Arrivals Assigned

@tegoid

Team

I thought it time I put forward my "observations" as to how & when one can "predict" the destination descent clearance Vox will issue.

But firstly, remember these "observations" are about IFR flight in jets & turboprops in Class A airspace. They  are also about the precedents of whether it is a "cleared via" or "descend via" arrival (STAR) irrespective of the type of approach (vectored or "full") that follows.

In the first instance, an arrival clearance will only be issued if one's flightplan "ends" at a fix on an included airac procedure, normal the start of the STAR or a transition to it.

At the moment, this assignment is generally correct for the "current" destination weather if one's is closer than 60nm direct to that destination. 

Vox will then only assign a "descend via" arrival (essentially an RNAV as distinct from a legacy procedure) if its last fix has an "at" altitude restraint & only consist of an arrival route portion (ie does not have a transition portion).

It will also depend on where Vox calculates one's TOD which is set against the "DescentRatio" parameter in its VASettings.xml file. A steep ratio (1.0) will stop Vox requiring one's descent begin before one reaches the start of the arrival & allow one to descend when ready / needed to follow VNAV profile of the procedure.

In broad terms then, "descend via" arrivals are less likely to be assigned because of these above precedents.

"Cleared via" arrivals where Vox additionally issues descent step instruction (as per one's request to descend or Vox's calculation of the TOD) as well as the route should thus be the expected the higher & the juristiction you "fly". As best I can summise, it is only with STAR's such as the SERFR arrival at
KSFO from  FL320 or below can a "descend via" be expected.

A footnote to add is that occasionally if you have a steep descent parameter set, Vox will assign a "descend via" to a RNAV STAR with / at a transition yet still subsequently issue descent steps effectively limiting one's ability to follow VNAV profile of the procedure. Thus one needs to then consider for example the HAWKZ STAR at KSEA a "cleared via" procedure.

Trust you are not too confused by this above. If you have different "observations" or comments, I would like to hear of such.