Summary
We are revising an earlier proposed airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-102, -103, -106, -201, - 202, -301, -311, and -315 airplanes. The NPRM proposed to require repetitive inspections for discrepancies on certain AC generator mounting adapters, and replacing discrepant adapters with serviceable ones. The NPRM also proposed to require revising the maintenance program to incorporate a repetitive task specified in certain temporary revisions. The NPRM was prompted by a report of a pilot commanding an in-flight engine shut down in response to a low oil pressure warning indication. Further investigation revealed the mounting studs in the engine mounted alternating current (AC) generator mounting plate were pulled out of position and the threaded interface in the plate was corroded. This action revises the NPRM by expanding the applicability. We are proposing this supplemental NPRM (SNPRM) to detect and correct corrosion in the AC generator mounting plate, which could result in a gap between the AC generator and the generator mounting plate, and cause loss of engine oil and consequent engine failure. Since these actions impose an additional burden over those proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these proposed changes.