David Megginson wrote
I wouldn't call this wisdom -- I got my rating only nine months ago -- but
for me, the important thing is not to muddle around. When you're IFR, you
want to be either on instruments (full scan) or visual (looking outside and
cross-checking instruments), but never halfway in-between.

I could not disagree more strongly. The essence of flying a good
visual segment in low visibility is exactly the opposite of this - the
blending of visual and instrument references for aircraft control. If
you fly in low vis, especially at night, you will encounter situations
where neither will be sufficient.

If I can see the runway clearly, I throw the virtual switch in my head to
"visual" and finish the landing; if not, I plan to stay on "instruments"
until the DH or MAP and then go missed (so far, I have not had to do a
missed approach -- my rule is never to start out unless my destination is
forecasting at least standard alternate minima).

I think you will discover that your method will not work on those days
when the conditions are iffy - ceiling within 100 ft of mins, and
flight visibility at MDA/DH of a mile or less (two miles or less for
night circling approaches).

Staring out the windshield saying "I can sort-of see the runway, but I still
need to sort-of follow the ILS and sort-of use the gyros to keep the plane
level" is probably not a good flying mode

If you ever hope to land out of an ILS at 3000 RVR or less, it's the
only viable flying mode. People have driven the gear through the
wings of the airplane more than once because they transitioned to
visual references with visibility that was legally sufficient to
descend below DH but not sufficient to maintain precise control of the
airplane.

If you are at the 200 ft DH on an ILS and you can just barely make out
the line of approach lights through the fog or rain - what is your
plan? If you think you're going to be able to control the plane with
just that line, you need to think again. If you're going to miss
that's certainly your choice - but it's not necessary. You can go
down to 100 ft without seeing the runway. Even at 100 ft, if you spot
the VASI, the REIL's, or the red terminating bar (or anything else
listed in 91.175), you can land. It is literally quite possible and
legal (at least in the US - Canadian rules may differ) to not see the
lights until 220 ft, not see the REIL's until 150, not see the runway
itself until crossing the threshold at 60 ft or so, land, roll out,
and still not see the far end of the runway. BTDT.

Since alternate minimums are always at least 2 miles, I don't suppose
you're ever going to encounter these conditions - until the day the
forecast goes bust.

Michael