Action
Notice of proposed rulemaking (NPRM).
Summary
We propose to supersede an existing airworthiness directive (AD) that applies to all Turbomeca S.A. Arriel 2B and 2B1 turboshaft engines. The existing AD currently requires checking the transmissible torque between the low-pressure (LP) pump impeller and the high- pressure (HP) pump shaft on HP/LP pump hydro-mechanical metering units (HMUs) that do not incorporate Modification TU 147. Since we issued that AD, EASA issued a new AD. This proposed AD would require inspection and possible replacement of the HMU. We are proposing this AD to prevent reduced engine power or, at worst, an uncommanded in- flight shutdown (IFSD), which can result in a forced autorotation landing or accident.