AMC 21.A.33 Inspections and tests
CAA ORS9 Decision No. 1
Use of the term ‘applicant’: point 21.A.33 is applicable to type certification, major changes, major repairs and supplemental type certificates (STCs), and through reference in point 21.A.604 to UKTSO for auxiliary power units (APUs). Despite using the word ‘applicant’, it is also applicable to major changes, major repairs and STCs approved under DOA privileges (see point 21.A.263(c)(5), (8) or (9)).
Proposed type design: this term defines the type design (or the portion of the type design) as it is determined at the time when the inspection or test is undertaken.
Statement of conformity: for each certification inspection or test, the statement of conformity issued in accordance with point 21.A.33(c) must address the conformity of the test specimen (see point 21.A.33(b)(1)) as well as of the test equipment and measuring equipment (see point 21.A.33(b)(2)).
Conformity of the test specimen: the statement of conformity required by point 21.A.33(c) is intended to ensure that the manufactured test specimen adequately represents the proposed type design. Possible types of non-conformity may be the following:
1. Non-conformity between the design of the test specimen and the proposed type design at the time of the test. These are typically identified in the early stage of the test planning, and should be addressed as early as possible (e.g. in the test plan). There may be several reasons for such a non-conformity: to account for interfaces with the test equipment, to conservatively cover several or future design configurations, etc.
2. Non-conformity between the manufactured test specimen and the design of the test specimen. Such a non-conformity may be the result of the manufacturing of the test specimen.
While it is convenient to define any possible non-conformity in (a) as early as possible, the applicant does not need to make the distinction between the two types of non-conformity above as long as they are explicitly addressed and justified in the statement of conformity or by cross reference to the test plan or other documents.
Type certification is typically an iterative process in which the design is under continuous evolution. If the type design evolves after the time of the inspection or test, then the final type design should be checked against the proposed type design (as it was at the time of the inspection or test), and the differences (if any) should be analysed to ensure that the inspection or test results are representative of the final configuration. However, such changes made to the type design may lead to the invalidation of the inspection or test results and a need to repeat the inspection or test. It is recommended that the design organisation should have a thorough configuration management process to track the evolving type design.
Conformity of test and measuring equipment: the configuration of the test and measuring equipment should be defined in the test plan and include the following:
3. definition/design of the test equipment (relevant tools, mechanical parts, electronic components used to execute the test); and
4. definition of the measuring equipment:
— type/model of sensors, together with their technical characteristics;
— position and orientation of exciters and sensors; and
— electronic measuring equipment (in some cases, this may also include the acquisition and post-processing of data).
The configuration of the test and measuring equipment should be defined and controlled through certification test plans and supporting documentation, according to the design assurance system, if applicable. The test plan should also include the following elements:
5. the test cases, methods, and procedures for test execution;
6. the pass–fail criteria; and
7. pre-, during- and post-test inspections.
The statement of conformity of point 21.A.33(c) should confirm that the test and measuring equipment conform to its purpose, and that the sensors and measuring system are appropriately calibrated. Any non-conformity should be assessed, and it should be justified that it will not compromise the test purpose and results. This can be done either in the statement of conformity or by cross reference to other documents (test minutes of meetings, test notes, etc.).
Use of the term ‘adequate’: the test specimen, as well as the test and measuring equipment, are considered to be ‘adequate’ as long as the test execution on the manufactured test specimen (including any non-conformity) and the use of the installed test set-up does not compromise the test purpose and results (for example, by providing better performance than the proposed type design, or masking any potential failure mode or behaviour).
Changes that affect the validity of the statement of conformity (see point 21.A.33(e)(2)): if changes need to be introduced to the test specimen or to the test and measurement equipment after the statement of conformity is issued (and before the test is undertaken), the statement of conformity must be updated. The updated statement of conformity must be made available to the CAA before the test if the CAA has informed the applicant that it will witness or carry out the tests.
Development versus certification tests: sometimes, tests of specimens that conform to a preliminary design, but are not intended for certification (known as development tests), are performed as part of a risk control strategy and to develop knowledge of a subject. Problems and failures found during development are part of the process of increasing the understanding of the design, including its failure modes and the potential for optimisation. Such development tests do not need to meet the requirements of point 21.A.33.
Any planned test event should be classified in advance as either a development test or a certification test. Tests that support the compliance demonstration should be classified as certification tests.
Nevertheless, if agreed by the CAA, it is acceptable for a development test to finally form part of the compliance demonstration, and it may be declared afterwards to be a certification test as long as it meets the requirements of point 21.A.33. For this reason, it is important to keep the configuration of such tests under the control of the design organisation.
In addition to this, the level of involvement (LoI) notified by the CAA as per 21.B.100(c) should be taken into account: if the CAA has determined that it will witness or conduct a certain test, this test may need to be repeated so that the CAA can witness or conduct the test.
If the test specimen used for a certification test has already undergone a series of previous tests that may affect or ultimately invalidate its acceptance as required by point 21.A.33(b), this aspect should be considered when issuing the statement of conformity required by point 21.A.33(c), and specific analyses or inspections may be required to support such a statement.
Because of the above aspects, the CAA advises applicants to inform the CAA if they intend to conduct a campaign of development tests that may eventually be used as certification tests.
Availability of compliance data (see point 21.A.33(d)(1)): data and information requested from the applicant for review should be made available in a reliable and efficient way that is agreed between the applicant and the CAA.
Point 21.A.33(d)(1) refers to any data or information related to compliance data; the scope of that requirement is therefore not limited to inspections and tests. In particular, point 21.A.33(d)(1) is not limited to data and information related to compliance demonstration items (CDIs) in which the CAA is involved.