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Expert knowledge

SII Netherlands B.V. offers specialist knowledge via Certification and Consultancy Services. The services are in many fields, for example Design Organisation Approval (DOA) under EASA Part 21 for CS 23 & CS 25.

Design Organisation Approval [DOA] under EASA Part 21

Aircraft modifications require airworthiness compliance. SII Netherlands BV is authorised to act in airworthiness issues on behalf of customers for aircraft modifications. These modifications range from minor and major structural modifications to acquiring the Supplemental Type Certificate (STC). Many aircraft equipment manufacturers, airlines and aircraft conversion projects have used this unique service.


In some projects only expert knowledge is required, without the necessity of extra resources. On those occasions, SII Netherlands can be requested by customers to provide such necessary know-how via consultancy. The expertise can range from simple individual involvement to multi discipline task-oriented teams. Our expertise offers everything from simple individual consultants to multi discipline task-oriented teams.