[Federal Register Volume 86, Number 56 (Thursday, March 25, 2021)]
[Rules and Regulations]
[Pages 15784-15787]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-06142]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0710; Project Identifier 2019-CE-037-AD; Amendment 
39-21457; AD 2021-05-14]
RIN 2120-AA64


Airworthiness Directives; Air Tractor, Inc., Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
Air Tractor, Inc., (Air Tractor) Models AT-250, AT-300, AT-301, AT-302, 
AT-400, AT-400A, AT-401, AT-401A, AT-401B, AT-402, AT-402A, AT-402B, 
AT-501, AT-502, AT-502A, AT-502B, AT-503, AT-503A, AT-504, AT-602, AT-
802, and AT-802A airplanes. This AD was prompted by reports of cracks 
in the flap torque tube actuator attachment brackets that may cause the 
flap actuator to detach from the flap torque tube. This AD requires 
repetitive visual and dye penetrant inspections of the flap actuator 
attachment bracket welds for cracks and replacement if cracks are 
identified. The FAA is issuing this AD to address the unsafe condition 
on these products.

DATES: This AD is effective April 29, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of April 29, 
2021.

ADDRESSES: For service information identified in this final rule, 
contact Air Tractor, P.O. Box 485, Olney, TX 76374: phone: (940) 564-
5616: email: info@airtractor.com: website: https://airtractor.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 
816-329-4148. It is also available at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2020-0710.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2020-0710; 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

[[Page 15785]]

other information. The address for Docket Operations is U.S. Department 
of Transportation, Docket Operations, M-30, West Building Ground Floor, 
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Kenneth A. Cook, Aviation Safety 
Engineer, Fort Worth ACO Branch, AIR-7F0, FAA, 10101 Hillwood Pkwy., 
Fort Worth, TX 76177; phone: (817) 222-5475; email: 
kenneth.a.cook@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to all Air Tractor Models 
AT-250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-401A, AT-
401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, AT-
503, AT-503A, AT-504, AT-602, AT-802, and AT-802A airplanes. The NPRM 
published in the Federal Register on July 28, 2020 (85 FR 45347). The 
NPRM was prompted by multiple reports of cracks in the brackets 
attaching the flap actuator motor to the flap torque tube on several 
models of Air Tractor airplanes.
    One of the reports was on a Model AT-802A airplane where the 
brackets separated from the torque tube at the welds. The flaps 
suddenly retracted while maneuvering, and the pilot temporarily lost 
control of the airplane. The pilot was able to regain control of the 
airplane before it impacted the ground. Since then, there have been 13 
reported airplanes with cracks in the flap torque tube attachment 
brackets.
    The design of the flap actuator motor brackets on the Model AT-802A 
airplane is the same as on Models AT-250, AT-300, AT-301, AT-302, AT-
400, AT-400A, AT-401, AT-401A, AT-401B, AT-402, AT-402A, AT-402B, AT-
501, AT-502, AT-502A, AT-503, AT-503A, AT-504, AT-602, and AT-802 
airplanes.
    In the NPRM, the FAA proposed to require repetitive dye penetrant 
and visual inspections with replacement of the flap torque tube if 
cracks are found. The FAA is issuing this AD to address the unsafe 
condition on these products.

Discussion of Final Airworthiness Directive Comments

    The FAA received comments from two commenters. The commenters were 
Air Tractor and Field Air Sales and Maintenance Pty Ltd (Field Air). 
The following presents the comments received on the NPRM and the FAA's 
response to each comment.

Requests Regarding the Compliance Times

    Air Tractor requested the FAA clarify whether the hours time-in-
service (TIS) compliance times are based on aircraft time or flap 
torque tube component time. The commenter requested that the AD require 
compliance based on the hours TIS of the flap torque tube component to 
account for new torque tubes installed on an existing aircraft.
    The FAA disagrees with this comment. The hours TIS compliance 
required by this AD refers to the hours TIS the airplane operates after 
the effective date of the AD and after each inspection. Air Tractor has 
not provided data analysis to identify the root cause of the failures 
of the torque tubes or to indicate whether the failures are related to 
the hours TIS of the torque tubes.
    Air Tractor and Field Air requested the FAA remove the proposed 
requirement to perform a dye penetrant inspection within 300 hours TIS 
after the effective date of the AD. Air Tractor said the proposed 
requirement does not provide consideration for flap torque tubes that 
have accumulated less than 900 hours and requested the FAA instead 
require visual inspections every 300 hours until the flap torque tube 
accumulates 900 hours TIS. Field Air requested the FAA provide its 
justification for requiring a dye penetrant inspection within 300 hours 
TIS.
    The FAA disagrees with this comment. The FAA has received no data 
to indicate that torque tubes with less than 900 hours TIS are 
unaffected by the unsafe condition. The initial dye penetrant 
inspection should reveal cracking that might be present on affected 
airplanes and ensure those cracks are addressed before the repetitive 
visual and dye penetrant inspections start.
    Field Air requested the FAA explain why the proposed AD does not 
allow the +/- 15 percent tolerance for the visual inspections as 
specified in Air Tractor Service Letter #347, Revision A, dated 
December 9, 2019 (SL #347A).
    The FAA acknowledges this comment and has changed the compliance 
time for the visual inspections from 300 hours TIS to 345 hours TIS.

