|Quoting Tg 747-300 (Thread starter):|
I also understand that ATC can not assign you a MOCA if you're not within 22 nm of navaid.
ATC, as I understand it, doesn't really care about MOCAs except for in instances where they have no radar. Where there is radar coverage available, they have Minimum Vectoring Altitudes which are often lower than the MEA
or MOCA, since they only have to account for localized obstacles, and radar coverage, not obstacles or navaid coverage along a full section of airway. If you're under radar coverage, ATC can assign you altitudes as low as their MVA. That said, if I were in mountainous terrain, I'd feel a bit iffy about accepting such a clearance if it were a ways below the MOCA.
|Quoting spudsmac (Reply 4):|
What about when the MOCA is more than 22 miles from the navaid. What then? I don't know what to tell my students and none of the other instructors seem to be able to give me a good answer.
Then you're guaranteed terrain clearance but not navaid reception. This presents no problem when navigating by GPS (though there are such things as GPS MOCAs, which may be higher than the regular MOCAs - don't ask me about how that makes sense, because I haven't a clue), so you can file any altitude at or above the MOCA that observes the regular altitude rules for flight plans. However, there are a couple of things to consider:
1) If you happen to be using an RNAV system dependent on VORs for its position, I wouldn't trust the MOCA - fly at or above the MEA
2) I wouldn't fly an airway whose MEA
I could not climb to if needed, unless conditions were VMC along the way. If my GPS quits on me, I'm going to need to use the VORs again, and that means getting up to the MEA
. By happy coincidence, the places where the MEAs are going to be highest are around mountainous terrain, where you really want to be able to get guaranteed navaid reception if you need it so that you don't fly into something hard and unforgiving. If it's VMC, then no problem - just climb as best you can, hope the navaids work properly, and see and avoid terrain.
|Quoting jetpilot (Reply 5):|
In case of comm failure you fly the MOCA, MEA or last assinged whichever is higher.
Not quite correct. If you don't need the navigation coverage provided by the MEA
(if you have GPS, for instance), you can fly at the MOCA if that is higher than any altitude you were assigned or have been told to expect - you don't have to go all the way up to the MEA