Airworthiness Directive · Amendment 39-13921 · Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) 250-B and 250-C Series Turboprop and Turboshaft Engines
Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) 250-B and 250-C Series Turboprop and Turboshaft Engines
This AD applies to 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 the following Table 1:
| 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 the following Table 2:
| Helicopters |
|---|
| Agusta Models. |
| A109, A109A, A109A II. |
| Bell Models. |
| 206A, 207B, 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. |
| Airplanes |
| B-N Group Ltd. Model. |
| BN-2T. |
The FAA is adopting a new airworthiness directive (AD) for Rolls-Royce Corporation (RRC) 250-B and 250-C series turboprop and turboshaft engines with certain part numbers (P/Ns) of compressor adaptor couplings manufactured by Alcor Engine Company (Alcor), EXTEX Ltd. (EXTEX), RRC, and Superior Air Parts (SAP) installed. This AD requires operators to remove from service affected compressor adaptor couplings. This AD results from nine reports of engine shutdown caused by coupling failure. We are issuing this AD to reduce the risk of failure of the compressor adaptor coupling and subsequent loss of all engine power.
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 Alcor compressor adaptor couplings, P/Ns 23039791AL, 23039791AL-1, -2, and -3 from service as follows:
(1) For couplings with 600 or more operating hours-since-new as of the effective date of this AD, or the operating hours are unknown and cannot be determined, remove couplings from service at next access but not to exceed 50 additional operating hours.
(2) For couplings with fewer than 600 operating hours-since-new on the effective date of this AD, remove couplings from service at next access but not to exceed 649 operating hours-since-new.
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 as follows:
(1) For couplings with operating hours that are unknown and cannot be determined, remove couplings from service at next access but not to exceed 50 additional operating hours.
(2) For couplings with 600 or more operating hours-since-new as of the effective date of this AD, remove couplings from service at next access but not to exceed 100 additional operating hours.
(3) For couplings with fewer than 600 operating hours-since-new on the effective date of this AD, remove couplings from service at next access but not to exceed 150 additional operating hours.
Remove RRC compressor adaptor couplings, P/Ns 23039791-1, -2, and -3 from service next time the compressor rotor is disassembled for any reason, but not later than March 1, 2012.
(i) Machine the compressor impeller as follows:
(1) Select and measure the pilot outside diameter (OD) of a new larger dash size coupling.
(2) For example, if a -1 coupling was removed, a -2 coupling must be installed.
(3) If a -3 coupling is removed, a new impeller is required.
(4) 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.
(5) Due to previous fretting, an impeller with a -1 coupling removed might have to be machined for a -3 coupling. Plating of the impeller ID is not allowed.
(6) Fluorescent penetrant inspect the impeller.
(7) Install a new compressor adaptor coupling, P/N 23076559-2 or -3; or
(8) If a new impeller is installed, then install compressor adaptor coupling, P/N 23076559-1.
(9) Heating of the impeller per the engine overhaul manual is required to install the coupling to achieve the target fit specified in the following Table 3:
| New adaptor | Adaptor OD | Fit (interference) |
|---|---|---|
| (i) 23076559-1 | 0.9000 to 0.9008 inch | 0.0000 to -0.0013 inch. |
| (ii) 23076559-2 | 0.9020 to 0.9028 inch | 0.0000 to -0.0013 inch. |
| (iii) 23076559-3 | 0.9040 to 0.9048 inch | 0.0000 to -0.0013 inch. |
(10) The mating surfaces of the impeller and coupling must not have any fretting. Do not install a -1 coupling into a used impeller.
For the purposes of this AD, next access is defined as when the compressor module is separated from the engine and disassembled for any reason.
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
Engines
