Document ID: FAA-2007-0258-0012
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Air Tractor, Inc. AT-400, AT-500, AT- 600, and AT-800 Series Airplanes
Posted Date: 2008-05-08T04:00Z

[Federal Register: May 8, 2008 (Volume 73, Number 90)]
[Rules and Regulations]               
[Page 25967-25970]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr08my08-3]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2007-0258; Directorate Identifier 2007-CE-090-AD; 
Amendment 39-15518; AD 2008-10-12]
RIN 2120-AA64

 
Airworthiness Directives; Air Tractor, Inc. AT-400, AT-500, AT-
600, and AT-800 Series Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: We are adopting a new airworthiness directive (AD) to 
supersede AD 2007-13-17, which applies to certain Air Tractor, Inc. 
(Air Tractor) Models AT-602, AT-802, and AT-802A airplanes. AD 2007-13-
17 currently requires you to repetitively inspect the engine mount for 
any cracks, repair or replace any cracked engine mount, and report any 
cracks found to the FAA. Since we issued AD 2007-13-17, Air Tractor has 
learned of a Model AT-502B with a crack located where the lower engine 
mount tube is welded to the engine mount ring. In addition, Air Tractor 
has developed gussets that, when installed according to their service 
letter, terminate the repetitive inspection requirement. Consequently, 
this AD would retain the inspection actions of AD 2007-13-17 for Model 
AT-602, AT-802, and AT-802A airplanes, including the compliance times 
and effective dates; establish new inspection actions for the AT-400 
and AT-500 series airplanes; incorporate a mandatory terminating action 
for all airplanes; and terminate the reporting requirement of AD 2007-
13-17. We are issuing this AD to detect and correct cracks in the 
engine mount, which could result in failure of the engine mount. Such 
failure could lead to separation of the engine from the airplane.

DATES: This AD becomes effective on June 12, 2008.
    On June 12, 2008, the Director of the Federal Register approved the 
incorporation by reference of Snow Engineering Co. Service Letter 
253, Rev. C, dated April 17, 2008; Snow Engineering Co. 
Service Letter 253, Rev. B, dated November 30, 2007; and Snow 
Engineering Co. Service Letter 253 Rev. A, dated October 16, 
2007, as listed in this AD.
    As of August 10, 2007 (72 FR 36863, July 6, 2007), the Director of 
the Federal Register approved the incorporation by reference of Snow 
Engineering Co. Service Letter 253, revised January 22, 2007, 
as listed in this AD.

ADDRESSES: For service information identified in this AD, contact Air 
Tractor Inc., P.O. Box 485, Olney, Texas 76374; telephone: (940) 564-
5616; fax: (940) 564-5612.
    To view the AD docket, go to U.S. Department of Transportation, 
Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 
New Jersey Avenue, SE., Washington, DC 20590, or on the Internet at 
http://www.regulations.gov. The docket number is FAA-2007-0258; 
Directorate Identifier 2007-CE-090-AD.

FOR FURTHER INFORMATION CONTACT: Andy McAnaul, Aerospace Engineer, 
10100 Reunion Pl., Suite 650, San Antonio, Texas 78216; telephone: 
(210) 308-3365; fax: (210) 308-3370.

SUPPLEMENTARY INFORMATION: 

Discussion

    On November 23, 2007, we issued a proposal to amend part 39 of the 
Federal Aviation Regulations (14 CFR part 39) to include an AD that 
would apply to all Air Tractor AT-400, AT-500, AT-600, and AT-800 
series airplanes. This proposal was published in the Federal Register 
as a notice of proposed rulemaking (NPRM) on November 30, 2007 (72 FR 
67687). The NPRM proposed to supersede AD 2007-13-17 with a new AD that 
would retain the inspection actions of AD 2007-13-17 for Models AT-602, 
AT-802, and AT-802A airplanes, including the compliance times and 
effective dates; establish new inspection actions for the AT-400 and 
AT-500 series airplanes; incorporate a mandatory terminating action for 
all airplanes; and terminate the reporting requirement of AD 2007-13-
17. That proposed AD would have required you to use Snow Engineering 
Co. Service Letter 253 Rev. A, dated October 16, 2007.
    Air Tractor revised the Snow Engineering Co. Service Letter 
253 to the Rev. B level (dated November 30, 2007), and:
     The FAA determined the actions in the revised service 
letter were necessary and needed to be incorporated into the proposed 
AD; and
     Because incorporating the revision increased the burden 
upon the public over that proposed in the NPRM, the FAA issued a 
supplemental NPRM to give the public an additional opportunity to 
comment.
    The supplemental NPRM was published in the Federal Register on 
December 14, 2007 (72 FR 71086).

