Obstacle evaluation and obstacle limitation surfaces

Obstacle Limitation Surfaces and Obstacle Evaluation

What is an aerodrome surface assessment?

To prevent aerodromes from becoming unusable, ICAO Annex 14 obstacle limitation surfaces (OLS) are established at each aerodrome to define an airspace that ideally should be kept free from obstacles. Therefore, whenever an object is supposed to be built in the vicinity of an airport, it is necessary to conduct an assessment of these surfaces with regard to penetrations.

However, non-infringed obstacle limitation surfaces do not guarantee safe flight operations, and objects below these surfaces might have an impact on aircraft operations. Consequently, protection areas of each particular instrument flight procedure published for the aerodrome are required to be examined.
What are protection areas of instrument flight procedures?

Each instrument flight procedure has associated protection areas to ensure that the flight path is sufficiently protected. Within protection areas an obstacle clearance needs to be provided in order to define the lowest flight altitude for the instrument flight segment. Therefore, every new or modified (height or location) object in the vicinity of an aerodrome requires a thorough analysis to determine a possible impact on published IFPs.

Evaluating new and existing obstacles against obstacle limitation surfaces (OLS) and protection areas of IFP is a safety-critical activity. It is essential to determine the impact on aircraft operations which may entail necessary measures such as imposing restrictions on obstacle parameters, changes to existing instrument flight procedures or in particular cases a conduct of an aeronautical study.



 What are our activities?

  • Obstacle assessment in accordance with ICAO Annex 14 obstacle limitation surfaces (OLS).
  • Assessments of national obstacle protection surfaces.
  • Obstacle impact assessment on instrument flight procedures.
  • Conduct of aeronautical studies.
  • Assessment of objects regarding interference with communication, navigation and surveillance (CNS) facilities.
What is an aeronautical study?

An aeronautical study is a process intended to address situations where applicable regulations or aviation standards cannot be fulfilled. It consists of detailed analysis of the aeronautical problem, identification of all possible safety concerns and presentation of solutions that are acceptable without degrading safety of aircraft operations.

Why an aeronautical study might be a good idea?

A typical example of when an aeronautical study is advised, is a penetration of obstacle limitation surfaces or visual segment surface. Such cases may result in a reduction of the height of an object concerned or withdrawal of an instrument flight procedure influencing economic profitability or reducing accessibility of the airport.

A more appropriate solution is the conduct of an aeronautical study. In this way the actual influence on safety of aircraft operations will be identified. If mitigation measures are required, NavDelta can determine alternative means and recommend solutions to compensate for the deviation. With the aid of an aeronautical study, we support our client to get the necessary approval or regulator’s acceptance for deviations from applicable regulations.