Stupid ILS question

[djrisc]

Is there a particular reason why ATC will tell you to cross a nav point at a particular altitude. Last night when flying the ILS in to John Wayne I was told to cross LEMON at or above 3000. This is pretty far above glide slope.

Then when I flew it a second time I was instructed to pass LEMON at or above 2500.

Out of curiosity, is ATC just instructing to try and keep you on glide slope, or are there other reasons as well?

Just curious,

Brett

[Keith Smith]

Brett, can you find the recording for this one? You shouldn't have received that instruction. Are you sure it wasn't to "maintain 3000 until established on the localizer?"

If it happened as you said, though, I'll look into it. That shouldn't have happened, and I haven't heard it happen on the network so far (not saying you're wrong, just saying it would be a very rare mistake, thankfully).

[djrisc]

I'm pretty sure I was already established on the localizer at that point. I can't seem to find any of the recordings from last night, was there an issue with recording last night as I did 2-3 flights last night and there is hardly anything shown as recorded for yesterday.

Brett

[djrisc]

There are also no recordings shown for today either.

Brett

[Keith Smith]

*sigh*. Thanks. I've kicked the recorders again. Having this stuff distributed in various places is painful sometimes. Unfortunately, we can't move the recorders to the new hosted infrastructure...the linux kernels don't have dummy soundcard support which is needed for the recording tech to work.

[djrisc]

I wouldn't put it past myself to have heard the call completely wrong though. I was flustered on that first flight as X-Plane was acting up and I had to recalibrate my controls after landing, so I did the flight a second time.

You can see it on the horizontal graph though:

Notice at 19:43 I level off just below 4,000ft:
http://peaware.pilotedge.net/flight.cfm?id=25236

Here is my second flight, notice that shelf is now missing:
http://peaware.pilotedge.net/flight.cfm?id=25255

[djrisc]

Keith,
Anyway to setup a cronjob to check if the recording process is running and if not kick it off again?

I have no idea obviously how it's setup, just thought I'd throw out a potential idea to save you time from having to check on it?

Brett

[Keith Smith]

Not that simple...the software is running. It's just lost it's connection to the server. That's what we need to check for. It's on the list. A very big list.

[Keith Smith]

Brett, we're going to ping the controller that worked the approach, I would be surprised if that was the instruction, as it wouldn't be legal. They're required to have you intercept the glideslope from below. Both of the instructions you mentioned would put you above the GS right at the precision final approach fix, as you suspect.

Given how frequently we vector for that approach, I suspect you may have misheard the assigned altitude on the vector for a crossing altitude, but we'll look into it for sure.

[djrisc]

Fair enough! It wouldn't surprise me in the least if it was my mistake.

In fact, if I was a betting man, I'd put all my money on the controller.

Brett