06-3617. Airworthiness Directives; Air Tractor, Inc. Models AT-400; AT-401, AT-401B, AT-402, AT-402A, and AT-402B Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule; request for comments.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for certain Air Tractor, Inc. (Air Tractor) Models AT-400, AT-401, AT-401B, AT-402, AT-402A, and AT-402B airplanes. This AD requires you to lower the safe life for the wing lower spar cap for certain Models AT-402A and AT-402B airplanes and those that incorporate or have incorporated Marburger Enterprises, Inc. (Marburger) winglets. For Models AT-400, AT-401, AT-401B, AT-402, and certain AT-402A, airplanes, this AD requires you to repetitively inspect the wing lower spar cap in order to reach the safe life. We also developed an alternative method of compliance (AMOC) to the requirements of this Ad for certain Models AT-402A and AT-402B airplanes. The AMOC includes repetitive eddy current inspections, modification of the center splice connection, and lower spar cap replacement. This AD is the result of reports of cracks in the 3/8-inch bolt hole of the wing lower spar cap before reaching the approved safe life. We are issuing this AD to prevent fatigue cracks from occurring in the wing lower spar cap before the originally established safe life is reached. Fatigue cracks in the wing lower spar cap, if not detected and corrected, could result in wing separation and loss of control of the airplane.

DATES:

This AD effective on April 21, 2006.

As of April 21, 2006, the Director of the Federal Register approved the incorporation by reference of certain publications listed in the regulation.

We must receive any comments on this AD by June 2, 2006.

ADDRESSES:

Use one of the following to submit comments on this AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility; US Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590-001.
• Fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

To get the service information identified in this AD, contact Air Tractor, Inc., P.O. Box 485, Olney, Texas 76374; telephone: [phone]; facsimile: [phone]; or Marburger Enterprises, Inc., 1227 Hillcourt, Williston, North Dakota 58801; telephone: [phone] or [phone]; facsimile: [phone].

To view the comments to this AD, go to http://dms.dot.gov. The docket number is FAA-2006-23646; Directorate Identifier 2006-CE-05;AD.

FOR FURTHER INFORMATION CONTACT:

Direct all questions to:

—For airplanes that do not incorporate and never have incorporated Marburger winglets: Rob Romero, Aerospace Engineer, FAA, Fort Worth Airplane Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: [phone]; facsimile: [phone]; and

—For airplanes that incorporate or have incorporated Marburger Enterprises, Inc. winglets: John Cecil, Aerospace Engineer, Los Angeles Aircraft Certification Office, FAA, 3960 Paramount Boulevard, Lakewood, California, 90712; telephone: [phone]; facsimile: [phone].

SUPPLEMENTARY INFORMATION:

 

What is the background of the subject matter? There have been five previous airworthiness directives (ADs) issued related to the wing spar inspection and safe life on Air Tractor airplanes:

• AD 2000-14-51, Amendment 39-11837 (65 FR 46567, July 31, 2000).
• AD 2001-10-04, Amendment 39-12230 (66 FR 27014, May 16, 2001).
• AD 2001-10-04 R1, Amendment 39-12247 (66 FR 2990, June 4, 2001).
• AD 2002-11-05, Amendment 39-12766 (67 FR 37967, May 31, 2002).
• AD 2002-26-05, Amendment 39-12991 (68 FR 18, January 2, 2003).

AD 2000-14-51: An Air Tractor Model AT-502A experienced an in-flight wing separation. As a result, the FAA issued AD 2000-14-51 as an emergency AD. This AD required the inspection of the wing lower spar cap for cracks on Air Tractor Models AT-501, AT-502, and AT-502A airplanes and modification or replacement of any cracked wing lower spar cap. Following the release of this AD, the manufacturer evaluated the AT-400 and AT-800 series lower spar cap fatigue life.

