View Full Version : MORA and GRID MORA

blue sky 1
14th Sep 2022, 17:59

what is the difference between MORA and GRID MORA , and how I can distinguish between MORA and GRID mora in Jeppesen chart.


15th Sep 2022, 05:49
Minimum Off-Route Altitude is an altitude derived by Jeppesen. The MORA provides clearance from known obstructions within 10nm of the route centreline including a 10nm radius at the ends of the route segment. The MORA is shown close to the route identification in magenta, followed by an 'a'; e.g. 2600a in magenta means a MORA of 2600ft.

This is an altitude derived by Jeppesen or provided by State authorities. It provides clearance from terrain and man-made structures within the section outlined by latitude and longitude lines. Values 10,000ft or higher are depicted in maroon, whereas values below 10,000ft are green. Values are in hundreds of feet; e.g. 77 in green means a Grid MORA of 7,700ft, and 126 in maroon means a Grid MORA of 12,600ft.

Grid MORA values derived by Jeppesen clear all terrain and man-made structures by 1000ft if the highest elevations are 5000ft amsl or lower. The clearance increases to 2000ft where the highest elevations are 5001ft or higher.

Grid MORA values provided by State authorities provide 1000ft clearance in non-mountainous areas and 2000ft clearance in mountainous areas.

So, to answer your two questions:
The difference between MORA and GRID MORA is that MORA is only used within 10nm of a defined route, whereas GRID MORA can be used anywhere within the latitude and longitude lines (the grid) in which the GRID MORA appears.

To distinguish between them, the MORA is written in magenta right by the route to which it applies, in feet, followed by an 'a'.
The GRID MORA is written in green or maroon and appears near the centre of the grid in hundreds of feet.