QNE & QNH in mexico?

[Wankel7]

I was looking at the charts for Mexico and it says :

Approach charts:
QNE (Transition level) is FL195
QNH (Transition altitude) is 18500

Then on the airway chart:
QNE FL200 or above
QNH 18000 or below

So , which one do you use?

What do you use if you are at 19,000?

Thanks!

 

[Captain Oveur]

My guess would be QNH on the way up, QNE on the way down (until you reach
18500)

 

[TransMach]

Transition Level/Transition Altitude

I was looking at the charts for Mexico and it says :

Approach charts:
QNE (Transition level) is FL195
QNH (Transition altitude) is 18500

Then on the airway chart:
QNE FL200 or above
QNH 18000 or below

So , which one do you use?

What do you use if you are at 19,000?

Thanks!

This is simply not the place to attempt to learn/gain important information such as this. You should utilize the IAFM, ICAO Supplements or other regulatory documentation. No less.

"A fool who asks a fool a question should expect a fool's answer."

TransMach

 

[Loco Gringo]

Typically Mexico will not assign an altitude in the transition region. I have only once been leveled between the boundaries and only for a couple of minutes at that. I advised we were using QNH altimetry as we were descending and the response was affirmative . FL200 and 18,000' are typical for Mexico with some exceptions and variations in MMMX FIR and farther south. In your example If I was climbing and the leveled at 190 QNE. If I was descending and leveled at 19,000 QNH. Any doubts just ask and they will tell you what they want.

 

[Fernando]

yeah, youre not gonna fly level at 190

 

[fokkerjet]

yeah, youre not gonna fly level at 190

Except when you're cleared there. Flew between KELP and MMHO on a regular basis, and have been cleared to "190" frequently. TransMach has some good advice regarding this question.

 

[Daytonaflyer]

Most pilots don't know the correct way, so it doesn't really matter. I flew in and out of Mexico almost every week for 2 years and not one single pilot I met ever knew the proper way to set the altimeter. They all just set it at FL180 like in the USA.

It doesn't really matter how you set it because half the airplanes around you will have it set wrong and may or may not be at your altitude. Luckily we never leveled at those altitudes.

 

[twikysmalls]

TransMach or Daytona, can you guys please elaborate a bit on this?

I fly down there quite a bit and have never heard of this stuff. Where do you find the IAFM, or ICAO supplements?

Anything else you would consider very important info for Mexico ops?

Also, any troubles with Mexican ATC? Deviation reports and the like?

Thanks for your help.

 

[habubuaza]

I was looking at the charts for Mexico and it says :

Approach charts:
QNE (Transition level) is FL195
QNH (Transition altitude) is 18500

Then on the airway chart:
QNE FL200 or above
QNH 18000 or below

So , which one do you use?

What do you use if you are at 19,000?

Thanks!

It depends on which phase of flight you are in. Use the information from your terminal charts. In your example during climb out you would set your altimeter to 29.92 climbing through 18,500'. On descent you would have your altimeter set to the current local altimeter and you would be flying 19,000' QNH.

This is something you should include in departure briefings and arrival briefings. Don't pay attention to those who say it doesn't matter, transition flight levels and altitudes can vary significantly in different parts of the world and having the wrong setting can have serious consequences.