AD 2020-20-03 Was Prompted By Reports Of Some NR Indicators Displaying Incorrect Information

The FAA is adopting a new airworthiness directive (AD) for certain Airbus Helicopters Model AS350B2 helicopters.

This AD requires performing a test of the main rotor RPM (NR) indicator, and depending on the results, altering the wiring. This AD was prompted by reports of some NR indicators displaying incorrect information. The actions of this AD are intended to address an unsafe condition on these products. This AD is effective November 3, 2020.

Supplementary Information: The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to Airbus Helicopters Model AS350B2 helicopters with a certain part-numbered NR sensor installed. The NPRM published in the Federal Register on March 23, 2020 (85 FR 16279). The NPRM proposed to require compliance with certain procedures described in the manufacturer's service bulletins. For Model AS350B2 helicopters with an NR sensor part number 704A37614007 installed, the NPRM proposed to require, before further flight, performing a test to determine if the NR indicator display changes or drops to zero when the emergency cut-out control is activated. If the NR display changes or drops to zero during the ground run, the NPRM proposed to require, before further flight, altering the NR sensor wiring.

The NPRM was prompted by EASA AD No. 2016-0260, dated December 21, 2016, issued by EASA, which is the Technical Agent for the Member States of the European Union, to correct an unsafe condition for Airbus Helicopters Model AS350B2 helicopters with a certain part-numbered NR sensor installed. EASA advises of several occurrences where the NR indicator has displayed incorrect data. According to EASA, an investigation determined that whenever the emergency cut-out control was activated, such as during a practice autorotation, electrical power to the NR indicator was lost. The EASA AD states that this condition, if not detected and corrected, could result in a significant increase in pilot workload, disruption of the autorotation training, and subsequent reduced control of the helicopter. To address this unsafe condition, the EASA AD requires a functional check of the NR indicator display, and, if required, altering the wiring to ensure a dual power supply to the NR indicator.

FMI: www.regulations.gov