AD 2001-10-04: The manufacturer recalculation the fatigue life of the wing lower spar cap on Air Tractor AT-400, AT-500, and 800 series airplanes. The manufacturer also received reports of in-service cracks on airplanes with hours time-in-service (TIS) less than the published safe life. The cracks originated in the wing main spar lower cap at the center splice joint outboard 3/8-inch bolt hole. To address this condition, we issued AD 2001-10-04 to lower the safe life for the wing lower spar cap on Air Tractor AT-400, AT-500, and AT-800 series airplanes. The safe for the wing lower spar cap ranged from a low of 3,000 hours TIS to a high of 13,300 hours TIS depending upon model and serial number. This AD superseded AD 2000-14-51 and allowed for inspection (using eddy current methods) of the wing lower spar cap for airplanes that were at or over the lower life and for which parts were not available. Operation of the airplane was not allowed if you found cracks or you reached TIS limit.

AD 2001-10-04 R1: We inadvertently included those AT-800 series airplanes in the applicability of AD 2001-10-04 that were equipped with the factory-supplied computerized fir gate (part number 80540) and engaged in full-time firefighting. Consequently, we revised the AD to clarify that those airplanes were not affected.

AD 2002-11-05: In response to AD 2001-04 R1, we received a comment from the National Transportation Safety Board (NTSE) to recommend an eddy-current inspection requirement immediately before doing the two-part modification described in Snow Engineering Service Letter #202, revised March 26, 2001. Doing the eddy current inspection before the modification makes the crack easier to detect and gives the mechanic an area to concentrate on during any post-modification inspections. We issued AD 2002-11-05 to minimize the possibility that a crack existing in a bolt hole before doing the modification was still present after doing the modification. Additional analysis by the manufacturer also indicated the need to further the safe life for certain AT-400 series airplanes and certain AT-500 series airplanes that either incorporate or have incorporated Marburger winglets. These winglets were installed following Supplemental Type Certificate (STC) No. SA00490LA. We developed criteria for determining what the new safe life would be for airplanes that either incorporate or have incorporated these winglets. The safe life was reduced for airplanes that either incorporate or have incorporated these winglets by a usage factor reduction that is applied to the basic safe life. We used this information and issued AD 2002-11-05 to supersede AD 2001-10-04 R1 and require eddy-current inspections of the wing lower spar cap immediately before doing the replacement/modification to detect and correct any crack in a bolt hole before it extends to the modified center section of the wing. This AD further reduced the safe life for certain Models AT-401, AT-401B, AT-402, AT-402A, AT-402B, and AT-501 airplanes that incorporate or have incorporated Marburger winglets and removed the Models AT-502, AT-502A, AT-502B, and AT-503A airplanes from the applicability.

AD 2002-26-05: To address the Models AT-502, AT-502A, AT-502B, and AT-503A airplanes that were removed from AD applicability by AD 2002-11-05, we issued AD 2002-26-05. This AD is still in effect and lowers the safe life requires the eddy-current inspections of the wing lower spar cap immediately before doing the replacement/modification. This would allow you to detect and correct any crack in a bolt hole before it extends to the modified center section of the wing.

What has happened to initiate this AD action? The FAA received reports of fatigue cracking found on three AT-400 series airplanes and on three Model AT-802A airplanes that were below the reduced safe life established in AD 2002-11-05. One of the AT-400 series airplanes had Marburger winglets and the other incident airplanes did not Specifically:

• One AT-400 series airplanes equipped with winglets cracked at 5,340 hours TIS where the reduced safe life was 5,380 hours TIS. A second AT-400 series airplane cracked at 3,359 hours TIS where the reduced safe life was 4,589 hours TIS. A third AT-400 series airplane cracked at 4,176 hours TIS where the reduced safe life was 4,589 hours TIS, and the cracks were severe enough to not allow modification and required immediate wing spar replacement; and
• One AT-802A airplane cracked at 2,378 hours TIS where the reduced safe life was 4,531 hours TIS. A second AT-802A airplane cracked at 3,809 hours TIS where the reduced safe life was 4,531 hours TIS. A third AT-802A airplane cracked at 4,479 hours TIS where the reduced safe life was 4,531 hours TIS.

Further analysis shows the continued operation of these airplanes without inspection and/or modification could severely jeopardize the safety of the fleet.

What is the potential impact if the FAA took no action? This condition could result in fatigue cracks in the wing lower spar cap before the established safe life is reached. Fatigue cracks in the wing lower spar cap, if not detected and corrected, could result in wing separation and loss of control of the airplane.

