MSA, MEA, MOCA, MORA, MVA. What are they?

Today we are going to have a look at altitudes that will come in handy when flying, planning IFR flights and interviews (these can be asked quite a bit)
So lets jump straight into it.

MSA (Minimum Sector Altitude)

MSA is the minimum safe altitude within a 25 nm (Nautical Mile) radius of a navigational aid. MSA will give you 1000 ft separation from the highest terrain within that sector. We normally see the MSA on our Approach plates for runways.
Can we descend below MSA? Yes, provided we are under radar control and we still remain above the radar altitudes. (Remember it is still your responsibility to make sure you don’t fly into terrain!)

MSA

MEA (Minimum En-Rout Altitude)

MEA is the minimum altitude that will guarantee signal of navigation aids along the route, give you two way communication with ATC and provide obstacle clearance. MEA will give you 1000 ft separation from terrain in non mountainous areas and 2000 ft separation in mountainous areas. (Mountainous area is when a terrain change of more than 3000 ft is experienced within 10 nm)

MEA Non-Mountainous
Mountainous

MOCA (Minimum Obstacle Clearance Altitude)

MOCA will give you a minimum altitude above terrain and guarantee VOR reception within 22 nm from the beacon. MOCA will give you 1000 ft separation from terrain when terrain is less than 5001 ft and 2000 ft separation when terrain is more than 5000 ft.

MOCA

MORA (Minimum Off-Route Altitude)

MORA will give you separation from terrain up to 10 nm off the route center line and 10 nm radius around the ends of the route. MORA will give you 1000 ft separation from terrain in non mountainous areas and 2000 ft separation in mountainous areas.

MORA

GRID MORA (Grid Minimum Off-Route Altitude)

GRID MORA gives you terrain separation within latitude and longitude lines. GRID MORA will give you 1000 ft separation from terrain when terrain is less than 5001 ft and 2000 ft separation when terrain is more than 5000 ft.

MVA (Minimum Vector Altitudes)

MVA gives you terrain separation when Vectored by ATC, remember you have to be under radar control to be able to go down to these altitudes. (often lower than the MSA) MVA will give you 1000 ft separation from terrain in non mountainous areas and 2000 ft separation in mountainous areas.

I hope these brief explanations help for interviews and make you a more knowledgeable pilot. Please comment if you have a different understanding of the above or if you would like to see any other topics.

If you would like to read more on the subject have a look at Intro to Jepp Navigation Charts

 

7 Comments on “MSA, MEA, MOCA, MORA, MVA. What are they?”

  1. Hi, great explanation but what about AMA (Area minimum altitude), could you elaborate on this a little bit, please? Thanks in advance.

    1. Hi Miguel,

      The AMA is the lowest off-airway altitude that can be flown under IMC that will provide a minimum vertical clearance of 1,000 feet (AGL), or in designated mountainous terrain 2,000 feet above all obstacles located in the area specified, rounded up to the nearest 100 foot increment.

      Remember to always check your local laws though, they may differ.

      Here is a quick link as well

      https://ext.eurocontrol.int/lexicon/index.php/Area_Minimum_Altitude#Definition_Source

Leave a Reply

Your email address will not be published.