Page 78 - UK Regulation Part 21 Initial Airworthiness Annex I (consolidated) March 2022

PART 21 - INITIAL AIRWORTHINESS (ANNEX I)

The term ‘change’ refers to a change to a product type certificate (as defined in point
21.A.41) approved or to be approved under Subpart D or Subpart E (as a supplemental
type certificate) of Part 21, including a change to an STC or a change to the UKTSOA for
auxiliary power units (APUs) under Subpart O. A change may consist of a single
standalone change to one TC component or several interrelated changes to different TC
components (e.g. the type design, operating characteristics, OSD, environmental
protection characteristics, etc. (see point 21.A.41 and GM to 21.A.90A)).
J.6 Design change.
The term ‘design change’ refers to a change to the type design (as defined in point
21.A.31) of an aeronautical product. In the context of this document, the terms ‘change to
the type design’, ‘modification’, ‘design change’, and ‘type design change’ are
synonymous.
J.7 Earlier standards.
The certification specifications or previous standards in effect prior to the date of
application for the change, but not prior to the existing certification basis.
J.8 Existing certification basis.
The certification specifications or previous standards incorporated by reference in the type
certificate of the baseline product to be changed.
J.9 Latest standards.
The certification specifications in effect on the date of application for the change.
J.10 Previous relevant design changes.
Previous design changes, the cumulative effect of which could result in a product
significantly or substantially different from the original product or model, when considered
from the last time the latest standards were applied.
J.11 Product-level change.
A change or combination of changes that makes the product distinct from other models of
the product (e.g. range, payload, speed, design philosophy). Productlevel change is
defined at the aircraft, aircraft engine, or propeller level of change.
J.12 Secondary change.
A change that is part of a significant physical change that does not contribute materially to
the level of safety. Guidance is contained in paragraph 3.10.1.4 of this GM.
J.13 Significant change.
A change to the type certificate to the extent that it changes one or more of the following,
but not to the extent to be considered a substantial change: the general configuration,
principles of construction, or the assumptions used for certification. The significance of
the change is considered in the context of all previous relevant design changes and all
related revisions to the applicable standards. Not all productlevel changes are significant.
J.14 Significant change to area.
For aircraft excepted under point 21.A.101(c) only: a change to an area is significant if the
general configuration or the principles of construction in that area are not retained, or the
assumptions used for the certification of that area do not remain valid.
J.15 Substantial change.
A change that is so extensive that a substantially complete investigation of compliance
with the applicable certification basis is required, and consequently a new type certificate
is required pursuant to point 21.A.19.
21.A.101 GM Establishing the certification basis of changed aeronautical products
Foreword
This guidance material (GM) provides guidance for the application of the ‘Changed Product Rule
(CPR)’, pursuant to point 21.A.101, Designation of the applicable certification specifications and
environmental protection requirements, and 21.A.19, Changes requiring a new type certificate, for
changes made to type-certified aeronautical products.
1) INTRODUCTION
1.1. Purpose.
This GM provides guidance for establishing the certification basis for changed
aeronautical products pursuant to point 21.A.101, Designation of the applicable
certification specifications and environmental protection requirements. The
guidance is also intended to help applicants and approved design organisations to
determine whether it will be necessary to apply for a new type certificate (TC) under
point 21.A.19, Changes requiring a new type certificate. The guidance describes the
process for establishing the certification basis for a change to a TC, for a
supplemental type certificate (STC), or for a change to an STC, detailing the
requirements (evaluations, classifications, and decisions) throughout the process.
1.2. Applicability.
1.2.1 This GM is for an applicant that applies for changes to TCs under Subpart D,
for STCs, or changes to STCs under Subpart E, or for changes to UK
Technical Standard Order Authorisations (UKTSOAs) for auxiliary power units
(APUs) under Subpart O. This GM is also for approved design organisations
that classify changes and approve minor changes under their 21.A.263(c)(1)
and (2) privileges.
1.2.2 This GM applies to major changes under point 21.A.101 for aeronautical
products certified under Part 21, and the certification specifications (CSs)
applicable to the changed product (CS-23, CS-25, CS-27, CS-29, CS-MMEL,
CS-FCD, CS-CCD, etc.). References to ‘change’ include the change and
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