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Federal Register / Vol. 86, No. 179 / Monday, September 20, 2021 / Proposed Rules EASA AD 20210088 was revised by EASA AD 20210088R1, dated July 26, 2021 EASA AD 20210088R1 referred to after this as the MCAI, to address the unsafe condition on these products.
The MCAI states:
An occurrence was reported of simultaneous loss of automatic control in flight of both ARRIUS 2B1 engines on an EC135 T1 helicopter. Loss of automatic control would result, for each engine, from a difference between the position datum of the fuel metering valve and its measured position.
This condition, if not corrected, could lead to increased work for flight crew during certain flight phases, possibly resulting in reduced control of the helicopter.
To address this potential unsafe condition, Turbomeca developed mod TU80C, TU81C, TU82C and TU90C to improve the DECU
software for ARRIUS 2B1 engines without overspeed option, ARRIUS 2B1 engines with overspeed option, ARRIUS 2B1A and ARRIUS 2B2 engines, and DGAC France issued AD F2004017 later revised to require engine modification.
Since that DGAC France AD was issued, it was determined that a DECU having a P/N which corresponds to Turbomeca mod TU80C, TU81C, TU82C, TU90C or later software is not affected by the software modification requirement. DGAC France AD
F2004017R1 did not specifically identify any affected DECU P/Ns.
For the reason described above, this EASA AD retains the requirements of DGAC
France AD F2004017R1 EASA approval 20041618, which is superseded, and limits the required actions to engines with an affected DECU P/N installed. This EASA
AD also prohibits reinstallation of affected DECU on any engine.
This EASA AD is revised to provide clarification on affected and serviceable DECU.

You may obtain further information by examining the MCAI in the AD
docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210793.
In addition, Turbomeca issued Mandatory Service Bulletin MSB No.
319 73 2082, Version D, dated June 6, 2011. The manufacturer discovered an error in Version C of the MSB and determined that the requirement to replace the EECU or upgrade the EECU
software should be applicable to only
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engines with a certain EECU P/N
installed.

Proposed AD Requirements in This NPRM

FAAs Determination
This proposed AD would retain all the requirements of AD 20051208.
This proposed AD would require replacement of the EECU or upgrade of the EECU software for engines with a certain EECU P/N installed. This proposed AD would also prohibit installation of an affected EECU onto any engine.

This product has been approved by EASA and is approved for operation in the United States. Pursuant to our bilateral agreement with the European Community, EASA has notified the FAA
of the unsafe condition described in the MCAI and service information. The FAA is issuing this NPRM because the agency evaluated all the relevant information provided by EASA and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.
Related Service Information Under 1
CFR Part 51
The FAA reviewed Turbomeca Mandatory Service Bulletin MSB No.
319 73 2080, Update No. 1, dated February 13, 2004; Turbomeca MSB No.
319 73 2081, Update No. 1, dated February 13, 2004; Turbomeca MSB No.
319 73 2082, Update No. 1, dated February 13, 2004, Version C, dated July 31, 2008, and Version D, dated June 6, 2011; and Turbomeca MSB No. 319 73
2090, Original Issue, dated February 13, 2004. This service information specifies procedures for upgrading the EECU by either replacing the EECU or by uploading the software to the EECU.
These documents are distinct since they apply to different engine models in different configurations. The Director of the Federal Register previously approved Turbomeca MSB No. 319 73
2080, Update No. 1, dated February 13, 2004; Turbomeca MSB No. 319 73 2081, Update No. 1, dated February 13, 2004;
Turbomeca MSB No. 319 73 2082, Update No. 1, dated February 13, 2004;
and Turbomeca MSB No. 319 73 2090, Original Issue, dated February 13, 2004
for incorporation by reference on June 29, 2005 70 FR 34334, June 14, 2005.
This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in ADDRESSES.

Differences Between the Proposed AD
and MCAI or Service Information EASA AD 20210088R1, dated July 26, 2021, uses the term digital engine control unit DECU, whereas the Turbomeca MSBs and this proposed AD
use EECU. These terms refer to the same part.
Turbomeca MSB No. 319 73 2080, Update No. 1, dated February 13, 2004;
Turbomeca MSB No. 319 73 2081, Update No. 1, dated February 13, 2004;
Turbomeca MSB No. 319 73 2082, Update No. 1, dated February 13, 2004, Version C, dated July 31, 2008, and Version D, dated June 6, 2011; and Turbomeca MSB No. 319 73 2090, Original Issue, dated February 13, 2004, instruct operators to notify Turbomeca that the EECUs have been replaced by returning the completed compliance certificate. This proposed AD would not mandate returning the completed compliance certificate to Turbomeca.
EASA AD 20210088R1 and the Turbomeca service information reference Arrius 2B1A_1 or Arrius 2B1A1 model turboshaft engines, whereas this AD references Arrius 2B1A
model turboshaft engines. Arrius 2B1A_
1 model turboshaft engines are Arrius 2B1A model turboshaft engines with modification mod TU45C.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 221
engines installed on helicopters of U.S.
registry.
The FAA estimates the following costs to comply with this proposed AD:

ESTIMATED COSTS
Action
Labor cost
Replace the EECU
Upgrade the EECU software

1 work-hour $85 per hour = $85
2 work-hours $85 per hour = $170

Authority for This Rulemaking Title 49 of the United States Code specifies the FAAs authority to issue
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Parts cost
rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII,
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$35,000
0

Cost per product $35,085
170

Cost on U.S.
operators $7,753,785
37,570

Aviation Programs, describes in more detail the scope of the Agencys authority.

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