Approaches and takeoff mins.

In article
outaviation.com,
jamin3508 wrote:

Today I awoke to find a cloud sitting on the ground bringing the vis down
to 1/16th of a mile. All the airlines here in KROC were forced to hold
from takeoff until it lifted a little. I know that the part 91 is 0/0
unless otherwise noted, what about part 131 or the airlines? Do they have
different takeoff mins?

Part 121, I assume you mean, and yes, they have different takeoff mins.
At my company, we basically use the minimums on the Jeppesen charts.
It depends how the runway is equipped, but normally we need 1600RVR
(1/4mi) on a runway with standard takeoff minimums and adequate visual
references. In many places, we can take off with as low as 600 RVR,
but that requires multiple RVR sensors and a runway with centerline
lights. (Some operators can use 500RVR; 600 is as low as we can go.
It's in each specific airline's FAA ops specs.)

My next question is about the approach to
landing....if the wx during the landing was like this morning right, below
mins for sure (1/16th SM VV100), could a part 91 still attempt the approach
hopeing the was a hole in the scud and see the runway, but knowing its
below mins and will most likely go missed?

Sticky area. You can definitely shoot the approach, but landing from
it could be problematic. The rules say "flight visibility," which you
can only really judge in-flight. Tower visibility really isn't a good
indicator of flight visibility, but RVR is a much more accurate view of
what you'll probably see from the cockpit.

I understand they *have* hung pilots out to dry for landing with RVR
below minimums. I don't have a specific cite for that, so it may be
urband legend. Perhaps someone can chime in on this one?

What about the airlines and air
carriers, could they attempt the approach when the wx is below mins?

No. If the visibility/RVR is below approach minimums, an air carrier
can't continue past the final approach point; he'd have to go missed at
that point if there wasn't a report of the visibility being at or above
the minimum. If touchdown zone RVR is available, it's the controlling
value that decides whether they can start the approach. If not, it's
visibility.

If they're already on the final approach segment and the visibility/RVR
goes down, they may continue the approach, but as far as landing goes,
we're back to "flight visibility." If the RVR is below minimums,
you're not likely to see the visual cues you need anyway. I'd continue
the approach and hope the reported RVR comes back up before DH, but a
missed approach is most likely at that point.

I guess what Im trying to ask is.....anyone allowed to attempt a approach
when the wx is below mins?

Yes, part 91 operators are completely free to attempt the approach, at
least down to DH.

What if the field is uncontrolled with an ILS
and does have AWOS reporting below mins. Does is matter if its controlled
or not?

No, it doesn't matter. It's the only reported weather, which means if
it's reporting visibility below minimums, an air carrier can't fly the
approach. My company serves a couple of uncontrolled airports, and we
run into that from time to time. But a part 91 aircraft can start the
approach, definitely.

At an uncontrolled airport with an AWOS reporting below minimums, I'd
absolutely try the approach under part 91, because the visibility of an
AWOS is not often a good indicator of what you'll see. Flight
visibility may be just fine on the runway, often because it's on a
different part of the airport from the AWOS visibility measurement.
I've often seen a fog bank covering just half an airport, leaving most
of my landing runway completely clear.

Im just wondering about this, dont get me wrong, I would NEVER
attempt a approach thats below mins. Just courious if its stated somewhere
in the FARS (I couldnt find it) about the approach to landing with below
mins WX.....thanks for the imput!

The specific FAR is 91.175. It says an aircraft may not descent below
DH/MDA unless, among other things, "The flight visibility is not less
than the visibility prescribed in the standard instrument approach
being used." But it says nothing about *starting* the approach;
that's specific to air carrier operations. You're perfectly legal to
fly the approach; you just need to meet that reg in order to continue
past the bottom of the approach.

Hope that hhelps.

--
Garner R. Miller
ATP/CFII/MEI
Clifton Park, NY =USA=