Aircraft Accident & Incident Investigation Services

Independent Investigation, Internal Investigation Methodology Support, Expert Advisory, AAIB Liaison, Regulatory Engagement and Investigation Training for Aviation Operators, Insurers, Regulators and Legal Proceedings

When an aircraft accident or serious incident occurs, the quality of the investigation that follows determines whether the organisation — and the broader aviation system — learns from it or simply records it. A technically rigorous, systemically focused investigation produces findings that explain how the event developed, identifies the organisational and procedural conditions that enabled it, and generates corrective actions that address root causes rather than surface symptoms. An investigation that identifies the proximate human error, attributes the event to the individual involved and closes with a recommendation for retraining produces a record of what happened without producing the understanding of why — and without that understanding, the conditions that produced the event remain in place, waiting to produce it again.

The gap between these two outcomes is not a function of investigative intent. It is a function of investigative methodology, independence and expertise. Investigation that is conducted without structured analytical frameworks — without the systematic approach to evidence collection, timeline reconstruction, causal factor identification and systemic analysis that distinguishes genuine accident investigation from narrative event description — produces findings that reflect the limitations of the methodology rather than the full causal picture of the event. Investigation that is conducted internally, by people embedded in the organisation in which the event occurred, faces structural constraints on independence that even the most committed internal investigator cannot fully overcome. And investigation that lacks specialist knowledge of the operational environment, the regulatory framework and the Human Factors conditions of the event cannot reliably identify the full range of causal and contributing factors.

Aviation accident and incident investigation is governed by a specific international and national framework — ICAO Annex 13, the Air Accidents Investigation Branch’s investigative primacy for notifiable accidents and serious incidents, and the UK mandatory occurrence reporting system that generates the occurrence data that feeds into operators’ SMS improvement cycles. For operators, the investigation obligations that arise outside the AAIB’s formal investigation process — the internal investigation of occurrences, the SMS-driven analysis of precursor events, the investigation of workplace safety events under RIDDOR and HSWA — require investigation capability and methodology that many organisations do not systematically maintain.

Aerospace and Aviation Consulting Services (AACS) provides specialist aircraft accident and incident investigation services across the full range of investigation contexts: independent investigation of occurrences that require external investigative objectivity, methodology support for organisations building and improving their internal investigation capability, expert witness and advisory services for insurers and legal proceedings, AAIB liaison support for operators involved in formal investigations, regulatory engagement support, and investigation training that develops genuine investigative competence rather than regulatory compliance documentation.

Why Investigation Quality Determines Safety Outcomes

The Purpose of Investigation Is Not to Establish What Happened

Every competent investigator can establish what happened. The sequence of events — the departure, the approach, the moment of impact — is typically established from flight data, cockpit voice recordings, witness accounts and physical evidence within hours of the event. What happened is the starting point of investigation, not its conclusion. The question that investigation must answer — and that most internal investigations fail to answer adequately — is why the event happened: what were the organisational conditions, the procedural vulnerabilities, the absent defences and the latent hazards that combined to produce this outcome? Without that understanding, corrective action cannot address the cause.

James Reason’s Organisational Accident Model — the Swiss Cheese framework — provides the conceptual basis for this understanding. Accidents do not occur because a single person makes a single mistake. They occur because latent conditions in the organisation — the holes in the layers of defence — align to create a trajectory from hazard to harm. Those latent conditions accumulate over time, often without detection, in the decisions made by management, in the procedures written by engineers, in the schedules set by planners and in the cultures built by leadership. By the time the event occurs, the conditions that produced it have often been present for months or years. Investigation that identifies them provides the intelligence to change them. Investigation that stops at the surface of the event does not.

Independence Is Not Optional for Effective Investigation

Internal investigation — investigation conducted by the organisation in which the event occurred, using the organisation’s own resources, reporting to the organisation’s own management — faces structural limitations that the most committed, most technically capable internal investigator cannot fully overcome. The internal investigator is embedded in the culture that contributed to the event. They have relationships with the personnel involved. They operate under the same organisational pressures, norms and assumptions that shaped the conditions the investigation must assess. They are accountable to a management structure that has institutional interests in the investigation’s findings. These are not personal failings — they are structural conditions that limit independence regardless of individual integrity.

