Minimum Off Route Altitude - Wikipedia, the free encyclopedia
well look here is the wikipedia on it.
and I learned something, you were talking about the route MORA and not the GRID MORA
if for some reason you don' see the link, google, MORA aviation
remember too that victor/VOR based airways have meas for the normal 4 nm/5sm from route centerline and route MORA are as described above, wider.
we have new methods of navigation in common practice now compared to the time the org altitudes were created.
So, in action to your question a ROUTE mora is 10 miles each side of an airway, GRID mora is for the whole box. Why? well, if you offset your route a little bit you can know a safe altitude. USING the whole box/GRID MORA might turn your safe altitude of 5000' to 17000' in certain parts of California for example
as for the other questions, MEA is dependent upon Navaid reception. Navaid is primarily VOR, but you could fly an airway with methods other than VOR and they are common now (gps for example), so MEA may be higher than an airway MORA in order to get LINE OF SIGHT ON VOR for nav.
At some point in your career you may want to be at the LOWEST possible SAFE altitude based on your plane's nav capability, so the lowest altitude might be lower than the MEA for obstacle clearance because your new nav doesn't have the same limitations as the VOR.
MOCA is obstacle clearance within 22nm of the VOR by definition, so you only see it with VORs. I will say it is possible for some airways to be predicated on NDB, but that is very rare now a days and then.
VORs were state of the art when original definitions were created.