Hi IFC, when approaching MMMX today I contacted ATC and requested a visual approach for runway 5L. I was told “continue as filed, expect the ILS approach runway 5R”. I followed ATC’s instructions and set myself up for the ILS approach on runway 5R (left traffic). I ensured I was at an altitude of no greater than 3,000 feet agl, had the correct speed and all was well. When I selected APPR my aircraft started going crazy. It was not descending properly and was shaking side to side continuously. I thought that this was normal because the autopilot usually makes final adjustments before touchdown, though the aircraft did not at all descend towards the runway as expected. When it became clear that my aircraft was not going to land it self I executed a missed approach and attempted this a second time and the same thing happened. I then took actions into my own hands and landed the plane manually even though I had been cleared to land on the ILS. Is there a reason why my aircraft did not perform the approach as expected? I’m used to landing visually and almost never do so on the ILS. I’m also unsure as to why I was given this approach even though I had requested a visual. I’ve read on other topics that this could have been for sequencing, though I’m unsure what this means. If anyone could help me understand what went wrong that would be great!
For MMMX on 05R at the clearance points today, 3K would’ve been too high, since people were being cleared just above halfway down the localizer. So, to be below the glide slope and have APPR work, you should’ve been below 2K AGL. 3K would’ve put you above it, and caused APPR to brick.
Thanks for replying, just to clarify 3,000 feet/no greater is the correct altitude for the glide slope right? I believe I have heard this on one of Infinite Flight’s tutorials covering the ILS approach. Since my APPR didn’t work as expected would it be fair to say that since I was lined up with the runway at 3,000 agl in the “middle” of the glide slope that this caused it to not work properly? I’m guessing that I should have been at a lower altitude before inputting the APPR fucntion.
Well, it’s all position-relevant. If you were at the top of the localizer, 3K would’ve been spot-on. But since you were intercepted and cleared further down the localizer than usual, you have to at be 2K or below (for today). A standard rule of thumb for a 3 degree glide slope is to be at no more than 3K 10nm out, and be no more than 1.5K 5nm out. Plug and play for the altitudes in between.
Thanks for letting me know, this helps a lot. I don’t usually land using the APPR so I’m not as experienced with it. I’ll play around with it in solo mode so that I can have a better judgment of the appropriate altitudes for each section of the glide slope. Also, would you be able to explain what sequencing is to me? I’ve heard that ATC will assign an ILS approach to aircraft in a scenario such as this.
PM me, and we can discuss sequencing there!
You can also quite happily tune in and fly the ILS by hand using the localiser and glide path to guide you. It’s a precision approach, not necessarily an automated one.
Hello @Ben_McCarthy, If you have not figured it out already I may be able to help you
- I think you were not descending properly because you may not have been on the glide-slope.
- I think you plane was rocking back and forth because it was over correcting trying to get onto the localizer (The plane would be turning too fast trying to get onto the localizer). This has happened to me while flying a MD-11F. I waited it out but ready to take over but it corrected its self.
If you need any more help or have any questions feel free to PM me!
Hey! It’s all related to your position within the “ILS cone.” For the ideal altitude that you should be at, I’d suggest taking a look at the instrument approach chart for MMMX.
Scroll down to the ILS 5R and check out the altitudes, headings etc., hope it helps!
shouldn’t the ATC assign you an LOC intercept altitude? how are pilots supposed to quickly determine the necessary height if he/she does not know DME from the runway threshold. What if we are instructed to turn base unexpectedly?
We do assign you the intercept altitude, so that you’re below the glideslope from intercept until you’re fully established. At MMMX, 2K would’ve been the altitude to guarantee that. We will have done all the calculating before we even open.
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