Comments

    The following presents the comment received on the proposal and 
FAA's response to that comment:

Comment Issue: Delay the Terminating Action

    Mr. Leland Snow, President of Air Tractor, and five other 
commenters recommend some kind of delay in mandating the terminating 
action in the proposed AD. Mr. Snow and one other commenter believe 
that the compliance time to install welded gussets on the engine mounts 
can be adjusted from before the airplane reaches 5,000 total hours 
time-in-service (TIS) to before the airplane reaches 8,000 hours total 
TIS. In order to get through the current spray season, three commenters 
believe the compliance time should be delayed 12 months or when the 
engine is removed.

[[Page 25968]]

The other commenter recommends shorter interval repetitive inspections 
with no mandatory terminating action.
    The FAA partially agrees. Our review of the current service history 
does not support allowing the installation of welded gussets to be 
extended from before the airplane reaches 5,000 total hours TIS to 
before the airplane reaches 8,000 hours total TIS. We have received no 
additional data to substantiate the airworthiness aspects of such an 
extension and show that the unsafe condition is addressed.
    After further evaluation of the service history and the risk 
involved, we have determined that terminating action can be delayed 
until the beginning of the 2009 spray season (May 1, 2009) provided 
100-hour TIS repetitive inspections are done and no cracks are found. 
Therefore, we are changing the final rule AD action to allow for the 
option of delaying the terminating action until April 30, 2009, with 
the provisions described above.
    In addition, Air Tractor has revised Snow Engineering Co. Service 
Letter 253 to the Revision C level (dated April 17, 2008). 
This revision incorporates new gusset part numbers for the AT-400 and 
AT-500 series airplanes. The gusset part numbers provided in Revision B 
or Revision C of the service letter address the unsafe condition. We 
will incorporate this service letter revision into the final rule.

Conclusion

    We have carefully reviewed the available data and determined that 
air safety and the public interest require adopting the AD as proposed 
except for the change and addition described above and minor editorial 
corrections. We have determined that the change, addition, and minor 
corrections:
     Are consistent with the intent that was proposed in the 
NPRM or supplemental NPRM for correcting the unsafe condition; and
     Do not add any additional burden upon the public than was 
already proposed in the NPRM or supplemental NPRM.

Costs of Compliance

    We estimate that this AD affects 1,264 airplanes in the U.S. 
registry.
    We estimate the following costs to do the inspection:

----------------------------------------------------------------------------------------------------------------
                                                                                  Total cost per   Total cost on
                           Labor cost                               Parts cost       airplane     U.S. operators
----------------------------------------------------------------------------------------------------------------
1.5 work-hours x $80 per hour = $120............................              $0            $120        $151,680
----------------------------------------------------------------------------------------------------------------

    We estimate the following costs to do the repair/modification:

----------------------------------------------------------------------------------------------------------------
                                                                                  Total cost per   Total cost on
                           Labor cost                               Parts cost       airplane     U.S. operators
----------------------------------------------------------------------------------------------------------------
24 work-hours x $80 per hour = $1,920...........................             $80          $2,000      $2,528,000
----------------------------------------------------------------------------------------------------------------

    The estimated total cost on U.S. operators includes the cumulative 
costs associated with AD 2007-13-17 and those airplanes and actions 
being added in this AD.

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.
    We are 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 AD.

Regulatory Findings

    We have determined that 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. Is not a ``significant rule'' under the DOT Regulatory Policies 
and Procedures (44 FR 11034, February 26, 1979); 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.
    We prepared a summary of the costs to comply with this AD (and 
other information as included in the Regulatory Evaluation) and placed 
it in the AD Docket. You may get a copy of this summary by sending a 
request to us at the address listed under ADDRESSES. Include ``Docket 
No. FAA-2007-0258; Directorate Identifier 2007-CE-090-AD'' in your 
request.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the Federal Aviation Administration amends part 39 of the Federal 
Aviation Regulations (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 removing Airworthiness Directive (AD) 
2007-13-17, Amendment 39-15121 (72 FR 36863, July 6, 2007), and adding 
the following new AD:

2008-10-12 Air Tractor, Inc.: Amendment 39-15518; Docket No. FAA-
2007-0258; Directorate Identifier 2007-CE-090-AD.

