Airport operators and planners will have to adapt to upcoming changes in the long-established ICAO Obstacle Limitation Surface (OLS) regulations.
ICAO Annex 14 for Aerodromes is designed to ensure a safe, obstacle-free airport environment. The regulations prescribe Standards and Recommended Practices (SARPs) on the physical characteristics and OLS for aerodromes, and certain facilities and technical services.
However, the ICAO OLS regulations were first introduced in the 1950s – and as an ICAO Working Group paper has noted, advancements since then in aircraft performance, navigation capability, ground equipment and procedures, meant it was time to update the criteria.
ICAO’s Aerodrome Design and Operations Panel set up an OLS Task Force to address the matter. It had several challenges – including how to harmonize different controlling and assessment surfaces found in the ICAO Annex, and the Procedures for Air Navigation Services and Aircraft Operations (PANS-OPS).
Other considerations included design surfaces that are both applicable today and adaptable to future operations, the sufficiency of OLS in safeguarding operations, surfaces with clear purposes and characteristics, and developing performance-based and adaptable guidelines.
New OLS requirements
The new proposed ICAO OLS requirements introduce a revised classification for surfaces – which are now classified either as Obstacle Free Surfaces (OFS), or Obstacle Evaluation Surfaces (OES).
According to a 2023 ICAO presentation, whether OFS or OES is applied depends on the type of runway, the Aeroplane Design Group to which aircraft operating into the runway belong, and the particular flight procedures for that runway.
Obstacle Free Surfaces (OFS) relates to surfaces within a defined airspace in the immediate vicinity of an aerodrome. OFS exists to protect the aerodrome’s existing and future operational capacity by limiting obstacles, and to preserve accessibility of the aerodrome by containing standard operations (straight-in approaches) with a high level of probability. Hard surfaces are to be kept free from obstacles except for existing obstacles and/or terrain that would have been assessed earlier.
The principles of OFS, according to the ICAO presentation, are for those operations (including approaches, go-arounds, balked landings, and take-off climbs) that cannot adapt to obstacles. It relates to fixed and mobile objects around a runway, and involves strict obstacle limitations.
Obstacle Evaluation Surfaces (OES) also relate to a defined area, but instead of an evaluation against fixed obstacles, they are classed as ‘triggering’ surfaces. They are used to determine the acceptability of obstacles in ensuring safety, and the regularity of intended aircraft operations at the aerodrome.
The ICAO presentation says OES of standard dimensions are proposed to cover the most common types of operations. Surfaces may be modified to address those operations that vary from the standard OES dimensions.
Dimensions of OFS and OES are determined based on Aeroplane Design Group categorization, which utilizes the aircraft’s indicated airspeed at threshold and wingspan.
Photo by Gustavo Mercado (Senior Product Manager at Transoft Solutions)
What happens next?
ICAO is undertaking an ‘aeronautical study’, which it describes as “a process of examining an aeronautical concern by assessing its impact on safety and regularity of aircraft operations and identify, if need be, possible mitigation measures”.
Various ICAO documents will require updates – namely, Annex 14, Vol I; Annex 4; Annex 15; PANS – Aircraft Operations (Doc 8168); PANS – Aerodromes (Doc 9981); PANS – AIM (Doc 10066); and Airport Services Manual, Part 6 (Doc 9137).
In terms of a timeline, a final review is expected in late 2024. Adoption of the revised OLS regulations is planned for 2025, with an effective date of July 2025. This will open an implementation period, ahead of a compliance date of November 21, 2030.
Preparing for the new OLS requirements
ICAO aims to enhance awareness and promote cooperation on OLS related issues between industry players. It intends to organize workshops and seminars, and specific targeted training and courses could be developed as necessary.
Transoft Solutions recommends airports to monitor ICAO’s implementation timeline, and start looking for tools that will prepare them for the OLS changes. By equipping themselves with the right tool to test scenarios, they become familiar with it, allowing for efficient use during the window from adoption to implementation.
Michael Frost, Senior Product Manager at Transoft Solutions, says: “The changes will require the industry to react and relearn the fundamental processes of OLS and aeronautical studies.
“Tools like SkySAFE hope to ease that burden by building in the regulations and workflows to expedite industry’s ability to evaluate airport airspace by both legacy and newly adopted regulations. We hope it clarifies and allows visualization and analysis of the magnitude of impact.”
Frost adds: “We are closely monitoring ICAO’s development and are standing by to provide access to the new regulations in SkySAFE in the near future.”