AD 2005-23-06 Airworthiness Directives; Learjet Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C, 25D, and 25F Airplanes Modified by Supplemental Type Certificate SA1731SW, SA1669SW, or SA1670SW

Models named: 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 24E, 24F, 25. Read the applicability below — it usually turns on serial or part numbers too.

This AD applies to Learjet Model 23, 24, 24A, 24B, 24B-A, 24D, 24D-A, 24E, 24F, 25, 25A, 25B, 25C, 25D, and 25F airplanes; certificated in any category; modified by Supplemental Type Certificate SA1731SW, SA1669SW, or SA1670SW; equipped with Nordam (formerly Dee Howard Company) thrust reverser accumulators having part number (P/N) 25-0570-127-1, -3, -7, -13, or -17.

You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done. Remove Thrust Reverser Accumulator (f) Within 60 days after the effective date of this AD, remove the thrust reverser accumulator, and make the thrust reverser hydraulic system and the thrust reversers inoperable, by doing all of the actions specified in the Accomplishment Instructions of The Nordam Group Alert Service Bulletin A3000 78-21, dated November 25, 2002. Where there are differences between the Master Minimum Equipment List and the AD, the AD prevails. Although the service bulletin referenced in this AD specifies to submit certain information to the manufacturer, this AD does not include that requirement. Parts Installation (g) As of the effective date of this AD, no person may install a thrust reverser accumulator having P/N 25-0570-127-1, -3, -7, -13, or -17 on any airplane. Alternative Methods of Compliance (AMOCs) (h)(1) The Manager, Special Certification Office, Rotorcraft Directorate, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19. (2) Before using any AMOC approved in accordance with 14 CFR 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office. Material Incorporated by Reference (i) You must use The Nordam Group Alert Service Bulletin A3000 78-21, dated November 25, 2002, to perform the actions that are required by this AD, unless the AD specifies otherwise. The Director of the Federal Register approved the incorporation by reference of this document in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Contact The Nordam Group, Nacelle/Thrust Reverser Systems Division, 6911 North Whirlpool Drive, Tulsa, Oklahoma 74117, for a copy of this service information. You may review copies at the Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street, SW., room PL-401, Nassif Building, Washington, DC; on the Internet at http://dms.dot.gov; or at the National Archives and Records Administration (NARA). For information on the availability of this material at the NARA, call (202) 741-6030, or go to http://www.archives.gov/federal-register/cfr/ibr-locations.html. Issued in Renton, Washington on October 28, 2005. Ali Bahrami, Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 05-22215 Filed 11-10-05; 8:45 am] BILLING CODE 4910-13-P

This AD was prompted by reports of the failure of two thrust reverser accumulators. We are issuing this AD to prevent failure of the thrust reverser accumulators, due to fatigue cracking on the female threads, which could result in the loss of hydraulic power and damage to the surrounding airplane structure.