System Safety Analysis for Defence

Understanding System Safety Analysis in Defence Applications

System safety analysis represents one of the most critical disciplines in defence engineering, encompassing the systematic identification, assessment, and mitigation of hazards throughout a system's entire lifecycle. For defence contractors and military organisations operating in Canada, particularly those supporting Royal Canadian Navy operations from Atlantic Canada's strategic maritime hubs, mastering these analytical techniques is essential for mission success and personnel protection.

The defence sector demands an uncompromising approach to safety that extends far beyond conventional industrial standards. Military systems operate in hostile environments, under extreme conditions, and often with minimal opportunity for maintenance or repair. A systematic approach to safety analysis ensures that potential failures are identified before they manifest in operational scenarios where the consequences could be catastrophic.

Nova Scotia's defence industry, anchored by shipbuilding operations in Halifax and supported by engineering firms throughout the province, plays a vital role in Canada's national security infrastructure. Engineers working on these programmes must demonstrate proficiency in internationally recognised safety analysis methodologies whilst adhering to Canadian defence procurement requirements and NATO standardisation agreements.

Foundational Methodologies in Defence System Safety

Defence system safety analysis employs several complementary methodologies, each designed to examine potential hazards from different perspectives. The selection and application of these techniques depend on the system's complexity, lifecycle phase, and specific regulatory requirements established by the Department of National Defence and allied nations.

Preliminary Hazard Analysis (PHA)

Preliminary Hazard Analysis serves as the foundation of the system safety programme, typically conducted during early design phases when system architecture remains flexible. This analysis identifies potential hazards associated with:

• System operating modes and mission profiles

• Interfaces between subsystems and external equipment

• Environmental factors including maritime conditions prevalent in Atlantic Canada

• Human-machine interactions and operator capabilities

• Energy sources and hazardous materials

For naval defence programmes, PHA must consider the unique operational environment of Canadian Forces vessels, including extreme North Atlantic weather conditions, Arctic operations, and the electromagnetic environment of modern maritime warfare. Engineers must document hazard severity classifications ranging from Catastrophic (Category I) through Negligible (Category IV), with corresponding probability levels from Frequent to Improbable.

Subsystem Hazard Analysis (SSHA)

As design progresses, Subsystem Hazard Analysis examines individual components and their potential contribution to system-level hazards. This methodology traces hazard causation pathways and identifies specific design features, procedures, or protective devices required to achieve acceptable risk levels. For complex defence platforms, SSHA may encompass hundreds of individual analyses covering propulsion systems, weapons handling equipment, communications arrays, and life support systems.

System Hazard Analysis (SHA)

System Hazard Analysis integrates findings from subordinate analyses to evaluate hazards arising from subsystem interfaces and interactions. This holistic perspective is essential for identifying emergent hazards that may not be apparent when examining components in isolation. SHA documentation typically includes hazard tracking matrices, risk assessment summaries, and verification cross-references demonstrating closure of all identified safety concerns.

Fault Tree Analysis and Quantitative Risk Assessment

Fault Tree Analysis (FTA) provides a powerful deductive technique for analysing system failures, working backwards from an undesired top event to identify all possible contributing causes. This methodology has become indispensable for defence programmes requiring quantitative safety assessments and probabilistic risk analysis.

The construction of a fault tree begins with defining the top event—typically a catastrophic failure or hazardous condition such as "Unintended Weapons Release" or "Loss of Ship Stability." Analysts then systematically identify the immediate causes of this event, represented as inputs to logic gates (AND, OR, or specialised gates for conditional events). This process continues through successive levels until reaching basic events representing component failures, human errors, or environmental conditions.

Quantitative Analysis Techniques

When component failure rate data is available, fault trees enable calculation of top event probability. Defence systems typically require achievement of specific safety integrity levels, often expressed as maximum acceptable probability of hazardous events per operating hour. For catastrophic hazards, target probabilities frequently fall below 1 × 10⁻⁷ per flight hour for aviation systems or per operational mission for naval platforms.

The quantitative analysis process involves:

• Assigning failure probabilities to basic events using historical data, reliability databases, or engineering estimates

• Calculating minimal cut sets—the smallest combinations of basic events causing the top event

• Computing top event probability using Boolean algebra and probability theory

• Conducting importance analyses to identify critical contributors to system risk

• Performing sensitivity studies to understand the impact of uncertainty in input data

Canadian defence programmes increasingly require compliance with MIL-STD-882E (Department of Defense Standard Practice for System Safety) and DEF STAN 00-56 (Safety Management Requirements for Defence Systems), both of which mandate rigorous hazard analysis and risk assessment processes. Engineers supporting these programmes must demonstrate familiarity with both American and British standards, reflecting Canada's position within the NATO alliance and Commonwealth defence relationships.

Failure Mode and Effects Analysis for Defence Systems

Failure Mode and Effects Analysis (FMEA) approaches system safety from an inductive perspective, examining how individual component failures propagate through the system to cause hazardous conditions. This bottom-up methodology complements the top-down approach of fault tree analysis, providing comprehensive coverage of potential failure scenarios.

FMEA Process Implementation

Effective FMEA implementation for defence systems requires systematic examination of every component, assembly, and subsystem within the analysis scope. For each item, analysts document:

• Function within the larger system context

• Potential failure modes (open circuit, short circuit, structural fracture, degraded performance, etc.)