Request To Allow Replacement Parts With More Than Zero Hours TIS

    Air Tractor and Field Air disagreed with the proposal to replace a 
cracked torque tube with a new (zero hours time-in-service) torque 
tube. Field Air requested the FAA explain its justification for this 
proposal. Air Tractor stated there is no safety reason to require 
replacement with a zero-time flap torque tube instead of a flap torque 
tube that has passed the inspection. Air Tractor noted that allowing 
replacement with an airworthy flap torque tube would minimize aircraft 
down time.
    The FAA agrees with this comment and has changed the AD to allow 
the replacement with a used (more than zero hours TIS) torque tube 
provided the dye penetrant inspection was completed and the part passed 
the inspection.

Request Regarding Reporting Requirement

    Air Tractor requested the FAA add a statement to the AD that the 
agency recommends that cracks be reported to the FAA or to Air Tractor 
for tracking. Air Tractor stated the language used in the proposed AD 
suggests that reporting is no longer recommended. Field Air requested 
the FAA explain its justification for not having a requirement in the 
AD to report to Air Tractor any cracked welds identified during the 
inspections.
    The FAA acknowledges this comment. This AD is not an interim 
action. Mandating a report of the results of the inspection is not 
necessary to correct the unsafe condition. However, the FAA agrees that 
voluntarily reporting to Air Tractor when cracks are found could aid 
safety analysis of the fleet.

Request To Expand Service Letter References

    Air Tractor requested that the requirement in the AD to perform a 
dye penetrant inspection include step 4B(1) from SL #347A, which 
specifies gaining access to the flap actuator area by removing skin 
panels and conducting a visual inspection of the flap control system.
    The FAA disagrees with adding step 4B(1) since this step is not 
required to address the unsafe condition.
    Air Tractor also requested the AD require step 4B(11) from SL 
#347A, which specifies recording in the aircraft records the results of 
the dye penetrant inspection and what type of dye penetrant was used. 
Air Tractor referenced the recommendations in FAA Special Airworthiness 
Bulletin CE-18-26, Liquid Penetrant Inspection: Using Visible Dye 
Penetrant, dated September 4, 2018, and noted that the type of dye 
penetrant is important information for future inspections.
    The FAA disagrees that a change to the AD is necessary. Persons 
performing maintenance are required by 14 CFR part 43 to make an entry 
in the airplane maintenance records describing the

[[Page 15786]]

work performed. That description should identify the same information 
specified in step 4B(11).
    The FAA did not change this AD based on this comment.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, and determined that air safety requires adopting this AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition on these products. Except for minor editorial changes, and 
any other changes described previously, this AD is adopted as proposed 
in the NPRM. None of the changes will increase the economic burden on 
any operator.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Air Tractor, Inc. Service Letter #347, Revision A, 
dated December 9, 2019. The service letter specifies procedures for 
repetitive visual inspections and dye penetrant inspections of the flap 
torque tube brackets for cracks and instructs operators to replace the 
torque tube as necessary. 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.

Differences Between the AD and the Service Information

    Air Tractor SL #347, Rev A specifies performing the dye penetrant 
inspection within 900 hours TIS, and this AD requires the initial dye 
penetrant inspection within 300 hours TIS. Air Tractor SL #347, Rev A 
specifies replacing a cracked torque tube, while this AD requires 
replacing a cracked torque tube with a torque tube that has zero hours 
TIS. Air Tractor SL #347, Rev A specifies reporting any cracked welds 
identified during the inspections.

Costs of Compliance

    The FAA estimates that this AD affects 1,662 airplanes of U.S. 
registry.
    The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
             Action                   Labor cost          Parts cost       Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Dye penetrant inspection........  4 work-hours x $85  Not applicable....  $340 per            $565,080 per
                                   per hour = $340                         inspection cycle.   inspection cycle
                                   per inspection
                                   cycle.
Visual inspection...............  .5 work-hour x $85  Not applicable....  $42.50............  $70,635 per
                                   per hour = $42.50                                           inspection cycle
                                   per inspection
                                   cycle.
----------------------------------------------------------------------------------------------------------------

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

                                 On-Condition Costs for Model AT-802 and AT-802A
                                            [Potential 485 Airplanes]
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replacement of torque tube...................  3 work-hours x $85 per hour =            $1,292           $1,547
                                                $255.
----------------------------------------------------------------------------------------------------------------


