Airworthiness Directives; Twin Commander Aircraft LLC Airplanes

DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 39</CFR> <DEPDOC>[Docket No. FAA-2025-3438; Project Identifier AD-2025-01163-A]</DEPDOC> <RIN>RIN 2120-AA64</RIN> <SUBJECT>Airworthiness Directives; Twin Commander Aircraft LLC Airplanes</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Notice of proposed rulemaking (NPRM). <SUM> <HD SOURCE="HED">SUMMARY:</HD> The FAA proposes to adopt a new airworthiness directive (AD) for all Twin Commander Aircraft LLC (Twin Commander) Model 685, 690, 690A, 690B, 690C, 690D, 695, and 695A airplanes. This proposed AD was prompted by reports of fatigue cracking affecting structural components within the fuselage and empennage structure. This proposed AD would require inspecting certain structural components within the fuselage and vertical stabilizer for any evidence of cracks, corrosion, or loose hardware, and inspecting the working fasteners at the diagonal braces of fuselage station (FS) 386 for cracks, elongation, or deformation; and depending on the results of the inspections, replacing with new parts or used parts or repairing, as applicable; and reporting inspection results to the FAA. The FAA is proposing this AD to address the unsafe condition on these products. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> The FAA must receive comments on this proposed AD by January 2, 2026. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods: • <E T="03">Federal eRulemaking Portal:</E> Go to <E T="03">regulations.gov.</E> Follow the instructions for submitting comments. • <E T="03">Fax:</E> (202) 493-2251. • <E T="03">Mail:</E> U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. • <E T="03">Hand Delivery:</E> Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. <E T="03">AD Docket:</E> You may examine the AD docket at <E T="03">regulations.gov</E> under Docket No. FAA-2025-3438; 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 NPRM, any comments received, and other information. The street address for Docket Operations is listed above. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Lekebis Russell, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337; phone: (404) 474-5510; email: <E T="03">ecb-cos@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Comments Invited</HD> The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments using a method listed under the <E T="02">ADDRESSES</E> section. Include “Docket No. FAA-2025-3438; Project Identifier AD-2025-01163-A” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may revise this proposal because of those comments. Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to <E T="03">regulations.gov,</E> including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM. <HD SOURCE="HD1">Confidential Business Information</HD> CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this NPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI should be sent to Lekebis Russell, Aviation Safety Engineer, FAA, 1701 Columbia Avenue, College Park, GA 30337. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking. <HD SOURCE="HD1">Background</HD> The FAA received reports of fatigue cracking throughout the fuselage and vertical stabilizer's structural components on Twin Commander Model 685, 690, 690A, 690B, 690C, 690D, 695, and 695A airplanes. The fatigue cracking was found in areas with insufficient access for inspections, which led to undetected crack development. Specifically, cracking was observed at FS 409, the vertical stabilizer's aft spar, the horizontal stabilizer's forward spar, and the vertical stabilizer skin. AD 95-13-02, Amendment 39-9283 (60 FR 32583, June 23, 1995) (AD 95-13-02) was issued to address cracking in the vertical stabilizer. This AD requires initially inspecting the vertical stabilizer for cracks, modifying any cracked vertical stabilizer, and, if not cracked, either repetitively inspecting or modifying the vertical stabilizer, and allowed for terminating action through modification or repair. Since the issuance of AD 95-13-02, continued cracking has been observed at FS 409. These findings show that previously implemented modifications in AD 95-13-02 did not provide an effective terminating action, along with the detection of additional cracking at FS 386 and FS 429 during later inspections. FS 386 and FS 429, where cracks were recently found, were not part of the inspections required by AD 95-13-02. Therefore, this proposed AD, while not superseding AD 95-13-02, addresses continued cracking in FS 409, including areas adjacent to prior repairs, by requiring inspections around repaired members, thereby complementing the ongoing requirements of AD 95-13-02. The FAA is proposing this AD to prevent the failure of the aft fuselage or empennage structural members. The unsafe conditions, if not addressed, could result in structural failure of the empennage, which could lead to loss of control of the airplane. <HD SOURCE="HD1">FAA's Determination</HD> 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. <HD SOURCE="HD1">Proposed AD Requirements in This NPRM</HD> This proposed AD would require inspecting certain structural components within the fuselage and vertical stabilizer for any evidence of cracks, corrosion, or loose hardware, and inspecting the working fasteners at the diagonal braces of FS 386 for cracks, elongation, or deformation; and depending on the results of the inspections, replacing with new parts or used parts or repairing, as applicable. This proposed AD would also require reporting the inspection results to the FAA. <HD SOURCE="HD1">Interim Action</HD> The FAA considers that this proposed AD would be an interim action. An investigation is ongoing, and the final corrective action has not yet been determined. Once corrective action has been determined, the FAA may consider additional rulemaking action. <HD SOURCE="HD1">Costs of Compliance</HD> The FAA estimates that this AD, if adopted as proposed, would affect 589 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: <GPOTABLE COLS="5" OPTS="L2,nj,i1" CDEF="s75,r60,10,10,12"> <TTITLE>Estimated Costs</TTITLE> <CHED H="1">Action</CHED> <CHED H="1">Labor cost</CHED> <CHED H="1">Parts cost</CHED> Cost on U.S. operators </CHED> <ROW> <ENT I="01">Perform detailed visual inspection FS 386, 409, 429, and vertical stabilizer</ENT> <ENT>60 work-hours × $85 per hour = $5,100</ENT> <ENT>$0</ENT> <ENT>$5,100</ENT> <ENT>$3,003,900</ENT> </ROW> <ROW> <ENT I="01">Perform general visual inspection of empennage structure</ENT> <ENT>30 work-hours × $85 per hour = $2,550</ENT> <ENT>0</ENT> <ENT>2,550</ENT> <ENT>1,501,950</ENT> </ROW> <ROW> <ENT I="01">Report inspection findings</ENT> <ENT>1 work-hour × $85 per hour = $85</ENT> <ENT>0</ENT> <ENT>85</ENT> <ENT>50,065</ENT> </ROW> </GPOTABLE> The extent of the fatigue cracking within the fuselage or empennage structural components may vary significantly from airplane to airplane. The FAA has no way to determine how much damage may be found on each airplane, the extent of the damage, the cost to repair the damaged areas (or replace the part, if needed), or the number of airplanes that might require repair or replacement. <HD SOURCE="HD1">Paperwork Reduction Act</HD> A federal agency may not conduct or sponsor, and a person is not required to respond to, nor shall a person be subject to a penalty for failure to comply with a collection of information subject to the requirements of the Paperwork Reduction Act unless that collection of information displays a currently valid OMB Control Number. The OMB Control Number for this information collection is 2120-0056. Public reporting for this collection of information is estimated to be approximately 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. 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