Baro-VNAV 1

21.04.2010

Submission:

I just had a closer look at the Baro-VNAV criteria in Doc 8168 Vol II Part III Section 3 Chapter 4 and there is one point that seems not really clear to me. In case of a missed approach obstacle, I compute the equivalent height ha with the formula in paragraph 4.4.3.1. To determine the OCH the MOCapp is added to the equivalent height ha. I asked myself why the MOCapp and not the MOCma for OBST in the missed approach, but this is probably due to the fact that MOCma is included in the construction of Zi and Zf surfaces (paragraph 4.4.1 b). However in case the missed approach obstacle penetrates the side surface of Zi, the MOCapp is modified according to the secondary area principle (paragraph 4.4.3.2). Due to the different MOCs the side surface of FAS and the side surface of Zi have different slopes. Is it still correct then to add the modified MOCapp to the equivalent height ha?
Romano Germann, Skyguide, Switzerland

Answer or Commentary:

I.W.
Yes that does seem strange in Pans-Ops and I think it is going to change. I personally think that the Baro-VNAV criteria is rather confusing. ICAO will be having a workshop concerning this at the end of May in Paris and I am sure that this will be discussed. However it would be nice to get some feedback from other procedure designers that have dealt with this criteria.


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