• Causes of each failure mode

• Local, next-higher-level, and end effects of failure

• Severity classification and probability of occurrence

• Existing detection methods and compensating provisions

• Recommendations for design improvements or procedural controls

For maritime defence applications common to Atlantic Canadian engineering work, FMEA must consider the corrosive marine environment, ship motion effects, electromagnetic interference from radar and communications equipment, and the potential for battle damage. These environmental factors significantly influence failure modes and rates compared to systems operating in more benign conditions.

Failure Mode, Effects, and Criticality Analysis (FMECA)

FMECA extends basic FMEA by incorporating criticality analysis, which prioritises identified failure modes based on their probability and consequence severity. The criticality number (Cm) for each item is calculated using failure rate data, failure mode ratios, failure effect probabilities, and operating time. This quantitative ranking enables efficient allocation of engineering resources to address the most significant risk contributors.

Defence contracts typically specify FMECA reporting formats compliant with MIL-STD-1629A or equivalent standards. The resulting documentation supports logistics planning, maintenance procedure development, and spare parts provisioning throughout the system's operational life.

Software Safety Analysis for Embedded Defence Systems

Modern defence systems increasingly rely on software-intensive architectures, with embedded processors controlling everything from engine management to weapons targeting. Software safety analysis has emerged as a distinct discipline addressing the unique challenges of verifying and validating safety-critical code.

Unlike hardware components, software does not fail in the traditional sense—it executes precisely as programmed, meaning software "failures" result from specification errors, coding mistakes, or unexpected input combinations. This characteristic necessitates specialised analysis techniques including:

• Software Fault Tree Analysis (SFTA) linking software behaviour to system-level hazards

• Code-level Failure Mode and Effects Analysis examining function and module failures

• Timing and sequence analysis for real-time embedded systems

• Interface analysis verifying correct data exchange between software components

• Requirements traceability ensuring all safety requirements are implemented and tested

Canadian defence programmes involving software-intensive systems must comply with stringent development standards such as DO-178C for airborne systems or IEC 61508 for general safety-related applications. These standards establish software development assurance levels based on the severity of potential failure effects, with corresponding requirements for design documentation, testing rigour, and independent verification activities.

Hazard Tracking and Risk Management Integration

Effective system safety programmes require robust hazard tracking systems that maintain visibility of all identified hazards from initial identification through final verification of corrective action effectiveness. For major defence programmes, hazard logs may contain thousands of individual entries requiring systematic management throughout multi-year development schedules.

Hazard Tracking System Elements

A comprehensive hazard tracking system documents:

• Unique hazard identification numbers enabling cross-reference throughout programme documentation

• Hazard descriptions including causes, effects, and affected operational scenarios

• Initial risk assessment based on severity and probability before mitigation

• Recommended corrective actions with responsible parties and target completion dates

• Verification methods demonstrating corrective action effectiveness

• Residual risk assessment following mitigation implementation

• Risk acceptance authority signatures for hazards accepted at each residual risk level

Integration with broader programme risk management ensures that safety risks receive appropriate visibility alongside cost, schedule, and technical performance risks. Defence programme managers require regular safety status reporting, typically including metrics such as open hazard counts by severity category, corrective action completion rates, and risk reduction trends.

Safety Assessment Report Development

The Safety Assessment Report (SAR) represents the culminating documentation of the system safety programme, demonstrating that all identified hazards have been addressed to achieve acceptable residual risk levels. This document synthesises findings from all subordinate analyses and provides the evidential basis for safety certification or acceptance decisions.

For Canadian defence acquisitions, Safety Assessment Reports must satisfy review requirements established by the applicable project management office and may require endorsement by Defence Quality Assurance authorities. Maritime programmes supporting Royal Canadian Navy vessels undergo particularly rigorous scrutiny given the confined operating environment and limited evacuation options in emergency situations.

Atlantic Canada's Role in Defence System Safety Engineering

The Maritime provinces have established themselves as a centre of excellence for defence engineering, with Nova Scotia's shipbuilding industry generating sustained demand for system safety expertise. Engineering firms throughout the region support programmes ranging from Arctic patrol vessels to advanced naval combat systems, contributing to Canada's domestic defence industrial capacity.

The proximity to CFB Halifax, Canada's primary Atlantic naval base, provides unique opportunities for engineers to understand operational requirements firsthand and maintain close relationships with end users throughout system development. This collaborative environment fosters practical, operationally-focused safety solutions rather than purely theoretical analyses disconnected from real-world military operations.

Regional engineering firms also support aerospace and land defence programmes, applying system safety methodologies to diverse applications including unmanned aerial systems, military vehicle platforms, and communications infrastructure. The transferability of core safety analysis skills across defence domains creates valuable career development opportunities for engineers building expertise in this specialised field.

Partner with Experienced Defence Safety Engineers

Sangster Engineering Ltd. provides comprehensive system safety analysis services to defence contractors and military organisations throughout Atlantic Canada and beyond. Our engineers bring extensive experience in hazard analysis methodologies, fault tree development, FMEA/FMECA preparation, and safety assessment report documentation compliant with Canadian, American, and NATO standards.

Whether you require support for a major platform development programme or specialised analysis for a system modification, our team delivers rigorous, defensible safety engineering that satisfies the most demanding regulatory and contractual requirements. Contact Sangster Engineering Ltd. today to discuss how our system safety expertise can strengthen your defence programme and protect the men and women who operate your systems in service of Canada's national security.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.