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Safety Analysis of eVTOL Operations based on STPA

Mariat James Elizebeth, Shufeng Chen, Halima El Badaoui, Siddartha Khastgir, Paul Jennings

TL;DR

This paper applies a novel prioritized STPA analysis to assess the safety of eVTOL operations in the UK by modeling multi-stakeholder control structures across five flight phases from regulatory prep to landing. It identifies 317 unsafe control actions (UCAs), prioritizes 110 high-risk UCAs, and generates 377 causal factors with 432 proposed requirements, distilled into 124 distinct high-priority requirements. A gap analysis against existing aviation regulations reveals 56 regulatory gaps, 27 of which overlap with helicopter operations, signaling targeted regulatory updates in areas such as organizational performance, training, energy management, collision avoidance, and automation. The study demonstrates STPA’s effectiveness in revealing emergent risks in a socio-technical, highly automated airspace domain and provides actionable implications for regulators and industry to advance safe deployment of eVTOLs. Future work includes deeper Level-2 control-structure analysis, broader stakeholder participation, and exploration of autonomous/automated ATM integration to further strengthen safety objectives.

Abstract

Electric Vertical Take-Off and Landing (eVTOL) aircraft are expected to be quieter and more cost-effective than helicopters, offering major economic and social benefits through improved connectivity. Their adoption will require new ground infrastructure and airspace redesign, introducing risks involving multiple stakeholders (Regulators, eVTOL operators, Air navigation service providers, Vertiport operators, OEMs, Pilots, etc.). To assess these risks for the UK airspace, systems-thinking based System Theoretic Process Analysis (STPA) was conducted. To manage the large number of Unsafe Control Actions (UCAs) and requirements generated due to the complexity of the analysis, a novel extension to STPA for the prioritization of results was applied. 317 UCAs were identified in total out of which 110 high-priority UCAs were analyzed (Step-4), resulting in 377 causal factors and 432 requirements. These were prioritized to produce a targeted list of 124 distinct high-priority requirements, 56 of which were identified as gaps in existing aviation regulations, policies, or procedures.. These highlight opportunities for regulatory updates in areas such as organizational performance, certification processes, training, collision avoidance, energy management, and automation. The findings provide regulators with safety considerations that could shape new or updated regulations, compliance methods, and guidance materials for the safe deployment of eVTOLs.

Safety Analysis of eVTOL Operations based on STPA

TL;DR

This paper applies a novel prioritized STPA analysis to assess the safety of eVTOL operations in the UK by modeling multi-stakeholder control structures across five flight phases from regulatory prep to landing. It identifies 317 unsafe control actions (UCAs), prioritizes 110 high-risk UCAs, and generates 377 causal factors with 432 proposed requirements, distilled into 124 distinct high-priority requirements. A gap analysis against existing aviation regulations reveals 56 regulatory gaps, 27 of which overlap with helicopter operations, signaling targeted regulatory updates in areas such as organizational performance, training, energy management, collision avoidance, and automation. The study demonstrates STPA’s effectiveness in revealing emergent risks in a socio-technical, highly automated airspace domain and provides actionable implications for regulators and industry to advance safe deployment of eVTOLs. Future work includes deeper Level-2 control-structure analysis, broader stakeholder participation, and exploration of autonomous/automated ATM integration to further strengthen safety objectives.

Abstract

Electric Vertical Take-Off and Landing (eVTOL) aircraft are expected to be quieter and more cost-effective than helicopters, offering major economic and social benefits through improved connectivity. Their adoption will require new ground infrastructure and airspace redesign, introducing risks involving multiple stakeholders (Regulators, eVTOL operators, Air navigation service providers, Vertiport operators, OEMs, Pilots, etc.). To assess these risks for the UK airspace, systems-thinking based System Theoretic Process Analysis (STPA) was conducted. To manage the large number of Unsafe Control Actions (UCAs) and requirements generated due to the complexity of the analysis, a novel extension to STPA for the prioritization of results was applied. 317 UCAs were identified in total out of which 110 high-priority UCAs were analyzed (Step-4), resulting in 377 causal factors and 432 requirements. These were prioritized to produce a targeted list of 124 distinct high-priority requirements, 56 of which were identified as gaps in existing aviation regulations, policies, or procedures.. These highlight opportunities for regulatory updates in areas such as organizational performance, certification processes, training, collision avoidance, energy management, and automation. The findings provide regulators with safety considerations that could shape new or updated regulations, compliance methods, and guidance materials for the safe deployment of eVTOLs.

Paper Structure

This paper contains 27 sections, 7 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Literature Review
  3. Research Objectives and Contribution
  4. Methodology
  5. Standard STPA methodology
  6. Step 1: Define purpose of the analysis
  7. Step 2: Model the control structures
  8. Step 3: Identify Unsafe Control Actions (UCA)
  9. Step 4: Identify Loss Scenarios
  10. Extension of Standard STPA Process for Prioritization of Results
  11. Extension to Step 3: Prioritization of UCAs
  12. Extension to Step 3: Prioritization of Requirements
  13. Results
  14. Step 1: Define Purpose of the Analysis
  15. Step 2: Model the Control Structures
  16. ...and 12 more sections

Figures (7)

  • Figure 1: Standard STPA Process and extensions to Steps 3 and 4 for Prioritization
  • Figure 2: Flight Phases for eVTOL Operations
  • Figure 3: Control Structure for Phase 0.1
  • Figure 4: Control Structure for Phase 0.2
  • Figure 5: Control Structure for Phase 1
  • ...and 2 more figures