From LASORS:
Differences Training requires both theoretical
knowledge instruction and training on an aeroplane or
appropriate training device.
Familiarisation Training merely requires the acquisition
of additional knowledge, relevant to the new type or
variant. This may be achieved with the assistance of an
instructor, another pilot experienced on type, or by
self-study. Familiarisation Training is only sufficient
where Differences Training is not required.
It should be noted that when changing to different
types, or variants of types, that fall within the single-pilot
single-engine piston (SEP) class rating, the Differences
Training is specifically required to encompass
particular ‘complex’ features with which the new type or
variant may be equipped.
These features are:-
Variable Pitch (VP) Propellers
Retractable Undercarriage
Turbo/Super-charged Engines
Cabin Pressurisation
Tail-Wheel
However, these same features are also required to be
the subject of Differences Training, when changing
between types or variants that fall within the
multi-engine piston (MEP) class rating or when
qualifying for new variants within the same single-pilot
type rating.
and
Many pilots with a MEP class or type rating may only
have had experience on SEP aeroplanes with Fixed
pitch propellers. Where a Constant Speed Unit (CSU)
is fitted to a ‘single’, some of the MEP training will be of
value, but comparison should be made of the effect of
the propeller, on performance and handling between
types and variants within the SEP class.
The handling of a non-feathering VP propeller, on a
SEP aeroplane, during an emergency, may also be
quite different from the technique used in a single pilot
ME aeroplane. For example, not all VP propellers in
SEP aeroplanes have counterweights in the hub, so the
failsafe propeller pitch may be either fine or course, and
the effect on glide performance, may vary considerably
from type to type.
Where Differences Training on a particular feature has
been completed within the MEP class, these
differences may be covered, for SEP aeroplanes, by
Familiarisation. It is recommended, however, that
some flying training be carried out on the SE type, to
demonstrate these differences.