Is there service information that applies to this subject? Snow Engineering Co. has issued Process Specification #197, page 1, revised June 4, 2002, pages 2 through 4, dated February 23, 2001, and page 5, dated May 3, 2002; Drawing Number 21088, dated November 3, 2004; and Service Letter #202, page 3, dated October 16, 2000.

Snow Engineering Co. has a licensing agreement with Air Tractor that allows them to produce technical data to use for Air Tractor products.

What are the provisions of this service information? The process specification and drawing include procedures for doing the eddy-current inspection and replacing the spar caps and associated hardware. The service letter provides information for installing access panels, if not already installed.

The FAA's Determination and Requirements of the AD

What has the FAA decided? We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other Air Tractor Models AT-400, AT-401, AT-401B, AT-402, AT-402A, and AT-402B airplanes of the same type design. Therefore, we are issuing this AD to prevent fatigue cracks from occurring in the wing lower spar cap before the originally established safe life is reached. Fatigue cracks in the wing lower spar cap, if not detected and corrected, could result in wing separation and loss of control of the airplane. The FAA is also issuing a similar AD on the AT-800 series airplanes and revising AD 2002-11-05 to retain the applicability of the Model AT-501 airplanes.

What does this AD require? This AD requires you to:

• Lower the safe life for the wing lower spar cap for certain Models AT-402A and AT-402B airplanes and those that incorporate or have incorporated Marburger winglets;
• Eddy-current inspect the wing lower spar cap at specified thresholds and intervals for Models AT-400, AT-401, AT-401B, AT-402, and certain AT-402A airplanes in order to reach the safe life;
• Eddy-current inspect the wing lower spar cap immediately before doing the modification for certain Models AT-402A and AT-402B airplanes to detect and correct any crack in a bolt hole; and
• Report the results of this inspection to the FAA if any cracks are found.

We also included an alternative method of compliance to the requirements of this AD for certain Models AT-402A and AT-402B airplanes.

In preparing this rule, we contacted type clubs and aircraft operators to get technical information and information on operational and economic impacts. We did not receive any information through these contacts. If received, we would have included a discussion of any information that may have influenced this action in the rulemaking docket.

Comments Invited

Will I have the opportunity to comment before you issue the rule? This AD is a final rule that involves requirements affecting flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any written relevant data, views, or arguments regarding this AD. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2006-23646; Directorate Identifier 2006-CE-05-AD” in the subject line of your comments. If your want us to acknowledge receipt of your mailed comments, send us a self-addressed, stamped postcard with the docket number written on it; we will date-stamp your postcard and mail it back to you. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify it. If a person contacts us through a nonwritten communication, and that contact relates to a substantive part of this AD, we will summarize the contract and place the summary in the docket. We will consider all comments received by the closing date and may amend the AD in light of those comments.

Authority for This Rulemaking

What authority does the FAA have for issuing this rulemaking action? Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 206 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

Will this AD impact various entities? 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.

Will this AD involve a significant rule or regulatory action? For the reasons discussed above, I certify that this AD:

1. It 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 “AD Docket FAA-2006-23646; Directorate Identifier 2006-CE-05-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 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

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):

2006-08-08 Air Tractor, Inc.: Amendment 39-14563; Docket No. FAA-2006-23646; Directorate Identifier 2006-CE-05-AD.

When Does This AD Become Effective?

(a) This AD becomes effective on April 21, 2006.

What Other ADs Are Affected by This Action?

(b) As of the issuance of this action, AD 2002-11-05 applies to Models AT-400, AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-802, and AT-802A airplanes. The FAA is revising AD 2002-11-05 to remove the AT-400 series and AT-800 series airplanes from the applicability. The FAA is also issuing another similar AD on the AT-800 airplanes.

What Airplanes Are Affected by This AD?

(c) This AD applies to certain Models AT-400, AT-401, AT-401B, AT-402, AT-402A, and AT-402B airplanes that are certificated in any category. Use paragraph (c)(1) of this AD for affected airplanes that do not incorporate and never have incorporated Marburger winglets. Use paragraph (c)(3) of this AD for airplanes that have been modified to install lower spar caps, part number (P/N) 21058-1, and P/N 21058-2. Use paragraph (c)(4) of this AD for certain Models AT-401, AT-401B, AT-402, AT-402A, and AT-402B airplanes that incorporate or have incorporated Marburger winglets.

