[Federal Register Volume 89, Number 161 (Tuesday, August 20, 2024)]
[Rules and Regulations]
[Pages 67267-67270]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-18586]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-2013; Project Identifier AD-2024-00363-A; 
Amendment 39-22812; AD 2024-16-06]
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 superseding Airworthiness Directive (AD) 2023-15-
07, which applied to all Air Tractor, Inc. (Air Tractor) Model AT-802 
and AT-802A airplanes with Wipaire, Inc. Supplemental Type Certificate 
(STC) No. SA01795CH installed. AD 2023-15-07 required repetitively 
inspecting the left and right forward horizontal stabilizer spars for 
cracks, replacing any forward horizontal stabilizer spar found cracked, 
and reporting inspection results to the FAA. This AD requires 
repetitively inspecting the left and right, forward and rear, 
horizontal stabilizer spars for cracks at shorter intervals than those 
required by AD 2023-15-07, replacing any horizontal stabilizer spar 
found cracked or damaged, installing bathtub fittings, and reporting 
inspection results to the FAA. This AD was prompted by additional 
reports of cracks in the horizontal stabilizer spars and the need to 
incorporate a new finlet attach design on the horizontal stabilizer 
spars to reduce the cracking. The FAA is issuing this AD to address the 
unsafe condition on these products.

DATES: This AD is effective September 4, 2024.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of September 4, 
2024.
    The FAA must receive comments on this AD by October 4, 2024.

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-2024-2013; 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 Wipaire, Inc. material identified in this AD, contact 
Wipaire, Inc., 1700 Henry Avenue, Fleming Field (KSGS), South St. Paul, 
MN 55075; phone: (651) 451-1205; email: wipaire.com">customerservice@wipaire.com; 
website: wipaire.com.
     You may view this material 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-2024-2013.

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: [email protected].

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 
the ADDRESSES section. Include ``Docket No. FAA-2024-2013; Project 
Identifier AD-2024-00363-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 S. 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 issued AD 2023-15-07, Amendment 39-22519 (88 FR 53761, 
August 9, 2023) (AD 2023-15-07), for all Air Tractor Model AT-802 and 
AT-802A airplanes with Wipaire, Inc. STC No. SA01795CH installed. AD 
2023-15-07 required repetitively inspecting the left and right forward 
horizontal stabilizer spars for cracks, replacing any forward 
horizontal stabilizer spar found cracked, and reporting inspection 
results to the FAA. For certain airplanes, AD 2023-15-07 required the 
inspection before the airplane accumulated 200 hours time-in-service 
(TIS) after installation of STC No. SA01795CH. AD 2023-15-07 resulted 
from cracks found in the forward horizontal stabilizer spar bend radius 
located at the STC finlet mounting locations. The FAA issued AD 2023-
15-07 to detect and correct cracks in the forward horizontal stabilizer 
spar, which could result in structural failure of the horizontal tail 
with consequent loss of control of the airplane.

Actions Since AD 2023-15-07 Was Issued

    As a result of the reports of the inspections required by AD 2023-
15-07, additional cracks have been found in the forward horizontal 
stabilizer spar, including cracks found before the airplane accumulated 
200 hours TIS after installation of the STC.

[[Page 67268]]

Accordingly, the FAA determined that reducing the inspection interval 
is necessary. In addition, based on a new fatigue analysis, the FAA 
determined that there is the potential for cracks in the rear 
horizontal stabilizer spar. Wipaire, Inc. has developed a change to STC 
No. SA01795CH, which incorporates an improved design that includes 
modification kits to install bathtub fittings on the horizontal 
stabilizer spars to mitigate this condition by improving the structural 
load path. This includes more accessible repetitive inspection 
intervals of 110 hours TIS. 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 determined the unsafe 
condition described previously is likely to exist or develop in other 
products of the same type design.

Material Incorporated by Reference Under 1 CFR Part 51

    The FAA reviewed Wipaire, Inc. Service Letter 253, Revision D, 
dated July 3, 2024 (Wipaire SL 253D), which specifies procedures for 
repetitively inspecting the left and right, forward and rear, 
horizontal stabilizer spars for cracks and installing bathtub fittings 
using Service Kit 1012347-01 or 1012347-02. This material also 
specifies procedures for repetitively inspecting the left and right, 
forward and rear, horizontal stabilizer spars for cracks, elongated 
holes, and corrosion after installation of the bathtub fittings. This 
material is reasonably available because the interested parties have 
access to it through their normal course of business or by the means 
identified in the ADDRESSES section.

AD Requirements

    This AD retains none of the requirements of AD 2023-15-07. This AD 
requires repetitively inspecting both the left and right, forward and 
rear, horizontal stabilizer spars for cracks, replacing any horizontal 
stabilizer spar found cracked or damaged, installing bathtub fittings 
(Service Kit 1012347-01 or 1012347-02), and reporting inspection 
results to the FAA. The inspection intervals in this AD are shorter 
than the intervals required by AD 2023-15-07.

Differences Between This AD and the Referenced Material

    As part of the instructions for installing the bathtub fittings, 
Wipaire SL 253D specifies that to be eligible for reinstallation, 
finlet mount weldments must include a certain welded gusset, but that 
constraint is not required by this AD.
    Wipaire SL 253D includes an inspection of the finlets and forward 
bathtub fittings at intervals of 1,500 hours TIS and establishes a life 
limit of 7,800 hours TIS on the forward spar and forward bathtub 
fittings. This AD does not include those requirements because the 
compliance times would allow sufficient time to provide notice and 
opportunity for public comment. The FAA is evaluating these actions and 
may consider future rulemaking.
    This AD requires an initial compliance time of within 7 days or 
before the airplane accumulates 110 hours TIS since installation of STC 
No. SA01795CH, whichever occurs later, while Wipaire SL 253D specifies 
different compliance times for different configurations of STC No. 
SA01795CH.
    Wipaire SL 253D specifies repeating the inspections at intervals of 
200 hours TIS, but this AD requires the repetitive inspections at 
intervals not to exceed 110 hours TIS.

Interim Action

    The FAA considers this AD to be an interim action. The FAA is 
evaluating the need to establish a life limit (potentially as low as 
2,000 hours TIS) on the horizontal stabilizer spars to further mitigate 
the unsafe condition long term. The FAA may consider future rulemaking 
on this subject.

Justification for Immediate Adoption and Determination of the Effective 
Date

    Section 553(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 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 (about 100 hours TIS 
monthly). Based on the number of cracks found to date, a significant 
number of airplanes need to be inspected within 7 days after the 
effective date of this AD and modified with bathtub fittings within 300 
hours TIS (about 3 months for the high utilization airplanes). These 
compliance times are 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).
    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
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                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost     Cost per airplane        operators
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Inspect horizontal stabilizer      20 work-hours x $85              $0  $1,700 per           $51,000 per
 spars (without bathtub fittings).  per hour = $1,700.                   inspection cycle.    inspection cycle.
Install bathtub fittings.........  40 work-hours x $85           3,100  $6,500.............  $195,000.
                                    per hour = $3,400.

[[Page 67269]]

 
Inspect horizontal stabilizer      3 work-hours x $85                0  $255 per inspection  $7,650 per
 spars (with bathtub fittings).     per hour = $255.                     cycle.               inspection cycle.
Report inspection results........  1 work-hour x $85                 0  $85 per inspection   $2,550 per
                                    per hour = $85.                      cycle.               inspection cycle.
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    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
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                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost       airplane
----------------------------------------------------------------------------------------------------------------
Replace horizontal stabilizer spar............  40 work-hours x $85 per hour =            $2,800          $6,200
                                                 $3,400.
----------------------------------------------------------------------------------------------------------------

    The FAA has included all known costs in its cost estimate. 
According to the manufacturer, however, some of the costs of this AD 
may be covered under warranty, thereby reducing the cost impact on 
affected operators.

