Page 208 - UK Regulation Part 21 Initial Airworthiness Annex I (consolidated) March 2022

PART 21 - INITIAL AIRWORTHINESS (ANNEX I)

CDI level;
- risk Class 2: The the CAA's LoI is typically limited to the review of a small
portion of the compliance data; there is either no participation in the
compliance activities, or the CAA participates in a small number of
compliance activities (witnessing of tests, audits, etc.);
- risk Class 3: in addition to the LoI defined for Class 2, the CAA’s LoI typically
comprises the review of a large amount of compliance data, as well as the
participation in some compliance activities (witnessing of tests, audits, etc.);
and
- risk Class 4: in addition to the LoI defined for Class 3, the CAA’s LoI typically
comprises the review of a large amount of compliance data, the detailed
interpretation of test results, and the participation in a large number of
compliance activities (witnessing of tests, audits, etc.).
By default, the following activities require the CAA'sinvolvement in all cases:
- initial issues of, and changes to, a flight manual (for those parts that require
the CAA approval and that do not fall under the DOA holder’s privilege);
- classification of failure cases that affect the handling qualities and
performance, when:
- performed through test (in flight or in a simulator); and
- initial issues of, and noneditorial changes to, airworthiness limitations.
If the risk assessment (Steps 1 and 2 above) is made on the level of a compliance
demonstration activity or on the level of a document, the risk class provides an
indication for the depth of the involvement, i.e. the verification may take place only
for certain compliance data within a compliance document.
4. Documentation of the LoI
The LoI proposal in the certification programme should include the applicant’s proposal
regarding the compliance demonstration verification activities and data that would be
retained by the CAA, as well as the data on which the LoI proposal has been based. For
this purpose, the applicant should appropriately document the analysis per CDI,
considering the above criteria. In cases where the rationale for the assessment is obvious,
it is considered to be sufficient for the applicant to indicate whether or not a CDI is novel or
complex, and whether or not the impact is critical.
the CAA documents the LoI determination by accepting the certification programme or, if it
deviates from the proposal, by recording its analysis regarding the deviations from the
proposal, and notifies the applicant accordingly.
5. Sampling during surveillance of the DOA holder
It should be noted that all the previously defined risk classes may be complemented by the
sampling of project files during surveillance of the DOA holder, independently from the
ongoing certification project. This is necessary in order to maintain confidence in the DOA
system and to constantly monitor its performance.
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¹ The ultimate objective is to define the organisation’s performance at the discipline level.

21.B.100(b) AMC1 Level of involvement (LoI) in projects for minor changes and minor repairs
In contrast to 21.B.100(a), the assessment of the LoI for minor rUKPAir designs and minor changes is
performed by the CAA at the level of the certification project.
The CAA reviews the information provided by the applicant in accordance with point 21.A.93(b) for
novel or unusual features, the complexity of the design and/or the compliance demonstration, as well
as the criticality of the design or technology.
An application for the CAA's approval of a minor change implies that the applicant either does not hold
a design organisation approval (DOA) or that the change is outside the DOA holder’s terms of
approval. However, teh CAA takes into account the performance and experience of the applicant with
similar design changes, for which data may be already available at the CAA. The applicant may be
also requested to present its experience with similar design changes if insufficient information is
available at the CAA.
By definition (see point 21.A.91), a minor change has no appreciable effect on the airworthiness of the
product. Therefore, the potential impact of a non-compliance with part of the certification basis
regarding the airworthiness or environmental protection aspects of the product should, in most cases,
be non-critical.
This facilitates the assessment of the likelihood of an unidentified non-compliance.
A process similar to the one described in AMC 21.B.100(a) and 21.A.15(b)(6) should be used to justify
and document the CAA's LoI.
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