for Tom, et al VEB,
Tom, interesting explanation. While the VEB is certainly a beginning, many of the variables are a bit less detailed, and really havent progressed, such as the FTE/ATIS assumptions. The attempts with the precipitous terrain algorithm were a disaster.
For most people. looking at the VEB calcs provides an understanding of the complexity of the obstacle surfaces used for the flight path.
I am just not sure how one can get to the RNP 0.003 you speak of, when there are assumptions in the variables, the different combinations of FMC equipment, and the variations associated with the surveyed location of the threshold.
EDIT: BTW, for those of you wondering about the PT algorithm (isnt everyone), this calculation assumes that as the aircraft radar is scanning forward at intervals, if the terrain suddenly rises, the aircraft believes there is an object above it, and tends to dive down instead of up. (this is actually left over from Vietnam, when the VC would fire as much ak-ak above the jet as they had, causing it to dive into terrain...my how the FMS has changed..???
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