Waypoints are not Fixes

[Calvin Waterbury]

In a discussion with a real world ATC student-in-training I was surprised to discover the "waypoints" and "fixes" are not the same thing. Here is what I came away from the conversation with...

• "Fixes" are the "Intersections" of the radials of two VORs.There geographic locations are defined by lat/lon descriptions printed on SIDs and STARs.
• "Waypoints" are defined locations from surface to infinity which can only be located on FMCs or GPSs. I never received a solid answer if they were defined by VOR intersections too.

I've been at simming since '96 and always used "fix," "waypoint," and "intersection" interchangeably. I never even heard of the distinction until yesterday, so I am posting to help any other simpilots.

[Keith Smith]

Fixes are a subset of waypoints. Fixes are located at the intersection of ground-based navaids and are flight checked based on the published MEA's and MRA's (minimum enroute altitudes and minimum reception altitudes). Waypoints have no such restriction and can simply be a point in space with no reference to ground based navaids.

[Calvin Waterbury]

Fixes are a subset of waypoints. Fixes are located at the intersection of ground-based navaids and are flight checked based on the published MEA's and MRA's (minimum enroute altitudes and minimum reception altitudes). Waypoints have no such restriction and can simply be a point in space with no reference to ground based navaids.

Thanks for clarifying.

[Keith Smith]

Practical demo:
http://airnav.com/airspace/fix/YOCUL (this is a waypoint on the RNAV Y 13L approach into PSP)

now check out CLARR from the beloved arrival of the same name into Las Vegas:
http://airnav.com/airspace/fix/CLARR

Note the considerable difference in the data that defines them. I know you already had the idea Calvin, but I am guessing that many people aren't aware of the FIXES menu option (interesting naming, in light of this!) in airnav and wanted to demo that, too.

[Alex Stjepanovic]

Outside the mundane definitions that might exist, I've always separated those "things", into three different groups: Fixes, intersections and waypoints.

Fixes are simply that, something that's somewhere "geographically", and is literally fixed. You can or could, but needn't necessarily need or be able to use navaids to get to them.
Intersections are effectively same as fixes, but as the name suggests, they are actual intersections of navaid bearings, radials, etc, analogous to road/rail/etc intersections.
Waypoints are points along your way, that can be anything.

Since the actual contents of the US AIP aren't all that accessible, it's hard to say, but each country generally has a section in the ENR portion, that lists all the "significant fixes". It's logical enough since they are the lowest level.

That's my take on it.


Slight EDIT:

(interesting naming, in light of this!)

I'd say it's perfect, as "fixes" would be at the lowest level, acting as a superset of intersections and waypoints

[Mark Hargrove]

Using the student controller-in-training's definitions, what would he or she call HUNDA (a named-thing-which-we-can't-call-an-intersection according to the student's definitions) that appears on the KLAX ILS RWY 25L approach?

-M.

[Alex Stjepanovic]

I'd call them all three

1. It's a fix, since it's there

2. It's a vague form of an intersection, where the localizer and the 12.8DME meet. Not ideal, but if you have DME, then you could treat it as such, if you wanted.

3. It's also a waypoint, albeit not a very interesting one, as you are flying in a straight line for 46.5nm, merely stepping down, and could do just as good a job of noting that you are over the fix(hahahahhahahahah), when I-LAX 12.8DME comes up.

My 2% of 1$!

[Ryan B]

I know I'm wrong but I interchange them all the time... in real life and on PE.... don't hate me!