# [Amended]
**AGENCY:**
Federal Aviation Administration (FAA), DOT.
**ACTION:**
Notice of proposed rulemaking (NPRM).
**SUMMARY:**
The FAA proposes to adopt a new airworthiness directive (AD) for all restricted category Model CH-47D helicopters. This proposed AD was prompted by reports of fatigue cracking of the right-hand (RH) forward transmission support beam fitting. This proposed AD would require repetitively inspecting the RH forward transmission support beam fitting for cracking and, depending on the results, repairing any crack(s). This proposed AD would also require submitting data on any previous repairs and replaced fittings. The FAA is proposing this AD to address the unsafe condition on these products.
**DATES:**
The FAA must receive comments on this proposed AD by February 5, 2026.
**ADDRESSES:**
You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods:
• *Federal eRulemaking Portal:* Go to *regulations.gov.* Follow the instructions for submitting comments.
• *Fax:* (202) 493-2251.
• *Mail:* U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
• *Hand Delivery:* Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
*AD Docket:* You may examine the AD docket at *regulations.gov* under Docket No. FAA-2025-5394; 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.
**FOR FURTHER INFORMATION CONTACT:**
Sarah Illg, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: (206) 231-3517; email: *[email protected]* .
**SUPPLEMENTARY INFORMATION:**
**Comments Invited**
The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments using a method listed under *ADDRESSES* . Include “Docket No. FAA-2025-5394; Project Identifier AD-2025-01194-R” 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 *regulations.gov* , including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.
**Confidential Business Information**
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 Sarah Illg, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.
**Background**
The FAA received reports of fatigue cracking of the RH forward transmission support beam fitting having part number 145S1838-1 on CH-47D helicopters. CH-47D type certificate holders and operators have reported experiencing at least one cracking event around the fastener on the RH forward transmission support beam fitting at the right butt line (RBL) 18 from station (STA) 76 to STA 120. This condition, if not addressed, could result in crack propagation and lead to failure of the RH forward transmission support beam fitting, excessive vibration, and consequent loss of control of the helicopter.
**FAA's 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.
**Proposed AD Requirements in This NPRM**
This proposed AD would require repetitively inspecting the RH forward transmission support beam fitting for cracking and, depending on the results, repairing any crack(s) or replacing parts. This proposed AD would also require submitting data on any previous repairs and replaced fittings to the FAA.
**Costs of Compliance**
The FAA estimates that this AD, if adopted as proposed, would affect 42 helicopters of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD:
| Action | Labor cost | Parts | Cost per | Cost on U.S. |
| --- | --- | --- | --- | --- |
| Inspect RH forward transmission support beam fitting | 2 work-hours × $85 per hour = $170 | $0 | $170 | $7,140 |
| Report previous repairs and replaced fittings | 1 work-hour × $85 per hour = $85 | 0 | 85 | 3,570 |
The FAA has received no definitive data on which to base the cost estimates for the on-condition repairs specified in this proposed AD.
**Paperwork Reduction Act**
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. All responses to this collection of information are mandatory. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to: Information Collection Clearance Officer, Federal Aviation Administration, 10101 Hillwood Parkway, Fort Worth, TX 76177-1524.
**Authority for This Rulemaking**
Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.
The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.
**Regulatory Findings**
The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.
For the reasons discussed above, I certify this proposed regulation:
(1) Is not a “significant regulatory action” under Executive Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.
**List of Subjects in 14 CFR Part 39**
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
**The Proposed Amendment**
Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
**PART 39—AIRWORTHINESS DIRECTIVES**
1. The authority citation for part 39 continues to read as follows:
**Authority:**
49 U.S.C. 106(g), 40113, 44701.
§ 39.13
2. The FAA amends § 39.13 by adding the following new airworthiness directive:
*Restricted Category Model CH-47D Helicopters:* Docket No. FAA-2025-5394; Project Identifier AD-2025-01194-R.
**(a) Comments Due Date**
The FAA must receive comments on this airworthiness directive (AD) by February 5, 2026.
**(b) Affected ADs**
None.
**(c) Applicability**
This AD applies to restricted category Model CH-47D helicopters; current type certificate holders include but are not limited to Billings Flying Service, Inc.; Columbia Helicopters, Inc.; Tandem Rotor, LLC; and Unical Air Inc.
**(d) Subject**
Joint Aircraft System Component (JASC) Code 6330, Main Rotor Transmission Mount.
**(e) Unsafe Condition**
This AD was prompted by reports of fatigue cracking of the right-hand (RH) forward transmission support beam fitting. The FAA is issuing this AD to detect and address fatigue cracking of the RH forward transmission support beam fittings. The unsafe condition, if not addressed, could result in crack propagation and lead to failure of the RH forward transmission support beam fitting, excessive vibration, and consequent loss of control of the helicopter.
**(f) Compliance**
Comply with this AD within the compliance times specified, unless already done.
**(g) Required Actions**
(1) Within 30 hours time in service (TIS) after the effective date of this AD and thereafter at intervals not to exceed 100 hours TIS, using a 7X or higher power magnification and light source, visually inspect the RH forward transmission support beam fitting having part number 145S1838-1 at right butt line (RBL) 18 from station (STA) 76 to STA 120 for cracks. Fastener holes in the area circled in figure 1 to paragraph (g)(1) of this AD are most susceptible to cracking. If any crack is detected, before further flight, repair or replace parts using a method approved by the Manager, West Certification Branch, FAA, in accordance with the procedures specified in paragraph (i) of this AD.
**Figure 1 to Paragraph (g)(1)—Transmission Support Beam Inspection**
(2) For repairs accomplished before the effective date of this AD, within 30 days after the effective date of this AD, submit the information specified in paragraphs (g)(2)(i) through (v) of this AD to the person identified in paragraph (j) of this AD.
(i) Aircraft serial number, registration number, and TIS when fitting was repaired.
(ii) Design data used to accomplish repair (drawings, engineering orders, etc.).
(iii) Substantiation data used to approve repair.
(iv) Copy of FAA Form 337 “Major Repair or Alteration” or other approval of return to service. If repair was performed by the U.S. military, provide a copy of Form 2408-15 (or equivalent) documenting major repair.
(v) Alternative methods of compliance for previously approved repairs.
(3) For fittings that have been replaced before the effective date of this AD, within 30 days after the effective date of this AD, submit the information specified in paragraphs (g)(3)(i) and (ii) of this AD to the person identified in paragraph (j) of this AD.
(i) If the replacement fitting was new production (under 14 CFR 21.9 or exemption): where the part was sourced from, when the part was produced, and the manufacturer of the part.
(ii) If the replacement fitting was used: where the part was sourced from (aircraft registration and serial number or manufacturer), TIS of the used part prior to installation, and TIS after installation.
**(h) Special Flight Permits**
Special flight permits are prohibited.
**(i) Alternative Methods of Compliance (AMOCs)**
(1) The Manager, West Certification Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or local Flight Standards District Office, as appropriate. If sending information directly to the manager of the West Certification Branch, send it to the attention of the person identified in paragraph (j) of this AD and email to: *[email protected]* .
(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the local flight standards district office/certificate holding district office.
**(j) Additional Information**
For more information about this AD, contact Sarah Illg, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: (206) 231-3517; email: *[email protected].*
**(k) Material Incorporated by Reference**
None.
Issued on December 17, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.