AD 2008-10-12

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.

Final rule.

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.

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 Numbers
AT-400, AT-400A, AT-402, AT-402A, and AT-402B
-0001 through -1175
AT-502, AT-502A, AT-502B, and AT-503A
-0001 through -2597
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. Suchfailure 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, AT-802, and AT-802A airplanes.
Initially before the airplane reaches a total of 1,300 hours TIS or within the next 100 hours TIS after August 10, 2007 (the effective date of AD 2007-13-17), whichever occurs later. Repetitively thereafter at intervals not to exceed 300 hours TIS.
Follow one of the following:
(A) Snow Engineering Co. Service Letter#253, Rev. C, dated April 17, 2008;
(B) Snow Engineering Co. Service Letter #253, Rev. B, dated November 30, 2007;
(C) Snow Engineering Co. Service Letter #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 airplanes.
Initially before the airplane reaches a total of 1,300 hours TIS or within the next 100 hours TIS after June 12, 2008 (the effective date of this AD), whichever occurs later. Repetitively thereafter at intervals not to exceed 300 hours TIS.
Follow one of the following:
(A) Snow Engineering Co. Service Letter #253, Rev. C, dated April 17, 2008; or
(B) Snow Engineering Co. Service Letter #253, Rev. B, dated November 30, 2007.
(iii) For all Models AT-400, AT-400A, AT-402, AT-402A, AT-402B, AT-502, AT-502B, and AT-503A airplanes.
Initially within the next 12 months after June 12, 2008 (the effective date of this AD). Repetitively thereafter at intervals not to exceed 12 months.Follow one of the following:
(A) Snow Engineering Co. Service Letter #253, Rev. C, dated April 17, 2008; or
(B) Snow Engineering 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 thecracked 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 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.

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. 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 cracksare 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 correctingthe 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:

Labor Cost
Parts Cost
Total Cost Per Airplane
Total Cost on 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:

Labor Cost
Parts Cost
Total Cost Per Airplane
Total Cost on 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 describesthe 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 thevarious 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

Accordingly, under theauthority 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

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 removing Airworthiness Directive (AD) 2007-13-17, Amendment 39-15121 (72 FR 36863, July 6, 2007), and adding the following new AD: