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

In a previous article, Mxsmanic said:
Paul Tomblin writes:

Corner cases - cases where the rules say one thing and common sense says
another, where the rules seem to contradict each other, or things that
weren't covered in normal IFR training. It's not here to act as a
person's CFI-I.

Are you the moderator?

It's not a moderated group. You asked what the purpose of the group was,
I answered. If that upsets you, then let me know so I can join the legion
of people who have you kill filed.


--
Paul Tomblin http://blog.xcski.com/
"All this news about Terri Schiavo, and i JUST realized that when they
talk about her living in a persistent vegetative state, they don't mean
Florida." - Rone

In a previous article, Mxsmanic said:
Paul Tomblin writes:

If your FMC wants to descend, ask ATC for a descent. If you're going to
be descending with multiple segments of different descent rates, ask ATC
for "descent at pilots discretion".

OK, thanks. Is that the procedure followed by pilots in the real
world as well?

I live and fly in the real world, so I can only talk about the real world.
My "real world" is part 91 IFR below the oxygen altitudes, however, so
some of what I say isn't applicablle to part 121 in class A airspace.

Another "trick" is to ask for a cruise clearance, which also allows you to
manage your own descent profile. However in my chunk of the real world,
I've never seen it used or needed it.

I fly with a Garmin 296 handheld GPS. In my experience, nearly always
just around the same time it says I need to start my descent if I want to
descend at 500fpm to my destination, ATC clears me down to a lower
altitude without being asked.

--
Paul Tomblin http://blog.xcski.com/
A male pilot is a confused soul who talks about women when he's flying,
and about flying when he's with a woman.

You can always ask. If it is not convenient they will tell you. They might
clear you to descend at a different waypoint or "not before XYZ".

Gus
EGYC
"Mxsmanic" wrote in message
...
Gus Cabre writes:

Affirm, exactly that. And if you are not going to collide against another
aircraft or terrain, they usually clear you to descend.

I'll try that, then. Is there any difference between "request
descent" and "request lower"? Can I be more specific, like "request
descent to cross BUBBL at 12000" (if the FMC is trying to do that)?

--
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Gus Cabre writes:

Where in Europe do you live?

Paris.

Depending where you are, I could put you in
contact with local experimental aircraft associations and/or simmers who are
well versed in simulated flying.

Thanks, but here they would probably all speak French and talk about
French flying, which doesn't interest me that much because I want to
learn U.S. regulations and fly in English. I usually like to fly in
the American Southwest when I'm simming.

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Pixel Dent writes:

Well, I don't fly airliners. I fly a single engine prop that rarely sees
anything above 9000'. That being said I fly a lot of IFR and have never
heard a pilot say "Center, my FMC says I need to start descending now."
Somehow in real life they manage it.

I presume they don't say it in so many words, if they say it at all.

Small aircraft seem to be easier to get down towards the ground, or
perhaps they just don't have as far to go. In the Baron that I
prefer, there's no automation of descents, anyway. You can set the AP
to a new altitude and the aircraft will descend to it at your choice
of rates, but it's not fancy like a FMC (nor does it object if you
give it unreasonable objectives).

If you're having trouble descending fast enough in the Sim maybe you
just need to slow down the plane to give you more time.

It's hard to slow the plane down, too. With spoilers deployed on a
737-800, I can descend quickly or slow down quickly ... but not both.

Sure. But even if it's approved that doesn't mean you can just descend
at will to the airport. What you're likely to get is something like
"AB123, descending and maintain one two thousand expect lower in 20
miles."

That would still help me, I think.

In general what happens is you gradually get "stepped down" in altitude
via a series of descents as you get closer to the airport until the
final approach controller gets you down to whatever altitude is needed
to start your approach (usually something like 2000' AGL). Once you're
given each new altitude assignment the controller really wants you to
hurry down to the next altitude and level off there so you get out of
the way of other traffic. At times you'll even get requests like "AB123
I need best speed down to one five thousand, I have conflicting
traffic."

Yes, I've had that. Usually the FMC decides what's best, but at least
I can override that and force a descent at a higher rate (provided
that I can tolerate the airspeed increase).

To really get a feel of how this all works I'd suggest you go to one of
those live atc sites and listen to an approach controller. You'd be
amazed how much you can learn listening to one for a half hour. At first
it will seem chaotic and then you'll realize there are patterns to what
he's doing with the planes.

I have a really hard time just understanding what they are saying
sometimes. I don't know how pilots and controllers manage to
understand each other without making mistakes. Unfortunately, the
same problem exists with virtual flight networks like VATSIM (but for
different reasons).

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Paul Tomblin writes:

If that upsets you, then let me know so I can join the legion
of people who have you kill filed.

Nothing upsets me, but I'd prefer that you killfile me, just the same.

--
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Paul Tomblin writes:

I fly with a Garmin 296 handheld GPS. In my experience, nearly always
just around the same time it says I need to start my descent if I want to
descend at 500fpm to my destination, ATC clears me down to a lower
altitude without being asked.

I have noticed this as well. I suppose if they know the route well,
they know when the descent usually starts.

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Okay.. KLAX LOOP4.DAG.KEPEC1 KLAS at FL290? 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. Also as I am doing this objectively, anyone
else who would like to objectively chime in, please do so.

Look CLOSELY at those charts, and I mean closely. There are
some things you will need to adhere to that your FMS may or may not
know about that is not depicted totally in words.

CAVEAT. the charts I'll list are not to be used for real world
flight.

LOOP4: http://www.laartcc.org/charts/DP-LOOP.pdf

KEPEC1: http://www.laartcc.org/arrivals/STAR-KEPEC.pdf

KLAS ILS 25L: http://www.laartcc.org/charts/KLAS-I25L.pdf

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.

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.

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

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.

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

ATC should tell you something like the following:

"Cross MISEN at and maintain FL240".

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".

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

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.

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".

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.

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.

BL.
- - --
Brad Littlejohn | Email:
Unix Systems Administrator, |
Web + NewsMaster, BOFH.. Smeghead! | http://www.wizard.com/~tyketto
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On 2007-01-03, Mxsmanic wrote:
Pixel Dent writes:

I think I read this section before; this paragraph sounds familiar. I
always get instructions to "maintain," though. What's the phraseology
when I get a block of altitudes? Or does it even happen with
frequency in real life? How do I request it (or do I even need to
request it)?

From a flight today, west of Billings, MT:

N12345: Unable to maintain 16,000 for turbulence.
ATC: N12345 maintain between 14,000 and 16,000

or you can just request it directly:

N12345: Request block altitude between 15,000 and 17,000.
ATC: N12345 maintain block altitude between 15,000 and 17,000.

-Milen

In a previous article, Mxsmanic said:
Paul Tomblin writes:
I fly with a Garmin 296 handheld GPS. In my experience, nearly always
just around the same time it says I need to start my descent if I want to
descend at 500fpm to my destination, ATC clears me down to a lower
altitude without being asked.

I have noticed this as well. I suppose if they know the route well,
they know when the descent usually starts.

Except they know where to start my descent whether I'm flying a 100 knot
Archer or a 140 knot Lance, or on one occasion, a Piper Dakota with a 70
knot tail wind.

I suspect there is software they use to handle this.

--
Paul Tomblin http://blog.xcski.com/
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