S.I. No. 423/1999 - Irish Aviation Authority (En Route Obstacles To Air Navigation) Order, 1999.

The Irish Aviation Authority, in exercise of the powers conferred on it by sections 5 , 58 and 60 of the Irish Aviation Authority Act, 1993 (No. 29 of 1993) as amended by the Air Navigation and Transport (Amendment) Act, 1998 (No. 24 of 1998), hereby orders as follows:—

1. This Order shall come into operation on the date of its publication in the Iris Oifigiúil.

2. Definitions

For the purposes of this Order:—

“the Authority” means the Irish Aviation Authority;

“the Act” means the Irish Aviation Authority Act, 1993 (No. 29 of 1993);

“aerodrome” has the meaning ascribed to it in the Act;

“aerodrome” obstacle limitation surfaces” means a series of imaginary surfaces in space defined in Annex 14 which describe the limits to which objects may project vertically into the airspace surrounding an aerodrome and designed to protect that airspace so as to permit aircraft to be operated safely. These surfaces may extend up to 15 kilometres from an aerodrome reference point;

“aerodrome reference point” means the designated geo- graphical location of an aerodrome and is a point near the initial or planned geometric centre of the aerodrome;

“aeronautical study” means a safety analysis of the hazard posed to the operation of an aircraft in flight;

“Annex 14” means Annex 14 to the Chicago Convention as referenced in the Schedule to the Act and identified in the Schedule to this Order;

“en-route obstacle” means an object outside the airspace defined by aerodrome obstacle limitation surfaces or obstacle protection surfaces, extending to a height of 90 metres or more above ground level at the site of the object, thereby having significance for the en-route operation of aircraft;

“obstacle” means any fixed (whether temporary or permanent) or mobile object or a part thereof that extends above a defined surface intended to protect aircraft in flight or that exceeds a specific height above ground level at the site of the object;

“aerodrome obstacle protection surface” means an imaginary inclined plane surface preceding a runway served by a visual approach slope indicator system as defined in Annex 14;

“potential en route air navigation obstacle” means an object extending to a height of 45 metres or more above ground level at the site of the object and which thereby may have significance for the en-route operation of aircraft.

3. Applicability

This Order shall apply to existing and proposed manmade objects of permanent or temporary construction or alteration and apparatus of a permanent or temporary nature or any alteration thereto and to objects of natural growth and terrain which may constitute obstacles to the navigation of aircraft but which lie outside the airspace defined by aerodrome obstacle limitation surfaces or obstacle protection surfaces as defined in this Order. The standards defined herein shall apply to the use of navigable airspace by aircraft and to existing or proposed air traffic routes.

4. Determination of an Obstacle

An existing object, including a mobile object, is and a future object would be, an obstacle to air navigation if it constitutes an en-route obstacle or a potential en-route obstacle in accordance with this Order.

5. Marking and Lighting of Obstacles

The Authority may require the marking and lighting of any obstacle determined in accordance with Article 4 of this Order in accordance with such instructions as the Authority may give in a particular case or as prescribed by a direction under this Order.

6. Directions

The Authority may give directions in relation to such matters to which the Order relates. Directions under this Order may be issued as Notices to Aerodrome Licensees, Aeronautical Information Circulars or by private or public notice in writing to the organisation, person or persons affected.

7. Guidance Material

The Authority may from time to time publish or otherwise provide guidance documentation on the determination and classification of obstacles for the purposes of this Order.


Annex 14 to the Chicago Convention is entitled International Standards and Recommended Practices (for) Aerodromes and is published in two volumes by the International Civil Aviation Organisation, Document Sales Unit, 999 University Street, Montreal, Quebec, Canada H3C 5H7.


PRESENT when the Common Seal of the Irish Aviation Authority was affixed hereto on the 17th day of December, 1999.

B. D. McDONNELL          Director

PAUL DUFFY                   Director


(This note is not part of the Instrument and does not purport to be a legal interpretation.)

This Order defines obstacles to en route air navigation in the State and is for the purpose of airspace protection in the State. It does not relate to obstacles in the vicinity of an aerodrome determined as such in accordance with the obstacle limitation and protection surfaces associated with that aerodrome in accordance with Annex 14 implemented by The Irish Aviation Authority (Aerodrome Standards) Order, 1996 ( S.I. No. 323 of 1996 ) to which it is complementary.