Airworthiness Directive · Amendment 39-16902 · Turbomeca Turboshaft Engines
Turbomeca Turboshaft Engines
This AD applies to Turbomeca Arriel 1B turboshaft engines with M03 modules modified by TU 76 or TU 202, and not modified by TU 148, and if fitted with a repaired 2nd stage turbine nozzle guide vane (NGV). The M03 module contains the 2nd stage turbine NGV, 1st stage turbine disc, and 2nd stage turbine disc. Guidance on determining if an engine has an unrepaired 2nd stage turbine NGV installed can be found in paragraph 1.C. of Turbomeca Mandatory Service Bulletin (MSB) No. A292 72 0829, Version B, dated December 13, 2010.
We are adopting a new airworthiness directive (AD) for Turbomeca Arriel 1B turboshaft engines. This AD results from mandatory continuing airworthiness information (MCAI) originated 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 an increase in hot gas ingestion and an increase of temperature in the gas generator (GG) turbine rotor, potentially resulting in turbine damage and an uncommanded in-flight shutdown. We are issuing this AD to prevent over-temperature damage of the GG turbine, which could result in an uncommanded in-flight engine shutdown, and a subsequent forced autorotation landing or accident.
(1) Starting from the effective date of this AD, perform a daily check (after last flight of the day) for:
(i) Normal rundown time of the GG rotor; and
(ii) The free rotation of the GG rotor; and
(iii) No grinding noise during the rundown check, and during the free rotation check of the GG rotor.
(2) Guidance on performing the daily checks can be found in the Maintenance Manual, task 71-02-09-760-801 and task 05-20-01-200-801.
(3) If the engine fails any of these daily checks, remove the engine from service before further flight.
(1) Inspect the 2nd stage turbine NGV for a non-conforming hole configuration, at the compliance times in Table 1 of this AD. Guidance on 2nd stage turbine NGV non-conforming hole configuration can be found in Turbomeca MSB No. A292 72 0829, Version B, dated December 13, 2010.
| If accumulated GG Cycles-in-Service (CIS) on the effective date of this AD are: | Then inspect: |
|---|---|
| (i) Fewer than 1,200 CIS on both the 1st and 2nd stage turbines | Before exceeding 1,500 GG CIS. |
| (ii) 1,200 or more but fewer than 1,800 CIS on either the 1st or 2nd stage turbines | Before exceeding 300 GG CIS after the effective date of this AD but not to exceed 2,000 CIS on either the 1st or 2nd stage turbines. |
| (iii) 1,800 or more but fewer than 2,400 CIS on either the 1st or 2nd stage turbine | Before exceeding 200 GG CIS after the effective date of this AD but not to exceed 2,500 CIS on either the 1st or 2nd stage turbines. |
| (iv) Greater than 2,400 CIS on either the 1st or 2nd stage turbine | Before exceeding 100 GG CIS after the effective date of this AD but not to exceed 3,000 CIS on either the 1st or 2nd stage turbine. |
(2) If the configuration of the holes in the repaired 2nd stage turbine NGV are conforming, then no further action is required.
(3) If the configuration of the holes in the repaired 2nd stage turbine NGV are non-conforming, then before further flight:
(i) Replace the 2nd stage turbine NGV with a 2nd stage turbine NGV eligible for installation; and
(ii) Replace the 1st stage turbine disc and 2nd stage turbine disc with discs eligible for installation.
Complying with paragraph (g)(1) and either paragraph (g)(2) or paragraphs (g)(3)(i) through (g)(3)(ii) of this AD, or replacing the M03 module with an M03 module that is eligible for installation, is terminating action for the requirements of this AD.
(1) Do not reinstall the 1st stage turbine disc and the 2nd stage turbine disc removed in paragraph (g)(3)(ii) of this AD into any engine.
(2) After the effective date of this AD, do not install an M03 module that has incorporated TU 202 but not incorporated TU 148, unless the module is in compliance with the requirements of this AD.
(3) After the effective date of this AD, do not install an M03 module that has incorporated TU 76 but not incorporated TU 148, unless the module is in compliance with the requirements of this AD.
(1) This AD differs from the Mandatory Continuing Airworthiness Information (MCAI) and/or service information as follows:
(i) This AD does not require sending data to Turbomeca to confirm whether Turbomeca MSB No. A292 72 0829, Version B, dated December 13, 2010, is applicable to the operator's engine; the MCAI does.
(ii) This AD does not incorporate by reference (IBR) Turbomeca MSB No. A292 72 0829, Version B, dated December 13, 2010; the MCAI does.
(iii) This AD requires replacing non-conforming 2nd stage turbine NGVs and 1st stage and 2nd stage turbine discs that were operated with non-conforming 2nd stage turbine NGVs but does not require replacing affected M03 modules. The MCAI requires replacing affected M03 modules with M03 modules eligible for installation.
For the purpose of this AD, a conforming repaired 2nd stage turbine NGV is one with cooling holes in the forward inner flange, and with no cooling holes in the rear flange.
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.
