Do you need
What we have
  • Indication of relevant obstacle limitation surfaces
  • To execute an obstacle assessment
  • Safety arguments
  • Recommendations for visual marking
  • Report to appropriate authorities

A high-rise building, a series of wind turbines or electricity poles may affect the safety of aircraft operations. International regulations from ICAO as described in Annex 14 specify an airspace around aerodromes to be maintained free from obstacles. This airspace is defined by surfaces that depend on the airport and its runways. Some of these surfaces should not be penetrated by any objects, while others may be penetrated under condition that safety and regularity of the operations are not adversely affected. The safety assessment to show that these conditions are being met is referred to (by ICAO) as an aeronautical study. For instance penetration may be allowed when procedures are defined to avoid the area where obstacles are present or when the visibility of the object is sufficiently ensured by means of lighting or marking.

We can carry out an aeronautical study, in order to supply you with objective facts which can support your building plans or to assess the airport obstacle environment.

In general four main issues may play a role:

Collision risk
This issue is mainly dealt with by International Civil Aviation Organisation Annex 14, Aerodromes, and sometimes some local regulations. The safety issue is in general that the obstacle protrudes one of the defined Obstacle Limitation Surfaces (OLS). The OLS define the maximum height that an obstacle near an airport is allowed to have. The OLS have been defined to protect approaches (approach and transitional surface), take-offs (take-off climb surface) and circling/manoeuvring operations at the airport (Inner Horizontal Surface (IHS) or Conical Surface). Due to the large area covered by HIS and Conical Surface, these surfaces are usually of most interest. The IHS is a circular surface a height of 45m with a radius ranging from 2 to 4 km, depending on the runway reference length. The Conical Surface slopes outward from the IHS with a specified slope up to a given height above the IHS, also depending on the runway reference length. In case one of these surfaces is protruded an aeronautical study is required to demonstrate that the obstacle does not affect the safety and regularity of the operations to/from the airport

Aircraft operational impact
Due to the erection of obstacles flight procedures may need to be changed, or aircraft performance requirements may be affected (for instance one-engine out performance). The impact of obstacles on procedure design is mainly covered by ICAO Doc 8168 (the so-called PANS-OPS)

Disturbances of radar, navigation aids and communication aids
Objects may also pose a danger to air traffic, because they may affect the proper functioning of the communication, navigation or radar surveillance systems. All these (CNS) services are safety-critical and therefore should not be disturbed significantly by obstacles.

The disturbance of radar, navigation aids and communications systems are mainly addressed by ICAO Annex 10 (Volumes 1-5). Within Europe further guidance material is provided by ICAO EUR Doc 15 on managing building restricted areas. Furthermore in the Netherlands a requirement exists that any wind turbine within 75 km from the instrumented range of a primary radar needs to be assessed for potential disturbances

Wind hindrance
Due to the large dimension of today’s wind turbines the wake and turbulence may become hazardous for aircraft passing downwind behind the wind turbine. However, no specific international regulations do exist that protect aircraft from entering the potential hazardous wake or induced turbulence behind a large wind turbine. However, based on specific studies by NLR, recommendations concerning an acceptable level of wind hindrance have been developed. Based, on a generic wind turbulence model, NLR is able to assess the impact of the wind turbine wake on aircraft and helicopters.

For any of these cases we have the expertise to support you.

Examples of our experience are an aeronautical study for planned high-rises (Kirchberg Plateau, near Luxembourg airport), safe positioning of power pylons (alongside Schiphol’s Polder runway), obstacle limitations in the defined zones at Schiphol terrain, obstacle assessment of wind turbines (Teuge), obstacle assessment of wind turbines (Curacao, near Hato airport), obstacle analysis high-rise zone Novartis North near Euro-airport Basel-Mulhouse, obstacle analysis for building zones near Sabiha Gokcen and Guvercinlik airports in Turkey.

Related Issues

  • Acceptable level of wind hindrance
  • Aeronautical study
  • Aircraft operational impact
  • Aircraft performance requirements
  • Annex 14
  • Approach and transitional surface
  • CNS
  • Conical Surface
  • Disturbances of communication aids
  • Disturbances of navigation aids
  • Disturbances of radar
  • Electricity poles
  • Flight technical assessment
  • High-rise buildings
  • High-rise zone
  • ICAO Annex 10
  • ICAO Doc 8168
  • ICAO EUR Doc 15
  • Induced turbulence
  • Inner Horizontal Surface (IHS)
  • Obstacle lighting
  • Obstacle Limitation Surfaces (OLS)
  • Obstacle marking
  • Take-off climb surface
  • Visual marking
  • Wake turbulence
  • Wind hindrance
  • Wind turbine turbulence
  • Wind turbine wake
  • Wind turbulence model