Effective Date

    (a) This AD becomes effective on June 12, 2008.

[[Page 25969]]

Affected ADs

    (b) This AD supersedes AD 2007-13-17, Amendment 39-15121.

Applicability

    (c) This AD applies to the following airplane models and serial 
numbers that are certificated in any category:

------------------------------------------------------------------------
               Models                            Serial Nos.
------------------------------------------------------------------------
AT-400, AT-400A, AT-402, AT-402A,    -0001 through -1175.
 and AT-402B.
AT-502, AT-502A, AT-502B, and AT-    -0001 through -2597.
 503A.
AT-602.............................  -0001 through -1141.
AT-802 and AT-802A.................  -0001 through -0227.
------------------------------------------------------------------------

Unsafe Condition

    (d) This AD results from a report of a Model AT-502B airplane 
with a crack located where the lower engine mount tube is welded to 
the engine mount ring. The airplane had 8,436 total hours time-in-
service (TIS). We are issuing this AD to detect and correct cracks 
in the engine mount, which could result in failure of the engine 
mount. Such failure could lead to separation of the engine from the 
airplane.

Compliance

    (e) To address this problem, you must do the following, unless 
already done:
    (1) For all airplanes with less than 5,000 hours total TIS that 
do not have gussets installed on the engine mount in accordance with 
Snow Engineering Co. Service Letter #253 Rev. A, dated October 16, 
2007; Snow Engineering Co. Service Letter #253 Rev. B, dated 
November 30, 2007; or Snow Engineering Co. Service Letter #253 Rev. 
C, dated April 17, 2008: Visually inspect the engine mount as 
follows:

------------------------------------------------------------------------
     Affected airplanes            Compliance            Procedures
------------------------------------------------------------------------
(i) For all Models AT-602,    Initially before the  Follow one of the
 AT-802, and AT-802A           airplane reaches a    following:
 airplanes.                    total of 1,300       (A) Snow Engineering
                               hours TIS or within   Co. Service Letter
                               the next 100 hours    253, Rev.
                               TIS after August      C, dated April 17,
                               10, 2007 (the         2008;
                               effective date of    (B) Snow Engineering
                               AD 2007-13-17),       Co. Service Letter
                               whichever occurs      253, Rev.
                               later. Repetitively   B, dated November
                               thereafter at         30, 2007;
                               intervals not to     (C) Snow Engineering
                               exceed 300 hours      Co. Service Letter
                               TIS.                  253, Rev.
                                                     A, dated October
                                                     16, 2007;
                                                    or
                                                    (D) Snow Engineering
                                                     Co. Service Letter
                                                     253,
                                                     revised January 22,
                                                     2007.
(ii) For all Model AT-502A    Initially before the  Follow one of the
 airplanes.                    airplane reaches a    following:
                               total of 1,300       (A) Snow Engineering
                               hours TIS or within   Co. Service Letter
                               the next 100 hours    253, Rev.
                               TIS after June 12,    C, dated April 17,
                               2008 (the effective   2008; or
                               date of this AD),    (B) Snow Engineering
                               whichever occurs      Co. Service Letter
                               later. Repetitively   253, Rev.
                               thereafter at         B, dated November
                               intervals not to      30, 2007.
                               exceed 300 hours
                               TIS.
(iii) For all Models AT-400,  Initially within the  Follow one of the
 AT-400A, AT-402, AT-402A,     next 12 months        following:
 AT-402B, AT-502, AT-502B,     after June 12, 2008  (A) Snow Engineering
 and AT-503A airplanes.        (the effective date   Co. Service Letter
                               of this AD).          253, Rev.
                               Repetitively          C, dated April 17,
                               thereafter at         2008; or
                               intervals not to     (B) Snow Engineering
                               exceed 12 months.     Co. Service Letter
                                                     253, Rev.
                                                     B, dated November
                                                     30, 2007.
------------------------------------------------------------------------

