The MCC course is a requirement today before a pilot does his first type rating on a Multi Pilot Aeroplane (MPA). It is found in JAR FCL (NOT JAR OPS!), because it has only to do with your license.
If you know you will never fly an aeroplane requiring two pilots, you don't need the MCC course (unless you do an integrated course, where it is required in any case).
As to whether it is relevant or not ? For the time and the money spent, I could use it in a better way, but to pilots going from a small piston straight to a big jet, it would be probably be an advantage. But you really don't need the fancy full flight sim - it is mainly for the "real time" aspect of the training.
If you are doing an integrated course, you have to do an MCC:
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Appendix 1 to JAR-FCL 1.160 & l.l65(a)(l)
ATP(A) integrated course
...
8 The course shall comprise:
(a)
(b)
(c)
theoretical knowledge instruction to the ATPL(A) knowledge level;
visual and instrument flying training; and
training in multi-crew co-operation for the operation of multi-pilot aeroplanes.
(The last part is the MCC course or equivalent)
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Appendix 1 to JAR-FCL 1.160 8 1.165(a)(4)
CPL(A) modular course
-- 2 Before commencing a CPL(A) modular course an applicant shall:
(a)
(b)
(c)
skill test.
be the holder of a PPL(A) issued in accordance with ICAO Annex 1;
have completed 150 hours flight time as a pilot; and
have complied with JAR-FCL 1.225 and 1.240 if a multi-engine aeroplane is to be used on the skill test
("Multi-engine" should not be confused with "Multi-crew")
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JAR-FCL 1.240 Type and class ratings -
Requirements
(See Appendices 1 to 3 to
(1) An applicant for a type rating for
JAR-FCL 1.240)
(a) General
a multi-pilot type of aeroplane shall comply
with the requirements for type ratings set out
in JAR-FCL 1.250, 1.261 and 1.262;
JAR-FCL 1.250 Type rating, multi-pilot -
Conditions
(See AMC FCL 1.261 (d))
(See IEM FCL 1.261(d))
(a) Pre-requisite conditions for training:
[An applicant for the first type rating for a multi-]
pilot aeroplane type shall:
(1) have at least 100 hours as pilot-in-
command of aeroplanes;
(2) have a valid multi-engine
[instrument rating (A);]
(3) hold a certificate of satisfactory
completion of multi-crew co-operation
(MCC). If the MCC course is to be added to
the type rating course (see JAR-FCL 1.261
and 1.262 and AMC FCL 1.261(d) and IEM
FCL 1.261(d)), this requirement is not
applicable; and ...
[more requirements !]