidence for Derived Re quirem ents 1 Dete rmining the Required Level of Confidence for Statutory Re quirem ents 1 to 2 Accep t ed Eviden ce Levels and Sou rces 3 HIGH - Requ ired Level of Con f idence Gene ral Re quirem ents 3 M E DIUM - Required Level of Confidence General 3 R i t LO W - Req uired Level of Con f idence Gen e ral Re quire ments 3

Re quired Level of Co nfide nce T a bles 4 High confidence test evidence 5 Medium confidence test evidence 6 Low confidence test evidence 7 High confidence field service evidence 8 Medium confidence field service evidence 9 Low confidence field service evidence 10 High confidence analytical evidence 11 Medium confidence analytical evidence 12 Low confidence analytical evidence 13

Foreword 1 I ntroduction International regulations an d stan dard s require that any ne w system, procedure or 1.1 o peration that has an im pact on th e safet y of aerodro m e operations shall be subj ect to a risk as se ssm ent and a mi tiga ti on process be subsequently established. Significant changes to existing Safety systems shall also be subject to the same regime. The result of the asse ssm ent should be do cumented and th is is typically achieved by developing a Safety Case . The te rm ‘ S afety Case' is used in respect of a set of one or more docume n ts that include claims, argumen ts and statistics and evidence that a system meets its safety requ irements. A S a fety Case provides all the documen tation and references necessary to de monstrate , bo th to the operator th emse lves an d to the S CAA, th at a ne w system or cha nge to an ex isting syst em is tolerably safe and will m eet specified Safety obje ctives. 1.2 T his do cume nt is a consolidated refere nce addressin g th e deve lopme nt of a Safety Case for th e purposes of assuring the safe ty aero drome operations. 1.3 T his gu idance is based on a safety asse ssment process. Other approach es may be take n for hazard identification and risk as sess ment; ultima tely , what is important is that the S a fety Case presents ad equate evidence an d argume nt to dem onstrate that the new system or change is tolerably safe . 1.4 T he purpose of th is document is to provide guid a nce to SCAA aerodro m e inspectors on The process for the de velopment of a Safe ty Case and , in particular , on hazard identificatio n, risk assessment and mitigation techniques that m a y be applied. 1.5 F or conciseness, the te rms ' system' and 'proje ct' are used th rougho ut this docume nt and should be considered to include the following constituents: a) any e quipm ent; b ) any procedure (e.g. operation al procedure used by the aerodro m e operator alternatively, a mainte nance procedure for re late d eq uipme nt); and c) the people involved. 1.6 During the life of a system or th e develop ment of a project there m ay be several iterations of risk asse ssment and m i tigation and updates to the Safety Case as mo re detailed system design an d pe rformance info rmati on be com es avail a ble. T he Safety Case is, the r efore, a 'living docu m ent’ and should be developed along with th e lifecycle of the system. Work on the Safety Case should t herefore begin when a pr oject is at its initial concept phase and t he co ntent should be adde d to as th e pr oject progresses throug hout its lifecycle thro ugh to its removal fro m service. 1.7 International and n a tio n ally recognised standards m ay be applicable to certain types of systems or e quipm ent. Th e guidance cont ained with in this do cume nt sh all not be used in place of any requ ireme n ts an d/or guid a nce contained in applicable stand a rds. T he standards take precedence over the gui dance cont ain ed within this document. 1.8 T he international require ments concerning sa fet y assessment of aerodrome operations are continually evolving. It is eminent that t he S CAA keeps abreast of such devel opments and produce additional guidance material or amendments as required. _____________________________________________________________________________ Page 1 of 31