ATSB assessment of CASA actions from 21 March 2017 and 27 April 2017
On 24 May 2017, the ATSB wrote a letter to CASA advising of the following assessment of the actions CASA informed the ATSB of having taken in correspondence on 21 March 2017 and 27 April 2017:
The ATSB acknowledges improvement in the processes that CASA has developed to address safety issue AO-2013-187-Sl-08 including the formalisation of a CAR 2A approval process and the inclusion of references to non-destructive testing (NDT) approvals. The addition of a peer review within the process will also provide an additional layer of assurance to the approval process.
Further, CASA's process also now includes consideration of seeking the views of the manufacturer for alternative methods of NDT approvals, which the ATSB believes will also provide an improved level of safety if such contact is made.
However, the ATSB considers that the safety actions taken by CASA to date have not addressed safety issue AO-2013-187-Sl-08 to the extent that, we feel would prevent a similar occurrence to the M18 eddy current inspection procedure.
While CASA's new procedures include references to comparison with standards for NDT they only provide information on how a particular inspection method should be carried out, not whether such a method is suitable for a particular application.
The assessment and approvals process also appears to rely on the engineering judgment of the assessor and lacks a systematic engineering approach to ensure that the applicant has shown that the proposed procedure provides an equivalent, or better, level of defect detection capability and probability.
The ATSB suggests that CASA's procedure be further developed to require the applicant to provide minimum justification data as part of their application. This would put the onus upon the applicant to satisfy CASA that the required level of safety has been assured without the need for CASA/NANDTB to provide "engineering judgments" during the approval process.
In addition, the process changes have only been applied to CAR 2A approvals and the ATSB is concerned that the same situation could occur with other types of alternate NDT approvals. For example, the CAR 2A approval procedure would not apply to the assessment of an application for an Alternate Means of Compliance (AMOC) to an Airworthiness Directive which needs to be approved under CASR 39. There is just as much, if not a greater, probability of an application for an AMOC than for a CAR 2A approval.
The ATSB considers that a formal process or guideline for CASA to follow as part of their assessment and approval of alternative non-destructive inspection procedures would assist CASA to fully address the safety issue. Some guidance to industry on the minimum requirements for non-destructive inspection processes may also assist in ensuring that adequate justification is provided with an application.