scope:

INTRODUCTION

The specifications in this part have been formulated with a view to achieving a reasonable degree of standardization although the improbability of being able to achieve worldwide uniformity of procedure, areas and obstacle clearance for any single type of facility is fully recognized. It is intended therefore that States should take into account their local conditions, in relation to these criteria, when establishing procedures, areas and obstacle clearances.

Only one procedure should be specified for each type of radio aid in relation to a particular runway. Exceptions to this should be permitted only after joint consideration by the State authorities and the operators concerned. The attention of States is particularly drawn, therefore, to the general and basic criteria on which the specifications have been based and the manner in which these criteria should be applied.

Obstacle clearance is the primary safety consideration in developing instrument approach procedures, and because of variable factors such as terrain, aircraft characteristics and pilot ability, the detailed procedures set out in this part are based on present standard equipment and practices. However, the obstacle clearance included in the specifications are considered to be the minimum: they have been evolved taking into consideration the COM and AGA specifications and it is considered that they cannot be reduced with safety.

The advent and burgeoning growth of RNA V procedures has meant that many pilots now habitually fly all instrument flight procedures using guidance based upon the on-board navigation database, regardless of whether the procedures are published as RNA V or conventional procedures. However, not all conventional procedures are capable of being coded into navigation databases. This is particularly the case with departure procedures. In order to mitigate this problem and to ensure improved flyability, procedure designers should:

a) keep the design of all,procedures as simple as possible;

b) develop RNA V procedures instead of conventional procedures wherever possible;

c) coordinate closely with the navigation database suppliers whenever introducing a conventional departure procedure;

d) ensure continuity between SIDs and the en-route structure and between the en-route structure; STARs and approaches with the use of a common fix and compatible altitude at the interface;

e) avoid the use of duplicate segments - i.e. a segment declared as part of a STAR and as part of an approach; and

f) avoid the use of heading legs intercepting VOR radials with turns of less than 30°.

In the interest of efficiency, regularity and economy, every effort should be made to ensure that equipment is sited and procedures are evolved so as to keep to the minimum consistent with safety, both the time taken in executing an instrument approach and the airspace necessary for the associated manoeuvres.