Reducing the consequences of runway overruns

Runway end safety areas and engineered materials arresting systems

Runway overruns are infrequent, but their consequences can be severe. Airport leaders should ensure that every runway end has appropriate protection, that any significant residual risk is understood, and that improvement decisions are funded and followed through.

Why runway-end protection matters

Runway excursions remain one of ICAO’s global high-risk occurrence categories. Preventing an overrun is the first priority, but runway-end protection provides an important final layer of defence when prevention is not enough. [1,4,5]

Airport leadership does not need to determine the technical design of that protection. It does, however, need assurance that the airport understands the risk at each runway end, has considered realistic ways to reduce it, and can explain why the resulting level of protection is appropriate.

Start with the requirements that apply to your airport

Airport operators must, at a minimum, comply with the national or regional regulatory requirements applicable to their airport and the conditions of their aerodrome certification.

ICAO provides the international framework and supporting guidance for runway-end safety. Guidance from other regulators and industry bodies may also help technical teams evaluate options, but it does not replace the requirements of the competent authority.

Where different sources provide different approaches or design criteria, the requirements applicable in the airport’s jurisdiction take precedence.

What a runway end safety area does

A runway end safety area (RESA) provides additional space beyond the runway strip to reduce the consequences of an aircraft overrunning or undershooting the runway.

ICAO Annex 14 establishes provisions for RESA dimensions, but effective runway-end protection is not simply a question of meeting a stated distance. Terrain, obstacles, roads, water, development and emergency access beyond the runway can materially affect the consequences of an excursion. [2,3]

Figure A-5: Runway end safety area for a runway where the code number is 3 or 4. Source: ICAO, Annex 14 — Aerodromes, Volume I — Aerodrome Design and Operations, ninth edition (2022), Attachment A, p. ATT A-15. © ICAO 2022. All rights reserved.

Choosing effective runway-end protection

Compliance is the starting point, not the whole question

A runway end may comply with the applicable dimensional requirements and still present significant consequence risk because of what lies beyond the protected area. Conversely, terrain, development, environmental constraints or land availability may make conventional runway-end protection difficult to provide.

Airport leadership therefore needs an answer to two separate questions:

Are we compliant with the requirements that apply to us? and Is the remaining risk understood and appropriately managed?

The airport’s safety management system should provide the framework for answering the second question.

The local runway safety team can support this work by bringing together the airport operator, aircraft operators and air traffic services to share operational information, identify hazards and consider coordinated mitigations. It should not, however, replace the airport’s established technical assessment, safety assurance or management decision-making processes.

Compare the practical ways to reduce risk

There is no single solution for every runway end. Where further risk reduction is warranted, the airport should compare the practical alternatives.

Improve conventional protection. Where practicable, options may include extending or improving the RESA, grading terrain, removing or mitigating obstacles, improving drainage, or improving emergency access.

For some airports, conventional improvements may provide the most straightforward and sustainable reduction in risk.

Reduce exposure where appropriate. In some circumstances, operational measures may also form part of the solution. These can include changes to runway use, declared distances or other operating arrangements developed with the regulator, aircraft operators and air traffic services.

Such measures may affect capacity or operational flexibility and should therefore be considered alongside their safety benefit.

Where hazards beyond the airport boundary contribute materially to the consequences of an overrun, coordination with road, municipal, land-use or other relevant authorities may also be necessary.

Consider an engineered arresting system where space is constrained. An engineered materials arresting system (EMAS) uses material designed to absorb energy and decelerate an aircraft that overruns the runway. It operates passively and does not require external activation.

ICAO recognizes aircraft arresting systems as an option for runway-end protection, subject to State acceptance. They may be particularly relevant where terrain, development or limited land makes conventional RESA provision difficult. [2,3]

EMAS is not automatically the preferred solution for every constrained runway end. Its suitability depends on the airport’s specific risk, physical constraints, fleet, operating environment and the alternatives that are realistically available.

An accident or incident elsewhere may provide a useful reason to review local arrangements, but it should not predetermine the solution at another airport.

The leadership question

Where a runway end presents significant residual risk, airport leadership should require a clear, documented recommendation before committing to an investment.