(1) The following table applies to airplanes that do not incorporate and never have incorporated Marburger winglets along with the safe life (presented in hours time-in-service (TIS)) of the wing lower spar cap for all affected airplane models and serial numbers:

Table 1.—Safe Life for Airplanes That Do Not Incorporate and Never Have Incorporated Marburger Winglets

Model	Serial Nos.	Wing lower spar cap safe life
AT-400	All beginning with 0416	13,300 hours TIS.
AT-401	0662 through 0951	10,757 hours TIS.
AT-401B	0952 through 1020, except 1015	6,948 hours TIS.
AT-401B	1015 and all beginning with 1021	7,777 hours TIS.
AT-402	0694 through 0951	7,440 hours TIS.
AT-402A	0738 through 0951	7,440 hours TIS.
AT-402A	0952 through 1020	2,000 hours TIS.
AT-402A	All beginning with 1021	2,300 hours TIS.
AT-402B	0966 through 1020, except 1015	2,000 hours TIS.
AT-402B	1015 and all beginning with 1021	2,300 hours TIS.

(2) If piston-powered aircraft have been converted to turbine power, you must use the limits for the corresponding serial number turbine-powered aircraft.

(3) If you have an aircraft that has been modified by installing lower spar caps, P/N 21058-1 and P/N 21058-2, you must use a wing lower spar cap life of 9,800 hours TIS. No inspections are required to reach this life.

(i) Airplanes that have been modified with replacement spar caps, P/N 21058-1 and P/N 21058-2, are not eligible to have Supplemental Type Certificate (STC) No. SA00490LA, Marburger winglets, installed.

(ii) If your airplanes currently has spar caps, P/N 21058-1 and P/N 21058-2, and winglets installed, then you must remove the winglets before further flight and you must contact the FAA at the address in paragraph (l)(1) of this AD for a new safe life.

(iii) Installation of Marburger winglets on airplanes that have been modified with replacement spar caps, P/N 21058-1 and P/N 21058-2, will require additional fatigue-data substantiating an appropriate safe life. If you have replacement spar caps and wish to install winglets, you must contact the FAA at the address in paragraph (l)(1) of this AD for additional information.

(4) The following table applies to airplanes that incorporate or have incorporated Marburger winglets. These winglets are installed following STC No. SA00490LA. Use the winglet usage factor in Table 2 of this paragraph, the wing lower spar cap safe life specified in Table 1 in paragraph (c)(1) of this AD, and the instructions included in Appendix 1 to this AD to determine the new safe life of airplanes that incorporate or have incorporated Marburger winglets:

Table 2.—Winglet Usage Factor To Determine the Safe Life for Airplanes That Incorporate or Have Incorporated Marburger Winglets per STC No. SA00490LA

Model	Serial Nos.	Winglet usage factor
AT-401	0662 through 0951	1.6
AT-401B	0952 through 1020, except 1015	1.1
AT-401B	1015 and all beginning with 1021	1.1
AT-402	0694 through 0951	1.6
AT-402A	0738 through 0951	1.6
AT-402A	0952 through 1020	1.1
AT-402A	All beginning with 1021	1.1
AT-402B	0966 through 1020, except 1015	1.1
AT-402B	1015 and all beginning with 1021	1.1

What Is the Unsafe Condition Presented in This AD?

(d) This AD is the result of fatigue cracking of the wing main spar lower cap at the center splice joint outboard fastener hole. The actions specified in this AD are intended to detect and correct cracks in the wing main spar lower cap, which could result in failure of the spar cap and lead to wing separation and loss of control of the airplane.

What Must I Do To Address This Problem?

(e) Safe Life Record: For all affected airplanes, modify the applicable aircraft records (logbook) as follows to show the safe life for the wing lower spar cap listed in this AD (use the information from paragraph (c) of this AD and Appendix 1 to this AD, as applicable).

(1) Incorporate the following into the Aircraft Logbook: “Following AD 2006-08-08 the wing lower spar cap is life limited to __ hours time-in-service (TIS).” Insert the applicable safe life number from the applicable tables in paragraph (c) of this AD and Appendix 1 to this AD.