    (2) For all airplanes: Before further flight after any 
inspection required by paragraph (e)(1) of this AD where crack 
damage is found, repair and modify the engine mount by installing 
gussets following Snow Engineering Co. Service Letter 253, 
Rev. C, dated April 17, 2008; or Snow Engineering Co. Service Letter 
253, Rev. B, dated November 30, 2007. This modification 
terminates the repetitive inspections required in paragraphs 
(e)(1)(i), (e)(1)(ii), and (e)(1)(iii) of this AD.
    (3) For all airplanes: Unless already done (mandated by 
paragraph (e)(2) of this AD when crack damage was found) inspect, 
repair if cracked, and modify the engine mount by installing gussets 
following Snow Engineering Co. Service Letter 253, Rev. C, 
dated April 17, 2008; or Snow Engineering Co. Service Letter 
253, Rev. B, dated November 30, 2007, at whichever of the 
following compliance times that occurs later. This modification 
terminates the repetitive inspections required in paragraphs 
(e)(1)(i), (e)(1)(ii), and (e)(1)(iii) of this AD.
    (i) Before the airplane reaches 5,000 hours total TIS; or
    (ii) Within the next 100 hours TIS after June 12, 2008 (the 
effective date of this AD).
    (4) For all airplanes: You may delay the modification specified 
in paragraph (e)(3) above until April 30, 2009, provided you do the 
following in accordance with the service information provided in the 
Procedures column of the table presented in paragraph (e)(1) of this 
AD:
    (i) Initially inspect upon reaching the applicable time in 
paragraph (e)(3)(i) or (e)(3)(ii) of this AD, unless already done 
within the last 100 hours TIS;
    (ii) Repetitively inspect thereafter at intervals not to exceed 
100 hours TIS; and
    (iii) If cracks are found during any inspection, before further 
flight, repair the cracked part and install the gussets.

    Note: As a terminating action to the repetitive inspections 
required in paragraphs (e)(1)(i), (e)(1)(ii), and (e)(1)(iii) of 
this AD, you may install the gussets before finding cracks or 
reaching the times specified above provided you inspect to assure 
the area is crack free before installing the gussets.

Alternative Methods of Compliance (AMOCs)

    (f) The Manager, Fort Worth Airplane Certification Office, FAA, 
has the authority to approve AMOCs for this AD, if requested using 
the procedures found in 14 CFR 39.19. Send information to ATTN: Andy 
McAnaul, Aerospace Engineer, ASW-150, FAA San Antonio MIDO-43, 10100 
Reunion Place, Suite 650, San Antonio, Texas 78216; phone: (210) 
308-3365; fax: (210) 308-3370. Before using any approved AMOC on any 
airplane to which the AMOC applies, notify your appropriate 
principal inspector (PI) in the FAA Flight Standards District Office 
(FSDO), or lacking a PI, your local FSDO.

Material Incorporated by Reference

    (g) You must use Snow Engineering Co. Service Letter 
253, Rev. C, dated April 17, 2008; Snow Engineering Co. 
Service Letter 253, Rev. B, dated November 30, 2007; Snow 
Engineering Co. Service Letter 253, Rev. A, dated October 
16, 2007; or Snow Engineering Co. Service Letter 253, 
revised January 22, 2007, to do the actions required

[[Page 25970]]

by this AD, unless the AD specifies otherwise.
    (1) The Director of the Federal Register approved the 
incorporation by reference of Snow Engineering Co. Service Letter 
253, Rev. C, dated April 17, 2008; Snow Engineering Co. 
Service Letter 253, Rev. B, dated November 30, 2007; and 
Snow Engineering Co. Service Letter 253 Rev. A, dated 
October 16, 2007, under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) On August 10, 2007 (72 FR 36863, July 6, 2007), the Director 
of the Federal Register approved the incorporation by reference of 
Snow Engineering Co. Service Letter 253, revised January 
22, 2007.
    (3) For service information identified in this AD, contact Air 
Tractor Inc., P.O. Box 485, Olney, Texas 76374; telephone: (940) 
564-5616; fax: (940) 564-5612.
    (4) You may review copies at the FAA, Central Region, Office of 
the Regional Counsel, 901 Locust, Kansas City, Missouri 64106; or at 
the National Archives and Records Administration (NARA). For 
information on the availability of this material at NARA, call 202-
741-6030, or go to http://www.archives.gov/federal_register/code_
of_federal_regulations/ ibr_locations.html.

    Issued in Kansas City, Missouri, on April 30, 2008.
Patrick R. Mullen,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E8-9925 Filed 5-7-08; 8:45 am]

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