That recommendation should explain:

• the risk being addressed
• the realistic options considered
• the expected safety benefit and limitations of each option
• the risk that will remain after implementation
• the operational and financial implications
• any regulatory approval or acceptance that will be required

The runway safety team can help inform the assessment by bringing operational perspectives from the airport, aircraft operators and air traffic services. The airport should then use its established safety, engineering, investment and governance processes to determine the appropriate course of action.

Where a proposed measure goes beyond minimum regulatory requirements, leadership should be satisfied that the additional investment is supported by the airport’s own risk assessment and delivers a proportionate safety benefit.

The decision should not be driven by the preference of a single stakeholder or simply by a reaction to an event at another airport.

What airport leadership should require

Airport executives do not need to select technical design parameters or calculate stopping performance. Their role is to ensure that the assessment is credible, the proposed response is proportionate to the risk, and the selected solution can be implemented and sustained.

A credible runway-end assessment should answer five questions:

• What can happen? Consider how the runway is used, the aircraft operating on it, approach and departure characteristics, surface conditions, weather, rejected take-offs and locally reported safety information. Previous experience is relevant, but the absence of an accident does not by itself demonstrate that the risk is adequately controlled.
• What are the consequences? Consider what lies beyond the runway end, including terrain, roads, water, embankments, buildings, infrastructure and other exposed activity. The assessment should not stop automatically at the regulatory RESA boundary. A significant hazard immediately beyond that boundary can still affect the consequences of an overrun even where the airport has met its minimum dimensional requirements.
• What options are genuinely practicable? Compare the realistic ways of reducing the risk. These may include improvements to conventional runway-end protection, removal or mitigation of hazards, operational measures and, where physical constraints justify it, an engineered arresting system.
  The purpose is not to progress through a predetermined hierarchy of solutions. It is to identify which option, or combination of options, provides the most appropriate risk reduction for that runway end.
• What risk remains? No measure eliminates every possible overrun consequence. The airport’s safety assessment should explain what the proposed improvement is expected to protect against, its important limitations and the residual risk that will remain after implementation. Management should be able to understand that residual risk before approving the decision.
• Can we sustain the solution? The decision should consider more than the initial capital investment. Leadership should understand the implications for inspection, maintenance, repair, system availability, emergency response, passenger evacuation and disabled-aircraft removal, together with the long-term resources required to keep the selected measure effective.

If EMAS is proposed

The competent authority should be engaged early where approval or acceptance will be required.

Before procurement, the airport’s technical and safety teams should be able to demonstrate that the proposed system is appropriate for the runway, the aircraft using it and the local operating environment. They should also identify important limitations and explain how the installation will be incorporated into maintenance, emergency response and aircraft removal arrangements.

ICAO Doc 9157 provides the principal international technical guidance for aircraft arresting systems. National or regional requirements govern their implementation at the individual airport. [3]

Use other regulatory material as supporting guidance

Several regulators, including EASA, Transport Canada, the UK CAA and the FAA, publish more detailed material relating to runway-end protection or EMAS.

Where those requirements do not apply directly, they may still provide useful technical experience or comparison for the airport and its regulator.

They should be treated as supporting guidance, not as requirements for airports outside the relevant jurisdiction.

Recommended action for airports

The objective for airport leadership is to make runway-end protection a deliberate, documented safety decision rather than a legacy condition that is reconsidered only after an accident, regulatory change or major infrastructure project.

Confirm the governance. Ensure that responsibility for runway-end safety is clear within the airport.

The airport’s safety and technical functions should own the necessary assessment and assurance processes. The runway safety team should provide a standing forum for operational information-sharing and coordinated input from aircraft operators and air traffic services.

Management should retain responsibility for investment decisions, resources and follow-through.

Review every runway end. Confirm the applicable regulatory requirements and the actual condition of the runway strip, RESA and surrounding area.

The review should also identify significant hazards beyond the protected area and any constraints affecting emergency response.

The objective is to understand where the consequences of an overrun could be greatest, not simply whether the airport meets a dimensional requirement.

Prioritise the highest-risk locations. Use the airport’s safety management system to determine which runway ends warrant further assessment or investment.

