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Federal Register / Vol. 86, No. 89 / Tuesday, May 11, 2021 / Proposed Rules
FAAs Determination The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.
Related Service Information Under 1
CFR Part 51
The FAA reviewed the following service documents proposed for compliance with this NPRM:
Textron Aviation Mandatory Single Engine Service Letter, SEL5708, Revision 2, dated August, 3, 2020 SEL
5708R2; and Textron Aviation Mandatory Single Engine Service Letter, SEL5709, Revision 1, dated August, 3, 2020 SEL
5709R1.
For the applicable airplanes specified, these service letters contain instructions for visually inspecting the carry-thru spar for corrosion, damage, and cracks and for completing an eddy current inspection. This service information also specifies applying protective coating and CIC.
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 of this NPRM.
Other Related Service Information The FAA reviewed the following service letters related to this NPRM, which, for the applicable airplanes specified, contain instructions for visually inspecting the carry-thru spar for corrosion and doing an eddy current inspection of the carry-thru spar regardless of whether corrosion was found and removed. This service information also contains instructions for applying CIC, but does not specify applying protective coating.
Textron Aviation Mandatory Single Engine Service Letter, SEL5706, dated June, 24, 2019 SEL5706;
Textron Aviation Mandatory Single Engine Service Letter, SEL5706, Revision 1, dated November 19, 2019;
Textron Aviation Mandatory Single Engine Service Letter, SEL5707, dated June 24, 2019 SEL5707; and Textron Aviation Mandatory Single Engine Service Letter, SEL5707, Revision 1, dated November 19, 2019.
The FAA also reviewed the service letters listed below related to this NPRM, which, for the applicable airplanes specified, contain the same instructions and repair criteria as SEL
5708R2 and SEL5709R1.
Textron Aviation Mandatory Single Engine Service Letter, SEL5708, dated November 1, 2019;

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Textron Aviation Mandatory Single Engine Service Letter, SEL5708, Revision 1, dated November 19, 2019;
and Textron Aviation Mandatory Single Engine Service Letter, SEL5709, dated November 19, 2019.
Proposed AD Requirements in This NPRM
This proposed AD would require accomplishing the actions specified in SEL5708R2 and SEL5709R1, except as discussed under Differences Between this Proposed AD and the Service Information. This proposed AD also requires reporting the inspection results to the FAA by email at Wichita-COS@
faa.gov.
Differences Between This Proposed AD
and the Service Information Although Textron SEL5708R2
also applies to Models 210G, T210G, 210H, T210H, 210J, T210J, 210K, T210K, 210L, T210L, 210M, and T210M
airplanes, this proposed AD would not.
The FAA issued AD 20200316 to address the immediate safety of flight for those airplanes.
Textron SEL5708R2 and Textron SEL5709R1 specify inspecting all interior surfaces of the carry-thru spar;
additionally, Textron SEL5709R1
specifies inspecting the lower surface of the outboard spar to wing attach lugs.
This proposed AD would only require inspecting the carry-thru spar lower cap, including the lower surface, edge, and upper surface of the lower cap. While the web, upper cap, and lugs of the carry-thru spar may be susceptible to corrosion, evidence does not support including inspection of these areas as part of this proposed AD. The FAA will continue to monitor reports of corrosion on all areas of the carry-thru spar for potential future action.
Textron SEL5708R2 and Textron SEL5709R1 do not require an eddy current inspection on the carry-thru spar unless the amount of material removed in the blended area exceeds 0.010 inch deep but is within limits.
This proposed AD would require an eddy current inspection of all locations on the carry-thru spar where corrosion was removed. The fatigue crack on the Model T210M airplane that suffered the fatal in-flight break-up initiated from a corrosion pit approximately 0.011 inch deep in the lower cap kick area. The visual and less restrictive eddy current inspection requirements specified in SEL5708R2 and SEL5709R1 could potentially miss similar fatigue cracks on airplanes currently operating in the field.

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Textron SEL5708R2 and Textron SEL5709R1 only require eddy current inspection of the lower cap kick of the carry-thru spar if corrosion is identified on the carry-thru spar cap. This proposed AD would require a one-time eddy current inspection of the lower cap kick area of all affected airplanes, regardless of the results of the visual inspection. The fatigue crack on the Model T210M airplane that suffered the fatal in-flight break-up initiated in the lower cap kick area. Cracks and corrosion damage may be difficult to identify through visual inspection alone. The FAA will use the results of the one-time eddy current inspection of the lower cap kick area, in part, to determine the necessity of future rulemaking action.
Textron SEL5708R2 and Textron SEL5709R1 specify contacting Textron for evaluation and disposition of certain damage. Instead, this proposed AD would require removing the carry-thru spar from service or repairing it if possible in accordance with the AMOC procedures identified in paragraph o of this proposed AD.
Operators should work with Textron to develop a repair in support of an AMOC
request.
Textron SEL5708 R2 and Textron SEL5709R1 provide instruction allowing airplanes that have complied with SEL5706 or SEL5707 to complete the application of the protective coating and CIC within 200
flight hours or at the next annual inspection, whichever occurs first. This proposed AD would permit those airplanes that have complied with the visual and eddy current inspections in SEL5706 or SEL5707, as required by paragraphs g and h of this proposed AD, to complete the application of the protective coating and CIC within 24 months from the date of the visual and eddy current inspections or within 12 months after the effective date of this AD, whichever occurs first.
Interim Action The FAA considers this proposed AD
an interim action. This proposed AD
would require a one-time visual inspection of specified areas on the carry-thru spar lower cap and an eddy current inspection of the lower cap kick area and any locations where corrosion was removed. This proposed AD would also require reporting the inspection results to the FAA. The FAA will analyze the inspection results received to determine further rulemaking action.

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