# [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 Textron Aviation, Inc., Model 525B airplanes. This proposed AD was prompted by the manufacturer's revision of the aircraft maintenance manual (AMM) to introduce more restrictive inspection intervals. This proposed AD would require revising the Airworthiness Limitations Section (ALS) of the existing AMM or instructions for continued airworthiness (ICA) and the existing approved maintenance or inspection program, as applicable. 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 January 12, 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-2025-5037; 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:**
Soban Saeed, Aviation Safety Engineer, FAA, 1801 South Airport Road, Wichita, KS 67209; phone: (316) 946-4123; 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 the *ADDRESSES* section. Include “Docket No. FAA-2025-5037; Project Identifier AD-2025-00212-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 *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 Soban Saeed, Aviation Safety Engineer, FAA, 1801 South Airport Road, Wichita, KS 67209. 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 was notified by Textron Aviation that the existing Model 525B AMM contained incorrect inspection intervals for airworthiness limitation tasks for Chapter 54—Nacelle/Pylons and Chapter 55—Stabilizers. The incorrect inspection intervals were introduced during a technical manual update. The FAA is issuing this AD to prevent undetected cracks in the engine mount and vertical stabilizer front and rear spar caps. The unsafe conditions, if not addressed, could result in reduced structural integrity and consequent reduced controllability of the airplane.
**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 revising the ALS of the existing AMM or ICA and the existing approved maintenance or inspection program, as applicable, by incorporating the actions and associated thresholds and intervals specified in table 1 to paragraph (g) of this proposed AD.
**Costs of Compliance**
The FAA estimates that this AD, if adopted as proposed, would affect 601 airplanes of U.S. registry.
The FAA estimates the following costs to comply with this proposed AD:
| Action | Labor cost | Parts cost | Cost per | Cost on U.S. |
| --- | --- | --- | --- | --- |
| Revise the ALS | 1 work-hour × $85 per hour = $85 | $0 | $85 | $51,085 |
**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:
*Textron Aviation Inc.:* Docket No. FAA-2025-5037; Project Identifier AD-2025-00212-A.
**(a) Comments Due Date**
The FAA must receive comments on this airworthiness directive (AD) by January 12, 2026.
**(b) Affected ADs**
None.
**(c) Applicability**
This AD applies to all Textron Aviation, Inc. (Type Certificate previously held by Cessna Aircraft Company) Model 525B airplanes, certificated in any category.
**(d) Subject**
Joint Aircraft System Component (JASC) Code 5530, Vertical Stabilizer Structure; 5415, Nacelle/Pylon, Attach Fittings.
**(e) Unsafe Condition**
This AD was prompted by the manufacturer's revision of the aircraft maintenance manual (AMM) to introduce more restrictive inspection intervals. The FAA is issuing this AD to prevent undetected cracks in the engine mount and vertical stabilizer front and rear spar caps. The unsafe conditions, if not addressed, could result in reduced structural integrity and consequent reduced controllability of the airplane.
**(f) Compliance**
Comply with this AD within the compliance times specified, unless already done.
**(g) Revision of the (ALS) or ICA**
Within 150 hours time-in-service (TIS) or 12 months after the effective date of this AD, whichever occurs first: Revise the Airworthiness Limitations Section (ALS) of the existing AMM or instructions for continued airworthiness (ICA) and the existing approved maintenance or inspection program, as applicable, by incorporating the revised tasks and associated thresholds and intervals identified in table 1 to paragraph (g) of this AD.
| Task No. | Task title | Existing task interval | Revised task interval | Inspection | Zone |
| --- | --- | --- | --- | --- | --- |
| 54-50-00-250 | Forward Engine Mount Channel Flange (Eddy Current) Special Detailed Inspection | 6,000 hours TIS | 6,100 hours TIS, then 4,100 hours TIS thereafter | 4-12-NA | 411, 412 |
| 54-50-00-252 | Aft Engine Beam Aft Upper Angle Common to Aft Web, BL 24.50 (Eddy Current) Special Detailed Inspection | 11,500 hours TIS | 14,100 hours TIS, then every 2,700 hours TIS thereafter | 4-12-MR | 311, 312 |
| 54-50-00-254 | Forward Engine Mount Aft Channel Web (Eddy Current) Special Detailed Inspection | 12,000 hours TIS | 16,300 hours TIS, then every 11,600 hours TIS thereafter | 4-12-MS | 410, 420 |
| 54-50-00-255 | Forward Engine Mount Forward Channel Web (Eddy Current) Special Detailed Inspection | 12,000 hours TIS | 15,600 hours TIS, then every 11,100 hours TIS thereafter | 4-12-NB | 410, 420 |
| 55-40-00-250 | Vertical Fin Left and Right Front Spar Cap at Attachment Hole #2 (Eddy Current) Special Detailed Inspection | 9,000 hours TIS, then every 7,500 hours TIS thereafter | 9,000 hours TIS, then every 7,000 hours TIS thereafter | 4-12-ML | 340 |
| 55-40-00-251 | Vertical Fin Left and Right Front Spar Cap at Attachment Hole #1 (Eddy Current) Special Detailed Inspection | 15,000 hours TIS | 17,700 hours TIS, then every 14,900 hours TIS thereafter | 4-12-MO | 340 |
| 55-40-00-252 | Vertical Fin Left and Right Rear Spar Cap at Attachment Hole #1 (Eddy Current) Special Detailed Inspection | 15,000 hours TIS, then every 14,500 hours TIS thereafter | 23,600 hours TIS, then every 12,100 hours TIS thereafter | 4-12-MQ | 340 |
*Note 1 to paragraph (g):* Additional guidance for accomplishing the actions required by this AD can be found in Textron Aviation Service Letter SL525B-05-04, Revision 1, dated January 7, 2025.
**(h) Provisions for Alternative Actions and Intervals**
After the action required by paragraph (g) of this AD has been done, no alternative actions and associated thresholds and intervals are allowed unless they are approved as specified in the provisions of paragraph (i) of this AD.
**(i) Alternative Methods of Compliance (AMOCs)**
(1) The Manager, Central 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 Central Certification Branch, send it to the attention of the person identified in paragraph (j)(1) of this AD. Information may be emailed 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**
(1) For more information about this AD, contact Soban Saeed, Aviation Safety Engineer, FAA, 1801 South Airport Road, Wichita, KS 67209; phone: (316) 946-4123; email: *[email protected].*
(2) For Textron Aviation material identified in this AD that is not incorporated by reference, contact Textron Aviation, Inc., P.O. Box 7706, Wichita, KS 67277; phone: (316) 517-6215; email: *[email protected];* website: *ww2.txtav.com/technicalpublications/.*
**(k) Material Incorporated by Reference**
None.
Issued on November 24, 2025.
Steven W. Thompson,
Acting Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.