Independent external investigation is not a criticism of internal investigative capability. It is the mechanism for accessing the objectivity that internal investigation structurally cannot provide. For events whose causes may be found in management decisions, organisational culture or systemic procedures, that objectivity is not a luxury. It is a prerequisite for findings that will be acted upon, trusted by the people they affect, and capable of generating the improvement they are designed to produce.

The Regulatory Investigation Framework and Operator Obligations

The UK’s formal accident investigation framework is operated by the Air Accidents Investigation Branch (AAIB), an independent body within the Department for Transport. The AAIB is responsible for the investigation of notifiable accidents and serious incidents involving UK-registered aircraft, and its investigations are conducted under ICAO Annex 13 principles — for the purpose of preventing future accidents, not for apportioning blame. The AAIB’s investigation is mandatory, independent of regulatory enforcement, and its reports are published for the benefit of the aviation safety community.

The AAIB’s investigation does not replace the operator’s own investigation obligations. Operators must conduct their own internal investigation of occurrences — including those under AAIB investigation — for the purpose of their SMS improvement cycle. These are parallel obligations with different purposes. The AAIB investigates for system-wide safety learning. The operator investigates for organisational learning and corrective action. Both are required. And for the very large number of occurrences that fall below the AAIB’s mandatory investigation threshold — the incidents, the near misses, the precursor events that are statistically the most valuable safety data an operator receives — the operator’s internal investigation is the only investigation that occurs.

The Regulatory & Legal Framework

Aircraft accident and incident investigation in the UK operates within a layered framework of international standards, primary legislation, statutory instruments and regulatory guidance. Understanding this framework — and the specific obligations it imposes on operators, investigators and other parties — is essential for anyone involved in an investigation or its consequences.

Independent Investigation Services

AACS provides independent investigation services for aviation accidents, serious incidents and incidents that require external investigative objectivity — whether because the internal investigation capability of the operator is insufficient for the event’s complexity, because the potential for conflicting organisational interests requires independent oversight, or because insurers, legal counsel or regulatory authorities require an investigation conducted outside the operator’s own management structure.

Our investigations are conducted using structured investigation methodology aligned with ICAO Annex 13 principles and ICAO Doc 9756 — for the purpose of identifying the causal and contributing factors of the event and generating safety learning, not for apportioning blame. Our investigation reports are produced to a standard that supports regulatory engagement, legal proceedings, insurance claims management and internal safety improvement simultaneously.

Independent Occurrence Investigation

For operators whose internal investigation capability cannot adequately address a specific event’s complexity, or where the nature of the event requires the objectivity that independent investigation provides, AACS conducts the full investigation on the operator’s behalf:

• Initial response and evidence preservation advisory — the immediate actions required in the hours following an event to preserve evidence, protect witness recollections and comply with notification obligations; time-critical guidance for operators who have not experienced a significant occurrence
• Scene assessment — where appropriate and lawful, physical examination of the accident site, aircraft wreckage and surrounding environment to collect direct physical evidence before scene clearance
• Flight data and cockpit voice recorder analysis — liaison with AAIB and NATS for flight data retrieval and analysis where applicable; review of Quick Access Recorder data, flight tracking data and ATC radar data for events within AACS investigative scope
• Technical record review — examination of aircraft maintenance records, technical log, defect records, MEL applications and maintenance task documentation relevant to the event
• Witness engagement — structured interviews with flight crew, cabin crew, maintenance personnel, ATC staff, ground handlers and other witnesses, conducted in accordance with just culture principles and structured interview methodology
• Timeline reconstruction — the precise chronological reconstruction of the event sequence, from the earliest identifiable precursor through to the event itself and the immediate aftermath
• Causal factor analysis — structured identification of the immediate, contributing and root causal factors using established investigation frameworks: the Systemic Occurrence Analysis Methodology (SOAM), HFACS, or the AAIB’s own causal factor taxonomy as appropriate
• Organisational and management system analysis — assessment of the organisational, management and systemic factors that created the conditions in which the event developed: safety management, training, procedures, supervision, scheduling and cultural factors
• Safety recommendation development — specific, actionable safety recommendations addressed to the responsible parties, targeted at the causal factors identified and proportionate to the risk they represent
• Investigation report production — a structured final investigation report presenting findings, causal factors, contributing factors and recommendations in a format appropriate to the intended audience and purpose

Serious Incident Investigation

Serious incidents — events that narrowly avoided becoming accidents, where the margin between the outcome and a catastrophic event was small — are among the most valuable investigation subjects in aviation safety. They provide complete information about the causal chain that nearly produced an accident, without the evidentiary destruction and investigative complexity that a full accident generates. Serious incident investigation that is conducted with rigour can identify and address the conditions that were days or weeks away from producing a fatal event.

AACS conducts serious incident investigation with the same methodological rigour applied to accident investigation — using the full range of investigation tools available to AAIB-parallel investigations and producing findings of the systemic depth that serious incident data warrants:

• Full causal factor analysis including organisational and systemic factors — not a narrative description of what nearly happened, but a rigorous analysis of why the causal chain developed and why the defences that should have prevented the event were absent or failed
• AAIB co-ordination — where the serious incident is under AAIB investigation, supporting the operator’s engagement with the formal investigation process while conducting the parallel internal investigation
• Safety recommendation and corrective action development — specific, actionable recommendations addressed to the causal factors identified, with a structured corrective action plan and tracking framework

Occurrence Investigation for SMS Purposes

The vast majority of the occurrences that generate safety learning are not accidents or serious incidents — they are the incidents, near misses, technical occurrences and precursor events that the SMS occurrence reporting system captures. Investigation of these events is the primary mechanism through which the SMS fulfils its preventive function. But internal investigation of occurrences — the investigation conducted by the safety manager or nominated person using the operator’s own resources — is frequently the weakest link in the SMS learning cycle.

Occurrences are recorded. Causal factors are identified as human error. Recommendations focus on retraining. The systemic conditions that produced the error-likely situation are not identified. The same causal patterns recur in subsequent occurrences. The SMS accumulates data but does not generate the systemic learning it is designed to produce. AACS provides occurrence investigation services for operators whose internal investigation capacity or methodology cannot adequately address the events in their safety data:

• Single occurrence investigation — full investigation of a specific occurrence identified as requiring deeper analysis than internal resources can provide: a precursor event with high risk significance, a recurring pattern whose cause has not been identified, or an event that the operator’s investigation found inconclusive
• Occurrence pattern analysis — analysis of clusters of similar occurrences to identify the shared causal conditions that individual occurrence investigation has not surfaced: the systemic risk factor that manifests repeatedly in different events
• Safety data review and investigation prioritisation — reviewing the operator’s occurrence data to identify the events and patterns that represent the highest investigation priority, ensuring that the limited investigation resource is directed where it will produce the most safety value

Operator Investigation Methodology Support

For operators who want to improve the quality and systemic rigour of their internal investigation capability — rather than commissioning external investigation of individual events — AACS provides structured methodology support that builds the investigation competence the organisation needs to investigate its own occurrences effectively.

Investigation Methodology Framework Design

AACS designs investigation methodology frameworks for aviation operators that provide the structured approach to occurrence investigation which SMS investigation typically lacks:

• Investigation methodology design — selecting and adapting the investigation framework appropriate to the operator’s size, occurrence volume and investigative resource: SOAM, HFACS, TapRoot, ICAO Annex 13-aligned methodology or a bespoke framework integrating elements of each
• Investigation threshold and triage framework — defining the investigation depth warranted for each occurrence category, ensuring that high-risk events receive the investigative resource they warrant and that the investigation programme is sustainable within the organisation’s resource
• Evidence collection protocols — the documented procedures for preserving, collecting and managing evidence in the immediate aftermath of an occurrence, before evidence degrades or is lost
• Witness interview framework — structured interview methodology for witness engagement in internal investigations, incorporating just culture principles, cognitive interview techniques and structured questioning approaches
• Timeline reconstruction tools — the methodology and documentation tools for constructing accurate event timelines from multiple evidence sources
• Causal factor analysis framework — the structured analytical methodology for identifying immediate, contributing and root causal factors, including the organisational and management system factors that generic investigation misses
• Safety recommendation framework — the standards for safety recommendation development: specific, actionable, proportionate to risk, addressed to the correct responsible party and capable of being tracked to verified closure
• Investigation report template and standards — the documentation framework for internal investigation reports that ensures consistent quality, complete analysis and clear presentation of findings
• Investigation quality assurance process — the review mechanism through which the organisation assesses the quality of its own investigation outputs and identifies methodology improvement opportunities

