Remote Altimeter Setting Source (RASS) MOC Adjustment

12.05.2009

Submission:

This concerns the FAA Order 8260.54A figure 3-3.

We use the term ROC (Required Obstacle Clearance) which is 250 feet in the primary area of a GPS procedure. In the secondary area the ROC tapers from 250 feet to 0 feet at the outer boundary.

The practise has always been to add a Remote Altimeter Setting Source (RASS) correction to the calculated ROC. As an example the ROC applied to an obstacle at the secondary mid point would be 125 feet plus the full RASS value.

If the RASS was 100 feet then the total ROC at that position would be 225 feet.

The proposal is to add only half the RASS value in the above example giving an ROC of 175 feet.

How does Pans-Ops handle RASS application to secondary area obstacles?

George Dewar, Procedure designer – Canada

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Answer or Commentary:

I. W.
I am not too sure as Pans-Ops does not really specifically cover this point. However I would be inclined to add the primary ROC with the RASS and then use the result (ROC-2) as my primary ROC which would then linearly taper to 0 at the edge of the secondary area, as in your second case.

What do the other procedure designers out there do?

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