MOCA, LSALT and MSA all have one thing in common. They all provide a minimum level of obstacle clearance of AT LEAST 1,000 FT. Well, in this half of the planet anyway. MORA also provides a minimum amount of obstacle clearance but also
GUARANTEES navaid reception.
MORA hasn't been implemented in this dark, dank part of the southern hemisphere because, with obstacles up to 13,000 feet quite close to all our major aerodromes, navaid reception can be problematic at the standard range of 60 NM for a VHF navaid such as VOR. Thus, we depend heavily on LSALT (aka MOCA) and MSA in the
normal course of operations. I'm aware that some countries refer to LSALT/MOCA and MSA as emergency altitudes but, for the most part, those countries can afford to be generous because they don't have the obstacle problems (and therefore the navaid range limitations) that we have to contend with.
Just thought I'd throw that in for the benefit of me mate
keithl, as a non-UK perspective.