Investigation Capability Assessment

For operators who want to understand the current state of their internal investigation capability before designing an improvement programme, AACS conducts independent investigation capability assessments:

• Investigation methodology review — assessing the investigation framework currently in use against the standard of systemic rigour, identifying where the methodology produces shallow causal analysis
• Investigation output review — examining a sample of recent investigation reports in detail, assessing the depth of causal factor analysis, the quality of safety recommendations, and the evidence that investigation findings are genuinely addressing root causes
• Investigation resource assessment — evaluating whether the organisation’s investigation resource — the people, time and tools allocated to occurrence investigation — is adequate for the volume and complexity of occurrences the operation generates
• Investigation training assessment — reviewing the investigation training and competency of the personnel conducting internal investigations, identifying gaps between current competency and the standard required for effective investigation
• Corrective action effectiveness assessment — evaluating whether the corrective actions generated by investigation are being implemented, whether implementation is verified, and whether the actions are demonstrably reducing the recurrence of the causal conditions they addressed
• Improvement roadmap — a structured, prioritised plan for developing the organisation’s investigation capability, addressing the specific gaps the assessment has identified

Post-Event Investigation Review

For operators who have conducted an internal investigation of a significant occurrence and want independent assessment of whether the investigation has adequately identified the causal factors and produced appropriate safety recommendations, AACS provides post-event investigation quality review:

• Independent review of investigation findings — assessing whether the causal factor analysis has identified the full range of immediate, contributing and root causes, or whether significant causal factors have been missed
• Safety recommendation adequacy assessment — evaluating whether the safety recommendations produced by the investigation are specific, actionable, proportionate and addressed to the correct causal factors
• Corrective action plan review — assessing whether the planned corrective actions will genuinely address the identified causal factors or whether they address surface symptoms without resolving the underlying conditions
• Supplementary investigation — where the review identifies significant investigative gaps, conducting the additional investigation required to complete the causal picture
• Revised investigation report — where the review identifies material investigative deficiencies, producing a revised or supplementary report that provides the complete causal analysis the original investigation did not achieve

AAIB Liaison & Regulatory Engagement

Supporting Operators Through AAIB Formal Investigation

When the AAIB notifies an operator that a formal investigation will be conducted, the operator faces a regulatory and operational situation that few of its personnel will have experienced. The AAIB’s investigators will require access to records, personnel and operational information. The operator’s legal advisors will have interests in the investigation that must be managed carefully alongside the AAIB’s independence requirements. The operator’s own SMS investigation must proceed in parallel without compromising the AAIB’s access to evidence. And the operator’s management must communicate with its personnel, its insurers, its clients and the media under conditions of significant uncertainty and public scrutiny.

AACS provides specialist support for operators engaged in AAIB formal investigation processes:

• Initial response advisory — the actions required in the immediate aftermath of a notifiable event: notification obligations, evidence preservation, personnel support, insurance notification, regulatory authority communication and internal communication management
• AAIB process orientation — explaining to the operator’s management and legal team how the AAIB investigation process works, what the operator’s obligations are, and what it should expect at each stage
• Document and records management — advising on the management of aircraft records, operational documents, maintenance records and personnel files during the AAIB investigation, including the legal constraints on document handling and the obligations of the operator to provide information
• Witness preparation advisory — advising the operator on how to support personnel who will be interviewed by AAIB investigators, within the framework of the investigation’s just culture principles and the operator’s legal obligations
• Parallel internal investigation management — designing and managing the operator’s parallel internal investigation in a way that does not interfere with the AAIB investigation and that maximises the operator’s own safety learning from the event
• Safety recommendation response — when the AAIB publishes its report and addresses safety recommendations to the operator, advising on the response, the corrective action plan and the engagement with the UK CAA on recommendation implementation
• AAIB report engagement — reviewing the published AAIB report with the operator’s management and safety team, assessing the recommendations, identifying those that apply to the operator and developing the implementation response

UK CAA Regulatory Engagement Following an Occurrence

A significant aircraft accident or serious incident will typically trigger regulatory engagement from the UK CAA alongside the AAIB’s investigation. The CAA’s interest is in regulatory compliance — whether the operator’s systems, procedures and oversight were adequate, and whether any regulatory action is appropriate in the aftermath of the event. This regulatory engagement must be managed carefully alongside the AAIB investigation and the operator’s legal position. AACS provides advisory support for operators managing post-event CAA engagement:

• Regulatory notification management — ensuring that all required notifications to the UK CAA are made accurately, on time and in the correct form, in addition to AAIB notification
• CAA engagement advisory — advising the operator’s management on how to engage with the CAA’s post-event enquiries in a way that is transparent, cooperative and consistent with the operator’s legal interests
• AOC condition review — advising on the potential implications of the event for the operator’s AOC conditions and the CAA’s oversight posture, and supporting the operator in managing any CAA-imposed additional oversight requirements
• Corrective action plan development for regulatory submission — producing the structured corrective action plan that the CAA will require to be satisfied that the operator has addressed the systemic conditions identified in the investigation

MOR System Management

The UK Mandatory Occurrence Reporting system requires operators to report occurrences meeting the mandatory threshold within defined timescales and in a specified format. Managing MOR submissions accurately — ensuring that reportable events are reported, that submissions are complete and factually accurate, and that the submission process integrates effectively with the operator’s internal investigation — is a compliance management obligation that many operators do not manage with the rigour it warrants. AACS provides MOR management advisory:

• MOR threshold assessment — advising the operator on whether specific occurrences meet the mandatory reporting threshold under retained Regulation 376/2014
• MOR submission quality review — reviewing draft MOR submissions for completeness, factual accuracy and consistency with the operator’s internal investigation findings
• MOR management framework design — designing the operator’s internal process for identifying reportable occurrences, preparing submissions, managing submission timescales and maintaining MOR records
• CAA MOR follow-up management — where the CAA requires additional information following an MOR submission, supporting the operator’s response

Expert Witness & Legal Advisory Services

Aviation accidents generate legal and insurance proceedings that require specialist aviation safety expertise — to explain the operational and technical context of the event to non-specialist audiences, to assess the adequacy of the investigation and its findings, to evaluate the operator’s safety management and regulatory compliance as relevant to liability, and to provide independent expert opinion on the causal factors and their institutional implications. AACS provides expert witness and advisory services for insurers, legal counsel and the judicial process:

Expert Witness Services

• Expert witness reports — producing structured expert reports on the operational, technical, regulatory and Human Factors dimensions of an aviation accident or incident for use in civil litigation, coroners’ inquests, public inquiries or regulatory proceedings
• Expert opinion on investigation methodology — assessing the adequacy of an accident investigation’s methodology and findings: whether the investigation was conducted with appropriate rigour, whether causal factors have been correctly identified, and whether findings are supported by the evidence
• Regulatory compliance assessment — expert opinion on whether the operator’s systems, procedures, training and oversight arrangements at the time of the event met applicable regulatory requirements
• Safety management system assessment — expert opinion on the adequacy and effectiveness of the operator’s SMS, the quality of its occurrence investigation, and the extent to which its safety management may have contributed to or prevented the event
• Human Factors expert opinion — specialist analysis of the Human Factors dimensions of the event: the error types and their causes, the error-producing conditions in the operational environment, the organisational and management factors that shaped the conditions for error, and the extent to which those conditions were foreseeable and manageable
• Oral evidence — providing oral expert testimony in court, arbitration, inquest or inquiry proceedings, explaining specialist aviation safety concepts to non-specialist decision-makers and responding to cross-examination

Insurance Advisory

Aviation insurers and underwriters involved in claims arising from aircraft accidents require specialist aviation safety expertise to assess the circumstances of the event, evaluate the investigation’s findings and advise on the technical and operational dimensions of the claim. AACS provides expert advisory for aviation insurers:

• Claim circumstances assessment — specialist review of the circumstances of an aviation accident or incident to provide the insurer with an independent technical assessment of how the event occurred and what factors contributed to it
• Investigation review — independent assessment of whether the operator’s internal investigation and any formal investigation adequately explain the causal factors of the event, or whether additional investigation is required before the claim can be properly evaluated
• Operator safety management assessment — evaluation of the adequacy of the operator’s safety management, maintenance organisation and regulatory compliance as relevant to the claim and any coverage considerations
• Subrogation assessment — advisory on whether investigation findings identify third-party responsibility that may support subrogation
• Technical report for claims management — structured technical report presenting the specialist aviation safety analysis of the event in a format suitable for the insurer’s claims management and legal process

