RESA is a prepared area beyond the runway, designed to enhance safety by minimizing damage risk in an overrun or undershoot scenario.
A Runway End Safety Area (RESA) is a specifically prepared, obstacle-free area located immediately beyond the end of a runway strip at an airport. Its primary purpose is to minimize the risk of damage to an aircraft that overruns or undershoots the runway. The International Civil Aviation Organization (ICAO) defines RESA standards in Annex 14, requiring a minimum length of 90 meters, and recommending 240 meters for runways serving large aircraft. The width must be at least twice that of the runway, aligned with the extended centerline.
RESA must be free of obstacles, properly graded, and maintained to support the occasional passage of aircraft and rescue vehicles. Structures are generally prohibited, except for frangible visual aids necessary for runway operations. Where topographical or infrastructural constraints limit RESA implementation, alternatives like Engineered Material Arresting Systems (EMAS) are used.
RESA enhances safety during landing and takeoff by providing a buffer zone where aircraft can come to rest in case of runway excursions. Regular inspections ensure compliance with international and national regulations, making RESA a critical focus for airport authorities and regulators.
The Runway Safety Area (RSA) is a larger safety zone that includes and extends beyond the runway ends and sides. Its purpose is to minimize the risk of aircraft damage during excursions, veer-offs, or undershoots. The RSA provides a graded, obstacle-free environment supporting both routine and emergency aircraft operations, including rescue and firefighting access.
RSA dimensions are determined by the size and speed of the critical aircraft. For example, the FAA requires an RSA of at least 1,000 feet (305 meters) beyond each runway end and 500 feet (150 meters) in width for large aircraft. The RSA must be maintained to bear the weight of emergency vehicles and, sometimes, aircraft. In cases where full RSA dimensions aren’t feasible, EMAS may be installed as an alternative.
An Engineered Material Arresting System (EMAS) is installed at runway ends where space is insufficient for a standard RESA or RSA. EMAS beds consist of crushable, energy-absorbing material (such as cellular concrete blocks) that decelerate overrunning aircraft by controlled crushing, preventing entry into hazardous terrain.
EMAS is recognized by ICAO and the FAA as an alternative when full RESA or RSA lengths are not possible. The system is engineered to stop the largest, fastest aircraft operating on that runway, typically at up to 70 knots. EMAS beds are tailored to each airport’s needs, and their effectiveness has been proven in incidents worldwide.
The Obstacle Free Zone (OFZ) is airspace above and around the runway, which must be free from obstacles (other than essential, frangible navigation aids). The OFZ ensures aircraft on or near the runway are not at risk of collision during takeoff, landing, or go-around. Its dimensions depend on runway type and aircraft approach category, extending laterally and longitudinally from the runway centerline, and includes portions of the RESA and runway strip.
The Object Free Area (OFA) is a ground-level zone surrounding the runway and taxiways, designed to keep aircraft clear of obstacles during ground movement. The OFA includes the RESA and RSA, and must be free from fixed or mobile objects except for frangible navigational aids. Dimensions are based on runway code and aircraft type; for large jets, the OFA may extend 250 feet or more from the runway centerline.
The Critical Aircraft is the largest, most demanding aircraft that regularly uses a runway, dictating the design and strength requirements for runways, taxiways, and safety areas. Airports determine the critical aircraft based on historic and projected traffic, ensuring all infrastructure can safely support its operations. The critical aircraft may change as airline fleets evolve, requiring periodic review of airport design standards.
An Overrun occurs when an aircraft departs the end of the runway at speed, typically due to an aborted takeoff or inability to stop during landing. Overruns are a leading cause of runway excursions and can result from wet or contaminated surfaces, high speeds, mechanical failure, or pilot error. The presence and design of RESA or EMAS are crucial in reducing overrun severity.
A Veer-off is a runway excursion where an aircraft departs the side of the runway. Causes include crosswinds, contamination, mechanical failure, or pilot action. While often less severe than overruns, veer-offs can still cause significant damage and operational disruption. Wide, clear RSA and OFA areas are vital for minimizing veer-off risks.
Declared Distances are official runway length values published for takeoff, landing, and accelerate-stop scenarios: Takeoff Run Available (TORA), Takeoff Distance Available (TODA), Accelerate-Stop Distance Available (ASDA), and Landing Distance Available (LDA). These figures influence flight planning and may be adjusted to account for RESA limitations.
Grading ensures the ground in RESA, RSA, and OFA is smooth, stable, and free of water accumulation. Slopes must not exceed regulatory limits (typically 5%), with transitions to adjacent areas kept gradual. Drainage systems, such as swales and storm sewers, prevent standing water, which could endanger aircraft and impede emergency responses. Routine inspection and maintenance are required.
Obstacle Clearance ensures RESA, RSA, and OFA are free of hazardous objects, except for essential, frangible navigation aids. Regular surveys and vegetation management are needed to prevent hazards and support rapid emergency access.
The Load-Bearing Capacity of RESA and related areas refers to their ability to support aircraft and emergency vehicles without rutting or collapse. Construction must be based on the weight of the critical aircraft and emergency vehicles. Regular testing ensures compliance and safe conditions, especially after adverse weather.
Rescue and Firefighting Access is essential for emergency response. RESA and adjacent areas must allow rapid access for rescue vehicles, with surfaces capable of supporting their weight. Emergency exercises and clear pathways are key to effective response.
A Stopway is a prepared area beyond the takeoff runway, constructed to the same standards as the runway, and intended for use in the event of an aborted takeoff. Unlike RESA, which is a passive safety buffer, a stopway is designed for rapid deceleration during emergencies.
Runway End Safety Areas (RESA) and related safety zones are foundational to airport safety worldwide. Their proper design, maintenance, and integration with systems like EMAS, RSA, OFA, and OFZ play a critical role in protecting aircraft, passengers, and airport personnel during routine and emergency operations. Continual compliance with international and national standards ensures the highest levels of operational safety and efficiency.
ICAO Annex 14 specifies a minimum RESA length of 90 meters, with a recommended length of 240 meters for runways used by large aircraft. The width should be at least twice the runway width, centered on the extended centerline.
A RESA is a graded, obstacle-free area beyond the runway, while EMAS is a bed of engineered, crushable material that arrests the motion of overrunning aircraft. EMAS is typically used where space for a full-length RESA is unavailable.
RESA areas serve as safety buffers, reducing the risk of severe damage or injury during overruns or undershoots. They also support rescue and firefighting access, playing a key role in emergency response and regulatory compliance.
Regular inspection and maintenance are required, including surface grading, drainage, vegetation control, and obstacle clearance. Any deterioration or non-compliance must be promptly addressed.
Yes, airports may reduce declared distances (TORA, LDA, etc.) to create additional safety buffer when a full RESA cannot be provided due to site constraints, helping to maintain safety standards.
Ensure your airport meets global safety standards with proper RESA design, maintenance, and emergency planning. Speak with our experts to enhance your runway safety and compliance.
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