Is the world flat, part 2 ?

05.03.2009

Submission:

A lot of thoughts on this one and it seems that the world IS mostly flat.
I. W

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While pilots continue to use a pressure altimeter to determine their altitude, we should believe, that the Earth is flat.

Ivan Ferencz - CAA Slovakia
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Apart from precision approaches, all aircraft operations are still primarily based on barometric altitudes. Pressure variations aside, this means what we call a level flight is actually following the curvature of the Earth. In other words, the Earth may not be flat, but we fly parallel to it, so for the purposes of OLS it's appropriate to treat it as flat.

Obrad Puskarica - Airways New Zealand
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A few hundred years after Columbus fell off the flat earth in the late 1400s searching for India, the US began correcting for earth curvature in RNAV procedures. So our obstacle evaluations do consider earth curvature with regards to RNAV approaches. But they do not for airport surfaces (14CFR Part 77 over here.). Since the Annex 14 standards have always been applied without earth curvature, I'd argue that your idea to include curvature amounts to a reduction in obstacle clearance from the current application. I'd think we'd want to look at that carefully before allowing it.

Vince Massimini - MITRE Corporation USA