Document ID: chunk:federal_register_of_legislation:F2012L00544:body:0:p1
Version: federal_register_of_legislation:F2012L00544
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AIRWORTHINESS DIRECTIVE
On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/AL 250/86 Amdt 2 and issues the following AD under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Allison Turbine Engines - 250 Series
AD/AL 250/86 Amdt 3  Compressor Adaptor Coupling  5/2012

Applicability:  Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) 250-B17, -B17B, -B17C, -B17D, -B17E,
                250-C20, -C20B, -C20F, -C20J, -C20S, and -C20W series turboprop and turboshaft engines with the compressor adaptor couplings installed listed in Table 1 of this Directive.

                Table 1. - Affected Compressor Adaptor Couplings
                Manufacturer                      Affected part numbers
                   Alcor Engine Company (Alcor)      P/Ns 23039791AL.
                                                     23039791AL-1/-2/-3.
                   EXTEX Ltd. (EXTEX)                A23039791.
                                                     E23039791.
                                                     E23039791-1/-2/-3.
                                                     EH23039791.
                                                     EH23039791-1/-2/-3.
                   Rolls-Royce Corporation (RRC)     23039791-1/-2/-3.
                   Superior Air Parts (SAP)          A23039791.

              These engines are installed on, but not limited to, the aircraft in Table 2 of this Directive:

              Table 2. - Applicable Aircraft

              Helicopters
                 Agusta Models.
                 A109, A109A, A109A II.
                 Bell Models.
                 206A, 206B, 206L.
                 Enstrom Models.
                 TH-28, 480, 480B.
                 Eurocopter France Models.
                 AS355E, AS355F, AS355F1, AS355F2.
                 Eurocopter Deutschland Models.
                 BO-105C, BO-105S.
                 MDHI Models.
                 369D, 369E, 369H, 369HM, 369HS, 369HE.
                 Schweizer Model 269D.

              Aeroplanes
                 B-N Group Ltd. Model.
                 BN-2T.

Requirement:     1. Alcor Compressor Adaptor Couplings

              Remove Alcor compressor adaptor couplings, P/Ns 23039791AL, 23039791AL-1, -2, and -3 from service.

                 2. EXTEX and SAP Compressor Adaptor Couplings

              Remove EXTEX and SAP compressor adaptor couplings, P/Ns A23039791, E23039791, E23039791-1, -2, and -3, EH23039791, and EH23039791-1, -2, and -3, from service.

      3. RRC Compressor Adaptor Couplings

   Remove RRC compressor adaptor couplings, P/Ns 23039791-1, -2, and -3 from service.

      4. Installation Requirements for Compressor Adaptor Couplings

   Machine the compressor impeller as follows:

        (a) Select and measure the pilot outside diameter (OD) of a new larger dash size coupling.

        (b) For example, if a -1 coupling was removed, a -2 coupling must be installed.

        (c) If a -3 coupling is removed, a new impeller is required.

        (d) Machine the inside diameter (ID) of the compressor impeller to achieve a fit of 0.0000 to -0.0013 inch. No fretting is allowed on the impeller after machining.

        (e) Due to previous fretting, an impeller with a -1 coupling removed might have to be machined for a -3 coupling. Plating of the