For the certification/validation of STCs, the STC holder shall demonstrate compliance for the configurations defined in the TCDS plus the change introduced by the STC. Combinations with other STCs may be considered, but this is not common practice.
Aircraft owners planning to install more than one STC should check before embedding them in the EASA Noise database whether a noise record has been established for this configuration.
If the configuration cannot be found, in most cases one of the STC holders must apply at EASA to establish a noise level. This is a prerequisite to register the S/N in Europe.
For any further question, please contact noise [at] easa.europa.eu.
