Annex 14 vs. OAS (1)

25.10.2004

Submission:

As you all probably remember, as a fledgling designer there are always too many questions and not always enough answers. I am currently looking at a situation for a new build airport that is located in pretty hostile territory and formulating the procedures is a challenge. I have come to a result but am unsure if the conclusion I have come too is the best advice. There is an obstacle (top of which is at 192m amsl) which is located on a hill (at 152m amsl) some 1400m abeam a threshold of a runway (at 90m amsl). The ILS procedure is Cat II and the missed approach is to be straight ahead until the required MOC clear of the hills is achieved and a turn can be initiated. When assessing the obstacle it is found that it is just outside the OAS surfaces. When applying the Annex 14 surfaces to the same problem, it is found that the object penetrates the inner horizontal surface by a significant margin (so does the hill). Annex 14 is not clear on the purpose of the inner horizontal surface and that is my first question - Why does it exist? Under what circumstances is penetration (e.g. by an obstacle that is essential to the airport task) permitted? Is there any precedence that I could quote to allow this situation to prevail?

B. Hawkins

Airspace designer and procedures specialist (UK)