Action
Supplemental notice of proposed rulemaking (NPRM); reopening of comment period.
Summary
We are revising an earlier proposed airworthiness directive (AD) for certain The Boeing Company Model 757-200 and -200PF series airplanes; and Model 767-200 and -300 series airplanes. The NPRM proposed to require doing an inspection to determine the part number and serial number of the hub assembly of the ram air turbine (RAT), and replacing the hub assembly of the RAT with a new, serviceable, or reworked and re-identified hub assembly if necessary. The NPRM was prompted by reports indicating that the counterweights in some hub assemblies of the RATs could be under strength and fracture when the RAT is rotating. This action revises the NPRM by adding airplanes to the applicability; adding an additional part number and serial number inspection to determine if certain RAT hub assemblies are installed; and, for affected RAT hub assemblies, doing an inspection for missing and fractured balance washer screws, and replacement if necessary to address an additional defect identified within the RAT hub assembly. We are proposing this supplemental notice of proposed rulemaking (SNPRM) to prevent an inoperative RAT, which, following a dual engine shutdown in flight, will cause loss of all hydraulic power to the primary flight controls, resulting in subsequent loss of control of the airplane. Since these actions impose an additional burden over that proposed in the NPRM, we are reopening the comment period to allow the public the chance to comment on these proposed changes.