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

In article ,
Mxsmanic wrote:

If the FMC has a programmed descent in its
route, do I let the FMC start the descent where it sees fit, or do I
force the aircraft to maintain FL290 until ATC explicitly clears me
for my own navigation or for a lower altitude?

It seems what you really want is to read the rules about clearances in
the AIM. The section on the altitude portion of a clearance is 4.4.3.d
and can be found at

http://www.faa.gov/atpubs/AIM/Chap4/aim0404.html


d. Altitude Data.

1. The altitude or flight level instructions in an ATC clearance
normally require that a pilot "MAINTAIN" the altitude or flight level at
which the flight will operate when in controlled airspace. Altitude or
flight level changes while en route should be requested prior to the
time the change is desired.

2. When possible, if the altitude assigned is different from the
altitude requested by the pilot, ATC will inform the pilot when to
expect climb or descent clearance or to request altitude change from
another facility. If this has not been received prior to crossing the
boundary of the ATC facility's area and assignment at a different
altitude is still desired, the pilot should reinitiate the request with
the next facility.

3. The term "cruise" may be used instead of "MAINTAIN" to assign a block
of airspace to a pilot from the minimum IFR altitude up to and including
the altitude specified in the cruise clearance. The pilot may level off
at any intermediate altitude within this block of airspace.
Climb/descent within the block is to be made at the discretion of the
pilot. However, once the pilot starts descent and verbally reports
leaving an altitude in the block, the pilot may not return to that
altitude without additional ATC clearance.