"Jack" wrote in message
. net...
Charles Oppermann wrote:

Something that bugs me is that
the ILS for 31C requires RVR of 4000 or 3/4 of mile visibility. The
METAR from just before the accident pegged visibility at 1/2 mile. Seems
to me that the approach shouldn't have even started.

Possibly.

However, the RVR report is not the same as prevailing visibility reported
in the METAR. It's not unusual for the two to be quite different when
there is a reduced visibility condition on or near the airport.

And, particularly with snow ands fog, the view from the cockpit doesn't
match either. They're a very good wakeup call. But the are often
irrelevant on final.

moo