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Federal Register / Vol. 86, No. 171 / Wednesday, September 8, 2021 / Rules and Regulations
Docket Operations is U.S. Department of Transportation, Docket Operations, M
30, West Building Ground Floor, Room W12140, 1200 New Jersey Avenue SE, Washington, DC 20590.
FOR FURTHER INFORMATION CONTACT:
Bang Nguyen, Aerospace Engineer, Certification Section, Fort Worth ACO
Branch, Compliance & Airworthiness Division, FAA, 10101 Hillwood Pkwy., Fort Worth, TX 76177; telephone 817
2224973; email bang.nguyen@faa.gov.
SUPPLEMENTARY INFORMATION:

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Background The FAA issued a notice of proposed rulemaking NPRM to amend 14 CFR
part 39 by adding an AD that would apply to Leonardo S.p.a. Model AB139
and AW139 helicopters with an MRB
that has less than 1,200 total hours timein-service TIS and has part number P/
N 3G6210A00131 with any serial number S/N listed in Table 1 of Leonardo Helicopters Alert Service Bulletin No. 139520, dated April 26, 2018 ASB 139520, installed. The NPRM published in the Federal Register on June 16, 2021 86 FR 31992.
In the NPRM, the FAA proposed to require, within 50 hours TIS, tap inspecting each MRB tip cap for disbonding using a tap hammer or equivalent. If there is no disbonding, the NPRM proposed to require tap inspecting the MRB tip cap at intervals not to exceed 50 hours TIS. If there is any disbonding that does not exceed the specified limits in ASB 139520, the NPRM proposed to require tap inspecting the MRB at intervals not to exceed 10 hours TIS. If there is any disbonding that exceeds the specified limits in ASB 139520, the NPRM
proposed to require removing the MRB
from service before further flight. The NPRM also specified that the accumulation of 1,200 total hours TIS
on the affected part without findings of any disbonded area or with findings of any disbonded area that is within the permitted limits in Annex A of ASB
139520 would constitute terminating action for the proposed repetitive inspections. Finally, the NPRM
proposed to prohibit installing any MRB
that is identified in the applicability section of this AD on any helicopter.
The NPRM was prompted by reports of incorrect bonding procedures on certain MRBs, which if not detected and corrected, could result in loss of the MRB tip cap, severe vibrations, and subsequent loss of control of the helicopter.
The FAA issued AD 20180301, Amendment 3919174 83 FR 4136, January 30, 2018 AD 20180301 for
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Agusta S.p.A. now Leonardo S.p.a.
Model AB139 and AW139 helicopters with MRB P/N 3G6210A00131 with an S/N 3615, 3634, 3667, or 3729 installed.
AD 20180301 requires inspecting the MRB tip cap for disbonding and was prompted by EASA AD 20170175E, dated September 13, 2017 EASA AD
20170175E, issued by EASA, which is the Technical Agent for the Member States of the European Union. EASA
advised of an in-flight loss of an MRB
tip cap on an AW139 helicopter where the pilot was able to safely land the helicopter. EASA further advised that an investigation determined the cause as incorrect bonding procedures used during production on MRB P/N
3G6210A00131, S/N 3615, 3634, 3667, and 3729. According to EASA, this condition could result in loss of an MRB
tip cap, increased pilot workload, and reduced control of the helicopter. To address this unsafe condition, EASA AD
20170175E requires a one-time inspection of the affected MRB tip caps within 5 flight hours FH and replacing the affected MRBs within 10 FH if not replaced as a result of the inspection.
EASA AD 20170175E also prohibits installing the affected MRBs on a helicopter. AD 20180301 requires the same corrective actions.
After the FAA issued AD 20180301, EASA issued EASA AD 20180130, dated June 18, 2018 EASA AD 2018
0130, to correct the same unsafe condition for Leonardo S.p.a. Model AB139 and AW139 helicopters with additional serial-numbered MRBs installed. EASA advises that further investigations after EASA AD 2017
0175E was issued determined that another batch of P/N 3G6210A00131
MRBs may have been subject to the incorrect bonding procedure, but to a less critical extent. EASA AD 2018
0130, which neither revises nor supersedes EASA AD 20170175E, applies to the following serial-numbered MRBs with less than 1,200 FH: 2709, 3558, 3624, 3707, 3790, 3486, 3561, 3625, 3717, 3795, 3488, 3569, 3626, 3720, 3798, 3495, 3570, 3627, 3725, 3803, 3500, 3574, 3628, 3726, 3807, 3501, 3575, 3633, 3734, 3812, 3502, 3582, 3636, 3735, 3822, 3503, 3583, 3638, 3738, 3824, 3508, 3586, 3642, 3739, 3825, 3510, 3590, 3648, 3741, 3827, 3513, 3592, 3649, 3743, 3831, 3520, 3595, 3650, 3744, 3832, 3527, 3597, 3651, 3745, 3838, 3528, 3599, 3657, 3753, 3841, 3529, 3602, 3665, 3754, 3842, 3531, 3603, 3672, 3761, 3847, 3536, 3605, 3682, 3766, 3850, 3539, 3609, 3684, 3770, 3851, 3544, 3612, 3686, 3771, 3852, 3549, 3613, 3690, 3777, 3853, 3551, 3616, 3691,
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3783, 3854, 3556, 3620, 3695, 3788, 3855, 3557, 3622, 3696, and 3789.
Accordingly, EASA AD 20180130
requires within 50 FH and thereafter at intervals not to exceed 50 FH, tap inspecting the MRB for disbonding. If there is disbonding within permitted limits, EASA AD 20180130 requires tap inspecting the disbonded area within 10 FH and thereafter at intervals not to exceed 10 FH. If disbonding that exceeds the permitted limits is found during any inspection, EASA AD 2018
0130 requires replacing the part. EASA
AD 20180130 also prohibits installing the affected part unless it is a serviceable part and includes a terminating action for the repetitive inspections, which is accumulation of 1,200 FH by an affected part without findings of disbonded area, or findings of disbonded area within the limits specified in Annex A of ASB 139520.
Discussion of Final Airworthiness Directive The FAA received no comments on the NPRM or on the determination of the costs.
Conclusion These helicopters have been approved by EASA and are approved for operation in the United States. Pursuant to the FAAs bilateral agreement with the European Union, EASA has notified the FAA about the unsafe condition described in its AD. The FAA reviewed the relevant data and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these helicopters.
Related Service Information Under 1
CFR Part 51
The FAA reviewed ASB 139520.
This service information specifies procedures for repetitively inspecting the tip cap on a certain batch of MRBs for disbonding using a tap test and replacing the MRB if disbonding is not within permitted limits.
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 the ADDRESSES section.
Differences Between This AD and the EASA AD
EASA AD 20180130 allows replacing an affected part with a serviceable part, which is marked with the letter R
repaired tip cap as the last digit of the S/N, as a terminating action for the repetitive inspections specified in that AD, whereas this AD does not.

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