Coroner’s Inquest & Public Inquiry Support

Where an aviation accident involves fatalities, the coroner’s inquest process engages the specialist aviation safety expertise of the investigation authority and the operator. AACS provides support for operators, families and other parties involved in the inquest and public inquiry process:

• Inquest process advisory — explaining the coroner’s process to operators and other involved parties, advising on the obligations of each party and how to engage constructively with the inquest
• AAIB report interpretation — assisting involved parties in understanding the findings and recommendations of the AAIB investigation report in the context of the inquest
• Technical explanation and expert evidence — providing technical explanations of aviation operational and safety concepts to assist the coroner, counsel and jury in understanding the specialist dimensions of the event
• Family liaison advisory — advising operators on appropriate and constructive engagement with the families of those involved in a fatal accident, within the framework of ongoing legal proceedings

Investigation Training & Capability Development

Effective internal investigation capability is not produced by reading an investigation methodology framework. It is produced by people who have been trained in structured investigation techniques, practised their application in scenario-based exercises, and understand the Human Factors dimensions of the events they are investigating. Most safety managers and nominated persons who conduct internal investigations have received little or no formal investigation training — they investigate using analytical intuition rather than structured methodology, and the limitations of that approach are visible in the quality of the investigation outputs they produce.

AACS designs and delivers investigation training that builds genuine investigative competence:

Aviation Occurrence Investigation Training

• Accident causation models — from Heinrich’s Triangle to Reason’s Swiss Cheese Model and the Organisational Accident; understanding how events develop from systemic conditions and why proximate cause analysis is insufficient
• Evidence collection and preservation — the principles and practice of evidence collection at an occurrence scene: physical evidence, documentary evidence, electronic data, and the time-critical actions that preserve evidence before it is lost
• Witness interview methodology — structured interview technique for occurrence investigation: cognitive interview principles, structured questioning approaches, recording and verification, and managing witness responses in a just culture framework
• Timeline reconstruction — the methodology for constructing accurate event timelines from multiple evidence sources, identifying the precise sequence of events and the decision points that shaped the outcome
• Causal factor analysis — the structured application of investigation frameworks to identify immediate, contributing and root causal factors: SOAM, HFACS, causal factor charting and systemic analysis of organisational and management contributory factors
• Human Factors in investigation — identifying and analysing the Human Factors dimensions of occurrence causation: error types and their causes, error-producing conditions, situational factors, team dynamics and organisational influences
• Safety recommendation development — the standards for effective safety recommendations: specific, actionable, proportionate, addressed to the correct party and capable of being verified as implemented and effective
• Investigation report writing — producing investigation reports that are analytically rigorous, clearly presented, appropriately confidential and capable of supporting both safety learning and, where required, legal and regulatory processes
• Just culture in investigation — applying just culture principles in the investigative process: the distinction between blameable and non-blameable human error, managing the investigation in a way that protects reporting culture while maintaining accountability

Investigation Workshop — Scenario-Based Practice

Training in investigation methodology is most effective when combined with structured scenario-based practice — the application of analytical frameworks to realistic occurrence scenarios that require the trainee to collect and assess evidence, construct timelines, identify causal factors and produce safety recommendations under the guidance of an experienced investigator. AACS designs and facilitates investigation workshops for aviation operators:

• Tabletop investigation exercises — structured scenario-based exercises in which participants apply investigation methodology to a realistic occurrence scenario, identifying evidence, constructing the event timeline and working through the causal factor analysis
• Case study analysis — review of real (anonymised) aviation accident and incident investigation reports, using them as analytical teaching material to develop participants’ understanding of systemic causation and investigation methodology
• Investigation team exercises — multi-participant exercises that develop the team investigation skills required when the occurrence requires more than one investigator: role allocation, parallel evidence collection, integration of findings and collaborative causal analysis
• Investigation report review — critical review of draft investigation reports produced by participants, providing structured feedback on analytical rigour, causal factor identification, recommendation quality and report presentation

Investigation Competency Development for Safety Managers

Safety managers and nominated persons who are responsible for internal investigation capability require investigation training that goes beyond initial awareness — developing the specific competencies required to lead internal investigations, to quality-assure the investigation outputs of others, and to maintain a coherent, improving investigation programme. AACS designs structured competency development programmes for safety managers:

• Lead investigator development programme — structured training in full investigation methodology, from initial response through to final report production, for individuals who will lead internal investigations
• Investigation quality management — developing safety managers’ ability to review investigation outputs critically, identify methodology gaps, provide structured feedback to investigators and maintain investigation quality standards across the organisation
• Investigation programme management — the governance, resource management and continuous improvement framework for the organisation’s internal investigation programme
• Mentored investigation support — AACS-mentored investigation of real occurrences, providing structured guidance and quality review as the safety manager conducts the investigation, developing capability through supervised practice

Maintenance Error Investigation & ATM Occurrence Investigation

Maintenance Error Investigation

Maintenance errors are a significant contributor to the aviation accident and incident record. The organisational conditions that produce maintenance errors — shift work and fatigue, task interruption, inadequate supervision, pressure to return aircraft to service, ambiguous or inadequate documentation, and the normalisation of non-compliance with maintenance procedures — are often present and detectable in the organisation’s safety data long before they combine into an airworthiness event. Investigation of maintenance errors that identifies these systemic conditions, rather than stopping at the error itself, provides the intelligence to address them.

AACS provides maintenance error investigation services calibrated to the Part 145 environment:

• Maintenance error investigation methodology — investigation frameworks specific to the maintenance environment, incorporating the Human Factors of maintenance operations: the Dirty Dozen, HFACS for maintenance, and the systemic causal factors specific to the Part 145 operational context
• Task interruption and incomplete maintenance investigation — specific investigation methodology for the maintenance error category most consistently associated with airworthiness events: the task that was interrupted and not correctly resumed
• Certifying staff decision investigation — investigation of the Human Factors and organisational conditions that shape certifying staff quality judgements, including the pressure to certify and the conditions under which non-compliances are normalised
• Maintenance organisation systemic analysis — assessment of the management, supervision, training, documentation and cultural factors in the Part 145 organisation that create the error-likely conditions in which maintenance errors occur

ATC Occurrence Investigation

Air traffic control occurrences — airprox events, losses of separation, runway incursions and related events — have a specific causal profile that requires investigation methodology calibrated to the ATM environment. The Human Factors of ATC — situational awareness, workload management, team communication, controller-automation interaction and the fatigue conditions of shift work — are the primary investigation focus alongside the procedural and systemic factors that shaped the event. AACS provides ATC occurrence investigation advisory:

• ATC occurrence investigation methodology — investigation frameworks calibrated to the ATM environment, addressing the specific Human Factors and systemic causal factors of air traffic control operations
• Radar and flight data analysis — review and interpretation of radar recordings, flight track data and ATC communication recordings as investigative evidence
• Controller Human Factors analysis — structured analysis of the situational awareness, workload, communication and decision-making factors in ATC occurrence causation
• ATM procedural and systemic causal factor analysis — identifying the procedural, equipment and organisational conditions that created the context for the ATC occurrence

The AACS Approach to Investigation

AACS investigators bring direct operational experience across the aviation environment — as pilots, as maintenance professionals, as safety managers and as regulatory advisors — combined with structured investigation training and methodology. We investigate using frameworks aligned with ICAO Doc 9756, SOAM, HFACS and the structured causation analysis that distinguishes professional aviation investigation from narrative event description.

Our investigations are independent. We have no institutional interest in any particular finding. We are not employees of the operator, and we are not subject to the organisational pressures that shape internal investigation outcomes. Our findings reflect the evidence. Where the evidence points to management decisions, systemic procedures or cultural conditions as causal factors, that is what our report says — directly, with the evidence that supports the finding and the recommendation that addresses it.

We are direct about what investigation can and cannot achieve. Investigation does not produce certainty in complex events with incomplete evidence. It produces the best-supported causal analysis the available evidence allows. We present our findings with appropriate epistemic precision — distinguishing what the evidence demonstrates from what it suggests, and what the analysis identifies as probable from what it identifies as certain. That precision is not a limitation. It is the standard of rigorous investigation.

Services at a Glance

Speak to an AACS Specialist

Whether you have experienced an occurrence that requires independent investigation, want to improve the quality and systemic rigour of your internal investigation capability, require expert advisory for insurance or legal proceedings, need support engaging with an AAIB formal investigation, or want to develop the investigation competency of your safety team, AACS provides the specialist expertise to deliver what you need.

We will be direct about what effective investigation requires, what it can achieve, and how we can help your organisation learn from its safety events rather than simply record them.