Reference: Regulation (EU) No 965/2012 Air Operations and the associated ED Decisions are available on EASA website.
The minimum number of cabin crew for an aircraft type, as determined by certification and approved by EASA, is stated on the Type Certification Data Sheet. The minimum number of cabin crew and the evacuation procedures form part of the Operations Manual. Reducing the minimum cabin crew is a deviation from the required minimum number and requires close monitoring. Changes to evacuation procedures with a reduced number of cabin crew are required to be acceptable to the Competent Authority.
The minimum number of cabin crew required in the passenger compartment may be reduced under conditions stated in ORO.CC.205 incl. AMC1 ORO.CC.205 (c)(1). Procedures must be established in the operations manual; it has to be ensured that an equivalent level of safety is achieved with the reduced number of cabin crew, in particular for evacuation of passengers.