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Federal Register / Vol. 86, No. 198 / Monday, October 18, 2021 / Rules and Regulations
Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210106; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this final rule, any comments received, and other information. The address for 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:
Dorie Resnik, Aerospace Engineer, Aviation Safety Section, Boston ACO
Branch, FAA, 1200 District Ave., Burlington, MA 01803; phone: 781
2387693; email: dorie.resnik@faa.gov.
SUPPLEMENTARY INFORMATION:
Background The FAA issued a notice of proposed rulemaking NPRM to amend 14 CFR
part 39 by adding an AD that would apply to Sikorsky Model S92A
helicopters with certain Martin-Baker side facing utility or observer seats installed. The NPRM published in the Federal Register on March 4, 2021 86
FR 12550. The NPRM was prompted by an incident of a side facing utility seat detaching from wall attachment points during dynamic testing. The root cause has been identified as a change in the finishing process of the main back tube.
Due to design similarity, certain observer seats are also subject to this unsafe condition. In the NPRM, the FAA
proposed to require replacing the main back tube assembly in affected side facing utility and observer seats. The NPRM also proposed to prohibit installing those seats unless the main back tube assembly has been replaced.
The FAA is issuing this AD to address the unsafe condition on these products.
Discussion of Final Airworthiness Directive
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Comments The FAA received comments from two commenters. One commenter supported the NPRM without change.
Sikorsky also commented on the NPRM.
The following presents the comments received on the NPRM and the FAAs response to each comment.
Request To Change the AD to an Appliance AD Against Martin-Baker Seats Sikorsky requested changes throughout the proposed AD to change it from an aircraft AD against Sikorsky to an appliance AD against Martin-

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Baker. Sikorsky stated that the defect is in Martin-Baker technical standard order TSO authorization seats and is not a defect of the Sikorsky Model S
92A helicopter, and that the seats sold to Sikorsky are manufactured under TSOC39b side facing utility seat and TSOC127a observer seat qualifications and are supplied with a TSOC39b or TSOC127a tag, as applicable. Sikorsky stated that the background of the AD should provide the result of the FAAs review with Martin-Baker Aircraft. According to Sikorsky, Martin-Baker indicated that seats for Sikorsky platforms are tracked separately from other platforms; and accordingly, the AD should be issued against affected Martin-Baker seats to ensure all affected parts Martin-Baker seat tube part number P/N MBCS4109
and/or seat P/Ns MBCS12410AA001, MBCS12200, MBCS73012, and other P/Ns as identified by Martin-Baker are corrected. Sikorsky further stated that during the review in support of the issuance of Sikorsky S92A Helicopter Alert Service Bulletin ASB 9225026, Basic Issue, dated March 5, 2020 ASB
9225026, Martin Baker Aircraft Company indicated that over 1,000
fielded seats are affected by the defect and that Sikorsky purchased 371 of the affected seats for the Model S92A
helicopter. Sikorsky stated that it issued ASB 9225026 to ensure its operators implemented the repairs specified in Martin-Baker Special Information Leaflet SIL No. 831, dated July 10, 2019 SIL 831, and SIL No. 833, dated July 11, 2019 SIL 833. Additionally, Sikorsky explained that ASB 9225026
identifies Model S92A helicopters with certain serial numbers S/Ns in its Effectivity paragraph because that was the known span at the time of its issuance; however, the AD should be against the seats because the seats can be moved from one serial-numbered aircraft to another serial-numbered aircraft and because the required change is to the articles.
The FAA disagrees. The FAA has confirmed that the manufacturing defect of Martin-Baker side facing utility seats supplier P/N MBCS12410AA001 did not cause non-compliance with TSOC39b Aircraft Seats and Berths. The unsafe condition does not exist in those seats, it resulted from the installation of those seats in Sikorsky Model S92A
helicopters. In this situation, it became Sikorskys responsibility to show compliance with 14 CFR 29.562 at Amendment 2941 for the installed seat because this is part of the certification basis of the aircraft as defined in FAA
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though the seat is TSOC39b qualified, the seat installation is required to meet the dynamic landing conditions defined in 14 CFR 29.562. Because the manufacturing defect caused noncompliance with the aircraft certification basis of 14 CFR 29.562, the AD is applicable to the aircraft.
Conversely, the FAA has confirmed that the manufacturing defect of MartinBaker observer seats supplier P/Ns MBCS12200 and MBCS73012 did cause non-compliance with TSOC127a, Rotorcraft, Transport Airplane, and Normal and Utility Airplane Seating Systems standards, which was the applicable TSO when the seats were manufactured. In this situation, the unsafe condition exists in those European State of Design seats, and not from the installation of those seats in Sikorsky Model S92A helicopters. The FAA recognizes that in this situation, the FAA customarily issues an AD
against the appliance instead of the aircraft. However, Sikorsky Model S
92A helicopters are the only model on the U.S. registry with those seats installed and the FAA has therefore determined that it is unnecessary to change this AD at this time and have a separate appliance AD against the observer seats. If additional information is later identified, the FAA might consider further rulemaking.
Request To Change the Consequences of Not Addressing the Unsafe Condition Sikorsky requested revising the consequences of not addressing the unsafe condition in paragraph e of this AD to not limit excessive lumbar loads during a crash event to just the observer seats because any seat with an improperly manufactured main back tube could induce excessive lumbar loads during a crash event.
The FAA agrees for the reasons provided. The FAA has revised paragraph e of this AD accordingly.
Request for Credit for Compliance With Service Information In a request to change requirements proposed in the NPRM, Sikorsky commented that compliance with ASB
9225026 was required by March 5, 2021, and that all affected seats installed on Sikorsky Model S92A
helicopters that have been updated with its procedures should be identified as complying with this AD with no further action required.
The FAA disagrees. This AD requires replacing each main back tube assembly by following procedures in ASB 9225
026. If this action has been accomplished prior to the effective date of this AD, then compliance for this
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