Originally Posted by oldlae
I hope that a valuable engineering lesson has been noted. Always check any changes in procedures with the engineers.
Ah, but WHICH engineers? The operator's engineers are unlikely to be familiar with the details of the certification of the design. Nor, for that matter, are the OEM's support staff, who may be an entirely different part of the organisation to the design staff. Similarly the Airworthiness Authority personnel dealing with operational matters may have little interaction with the Certification teams, and the same applies to those approving STCs, which may not even be approved by the original state of design.
Even if you can track down the right departments (the OEm's design staff, and/or the airworthiness people who actually did the cert approval), there's still no guarantee the people there NOW know why a specific design choice was made.