(i) Do the logbook entry within the next 10 hours TIS after April 21, 2006 (the effective date of this AD).

(ii) The owner/operator holding at least a private pilot certificate as authorized by section 43.7 of the Federal Aviation Regulations (14 CFR 43.7) may modify the aircraft records. Make an entry into the aircraft records showing compliance with this portion of the AD following section 43.9 of the Federal Aviation Regulations (14 CFR 43.9).

(2) Wing Spar Replacement: For all affected airplanes, replace the wing lower spar cap following Snow Engineering Drawing Number 21088, dated November 3, 2004. Replace upon accumulating the safe life used in paragraph (e)(1) of this AD or within the next 50 hours TIS after [date] (the effective date of this AD), whichever occurs later. The owner/operator may not do the spar cap replacement, unless he/she holds the proper mechanic's authorization.

(f) Inspection Requirements: For all affected airplanes, except Model AT-402A, all serial numbers beginning with 0952, and except Model AT-402B, all serial numbers beginning with 0966: Do the initial inspection of the outboard two lower spar cap bolt holes following Snow Engineering Co. Process Specification #197, page 1, revised June 4, 2002, pages 2 through 4, dated February 23, 2001, and page 5, dated May 3, 2002; and using the wing spar lower cap TIS schedules listed in the following table. After the initial inspection, perform repetitive inspections using the same procedure as the initial inspection at the repetitive inspection intervals listed in the following table. If not already done, install access panels at the time of the first inspection following Snow Engineering Service Letter #202, page 3, dated October 16, 2000.

Note 1:

Hours listed in the table are in hours TIS and the phrase “within __ hours” refers to “within __ hours after [date] (the effective date of this AD).”

Table 3.—Inspection Times

Model	Serial Nos.	Current wing spar lower cap TIS hours	Initial inspection	Repetitive inspection interval
AT-400	All beginning with 0416	Greater than 7,750	Within 50 hours or upon the accumulation of 8,000 hours, whichever is later	900 hours.
AT-401	0662-0951	Greater than 6,250	Within 50 hours or upon the accumulation of 6,500 hours, whichever is later	700 hours.
AT-401	0662-0951	Greater than 4,350 but less than or equal to 6,250	Within 250 hours or upon the accumulation of 4,850 hours, whichever is later	700 hours.
AT-401	0662-0951	Greater than 2,750 but less than or equal to 4,350	Within 500 hours	700 hours.
AT-401	0662-0951	Less than or equal to 2,750	Upon the accumulation of 3,250	700 hours.
AT-401B	0952-1020 except 1015	Greater than 3,950	Within 50 hours or upon the accumulation of 4,200 hours, whichever is later	600 hours.
AT-401B	0952-1020 except 1015	Greater than 2,650 but less than or equal to 3,950	Within 250 hours or upon the accumulation of 3,150 hours, whichever is later	600 hours.
AT-401B	0952-1020 except 1015	Greater than 1,600 but less than or equal to 2,650	Within 500 hours	600 hours.
AT-401B	0952-1020 except 1015	Less than or equal to 1,600	Upon the accumulation of 2,100 hours	600 hours.
AT-401B	1015 and 1021-1124	Greater than 4,450	Within 50 hours or upon the accumulation of 4,700, whichever is later	400 hours.
AT-401B	1015 and 1021-1124	Greater than 3,000 but less than or equal to 4,450	Within 250 hours or upon the accumulation of 3,500 hours, whichever is later	400 hours.
AT-401B	1015 and 1021-1124	Greater than 1,850 but less than or equal to 3,000	Within 500 hours	400 hours.
AT-401B	1015 and 1021-1124	Less than or equal to 1,850	Upon the accumulation of 2,350	400 hours.
AT-401B	All beginning with 1125	Greater than 4,450	Within 50 hours or upon the accumulation of 4,700 hours, whichever is later	1,000 hours.
AT-401B	All beginning with 1125	Greater than 3,000 but less than or equal to 4,450	Within 250 hours or upon the accumulation of 3,500 hours, whichever is later	1,000 hours.
AT-401B	All beginning with 1125	Greater than 1,850 but less than or equal to 3,000	Within 500 hours	1,000 hours.
AT-401B	All beginning with 1125	Less than or equal to 1,850	Upon the accumulation of 2,350	1,000 hours.
AT-402/4 02A	0694-0951	Greater than 4,250	Within 50 hours or upon the accumulation of 4,500, whichever is later	700 hours.
AT-402/4 02A	0694-0951	Greater than 2,850 but less than or equal to 4,250	Within 250 hours or upon the accumulation of 3,350, whichever is later	700 hours.
AT-402/4 02A	0694-0951	Greater than 1,750 but less than or equal to 2,850	Within 500 hours	700 hours.
AT-402/4 02A	0694-0951	Less than or equal to 1,750	Upon the accumulation of 2,250	700 hours.

