Airworthiness Directive · Amendment 39-19305 · Engine fuel and control
Safran Helicopter Engines, S.A., Turboshaft Engines
This AD applies to Safran Helicopter Engines, S.A., Arriel 2B and 2B1 turboshaft engines, except those incorporating Modification TU 178.
We are superseding Airworthiness Directive (AD) 2012-03-11 for all Safran Helicopter Engines, S.A., Arriel 2B and 2B1 turboshaft engines. AD 2012-03-11 required checking the transmissible torque between the low-pressure (LP) pump impeller and the high-pressure (HP) pump shaft on the HP/LP pump and metering valve assembly, hereafter referred to as the hydro-mechanical metering unit (HMU). Since we issued AD 2012-03-11, the manufacturer determined that incorporating Modification TU 178 is a more effective method to reduce the risk of uncoupling between the LP fuel pump impeller and the HP fuel pump shaft than the prior Modification TU 147. This AD requires inspection and possible replacement of the HMU. This AD was prompted by three cases of uncoupling of the HMU LP fuel pump impeller and the HP fuel pump shaft since AD 2012-03-11 was issued. We are issuing this AD to address the unsafe condition on these products.
(1) Check the transmissible torque between the LP fuel pump impeller and the HP fuel pump shaft as follows:
(i) For pre-Modification TU 147 HMUs, check the torque before accumulating 500 engine flight hours (FHs) since March 11, 2010 or before the next flight after the effective date of this AD, whichever occurs later. Use Paragraph 2.A. of Turbomeca Alert Mandatory Service Bulletin (MSB) A292 73 2830, Version B, dated July 10, 2009 to do the check.
(ii) For HMUs that incorporated Modification TU 147 on or before March 31, 2010, and those HMUs not listed in Figure 2 or 3 of Turbomeca Alert MSB A292 73 2836, Version A, dated August 17, 2010, check the torque before the next flight after the effective date of this AD. Use Paragraph 2.A. of Turbomeca Alert MSB A292 73 2836, Version A, dated August 17, 2010, to do the check.
(2) If the HMU does not pass the torque check, replace the HMU with a post-Modification TU 178 HMU before the next flight after the effective date of this AD.
Within 2,200 engine FHs or 72 months after the effective date of this AD, whichever occurs first, replace any pre-Modification TU 178 HMU with a post-Modification TU 178 configuration HMU.
After the effective date of this AD, do not install a pre-Modification TU 178 HMU on engines incorporating a post-Modification TU 178 HMU.
