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

In article ,
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)?

In general (i.e. I'm sure someone will come up with an exception), you
won't get things like cruise clearances, VFR on Top Clearances, or block
altitudes unless you specifically ask for them. 99% of the time ATC
gives you an altitude and expects you to stay there until they tell you
otherwise.

That doesn't mean you can't ask for a descent when your FMS tells you it
wants to start down, but there are a number of reasons you may not get
it. There may be conflicting traffic below you or the controlling
authority for the area you are in may have letters of agreement with the
surrounding areas that specify what altitude flights heading in various
directions or to various destinations must be at. In addition sometimes
the controller you're talking to doesn't control the altitude you want
to head down to. For a given ground position there may be three
different controllers handling different altitude blocks and your guy
may not have time to coordinate or even be allowed to descend flights
into the area below you.

Pixel Dent writes:

That doesn't mean you can't ask for a descent when your FMS tells you it
wants to start down, but there are a number of reasons you may not get
it. There may be conflicting traffic below you or the controlling
authority for the area you are in may have letters of agreement with the
surrounding areas that specify what altitude flights heading in various
directions or to various destinations must be at. In addition sometimes
the controller you're talking to doesn't control the altitude you want
to head down to. For a given ground position there may be three
different controllers handling different altitude blocks and your guy
may not have time to coordinate or even be allowed to descend flights
into the area below you.

OK. But this is a bit worrisome in that the FMC apparently already
calculates the optimal descent. If I can't start down in time, I may
not be able to make the other altitudes in the route without holding
or some other diversion to provide more time to descend. For some
reason, the FMC seems to be optimistic about how quickly it can force
the aircraft down. I have to deploy spoilers a lot, and that's even
when the descent starts on time.

Anyway, so I can just say "request descent" when I'm ready to start
down?

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In article ,
Mxsmanic wrote:

OK. But this is a bit worrisome in that the FMC apparently already
calculates the optimal descent. If I can't start down in time, I may
not be able to make the other altitudes in the route without holding
or some other diversion to provide more time to descend. For some
reason, the FMC seems to be optimistic about how quickly it can force
the aircraft down. I have to deploy spoilers a lot, and that's even
when the descent starts on time.


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.

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.

Anyway, so I can just say "request descent" when I'm ready to start
down?

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."

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."

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.

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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In article ,
Mxsmanic wrote:

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).

Well, once again I don't know much about airliners, but in smaller
planes at least you don't generally increase airspeed to descend you
reduce power. At least in the area of the country I fly ATC often has
speed restrictions on the airliners so they couldn't increase speed
during a descent if they wanted to. It's good practice to hold your
airspeed steady while reducing power to make your descent.


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.

Practice, practice, practice. Everyone has a hard time understanding at
first but the more you listen the more it makes sense.

Pixel Dent writes:

Well, once again I don't know much about airliners, but in smaller
planes at least you don't generally increase airspeed to descend you
reduce power.

The FMC does this through the autothrottle. At least the one I use
lets you choose between a descent path (altitudes respected, ignoring
speed constraints if necessary) and a speed path (speeds respected,
even if altitudes must be ignored), with the former being the default.
At least that's what I understand of it thus far.

Anyway, the FMC normally controls lateral and vertical navigation and
the throttle, and optimizes all in order to attain its preprogrammed
path, altitude, and speed.

At least in the area of the country I fly ATC often has
speed restrictions on the airliners so they couldn't increase speed
during a descent if they wanted to. It's good practice to hold your
airspeed steady while reducing power to make your descent.

The FMC tries to do this, although altitude and course are normally
the priorities. It does a good job in most cases.

In the world of simulation, we rarely have heavy traffic, so I only
occasionally get speed restrictions. They are not too hard to
respect, usually--just setting a different speed in the FMC is often
sufficient.

Practice, practice, practice. Everyone has a hard time understanding at
first but the more you listen the more it makes sense.

Probably, but it seems so easy to misunderstand that I should think it
would be very mistake prone. I read back almost every instruction I
get to ATC just to make sure that I've understood it.

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Mxsmanic wrote:
Anyway, the FMC normally controls lateral and vertical navigation and
the throttle, and optimizes all in order to attain its preprogrammed
path, altitude, and speed.

Is the FMC flying or are you? I'm not an airline pilot, so I'll go
ahead and ask the question (please real world answers only) is the FMC
the boss or is the pilot? If the FMC says optimal is such and such,
but ATC says do this, doesn't the airline pilot do what ATC says? I
always assumed that a FMS in a modern airliner was just a souped up
version of my Garmin 430. I.e. it has a plan, but what I get is ALWAYS
different. Even when I try to "guess" ahead of time.

In the world of simulation, we rarely have heavy traffic, so I only
occasionally get speed restrictions. They are not too hard to
respect, usually--just setting a different speed in the FMC is often
sufficient.

Yet another difference between your simulated world and the real world,
huh? Does the lack of heavy traffic make you a better simulated pilot?

Probably, but it seems so easy to misunderstand that I should think it
would be very mistake prone. I read back almost every instruction I
get to ATC just to make sure that I've understood it.

Two words, "Say again"

If you want to get a glimpse into real world ATC, take a look at Don
Brown's columns at Avweb
(http://www.avweb.com/news/sayagain/193881-1.html)

Pixel Dent writes:


Well, once again I don't know much about airliners, but in smaller
planes at least you don't generally increase airspeed to descend you
reduce power.

Not me. The descent is where I get back the speed I invested in the
climb. If turbulence allows I set up a 500 fpm descent, without
touching the power which is almost always max for cruise. I generally
then get 190 MPH indicated in the descent, which is the bottom of the
yellow arc.

Mxsmanic wrote:
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).

If you were in "real" IMC it's even worse (at least until you develop
some practice and learn to keep the picture in your head). Always
seems like ATC is telling you to do something just as you are in the
middle of something else.

Brian

bdl writes:

If you were in "real" IMC it's even worse (at least until you develop
some practice and learn to keep the picture in your head). Always
seems like ATC is telling you to do something just as you are in the
middle of something else.

I've already had that experience in simulation.

On VATSIM, you can communicate by voice or by text. I usually
communicate by text, simply because the sound quality is often so bad
for some controllers that I cannot make out what they are saying.
However, it is true that text is woefully unrealistic, and it also
makes it difficult or impossible to communicate during the most
critical phases of the flight, as one simply doesn't have time to type
(even fast typists like me).

When I listen to real ATC on liveatc.net, it sounds just as bad. The
quality problems aren't the same, but their magnitude is. I'm
surprised more aircraft aren't running into each other. I can only
hope that the audio quality is much better aboard the actual aircraft,
but I doubt it.

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