Reading DP/Sid

[tightmf]

Hi,

In one of the altitude constraint callouts in a departure plate I,m looking at it says 10000 or below (ATC).
What does the "(ATC)" mean?

Thanks

[StuSEL]

What plate are you looking at?

[tightmf]

BOACH4 from KLAS

[StuSEL]

On page two of that procedure, when it talks about altitude restrictions, the altitude which (ATC) is next to indicates "When ATC assigned." So, if ATC does not assign that altitude, then you maintain the altitude to the right of the slash. I can't find a reference in any of the AeroNav manuals, unfortunately, so someone with more knowledge would have to confirm that.

[tightmf]

Left of the slash, 7900 in this case is the minimum for that fix.  What I'm wondering is whether departure control assigns altitudes above 10000 early in the DP as a regular thing and the chart is accommodating that.

[tyketto]

Left of the slash, 7900 in this case is the minimum for that fix.  What I'm wondering is whether departure control assigns altitudes above 10000 early in the DP as a regular thing and the chart is accommodating that.

Normally, they would not, because if they assigned altitude restrictions there, they would effectively cancel all altitude restrictions on the SID. So unless they explicitly instructed to "climb and maintain FL190, comply with the altitude restrictions", the aircraft would be stuck at the altitude given throughout the lateral part of the SID.

Going off of page 2, pilots are given the initial altitude of FL190, so unless there is some compelling reason for ATC to assign an altitude (read: converging traffic, terrain, etc.), they won't give it.

BL.

[sykocus]

Here's some extra information from the AIM
5-2-8 e,5

5. ATC crossing altitude restrictions published
on SIDs are identified on the chart with “(ATC)” following
the minimum altitude restriction. This will
indicate to the pilot and the controller that this
restriction is for ATC purposes and may be deleted by
ATC. When an ATC crossing altitude has been
established prior to the beginning of a transition
route, a minimum altitude for obstruction clearance
or other design constraints will also be published at
the same fix adjacent/below the “(ATC)” altitude.
The absence of “(ATC)” at a “minimum altitude”
indicates the restriction is there to support obstacle
clearance, airspace restrictions, Navaid reception,
and/or other reason(s) that mandate compliance.
These altitudes CANNOT be lowered or cancelled by
ATC. A standalone “(ATC)” altitude restriction may
also be located on a transition route; however, it must
never be lower than the published Minimum Enroute
Altitude (MEA).