Federal Aviation Administration March 30, 2010 – Federal Register Recent Federal Regulation Documents

The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 220: Automatic Flight Guidance and Control.

We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as: Investigation of an uncommanded in-flight shutdown (IFSD) revealed that a third stage turbine wheel rupture was not contained by the turbine casings. The released portion consisted of a turbine blade together with the rim piece immediately below the blade. The rim piece was bounded by two adjacent axial slots and a fatigue crack that had developed between the holes in which the slots terminate. The slots and holes, which are closed by riveted plugs, were introduced by modification AB 173 in order to improve the vibration characteristics of the turbine wheel. Modification AB 208 brings an improvement to modification AB 173 by changing only the riveting detail. SN 283 72 0805 provides instructions for re-boring the holes at overhaul or repair in order to improve their surface condition. A manufacturing process modification has been introduced to improve the surface condition of these holes in third stage turbine wheels. Wheels subject to the improved manufacturing process have S/Ns outside the range specified in Table 1. Although there is only one known event, and although it resulted only in an uncommanded IFSD, with no damage to the aircraft, the possibility exists that additional events may occur, potentially involving damage to the aircraft.

We propose to supersede Airworthiness Directive (AD) 2009-24- 13, which applies to certain Cessna Aircraft Company (Cessna) Model 525A airplanes. AD 2009-24-13 currently requires you to repetitively inspect the thrust attenuator paddle assemblies for loose and damaged fasteners and for cracks. AD 2009-24-13 also requires you to replace loose or damaged fasteners and replace cracked thrust attenuator paddles found during any inspection. Since we issued AD 2009-24-13, Cessna has developed new design thrust attenuator paddles and universal head rivets as terminating action for the repetitive inspections. Consequently, this proposed AD would retain the requirements of AD 2009-24-13 until replacement of both thrust attenuator paddles and the eight countersunk fasteners with new design thrust attenuator paddles and universal head rivets. We are proposing this AD to detect and correct loose and damaged fasteners and cracks in the thrust attenuator paddles, which could result in in-flight departure of the thrust attenuator paddles. This failure could lead to rudder and elevator damage and result in loss of control.

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.