For aircraft in the SEPL class the concept of a co-pilot does not exist,
Incorrect.
JAR–FCL 1.080 Recording of flight time
(2) Co-pilot flight time
The holder of a pilot licence occupying a
pilot seat as co-pilot may log all flight time as
co-pilot flight time on an aeroplane on which
more than one pilot is required under the type
certification of the aeroplane, or the
regulations under which the flight is
conducted.
The type of aircraft has nothing to do with having a co-pilot. An aircraft certified for 2 crew requires a co-pilot - there is no option.
When a pilot wants to simulate instrument flight (fly under the hood) and they are not under instruction then the regulations require another pilot - in the english language termed a co-pilot.
Have a senneca with no autopilot and want to use an RVR of less than 800m when flying an ILS - two pilots are required unless certain other requirements are met, want to fly commercially at night and again two pilots required unless certain other requirements are met.
There are a host of reasons why aircraft certified for single pilot operations are required to have two pilots. When two pilots are required one has the PIC and their co-pilot. The roles are clear as is how the flight can be logged.
Why make something simple difficult?
If I want, I can operate a C172 with 4 crew members - PIC, co-pilot, navigator and radio operator. They can all record having performed their respective roles.
The important thing is to have exactly how such things are done clearly defined. i.e. who can be PIC, who can confirm the capabilities of prospective PIC's.
There are hundreds of aircraft flying round every day carrying hundreds of passengers on which training and checking is completed with no instructors on board. In the airlines they are called line training captains but they very often hold no instructor qualifications on their licence and simply instruct / check on the basis of operator approval - similar to being named by the group as the person who can do checkouts.
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Chuck,
The term "complex" came from your side of the pond!! 