2023-16964. Airworthiness Directives; Air Tractor, Inc. Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule; request for comments.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for all Air Tractor, Inc. (Air Tractor) Model AT–802 and AT–802A airplanes that have Wipaire Supplemental Type Certificate (STC) No. SA01795CH installed. This AD was prompted by reports of cracks found in the forward horizontal stabilizer spar where the vertical finlets tie to the horizontal tail forward spar. This AD requires repetitively inspecting both the left and right forward horizontal stabilizer spars for cracks and replacing any forward horizontal stabilizer spar found cracked. This AD also requires reporting inspection results to the FAA. The FAA is issuing this AD to address the unsafe condition on these products.

DATES:

This AD is effective August 9, 2023.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of August 9, 2023.

The FAA must receive comments on this AD by September 25, 2023.

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: [phone].

• 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–2023–1653; 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 street address for Docket Operations is listed above.

Material Incorporated by Reference:

• For service information identified in this final rule, contact Wipaire, Inc., 1700 Henry Ave., Fleming Field (KSGS), South St. Paul, MN 55075; phone: [phone]; email: [e-mail]; website: wipaire.com.

• You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 901 Locust, Kansas City, MO 64106. For information on the availability of this material at the FAA, call (817) 222–5110. It is also available at regulations.gov under Docket No. FAA–2023–1653.

FOR FURTHER INFORMATION CONTACT:

Tim Eichor, Aviation Safety Engineer, Central Certification Branch, FAA, 1801 S Airport Road, Wichita, KS 67209; phone: [phone]; email: [e-mail].

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written data, views, or arguments about this final rule. Send your comments to an address listed under ADDRESSES . Include “Docket No. FAA–2023–1653, Project Identifier AD–2023–00899–A” at the beginning of your comments. The most helpful comments reference a specific portion of the final rule, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this final rule 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 final rule.

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 AD 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 AD, 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 AD. Submissions containing CBI should be sent to Tim Eichor, Aviation Safety Engineer, Central Certification Branch, 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

During routine maintenance, an Air Tractor Model AT–802 airplane was found with a hairline crack in the flange of the right forward horizontal stabilizer spar. The airplane had STC No. SA01795CH installed and is used in fire-fighting missions, which can propagate crack growth more rapidly. Of the 144 Air Tractor Model AT–802 and AT–802A airplanes that have this STC, 45 have been inspected, and 24 of those inspected had cracks found in at least one forward horizontal stabilizer spar. The cracking is in the forward horizontal stabilizer spar bend radius located at the STC finlet mounting locations.

This condition, if not addressed, could result in structural failure of the horizontal tail with consequent loss of control of the airplane. The FAA is issuing this AD to address the unsafe condition on these products.

FAA's Determination

The FAA is issuing this AD because the agency has determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Wipaire, Inc. Service Letter 253, Revision B, dated July 27, 2023, which specifies procedures for inspecting the left and right forward horizontal stabilizer spars for cracks. 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 ADDRESSES .

AD Requirements

This AD requires repetitively inspecting both the left and right forward horizontal stabilizer spars for cracks and replacing any forward horizontal stabilizer spar found cracked. This AD also requires reporting inspection results to the FAA.

Interim Action

The FAA considers this AD to be an interim action. The STC design approval holder is working on a modification to the STC configurations to address this issue. The FAA may consider future rulemaking on this subject.

Justification for Immediate Adoption and Determination of the Effective Date

Section 553(b)(3)(B) of the Administrative Procedure Act (APA) (5 U.S.C. 551 et seq.) authorizes agencies to dispense with notice and comment procedures for rules when the agency, for “good cause,” finds that those procedures are “impracticable, unnecessary, or contrary to the public interest.” Under this section, an agency, upon finding good cause, may issue a final rule without providing notice and seeking comment prior to issuance. Further, section 553(d) of the APA authorizes agencies to make rules effective in less than thirty days, upon a finding of good cause.

An unsafe condition exists that requires the immediate adoption of this AD without providing an opportunity for public comments prior to adoption. The FAA has found that the risk to the flying public justifies forgoing notice and comment prior to adoption of this rule because cracks in the forward horizontal stabilizer spars could lead to structural failure of the horizontal tail with consequent loss of control of the airplane. Airplanes with the affected STC installed are used in fire-fighting missions and put frequent high repetitive fatigue loads in this area at a high utilization rate. Based on the number of cracks found to date, a significant number of airplanes need to be inspected within 3 to 15 days depending on the configuration. This compliance time is shorter than the time necessary for the public to comment and for publication of the final rule.

Accordingly, notice and opportunity for prior public comment are impracticable and contrary to the public interest pursuant to 5 U.S.C. 553(b)(3)(B).

In addition, the FAA finds that good cause exists pursuant to 5 U.S.C. 553(d) for making this amendment effective in less than 30 days, for the same reasons the FAA found good cause to forgo notice and comment.

Regulatory Flexibility Act

The requirements of the Regulatory Flexibility Act (RFA) do not apply when an agency finds good cause pursuant to 5 U.S.C. 553 to adopt a rule without prior notice and comment. Because FAA has determined that it has good cause to adopt this rule without prior notice and comment, RFA analysis is not required.

Costs of Compliance

The FAA estimates that this AD affects 30 airplanes of U.S. registry.

The FAA estimates the following costs to comply with this AD:

Estimated Costs

Action	Labor cost	Parts cost	Cost per product	Cost on U.S. operators
Inspect forward horizontal stabilizer spars	20 work-hours × $85 per hour = $1,700	$0	$1,700 per inspection cycle	$51,000 per inspection cycle.
Report inspection results	1 work-hour × $85 per hour = $85	0	85 per inspection cycle	2,550 per inspection cycle.

The FAA estimates the following costs to do any necessary replacements that would be required based on the results of the inspection. The agency has no way of determining the number of airplanes that might need this replacement:

On-Condition Costs

Action	Labor cost	Parts cost	Cost per product
Replace a cracked forward horizontal stabilizer spar	40 work-hours × $85 per hour = $3,400	$1,325	$4,725

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

This AD will not have federalism implications under Executive Order 13132. This AD will 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 that this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866, and

(2) Will not affect intrastate aviation in Alaska.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

The Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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

[Amended]

2. The FAA amends § 39.13 by adding the following new airworthiness directive:

2023–15–07 Air Tractor, Inc.: Amendment 39–22519; Docket No. FAA–2023–1653; Project Identifier AD–2023–00899–A.

(a) Effective Date

This airworthiness directive (AD) is effective August 9, 2023.

(b) Affected ADs

None.

(c) Applicability

This AD applies to Air Tractor, Inc. Model AT–802 and AT–802A airplanes, all serial numbers, certificated in any category, that have Wipaire, Inc. Supplemental Type Certificate (STC) No. SA01795CH installed.

(d) Subject

Joint Aircraft System Component (JASC) Code 5510, Horizontal Stabilizer Structure; 5511 Horizontal stabilizer, Spar/Rib; 5514, Horizontal Stabilizer Miscellaneous Structure; 5530, Vertical Stabilizer Structure.

(e) Unsafe Condition

This AD was prompted by reports of cracks found in at least one forward horizontal stabilizer spar on 24 of the affected airplanes where the vertical finlets tie to the forward horizontal stabilizer spar. The FAA is issuing this AD to prevent structural failure of the forward horizontal stabilizer spars. The unsafe condition, if not addressed, could result in structural failure of the horizontal tail with consequent loss of control of the airplane.

(f) Compliance

Comply with this AD within the compliance times specified, unless already done.

(g) Required Actions

(1) At the compliance times in paragraphs (g)(1)(i) through (iii) of this AD, as applicable, and thereafter at intervals not to exceed 200 hours time-in-service (TIS), inspect the left and right forward horizontal stabilizer spars for cracks in accordance with Steps 1 through 9 of the Work Instructions of Wipaire, Inc. Service Letter 253, Revision B, dated July 27, 2023.

(i) For STC configuration 7D1–4399–01: Within 3 days or 24 hours TIS after the effective date of this AD or before the accumulation of 200 hours TIS since installation of STC No. SA01795CH, whichever occurs later.

(ii) For STC configuration 7D1–4399–02: Within 5 days or 24 hours TIS after the effective date of this AD or before the accumulation of 300 hours TIS since installation of STC No. SA01795CH, whichever occurs later.

(iii) For STC configuration 7D1–4399–03: Within 15 days or 24 hours TIS after the effective date of this AD or before the accumulation of 600 hours TIS since installation of STC No. SA01795CH, whichever occurs later.

(2) If any crack is found in a forward horizontal stabilizer spar during any inspection required by paragraph (g)(1) of this AD, before further flight, replace the cracked forward horizontal stabilizer spar. Replacement of the cracked forward horizontal stabilizer spar starts the initial and repetitive inspections over.

(3) Within 10 days after each inspection required by paragraph (g)(1) of this AD or within 10 days after the effective date of this AD, whichever occur later, report the following to the FAA at the address in paragraph (j)(1) of this AD. Report this information regardless of whether cracks are found.

(i) Model, engine configuration (with horsepower limits), and propeller type;

(ii) Serial number and N number;

(iii) Total hours TIS on airframe;

(iv) Total hours TIS operated with floats, if known;

(v) STC configuration and total hours with STC installed;

(vi) Crack location (right or left, upper/lower caps inboard/outboard hole);

(vii) Crack size;

(viii) Photos of cracks found, if available; and

(ix) Any additional operator/mechanic comments

(h) Credit for Previous Actions

You may take credit for the initial inspection required by paragraph (g)(1) of this AD if, before the effective date of this AD, you complied with Wipaire, Inc. Service Letter 253, Revision A, dated April 5, 2023.

(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 Certification Branch, send it to the attention of the person identified in paragraph (j)(1) of this AD.

(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) Related Information

(1) For more information about this AD, contact Tim Eichor, Aviation Safety Engineer, Central Certification Branch, FAA, 1801 S Airport Road, Wichita, KS 67209; phone: [phone]; email: [e-mail].

(2) Service information identified in this AD that is not incorporated by reference is available at the addresses specified in paragraphs (k)(3) and (4) of this AD.

(k) Material Incorporated by Reference

(1) The Director of the Federal Register approved the incorporation by reference (IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.

(2) You must use this service information as applicable to do the actions required by this AD, unless the AD specifies otherwise.

(i) Wipaire, Inc. Service Letter 253, Revision B, dated July 27, 2023.

(ii) [Reserved]

(3) For service information identified in this AD, contact Wipaire, Inc., 1700 Henry Ave, Fleming Field (KSGS), South St. Paul, MN 55075; phone: [phone]; email: [e-mail]; website: wipaire.com.

(4) You may view this service information at the FAA, Airworthiness Products Section, Operational Safety Branch, 901 Locust, Kansas City, MO 64106. For information on the availability of this material at the FAA, call (817) 222–5110.

(5) You may view this service information that is incorporated by reference at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, email: [e-mail], or go to: www.archives.gov/​federal-register/​cfr/​ibr-locations.html.

Issued on July 28, 2023.

Ross Landes,

Deputy Director for Regulatory Operations, Compliance & Airworthiness Division, Aircraft Certification Service.