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

0
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]

0
2. The FAA amends Sec.  39.13 by:
0
a. Removing Airworthiness Directive 2023-15-07, Amendment 39-22519 (88 
FR 53761, August 9, 2023); and
0
b. Adding the following new airworthiness directive:

2024-16-06 Air Tractor, Inc.: Amendment 39-22812; Docket No. FAA-
2024-2013; Project Identifier AD-2024-00363-A.

(a) Effective Date

    This airworthiness directive (AD) is effective September 4, 
2024.

(b) Affected ADs

    This AD replaces AD 2023-15-07, Amendment 39-22519 (88 FR 53761, 
August 9, 2023) (AD 2023-15-07).

(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 additional reports of cracks found in 
the horizontal stabilizer spars and the need to incorporate a new 
finlet attach design on the horizontal stabilizer spars to reduce 
the cracking. The FAA is issuing this AD to prevent structural 
failure of the horizontal stabilizer spars. The unsafe condition, if 
not addressed, could result in structural failure of the horizontal

[[Page 67270]]

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) Within 7 days after the effective date of this AD or before 
the airplane accumulates 110 hours time-in-service (TIS) after 
installation of STC No. SA01795CH, whichever occurs later, and 
thereafter at intervals not to exceed 110 hours TIS until the 
airplane is modified as required by paragraph (g)(3) of this AD: 
Inspect the left and right horizontal stabilizer spars for cracks in 
accordance with Steps 1 through 9 of the Work Instructions--
Inspection, Method 1 in Wipaire, Inc. Service Letter 253, Revision 
D, dated July 3, 2024 (Wipaire SL 253D).
    (2) If any crack is found in a horizontal stabilizer spar during 
any inspection required by paragraph (g)(1) of this AD, or if any 
crack, elongated hole, or corrosion is found in a horizontal 
stabilizer spar during any inspection required by paragraph (g)(4) 
of this AD, before further flight, replace the horizontal stabilizer 
spar.
    (3) Within 300 hours TIS or 12 months after the effective date 
of this AD, whichever occurs first, install bathtub fittings 
(Service Kit 1012347-01 or 1012347-02) in accordance with Steps 1 
through 10 of the Work Instructions--Install Bathtub Fittings in 
Wipaire SL 253D except where Step 2 specifies that to be eligible 
for reinstallation, finlet mount weldments must include the welded 
gussets shown in figure 8 of Wipaire SL 253D, that constraint is not 
required by this AD. If any spars were previously modified by 
installing 7D1-4399 Revision L or earlier, regardless of condition, 
those spars must be replaced at the same time the bathtub fittings 
kit is installed.
    (4) Within 110 hours TIS after installing the bathtub fittings, 
and thereafter at intervals not to exceed 110 hours TIS, inspect the 
horizontal stabilizer spars for cracks, elongated holes, and 
corrosion in accordance with Steps 1, 2, 4 through 6, 9, and 10 of 
the Work Instructions--Inspection, Method 2 in Wipaire SL 253D.
    (5) Within 5 days after each inspection required by paragraphs 
(g)(1) and (4) of this AD or within 5 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; or Wipaire Service Letter 253, Revision B, 
dated July 27, 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 
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) 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: (847) 294-7141; email: 
[email protected].
    (2) Material identified in this AD that is not incorporated by 
reference is available at the address specified in paragraph (k)(3) 
of this AD.

(k) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference of the material listed in this paragraph 
under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this material as applicable to do the actions 
required by this AD, unless the AD specifies otherwise.
    (i) Wipaire, Inc. Service Letter 253, Revision D, dated July 3, 
2024.
    (ii) [Reserved]
    (3) For Wipaire, Inc. material identified in this AD, contact 
Wipaire, Inc., 1700 Henry Avenue, Fleming Field (KSGS), South St. 
Paul, MN 55075; phone: (651) 451-1205; email: 
wipaire.com">customerservice@wipaire.com; website: wipaire.com.
    (4) You may view this material 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 material at the National Archives and 
Records Administration (NARA). For information on the availability 
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].

    Issued on August 14, 2024.
Victor Wicklund,
Deputy Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2024-18586 Filed 8-15-24; 11:15 am]
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