                                       On-Condition Costs for Model AT-602
                                            [Potential 236 Airplanes]
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replacement of torque tube...................  3 work-hours x $85 per hour =            $1,140           $1,395
                                                $255.
----------------------------------------------------------------------------------------------------------------


           On-Condition Costs for Models AT-501, AT-502, AT-502A, AT-502B, AT-503, AT-503A, and AT-504
                                            [Potential 512 Airplanes]
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replacement of torque tube...................  3 work-hours x $85 per hour =              $955           $1,210
                                                $255.
----------------------------------------------------------------------------------------------------------------


On-Condition Costs for Models AT-250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-401A, AT-401B, AT-402,
                                              AT-402A, and AT-402B
                                            [Potential 429 Airplanes]
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replacement of torque tube...................  3 work-hours x $85 per hour =              $927           $1,182
                                                $255.
----------------------------------------------------------------------------------------------------------------


[[Page 15787]]

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,
    (2) Will not affect intrastate aviation in Alaska, and
    (3) Will 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 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 adding the following new airworthiness 
directive:
2021-05-14 Air Tractor, Inc.: Amendment 39-21457; Docket No. FAA-
2020-0710; Project Identifier 2019-CE-037-AD.

(a) Effective Date

    This airworthiness directive (AD) is effective April 29, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to Air Tractor, Inc., (Air Tractor), Models AT-
250, AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-401A, AT-
401B, AT402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, AT-
503, AT-503A, AT-504, AT-602, AT-802, and AT-802A airplanes, all 
serial numbers, certificated in any category.

(d) Subject

    Joint Aircraft System Component (JASC) of America Code: 2750, TE 
flap control system

(e) Unsafe Condition

    This AD was prompted by reports from Air Tractor that the flap 
actuator attachment brackets can crack and detach from the torque 
tube. The FAA is issuing this AD to detect and correct cracks in the 
flap actuator attachment brackets. The unsafe condition, if not 
addressed, could lead to the brackets detaching from the torque 
tube, which could result in an uncommanded retraction of the flaps 
with consequent loss of airplane control.

(f) Compliance

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

(g) Actions

    (1) Within 300 hours time-in-service (TIS) after the effective 
date of this AD and thereafter at intervals not to exceed 900 hours 
TIS, perform a dye penetrant inspection of each flap torque tube 
actuator attachment bracket for cracks in accordance with steps 
4B(2) through (7) of Air Tractor, Inc., Service Letter #347, 
Revision A, dated December 9, 2019 (Air Tractor SL #347, Rev A).
    (i) If there is a crack, before further flight, replace the flap 
torque tube with a flap torque tube that has zero hours TIS or a 
part that has been inspected in accordance with paragraph (g)(1) of 
this AD and passed the inspection.
    (ii) If there are no cracks, before further flight, complete the 
actions in steps 4B(9) and (10) of Air Tractor SL #347, Rev A.
    (2) Within 345 hours TIS after the inspection required by 
paragraph (g)(1) of this AD and thereafter at intervals not to 
exceed 345 hours TIS, visually inspect each flap torque tube 
actuator attachment bracket for cracks in accordance with steps 
4A(1) through (3) of Air Tractor SL #347, Rev A. If there is a 
crack, before further flight, replace the flap torque tube with a 
flap torque tube that has zero hours TIS or with a flap torque tube 
that has been inspected in accordance with paragraph (g)(1) of this 
AD and passed the inspection.
    (3) Replacing a flap torque tube does not terminate any of the 
inspections required by this AD.

(h) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Fort Worth ACO Branch, AIR-7F0, has the 
authority to approve AMOCs for this AD, if requested using the 
procedures found in 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 
Fort Worth ACO Branch, send it to the attention of the person 
identified in Related Information.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of your local Flight Standards District Office.

(i) Related Information

    For more information about this AD, contact Kenneth A. Cook, 
Aviation Safety Engineer, Fort Worth ACO Branch, AIR-7F0, FAA, 10101 
Hillwood Pkwy, Fort Worth, TX 76177; phone: (817) 222-5475; email: 
kenneth.a.cook@faa.gov.

 (j) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference 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) Air Tractor, Inc., Service Letter #347, Revision A, dated 
December 9, 2019.
    (ii) [Reserved]
    (3) For Air Tractor, Inc., service information identified in 
this AD, contact Air Tractor, Inc., P.O. Box 485, Olney, TX 76374: 
phone: (940) 564-5616: email: info@airtractor.com; website: https://airtractor.com/.
    (4) You may view this service information at FAA, Airworthiness 
Products Section, Operational Safety Branch, 901 Locust St, Kansas 
City, MO 64106. For information on the availability of this material 
at the FAA, call (816) 329-4148.
    (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: fedreg.legal@nara.gov, or go to: https://www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on February 24, 2021.
Gaetano A. Sciortino,
Deputy Director for Strategic Initiatives, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-06142 Filed 3-24-21; 8:45 am]
BILLING CODE 4910-13-P


