combination of technologies that involve the use of electric motors or a combination of electric motors and combustion engines to form a system which produces lift, thrust or power for flight

NOTE 1 An EHPS might include but is not limited to:
a) electric motors;
b) turbine engines;
c) piston engines;
d) generators;
e) electrical power generation;
f) distribution;
g) wirings;
h) propulsion batteries;
i) integrated fans;
j) cooling systems;
k) controllers;
l) power management system.

NOTE 2 A propulsion battery associated to an electric motor providing power to a fan, rotor or propeller is considered to be part of an EHPS. A propulsion battery alone (without any associated electric engine) is not considered to be part of an EHPS.

NOTE 3 All-electric aircraft systems use batteries as the only source of propulsion power.

NOTE 4 Hybrid systems include, but are not limited to, parallel hybrid, series hybrid and series/parallel partial hybrid configurations.

[SOURCE: EASA, Special Condition, SC E-19, Electric / hybrid propulsion system, modified – “the use of electric motors and/or combustion engines” replaced by “the use of electric motors or a combination of electric motors and combustion engines”] [21]