AD NUMBER: 2007-10-07
MANUFACTURER: Turbomeca
SUBJECT: Airworthiness Directive 2007-10-07
SUMMARY: We are superseding an existing airworthiness directive (AD) by adopting a new AD for the products listed above. This AD results from mandatory continuing airworthiness information (MCAI) issued 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: The deterioration of the splines on the HP/LP pump assembly drive shaft may eventually interrupt fuel supply andcause uncommanded in-flight engine shutdown. The result may be an emergency autorotation landing or, at worst, an accident. Two cases of in-flight shutdown resulting from splines deterioration have been reported for the ARRIUS 2B1 engine, which has the same HP/LP pump drive design as the ARRIEL 2. These cases prompted us to require the inspection at 500 hours and each time the HMU is removed/installed. This AD modifies the content of the previous DGACFrance AD F-2005-188 (EASA Approval Number 2005-6408) in adding a one time inspection within 30 operating hours from effective date of this AD as well as HMU re-installation according to a maintenance task modified to avoid this kind of wrong assembly. This has been set up following one case of improper clipping of the coupling shaft onto the drive gear shaft, which resulted in an uncommanded in-flight engine shutdown (on a twin engine rotorcraft). This precaution measure has been taken only on engines powering single engine rotorcraft. This AD requires actions that are intended to address the unsafe condition described in the MCAI.

FMI: www.faa.gov/regulations_policies/airworthiness_directives/