Page 149 - UK Regulation Part 21 Initial Airworthiness Annex I (consolidated) March 2022

PART 21 - INITIAL AIRWORTHINESS (ANNEX I)

21.A.239(a) GM2 Design assurance system for minor changes to type design or minor repairs to products
1. Purpose
This GM outlines some basic principles and objectives in order to comply with 21.A.239(a)
for organisations designing only minor changes to type design or minor repairs to
products.
2. Design assurance system
The design assurance system should include the following:
- an organisational structure to:
- control the design
- demonstrate compliance with applicable CS and environmental protection
requirements
- independently check demonstrations of compliance
- liaise with the CAA
- continuously evaluate the design organisation
- control subcontractors
- procedures and responsibilities associated with the functions listed above, taking
due account of Part 21 requirements applicable to design and approval of minor
changes to type design or minor repairs to products.
21.A.239(a)(3) AMC Design assurance system – Independent system monitoring
The system monitoring function required by 21.A.239(a)(3) may be undertaken by the existing quality
assurance organisation when the design organisation is part of a larger organisation.
21.A.239(b) AMC Design assurance system – Independent checking function of the demonstration of compliance
1. The independent checking function of the demonstration of compliance should consist of
the verification by a person not creating the compliance data. Such person may work in
conjunction with the individuals who prepare compliance data.
2. The verification should be shown by signing compliance documents, including test
programmes and data.
3. For a product, there is normally only one compliance verification engineer nominated for
each relevant subject. A procedure should cover the non-availability of nominated persons
and their replacement when necessary.
4. For STC cases, when compliance statement and associated documentation are
produced by the TC holder, and when these data are approved under the system of the
authority of TC holder, then the STC applicant does not need to provide, within its own
DOA, the independent checking function required in 21.A.239(b) for these data.
21.A.239(b) AMC1-ELA Design assurance system – Independent checking function
The design assurance system (DAS) defines methods to ensure there is an independent verification
of the compliance demonstration on the basis of which the organisation submits compliance
statements and associated documentation to CAA.
Compliance verification therefore means the approval of all those compliance documents that are
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