Consider both the likelihood of an overrun and the potential severity of the consequences.

Not every runway end will require the same level of attention or investment.

Require a credible options assessment. Where further improvement is warranted, require the responsible airport teams to compare realistic alternatives and provide management with a clear recommendation.

The recommendation should show the expected risk reduction, key limitations, operational implications, cost, regulatory pathway and long-term maintenance requirements.

The runway safety team and other stakeholders should contribute relevant operational information, but the airport should retain responsibility for its safety assessment and investment decision.

Collaborate with local authorities where prevention extends beyond the airport boundary. Some runway-end risks cannot be addressed by the airport alone.

Where roads, development, land use or other activities beyond airport control materially affect the consequences of an overrun, engage the relevant local or national authorities.

The runway safety team can help identify these interfaces and support information-sharing with affected stakeholders.

Maintain prevention as the first line of defence. Runway-end protection reduces consequences; it does not replace overrun prevention.

Runway safety data, local operating experience and relevant precursors should continue to inform preventive action. [4,5]

Maintain readiness. Whatever protection is selected, assign clear inspection and maintenance responsibilities and define how any loss of serviceability will be managed.

Emergency arrangements should address rescue access, passenger evacuation and disabled-aircraft removal, including the particular implications of an aircraft entering an arresting system where one is installed. [3]

Secure management follow-through. Document interim controls, approved investments, accountable owners and completion dates.

Reassess runway-end protection when there are material changes to the fleet, runway configuration, operating environment, surrounding development or identified risk.

Questions airport leadership should be able to ask – and get a clear answer to:

• Are we meeting the national or regional requirements that apply to this airport?
• Which runway ends present our greatest residual consequence risk, and why?
• Are there significant hazards beyond the regulated safety area that we should still be considering?
• Where additional protection is warranted, have the responsible airport teams compared the realistic alternatives?
• What safety benefit would the recommended option provide, and what are its important limitations?
• What risk will remain after the improvement, and are we satisfied that it is being appropriately managed?
• Have aircraft operators, air traffic services and other relevant stakeholders had an opportunity to contribute operational information through the runway safety team or another appropriate forum?
• Have we engaged the competent authority where regulatory approval or acceptance may be required?
• Can we afford to maintain the solution and keep it effective throughout its lifecycle?
• Is the decision funded, assigned to an accountable owner and integrated into our operational and emergency arrangements?

References and further guidance

For airport leadership, the national or regional regulatory framework and the conditions of the airport’s certification should be the first point of reference.

The sources below provide the principal international framework and selected supporting guidance for the safety, engineering and operational teams carrying out the detailed assessment.

Principal international sources

1. ICAO safety reporting and Global Aviation Safety Plan. Used for the global runway-excursion safety context and high-risk occurrence categories.
2. ICAO Annex 14 — Aerodromes, Volume I — Aerodrome Design and Operations. Establishes the international framework for runway end safety areas and the use of arresting systems.
3. ICAO Doc 9157, Aerodrome Design Manual, Part 1 — Runways. Provides supporting guidance on runway-end protection and aircraft arresting systems, including EMAS.
4. Global Action Plan for the Prevention of Runway Excursions (GAPPRE). Provides industry guidance on runway-excursion prevention and coordinated action.
5. ICAO Global Reporting Format implementation guidance. Supports consistent runway condition assessment, reporting and information exchange.
6. ICAO Runway Safety Team Handbook. Sets out how a runway safety team should be constituted and operated.

Selected national and regional technical guidance on EMAS

The following are examples for technical teams. They apply as requirements only within their respective regulatory frameworks, but may provide useful supporting material elsewhere where considered appropriate by the competent authority:

• EASA, Easy Access Rules for Aerodromes, including EMAS certification specifications and guidance material.
• Transport Canada, AC 300-007, Engineered Materials Arresting Systems for Aircraft Overruns.
• UK Civil Aviation Authority, CAP 168, Licensing of Aerodromes.
• FAA AC 150/5220-22B, Engineered Materials Arresting Systems (EMAS) for Aircraft Overruns.

About ACI

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