12
JUN
2015

NPA 2015-07

Use of comparative analysis when showing compliance with SLD icing specifications

Rulemaking task RMT.0058 aims to develop new CS-25 certification specifications for flight in icing conditions which were introduced through Amendment 16 of CS-25. A new Appendix O environmental standard representing Supercooled Large Drop (SLD) icing conditions has been created. These SLD icing conditions are therefore part of the certification specifications related to the ice protection of the aeroplane systems and equipment, powerplant and Auxiliary Power Unit (APU), as well as specifications related to aeroplane performance and handling qualities.

This Notice of Proposed Amendment (NPA) addresses a need identified by the Agency during the development of rulemaking task RMT.0058, i.e. to have the possibility of taking credit from previously certified large aeroplane type designs having proven to safely operate in SLD icing conditions.

The specific objective is to introduce an acceptable means of compliance which may be used by applicants in order to show compliance with the certification specifications related to SLD icing conditions. To this end, this NPA proposes changes to CS-25 Book 1 and Book 2 to enable the use of a means of compliance based on comparative analysis when showing compliance with SLD-related specifications.

The proposed changes are expected to maintain safety while increasing cost-effectiveness and facilitating the certification process.

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