AD 2021-17-02 Prompted By False Activation Of The Stall Warning System Due To Wiring Damage

The FAA is superseding Airworthiness Directive (AD) 2020-23-13, which applied to all ATR–GIE Avions de Transport Régional Model ATR42-200, -300, and -320 airplanes.

AD 2020-23-13 required a one-time inspection for discrepancies of the wire bundles between the left- and right-hand angle of attack (AOA) probes and the crew alerting computer, and, depending on findings, applicable corrective actions. This AD continues to require the actions in AD 2020-23-13, and also requires for certain airplanes, modifying the captain stick shaker wiring, and for all airplanes, revising the existing aircraft flight manual (AFM) and applicable corresponding operational procedures to incorporate procedures for the stick pusher/shaker, as specified in a European Union Aviation Safety Agency (EASA) AD, which is incorporated by reference. This AD was prompted by false activation of the stall warning system due to wiring damage on the wire bundle between an AOA probe and the crew alerting computer, and the development of a wiring modification and AFM update to address the unsafe condition. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective October 5, 2021.

Supplementary Information: EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2021-0024, dated January 19, 2021 (EASA AD 2021-0024) (also referred to as the Mandatory Continuing Airworthiness Information, or the MCAI), to correct an unsafe condition for all ATR–GIE Avions de Transport Régional Model ATR42-200, -300, and -320 airplanes. The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2020-23-13, Amendment 39-21330 (85 FR 73407, November 18, 2020) (AD 2020-23-13). AD 2020-23-13 applied to all ATR–GIE Avions de Transport Régional Model ATR42-200, -300, and -320 airplanes. The NPRM published in the Federal Register on May 13, 2021 (86 FR 26195). The NPRM was prompted by false activation of the stall warning system due to wiring damage on the wire bundle between an AOA probe and the crew alerting computer, and the development of a wiring modification and AFM update to address the unsafe condition. The NPRM proposed to continue to require the actions in AD 2020-23-13, and also proposed to require for certain airplanes, modifying the captain stick shaker wiring, and for all airplanes, revising the existing AFM and applicable corresponding operational procedures to incorporate procedures for the stick pusher/shaker, as specified in EASA AD 2021-0024.

The FAA is issuing this AD to address false activation of the stall warning system, which could result in loss of control of the airplane during take-off and landing phases. See the MCAI for additional background information.

FMI: www.regulations.gov