Federal Aviation Administration March 24, 2011 – Federal Register Recent Federal Regulation Documents

This notice contains a summary of a petition seeking relief from specified requirements of 14 CFR. The purpose of this notice is to improve the public's awareness of, and participation in, this aspect of FAA's regulatory activities. Neither publication of this notice nor the inclusion or omission of information in the summary is intended to affect the legal status of the petition or its final disposition.

We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD would require installing two warning level indicator lights on each of the P1-3 and P3-1 instrument panels in the flight compartment. This proposed AD would also require revising the airplane flight manual to remove certain requirements of previous AD actions, and to advise the flightcrew of the following changes: Revised non-normal procedures to use when a cabin altitude warning or rapid depressurization occurs, and revised cabin pressurization procedures for normal operations. This proposed AD was prompted by a design change in the cabin altitude warning system that would address the identified unsafe condition. We are proposing this AD to prevent failure of the flightcrew to recognize and react to a valid cabin altitude warning horn, which could result in incapacitation of the flightcrew due to hypoxia (lack of oxygen in the body), and consequent loss of control of the airplane.

We are superseding an existing airworthiness directive (AD) for the products listed above. That AD currently requires initial and repetitive torque inspections of the 3rd stage and 4th stage low- pressure turbine (LPT) blades for shroud notch wear and replacement of the blade if wear limits are exceeded. That AD also requires replacing LPT-to-exhaust case bolts and nuts with bolts and nuts made of Tinidur material. This new AD requires the same torque inspection, blade, and Tinidur nut replacement actions, but requires replacement of the LPT- to-exhaust case bolts with longer bolts made of Tinidur material. This AD also requires installation of crushable sleeve spacers on the bolts. This AD was prompted by nine reports of failure of Tinidur material LPT-to-exhaust case bolts, as a result of blade failure, since AD 2005- 02-03 became effective. We are issuing this AD to prevent turbine blade failures that could result in uncontained engine debris and damage to the airplane.