DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-1653; Project Identifier AD-2023-00899-A;
Amendment 39-22519; AD 2023-15-07]
RIN 2120-AA64

Airworthiness Directives; Air Tractor, Inc. Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; request for comments.

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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: 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-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: (651) 451-1205; email: customerservice@wipaire.com;
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: (847) 294-7141; email: tim.d.eichor@faa.gov.

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

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

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.

Sec. 39.13 [Amended]

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