Confusion about when it's my navigation, and when it's ATC

A Guy Called Tyketto writes:

Okay.. KLAX LOOP4.DAG.KEPEC1 KLAS at FL290?

Yes.

I'll actually give an objective tutorial on this, as it's in the
sector I'm affiliated with and do most of my time in.

OK. I often take my routes directly from FlightAware, so that I'm
flying the same routes people fly in real life. If I'm staying within
SoCal, I also use TEC routes.

Look CLOSELY at those charts, and I mean closely.

Which charts? I have VFR sectionals and TACs, plus SIDs, STARs, and
instrument approach plates, but no IFR charts.

I suggest looking at the KEPEC1 first before the LOOP4. Yes,
it's the arrival and you haven't even departed yet, but you are in the
flight planning stage at this moment, and there is something important
that needs to be learned. The KEPEC1 arrival is an RNAV procedure,
requiring RNAV-capable equipment. Aircraft that are /E, /F, /G, and /R
are RNAV capable. If said aircraft is RVSM capable, then the following
suffixes apply: /J, /K, /L, /Q (FAAO 7110.65, 2-3-7). If your aircraft
is not one of then your flight plan will be rejected because you can
not use the KEPEC1 arrival.

The aircraft is RNAV-capable, but I will grant that I didn't notice
that it was RNAV. I just look at the fixes and so on most of the
time, knowing that ATC will probably tell me to do something
different, anyway.

LOOP4. If your aircraft is not capable of climbing at 500ft per
nautical mile to 10000, you're using the wrong SID. LOOP4 requires it.

The aircraft is capable of this.

I'm going to assume that you a) have RNAV and RVSM capable
equipment onboard and your aircraft is able to meet the climbing
requirement, and that you are familiar with ATC in the terminal area.

Yes, it's a BBJ2 or 737-800, and I know ATC a little in the area, as I
fly around there a lot.

You've received your clearance, and will be cruising at FL290. Great.
ATC clears you to takeoff on 24L.

Yes. More specifically, I was told to climb and maintain 5000.
Departure told me to climb and maintain 15000 (IIRC) and to proceed
direct LAX, which I did.

You best look at the LOOP4 chart again, as you have 2 crossing
restrictions you must meet. You must cross the SMO R-160 at or
below 3000ft.

I believe the FMC knew that, although I wasn't watching to see. ATC
had already told me to climb and maintain 5000, which I assumed
overrode all other instructions.

From there, you should get vectors back to LAX
with something being told to you like:

"Turn left direct Los Angeles, resume the LOOP4 departure,
comply with all restrictions, climb and maintain 15000".

I was told proceed direct LAX, climb and maintain 15000. No mention
of restrictions, though. Had ATC said that, I probably would have
looked back at the plate to see (although the restrictions are mostly
coded into the FMC's database).

In reality, all I really did was dial 15000 into the MCP, letting the
FMC continue its climb, and I plugged LAX into the FMC as the current
leg, forcing it to proceed to LAX directly (LAX was the next leg,
anyway).

You do exactly that. Your restrictions are to cross LAX at or
above 10000, KEGGS at or above 13000, and COOPP at or above 15000.
Sometime at that point you'll be handed to the Center controller who
will climb you to your cruise altitude. That ends the use of LOOP4
unless you end up NORDO for some reason.

I was handed to Center, which then told me to climb and maintain
FL290.

Now, you're en route, and you're ready for the arrival. You're
still at FL290. Staying that high until your FMS starts to descend is
really going to increase your descent rate, as well as try its hardest
to maintain a slow speed for your descent. Not good.

I recall stepping through the legs looking for anything that seemed
like a steep descent and possibly tweaking some legs, although I don't
remember the details.

What I do remember is that I reached the top of my descent and the FMC
started down, then ATC called me and asked why I was low. So I reset
the MCP to FL290 and went back up. Seconds later, Center told me to
cross something at something (I don't remember what now). My guess
was that he forgot that I'd be starting my descent and remembered when
he saw me descending, so he called me on it and then cleared me down.

Also, the DAG/HEC corridor is one of the busiest streams in US Airspace.

It's extremely busy even in the virtual US airspace. The difference
in the simulated world is that pilots look for heavy traffic, whereas
I presume they aren't so thrilled about it in real life.

Just about every arrival into the LA Basin passes in that corridor, and all
northeastbound flights leave the basin through that corridor. You may
have a flight which ATC has positively separated you from, laterally
and vertically. It is best to let them control your descent instead of
asking.

Fine with me. I just wasn't sure about whether I was supposed to
start on my own or wait to be cleared down.

ATC should tell you something like the following:

"Cross MISEN at and maintain FL240".

I recall something like that, but I don't remember the fix or
altitude.

If you look at KEPEC1, you have a segment there where you have
a crossing restriction at MISEN of FL240 or higher. The closer you are
to that, the easier your descent will be for your next crossing
restriction, which is CLARR. ATC will tell you this:

"Cross CLARR at and maintain 13000 and 250kts. Las Vegas
altimeter xx.xx".

Yes, I recall getting that.

From here, you'll be descending and reducing speed for the
arrival, and must hit CLARR at that altitude and speed.

I recall some trouble hitting the descent, but I tweaked it and
arrived at the right altitude and speed. I think starting the descent
late messed it up.

From there, the arrival tells you everything you need to do.
Should ATC have you execute the full arrival, they will tell
you something like:

"Descend via the KEPEC1 arrival".

Unfortunately, they vectored me around, and then told me to follow
some traffic going the opposite way (towards the airport, whereas I
was still headed east). I messed up so much fiddling with the FMC and
autopilot that I couldn't follow the other guy in, so I had to go
around. Then it was more vectors, and following someone else in. I
gave up on the AP and flew by hand towards the other aircraft, then
intercepted the localizer and configured everything for a nice
autoland.

That's it. From there, you're crossing KEPEC below 13000 and
above 12000, IPUMY below 12000 and above 1000, NIPZO above 9000 and
below 1000, SUNST at 8000 and 210kts, KIMME at 210kts, CHIPZ at 170kts.

Yeah, if ATC doesn't send me hither and yon instead.

Look now at the ILS 25L chart. You'll notice that the altitude
you're at by the time you hit PRINO is the same altitude you should be
at for executing the ILS approach from PRINO. So ATC should only have
to tell you:

"After PRINO, cleared ILS 25L approach".

I think ATC was looking to have more fun. In simulation, ATC, like
pilots, tends to look for challenges rather than seeing traffic and
complexity as undesirable.

No PTAC is needed, as the RNAV arrival drops you off directly
on the IAF for the approach. From there, follow the chart down. 8000 or
above at PRINO, 6500 or above at LARRE, 4900 or above at SHAND, 3800 or
above at RELIN.

I wish.

In short, like everyone else has mentioned, just because your
FMS thinks it's okay to descend, doesn't mean that it's kosher with ATC
for you to descend. They may have other things impending your descent.
When in doubt, ask. The worst you'll get back is 'no', and a reason for
why you can't at that time.

OK. I will ask next time. I have yet to do an approach (in the
presence of ATC) that followed the plates, though. Somebody always
wants me to do something different.

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