Ron Garret writes:

Because ATC only provides separation from other airplanes. It does not
provide separation from terrain.

If you know your position and altitude, charts will provide you with
separation from terrain. There are probably moving-map systems that
will do the same, although I'm not personally familiar with them (it's
certainly feasible to a large extent).

Also, with VFR into IMC situations you often don't have contact with ATC.

You call them when you see the clouds or fog coming.

So you have to get out your chart, try to figure out where you are
(not all planes have moving map GPS), find the right frequency,
dial it in, call them up, wait for a response ... and all the time
you have to fly the plane without being able to see where you're going.

If I'm flying the plane, I'll already know where I am based on
instruments, irrespective of weather conditions. I'm not going to
start looking at the chart and instruments only as I approach the IMC.

Additionally, I'll avoid aircraft that do not appear to have
instrumentation adequate to make IFR flight safe and reliable (in
addition to legal).

It's not so easy in real life as it might appear in a sim.

Maybe. How much of it have you done in a sim? I wouldn't call
instrument flight in a sim easy--most sim pilots don't know how to do
it.

And what will you do if your GPS fails?

Since I'll already know the nearest VORs and I'll be tuned to them, I
can go with that. I often do, anyway, as it's sometimes easier than
fooling with the GPS.

However, if all radio navaids fail, I'm in a bit more of a quandry, as
I have very little experience so far with dead reckoning.
Fortunately, it's relatively unlikely that I would have a total
failure of all navaids at the same time that I happen to get stuck in
IMC. And, by definition, if you have no instruments, you cannot fly
IFR.

No. ATC does not provide terrain separation.

I can provide terrain separation myself. In most cases I will already
be thousands of feet above the highest terrain in the area, out of
sheer prudence, and I have charts and navigational equipment to tell
me where I am and how high the terrain below happens to be. I only
need ATC for separation from other aircraft (TCAS helps in this
respect, but I'm assuming I wouldn't have that onboard, and it's not
100% reliable). Hopefully I'll have a radar altimeter, too, although
it's only useful in certain situations.

Those are all big IFs.

That depends on your personal policies as a pilot. If you routinely
make use of instruments to verify your position, you'll already know
where you are if you lose visual contact with the outside world.
You'll just have to be a bit more careful since you won't be able to
double-check anything visually. And you'll need ATC to help you stay
clear of other aircraft.

Sure. But you keep switching the topic back and forth between "when you
approach IMC" and when you are IN IMC. Those are two very different
circumstances.

Visually, yes. But depending on how much you routinely use your
instruments, it might not be that much different in other ways.

I might well look for landmarks out the window in good weather. But
that would not prevent me from keeping track of a VOR or two, and
looking at the GPS display or EHSI occasionally to make sure that all
information sources agree on my position. If I see unavoidable IMC
approaching, I call ATC for separation services, and I watch my
instruments more carefully.

One of the things I like about aviation is that it _is_ possible to
fly without any external visibility at all (excluding landing and
take-off, which are special circumstances). All you need is a few
instruments, a couple of charts, and knowledge of how to use them. I
find it fascinating that I can fly for hours with nothing but fog out
the window, then descend below the weather and see a runway directly
ahead of me, _exactly where the instruments and charts promised it
would be_. It is very reassuring. It proves that if you follow the
rules, and you are careful and diligent, and you know your procedures,
you can always find your way home. Ultimately the only thing you have
to worry about is other aircraft ... and that's where ATC comes into
play.

The major differences a 1) in IMC you cannot rely on your peripheral
vision.

If you are flying with instruments, you're not relying on peripheral
vision, either.

If you are flying with instruments, visual contact with the outside
world is only one of several sources of information. It helps you to
make sure that all is well, but if it abruptly becomes unavailable,
you still know exactly where you are, if you know how to use your
instruments.

In anything other than the severest of clear weather all the way to
the horizon, in the daytime, I'd be nervous relying on visual cues
alone. If it were required for a test, I could do it, but left to my
own devices, I'd look for confirmation from instruments and charts.
Mountains and rivers tend to look the same after a while; I want to
know if that twisty little river ahead really is the one that I think
it is before I try to follow it home.

This makes a much bigger difference than you might imagine (and
you can't experience it in simulation unless you have a lot of
monitors).

I can "turn my head" in a sim, but it is true that visibilty is in
most ways much more limited than in real life (although I can look
directly backwards in the sim, whereas the aircraft would block much
of my view in real life).

2) approach to landing must be done in a much more stylized
and pre-planned way in order to avoid terrain that you can't see.

That's how I land already. I consider a purely visual landing to be
sloppy. I always check the instruments to see if I'm really at the
altitude I appear to be at, if I'm really aligned as I should be, and
so on. Even in perfect weather, I may still be tuned to the ILS for a
straight-in approach, just to make sure that my glide path and
alignment agree with the instruments.

Additionally, I always try to navigate in a way and plan ahead in a
way that allows me a straight-in approach. I'll fly a pattern if I
have to, but otherwise straight in is preferable. Even for flying a
pattern, I'll check instruments.

3) if you don't have a moving-map GPS you have to twiddle a lot
of knobs in the right way at the right time, which adds to your
workload.

Yes, but planning ahead seems to help a little. It makes me nervous
if I don't have at least a VOR or beacon or something that I can use
to double-check that I really am where I think I am, no matter how
familiar the view out the window might be.

I like to be sure that the little airstrip I see up ahead really is
the airstrip I'm looking for. I'm especially vigilant about this
because I understand that airports are hard to recognize in real life,
even though they are already hard to recognize in the sim.

The combination of all three of these factors makes for a very different
experience.

If one flies purely visually and is suddenly thrust into a situation
where visual information is unavailable, I can see how panic would set
in. But if one is already scanning instruments with an awareness of
one's position derived therefrom, a sudden transition into low
visibility should be far less stressful.

Some pilots are willing to fly aircraft that don't provide the minimum
necessary for instrument flight, but I don't think I'd be very
sanguine about trying that myself, no matter how great the weather
might seem. I spend a lot of time thinking "what if?"

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