The context of minimum sector altitudes is important...they are to be used
only in emergencies. I see many postings in which a pilot is trying to fit
an MSA into an approach procedure.

Bob Gardner

"O. Sami Saydjari" wrote in message
...
MSA is defined in the AIM as "altitudes depicted on approach charts
which provide at least 1,000 feet of obstacle clearance." So, if an MSA
is 3000 ft, does that necesarily mean that there is at least one
obstacle in the area that is 2000 ft tall or could there be some other
reason for the 3000 ft setting? If there are only one or two towers in
the north part of the MSA circle and the rest of the area is completely
flat at 1000 ft (MSL), then would they always break the sector into
pieces are create a sector at 2000 ft, and just put the northern half at
3000 ft, or is that too much trouble in general?

While I am at it, is there any easy way to find the obstacle in a quad
of VFR sectional that makes the quad's Maximum Elevation Feature (MEF)
at the level that is at. It is a bit of a pain to search the quad's
entire area to find that one tower that makes the MEF way above the
surrounding terrain. It seems that they could mark the highest feature
in some distinctive way. OK, so maybe I am lazy.


-Sami (N2057M, Piper Turbo Arrow III)