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Originally Posted by tgrayson  You won't find one, unless something has changed in the last few years. The FAA has never defined "established" in any meaningful way. The 1/2 scale deflection is ICAO, I believe. Wouldn't surprise me to see the FAA adopt that definition some day.
The needle "coming alive" is fine for a localizer....you won't be hitting anything with an active needle. However, on a VOR approach with the maximum allowed FAC length, 30 nm, a 1/2 needle deflection would put you outside the protected area (according to some calculations I've seen).
The most conservative point of view for a VOR or NDB is you're established when the needle is centered. |
AC120-91 Airport Obstacle Analysis suggests course guidance for LOC/VOR/NDB/ARC navigation. The limits povided are basically the 5/5/1/2 degree parameters. They are basically provided for Part 121/135 operators and are not mandatory and are used in the contexts of departure navigation tracks. The AC does make comment that if the air carrier adopts them...they become mandatory.
I'm betting...that those parameters are spelled out in some FAA internal document and have been applied as binding to my company's approach procedures...or stated in the full ops specs (I only get the Reader's Digest condensed version of the legal ops specs...written in plain language as procedures).