AD 2008-07-01 Airworthiness Directives; Turbomeca Arriel 1B, 1D, 1D1, and 1S1 Turboshaft Engines

This AD applies to Turbomeca Arriel 1B engines fitted with 2nd stage turbine modification TU 148, and Arriel 1D, 1D1, and 1S1 engines that do not incorporate TU 347. Arriel 1B engines are installed on, but not limited to, Eurocopter France AS-350B and AS-350A “Ecureuil” helicopters. Arriel 1D engines are installed on, but not limited to, Eurocopter France AS-350B1 “Ecureuil” helicopters. Arriel 1D1 engines are installed on, but not limited to, Eurocopter France AS-350B2 “Ecureuil” helicopters. Arriel 1S1 engines are installed on, but not limited to, Sikorsky Aircraft S-76A and S-76C helicopters.

You are responsible for having the actions required by this AD performed within the compliance times specified unless the actions have already been done. Initial Relative Position Check of 2nd Stage Turbine Blades (f) Do an initial relative position check of the 2nd stage turbine blades using the Turbomeca mandatory alert service bulletins (ASBs) specified in the following Table 1. Do the check before reaching any of the intervals specified in Table 1 or within 50 hours time-in-service after the effective date of this AD, whichever occurs later. Table 1.—Initial and Repetitive Relative Position Check Intervals of 2nd Stage Turbine Blade Turbomeca engine model Initial relative position check interval Repetitive interval Mandatory Alert Service Bulletin Arriel 1B (modified per TU 148) Within 1,200 hours time-since-new (TSN) or time-since-overhaul (TSO) or 3,500 cycles-since-new (CSN) or cycles-since-overhaul (CSO), whichever occurs earlier Within 200 hours time-in-service-since-last-relative-position-check (TSLRPC) A292 72 0807, Update 1, dated October 26, 2006. Arriel 1D1 and Arriel 1D Within 1,200 hours TSN or TSO or 3,500 CSN or CSO, whichever occurs earlier Within 150 hours TSLRPC A292 72 0809, Update No. 1, dated October 4, 2005. Arriel 1S1 Within 1,200 hours TSN or TSO or 3,500 CSN or CSO, whichever occurs earlier Within 150 hours TSLRPC A292 72 0810, dated March 24, 2004. Repetitive Relative Position Check of 2nd Stage Turbine Blades (g) Recheck the relative position of 2nd stage turbine blades at the TSLRPC intervals specified in Table 1 of this AD, using the mandatory ASBs indicated. Credit for Previous Relative Position Checks (h) Relative position checks of 2nd stage turbine blades done using Turbomeca Service Bulletin A292 72 0263, Update 1, 2, 3, or 4, or A292 72 0807, dated March 24, 2004, comply with the initial requirements of paragraph (f) of this AD. Initial Replacement of 2nd Stage Turbines on Arriel 1B, 1D, and 1D1 Engines (i) Initially replace the 2nd stage turbine with a new or overhauled 2nd stage turbine as follows: (1) Before accumulating 1,500 hours TSN or TSO on the module for Arriel 1D and 1D1 engines. (2) Before accumulating 2,200 hours TSN or TSO on the module or 3,000 total hours TSN on the 2nd stage turbine blades, whichever occurs first, for Arriel 1B engines. Repetitive Replacements of 2nd Stage Turbines on Arriel 1B, 1D, and 1D1 Engines (j) Thereafter, replace the 2nd stage turbine with a new or overhauled 2nd stage turbine within every 1,500 hours TSN or TSO on the module for Arriel 1D and 1D1 engines, and within every 2,200 hours TSN or TSO on the module or 3,000 total hours TSN on the 2nd stage turbine blades, for Arriel 1B engines. Criteria for Overhauled 2nd Stage Turbines (k) Do the following to overhauled 2nd stage turbines, referenced in paragraphs (i) and (j) of this AD: (1) You must install new blades in the 2nd stage turbines of overhauled Arriel 1D and 1D1 engines. (2) You may install either overhauled blades with fewer than 3,000 total hours TSN or new blades in the 2nd stage turbines of overhauled Arriel 1B engines. Relative Position Check Continuing Compliance Requirements (l) All 2nd stage turbines, including those that are new or overhauled, must continue to comply with the actions specified in paragraphs (f), (g), and (j) of this AD. Optional Terminating Action (m) Installing a new turbine, P/N 0 292 25 039 0, reference TU 347, terminates the requirements to perform the repetitive actions specified in paragraphs (g) and (j) of this AD. Alternative Methods of

This AD results from reports of failures of second stage blades. We are issuing this AD to prevent failures of the 2nd stage turbine blades, which could result in uncommanded in-flight engine shutdown, and subsequent forced autorotation landing or accident.