Certification Specifications (CS) means technical standards adopted by the Agency indicating means to show compliance with Regulation (EC) No 216/2008 and its Implementing Rules and which can be used by an organisation for the purpose of certification.

CS 27 and CS 29 cover the Airworthiness Requirements applying to small and large rotorcraft respectively, whereas CS 23 and CS 25 to small and large aeroplanes respectively.

According to CS 27.1 - Applicability:

• Small rotorcraft with maximum weight of 3 175 kg (7 000 lb) or less and a MOPSC of 9 or less are certified under CS 27.
• A small multi-engine rotorcraft may not be type certificated for Category A operation, unless it meets the design installation and performance requirements contained in Appendix C for CS 29, in addition to the requirements of this CS 27.

Thus, the Certification Specifications 27 (CS 27) is applicable only to Small Rotorcraft and may be either Category B or A, after meeting specific requirements.