3D software-1

25.10.2004

Submission:

It is delightful to have the opportunity to discuss interesting issues, especially when these questions are exposed in such an appealing visual/graphical way.

I made a very quick review of the concepts involved and as such please consider my comments with the appropriate reservations.

A- Non-precision procedures

1- One must differentiate between approach and missed approach segments

2- Segments and areas should be looked at as two different entities;

B-Approach segments

1b- A segment is a 3d entity within which a nominal 3d profile is being flown by the pilot (the segment specifications must be taken into consideration by the procedures designer, i.e., length, width, defining fixes and descent gradient)

2b- The area (primary) associated with the segment is a 2d projection of the segment, used for obstacle identification and as such, has no gradient.

3b- When flying a particular approach segment the pilot will only descend to an (published) altitude (this defines an horizontal surface) that provides the appropriate obstacle clearance for that segment

4b- In regards to the secondary areas, the minimum obstacle clearance is found (quoted from 8168) by linear interpolation from the applicable MOC at the inner edge to zero at the outer edge.

If the above comments are correct and the 3d software is written in accordance with 8168 then the facts stated should not happen. These comments are not complete but I hope they contribute to a general agreement on this issue.

Henrique Nunes

Pans-Ops Specialist

Azores Portugal