Summary
This document proposes to revise an earlier proposed airworthiness directive (AD), which would have superseded AD 81-20-01. That AD currently requires repetitively inspecting the nose landing gear (NLG) actuator support structure and the front pressure bulkhead for cracks on Jetstream Aircraft Limited (JAL) HP137 Mk1 and Jetstream series 200 airplanes, and replacing any cracked part. The previous document would have: retained the repetitive inspections required by AD 81-20-01; required repetitively inspecting the NLG retraction jack upper mounting fitting and attachment hardware for security bolt failure and for bolts with improper torque levels on the HP137 Mk1, Jetstream series 200, and Jetstream Model 3101 airplanes; required replacing any failed security bolts and adjusting any bolt with an improper torque level; and required modifying the NLG retraction jack on all affected airplanes as terminating action for the repetitive inspections. As currently written, the document allows continued flight if cracks are found in the front pressure bulkhead membrane and actuator support structure when cracks do not exceed certain limits. Since publication of that proposal, the Federal Aviation Administration (FAA) has established a policy to disallow airplane operation when known cracks exist in primary structure (the affected airplane parts are considered primary structure). The actions specified by the proposed AD are intended to prevent failure of the NLG caused by a cracked NLG actuator support structure or cracked front pressure bulkhead, which could lead to nose gear collapse and damage to the airplane. Since the comment period for the original proposal has closed and the change described above goes beyond the scope of what was originally proposed, the FAA is allowing additional time for the public to comment.