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Alt setting for Grid MORA

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Alt setting for Grid MORA

Old 19th Jul 2013, 11:57
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Alt setting for Grid MORA

Hello guys,

Couldn't find appropriate forum to ask this question, so i chose this one. I hope nobody will harm with such topic.

So, while a friend of my was interviewing in the airline for a job, a pilot has asked him this question: ok, imagine you're on emergency descend and you have a jeppesen enroute chart with grid mora, what altimeter setting will you put to your altimeter below transition level. Well, he said i would find nearest airport and listen to their atis. Ok, you have no airports, youre over ocean or desert. What is your intentions then?

We still could not find the right answer.

We though that maybe still maintain QNE, but still it wont guarantee safety.

What is your suggestions?

Thank you!
levashov is offline  
Old 19th Jul 2013, 14:57
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Old 19th Jul 2013, 15:48
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The correct altimeter setting to use with MORA/MEA etc would be area QNH from ATC. If you couldn't contact ATC, the QNH of a nearby airport would be close, but you may want to adjust your altitude upward until you are certain of your position relative to the terrain.
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Old 19th Jul 2013, 15:50
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The thing about an emergency descent is that you have to descent to 10.000ft ASAP, terrain permitting. Coming from a flight level you have to make corrections for nonstandard atmospheric conditions, hence the requirement for a local altimeter setting and a temperature.

Your friends answer for finding the nearest airport's QNH is correct, this should be done however before you fly over an area that you are about to cross, not during the possible emergency descent.

The question, what if there no airports because for example deserts or ocean.....
I doubt you will find any oceans where the obstacles will reach above mean sea level!!!! Not too many deserts above 10.000 ft too!!! There are a few mind you, but they do have airports where you can get the altimeter setting ( gobi desert for one).
Some countries publish regional altimeter settings though. So if you find yourself over a country with a large desert above 10.000 ft check the manuals you are provided to obtain the regional altimeter setting.

Personally, I think, that is a far stretched question!

Edit, I think, if your company regularly flies over areas with high terrain they will have to provide you with procedures to comply with regulations!!

Last edited by flyburg; 19th Jul 2013 at 16:11.
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Old 19th Jul 2013, 17:13
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If you really don't have time or means of getting local QNH, just add 1000 feet to Grid MORA and continue on QNE. It is easy to do in emergency rush and will save you from terrain in 99% of weather depressions, let alone normal weather.
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Old 20th Jul 2013, 01:20
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If your over the ocean, your grid MORA would be 0...
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Old 20th Jul 2013, 07:01
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What about your minimum terrain clearance, included in the grid mora then?
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Old 20th Jul 2013, 10:45
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Try reading the definition.
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Old 20th Jul 2013, 11:06
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[QUOTE]If your over the ocean, your grid MORA would be 0...

It would be 1.0 actually....
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Old 20th Jul 2013, 16:07
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In the good old days of a proper met brief from a proper met man, we were given a "Route Lowest Forecast QNH" which had its uses.

Still, it's no good looking backwards.
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Old 21st Jul 2013, 11:45
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1000 plus any cold temp correction
Sonny Hammond is offline  
Old 21st Jul 2013, 22:12
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So little knowledge about flying on a pressure altitude over high terrain?

In stead of finding the local QNH when you are in the middle of an emergency descent, plan ahaid and before crossing high terrain correct the pressure altitude for non standard pressure and temperature.

For every Hpa QNH < QNE ad 30' to the MORA/MEA
For every degree Tactual > Tisa ad 40' to the MORA/MEA per every 1000' altitude.

If the temperature or QNH is higher than ISA, no neef to correct becease the altimeter set to QNE will read to low, so you are on the safe side.

Anticipation is the key. When I overfly the alps, I know to what pressure altitude to descent in case of an emergency because I have planned ahead and corrected the true altitude.

Only takes 2 min, but saves a lot of stress in the middle of an emergency descent. It also improves our situational awareness because to pro-actively plan an escape altitude and route before entering high terrain.
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Old 22nd Jul 2013, 01:46
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Old 22nd Jul 2013, 12:23
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"So little knowledge about flying on a pressure altitude over high terrain?"

Please explain how my answer in post 3 is different from yours then?


That's a nice explanation of the history of grid mora's etc, but it doesn't really answer the OP question.

Once again, a far stretched question. There are not too many places where you can not get a local altimeter setting from an airport before and after crossing the high terrain, flying a four engined airplane I'm not too familiar with ETOPS, but worst case I think there should be an airport within 180 minutes at the least!!, get a couple of those and you should have an idea!!

Flying the HAMI route regularly, we get the alt from Urumqi and Hohhot and take the worst alt and lowest temp and calculate the worst correction from those and apply those to the enroute alt or mora in case of turn around BEFORE(pander) crossing the area.

Question asked and answer given!
flyburg is offline  
Old 22nd Jul 2013, 22:49
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The OP doesn't say anything about ATC, so just ask to the one you're in contact with. Or Volmet.
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