When can you descend

[milflyboy]

Must be on a parallel or intercept heading after positive station passage.

Straight from AFMAN 11-217 Happened to notice you have military background

 

[profile]

The general principal is that the ICAO rules (published in PANS-OPS, etc) are the underlaying foundation. Member States (read "Countries" in the U.S. version of English) may publish their own rules, generally listed as exceptions. It could be construed from this that in the absence of any guidance to the contrary, we should follow the ICAO rules. That is indeed what many companies publish for their own operations.

A look a the TERPS will show you that the guidance should keep you inside the TERPs protected boundaries as well.

 

[profile]

Should add that I seem to recall an interp that said that under FAA "centerline" means just that. I would definitely NOT advocate just waiting for the needle to be alive. That might work alright in an ideal world, but factor in possible errors on the station plus your allowable instrument errors, and you're out of the protected airspace.

 

[100LL... Again!]

Possible, but not likely. The Terps criteria takes those errors into account.

 

[profile]

Better look again. TERPs doesn't account for many things, not only what I mentioned but also very limited as to the amount of wind consideration given for turns.

 

[100LL... Again!]

I read the TERPS. The whole thing.

 

[profile]

Then I don't have to explain it to you. Why don't you take this up with Wally Roberts, you can find him at www.avsig.com, where he's a regular poster?

 

[Donsa320]

RE; The relevant crash was in the 70's, an arrival to Dulles, I believe. 727 or -9. Eastern? Accident aircraft was cleared for approach while still a ways out. And was not yet 'established' on any published segment of the approach procedure. And terminology back then was simply "cleared for the approach". Descended into terrain.


It was a TWA 727 which had missed at DCA and was divertiing to IAD. In days long ago, in the 4 course range days, when you picked up an approach chart the initial altitude shown over the station was a safe alititude to fly when approaching the station on any airway using that facility. The TWA crew used that logic, as we all did in those days, to start a descent enroute to the depicted intersection shown as the first part of the NO PT VOR approach that they were cleared to fly. They hit Mt. Weather on the way. To the crews' credit, they were discussing whether they were doing it correctly when they hit.