AD 2021-11-25 Prompted By A Report Of Failure Of An Engine Digital Electronic Control Unit

The FAA is adopting a new airworthiness directive (AD) for certain Airbus Helicopters (Type Certificate previously held by Eurocopter France) Model AS350B3 and EC130T2 helicopters.

This AD was prompted by a report of failure of an engine digital electronic control unit (DECU). This AD requires revising the existing Rotorcraft Flight Manual (RFM) for your helicopter. The FAA is issuing this AD to address the unsafe condition on these products. This AD is effective July 29, 2021.

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 (Type Certificate previously held by Eurocopter France) Model AS350B3 and EC130T2 helicopters with an ARRIEL 2D engine and THALES full authority digital engine control (FADEC) part number (P/N) C13165DA00 without amendment A or P/N C13165FA00 without amendment B, installed. The NPRM published in the Federal Register on March 22, 2021 (86 FR 15140). In the NPRM, the FAA proposed to require revising the Emergency Procedures of the existing RFM for your helicopter by inserting Appendix 4. of Airbus Helicopters Alert Service Bulletin (ASB) No. AS350-01.00.67 or ASB No. EC130-04A004, each Revision 2 and dated February 17, 2014 (ASB AS350-01.00.67 and ASB EC130-04A004) or a different document with information identical to that in Appendix 4., as applicable to your helicopter model. As an optional terminating action for the RFM revision, the NPRM proposed to allow installing amendment A on FADEC P/N C13165DA00 or amendment B on FADEC P/N C13165FA00.

The NPRM was prompted by EASA AD 2013-0287, dated December 5, 2013 (EASA AD 2013-0287), issued by EASA, which is the Technical Agent for the Member States of the European Union, to correct an unsafe condition for Eurocopter (formerly Eurocopter France, Aerospatiale) Model AS 350 B3 and EC 130 T2 helicopters with an ARRIEL 2D engine and THALES FADEC P/N C13165DA00 or P/N C13165FA00 installed. EASA advises of a report of an in-flight event where the pilot noticed that the temporary amber governor (GOV) light had illuminated, followed by the failure of the vehicle engine monitoring display (VEMD) screens, and no availability of the automatic or auxiliary engine back-up control ancillary unit (EBCAU). Subsequent investigation identified an internal failure of the engine DECU, which led to loss of fuel flow regulation (frozen fuel metering unit). This failure was not indicated to the pilot by a red GOV warning light as expected, but with amber GOV indication and loss of VEMD display instead. EASA also advises that if this fuel metering unit is frozen in the open position, it may lead to a rotor overspeed, and if it is frozen in the closed position, it may lead to unavailability of engine power. EASA states that this condition, if not addressed, could result in the pilot identifying the type of failure condition incorrectly, possibly resulting in an improper response.

Accordingly, and pending the development of a DECU assembly design improvement, the EASA AD requires incorporating a new procedure into the Emergency Procedures section of the RFM and informing all flight crews of the RFM change. EASA considers its AD an interim action and states that further AD action may follow.

After EASA issued EASA AD 2013-0287, EASA issued SIB No. 2013-23, dated December 19, 2013, for Eurocopter AS 350 B3 and EC 130 T2 helicopters with a Turboméca ARRIEL 2D engine installed. The SIB recommends modifying certain electronic engine control units (EECUs).

FMI: www.regulations.gov