Aeronautical Study

28.10.2004

Submission:

An ongoing project involves dispensations regarding penetrations of the inner horizontal surface (IHS) and the practices in different States. In the following Annex 14 recommendation there are two options - an aeronautical study or shielding by an existing obstacle.

"4.2.4 Recommendation.- New objects or extensions of existing objects should not be permitted above the conical surface or inner horizontal surface except when, in the opinion of the appropriate authority, the object would be shielded by an existing immovable object, or after aeronautical study it is determined that the object would not adversely affect the safety or significantly affect the regularity of operations of aero-planes."

The Airport Design Manual Part 6 indicates that shielding practices vary between States. It indicates two criteria are involved - safety and regularity. On that basis the PANS-OPS criteria appear more relevant since they indicate whether or not an OCA/H would be increased. But - even the Basic ILS surfaces - and non precision clearance surfaces - are normally well above the IHS away from the immediate airport vicinity.

Initial discussions suggest that some States disregard the IHS and just check if the circling minima is increased; others insist there should be NO penetrations and do not even allow shielding. Whilst it is always a good idea to limit new constructions around airports, there must be a balance somewhere, and I find it difficult to justify having no dispensations for the IHS - it does not match the circling areas (particularly for Cat D and E aircraft - and they are protected by the circling minima anyway); the approach and transitional surfaces look after the visual phase following an instrument approach.

When there are already 50 penetrations by existing objects, what are the arguments for denying another, particularly when it does not increase the OCA/H for any instrument or visual procedure? Is the setting of a precedent for new constructions a good enough reason for denial...Comments from anyone who has experience similar problems would be appreciated.


Robert Woodhouse - ICAO OCP member (retired) - Canada

Answer or Commentary:

(I.W.

In my opinion the ICAO Annex 14 surfaces are an airports first line of defence against urban obstacle encroachment. However there must be a balance between required urban facilities (i.e. Hotels) and safe airport operations. In fact in a lot of airports throughout the world the IHS is penetrated either by terrain or man made obstacles (usually the ATC control tower). If the aeronautical study done by competent experts shows that the infringement of the IHS has no effect on airport operations I can see no reason why a building should not be built.

Most CAAs in the world are not too sure as to what is involved in an aeronautical study. However the United Arab Emirates specifies in detail the requirements of an aeronautical study. The UAE Aeronautical Information Circular number 03 / 2002 issued on the 7th of July 2002 deals specifically with Aeronautical studies. In the section detailed "Action" the requirements of an aeronautical study are detailed as follows:


a) The company references and the credentials of the person(s) who made the study.

b) Site survey to aeronautical data quality standards,

c) Operational considerations including air traffic management, present and projected air traffic flow.

d) Annex 14 considerations

e) PANS - OPS considerations,

f) Other ICAO standards and recommended practices,

g) Aviation law and regulations

h) Affect on air navigation facilities including radio navigation aids and airport lighting,

i) Environmental concerns,

j) Mitigating factors

k) Risk analysis.

The above list is quite comprehensive and covers all areas that could effect safe operations at an airport. In my opinion if all the above requirements are fully checked and found to be non-influential to safe aircraft operations I don't think that there would be any objection from the airport or CAA.

Even if the study reveals a problem the unit doing the study should recommend changes to the procedures that do not affect the overall operation at the airport but still enable both operations (aviation / construction) to take place.


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Just as a point of interest, ASAP s.r.o. has done over 25 aeronautical studies so far

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