(g) For all affected airplanes: Replace any cracked wing lower spar cap following Snow Engineering Drawing Number 21088, dated November 3, 2004, before further flight after the inspection in which cracks are found.

(h) For all affected airplanes, except Model AT-402A, all serial numbers beginning with 0952, and except Model AT-402B, all serial numbers beginning with 0966: Report to the FAA any cracks detected as the result of each inspection required by paragraph (f) of this AD on the form in Figure 1 of this AD.

(1) Only if cracks are found, send the report within 10 days after the inspection required in paragraph (f) of this AD.

(2) The Office of Management and Budget (OMB) approved the information collection requirements contained in this regulation under the provisions of the Paperwork Reduction Act and assigned OMB Control Number 2120-0056.

(i) For all affected airplanes: Upon the accumulation of the life used in paragraph (e)(1) of this AD or within the next 50 hours TIS after [date] (the effective date of this AD), whichever occurs later, you must replace your wing lower spar cap before further flight following Snow Engineering Drawing Number 21088, dated November 3, 2004.

(j) For Model AT-402A airplanes, all serial numbers beginning with 0952; and Model AT-402B airplanes, all serial numbers beginning with 0966: In lieu of the safe life used in paragraph (e)(1) of this AD, you may eddy-current inspect and modify the wing lower spar cap. The inspection schedule and modification procedures are included in Appendix 2 to this AD.

(k) For all affected airplanes (those complying with the actions in the AD or AMOC): One of the following must do the inspection:

(1) A level 2 or 3 inspector certified in eddy current inspection using the guidelines established by the American Society for Nondestructive Testing or MIL-STD-410; or

(2) A person authorized to perform AD work and who has completed and passed the Air Tractor, Inc. training course on Eddy Current Inspection on wing lower spar caps.

May I Request an Alternative Method of Compliance?

(1) The Manager, Fort Worth or Los Angeles Airplane Certification Office (ACO), as applicable, FAA, has the authority to approve alternative methods of compliance (AMOCs) for this AD, if requested using the procedures found in 14 CFR 39.19. For information on any already approved alternative methods of compliance, contact:

(1) For the airplanes that do not incorporate and never have incorporated Marburger winglets: Rob Romero, Aerospace Engineer, FAA, Fort Worth Airplane Certification Office, 2601 Meacham Boulevard, Forth Worth, Texas 76193-0150; telephone: [phone]; facsimile: [phone].

(2) For airplanes that incorporate or have incorporated Marburger winglets: John Cecil, Aerospace Engineer, Los Angeles Aircraft Certification Office, FAA, 3960 Paramount Boulevard, Lakewood, California 90712; telephone: [phone]; facsimile: [phone].

(m) AMOCs approved for AD 2001-10-04, AD 2001-10 R1, or AD 2002-11-05 for the AT-400 series airplanes are not considered approved for this AD.

Special Flight Permit

(n) Under 14 CFR part 39.23, we are allowing special flight permits for the purpose of compliance with this AD under the following conditions:

(1) Only operate in day visual flight rules (VFR).

(2) Ensure that the hopper is empty.

(3) Limit airspeed to 135 miles per hour (mph) indicated airspeed (IAS).

(4) Avoid any unnecessary g-forces.

(5) Avoid areas of turbulence.

(6) Plan the flight to follow the most direct route.

Does This AD Incorporate Any Material by Reference?

(o) You must do the actions required by this AD following the instructions in Snow Engineering Drawing 21088, dated November 3, 2004; Snow Engineering Co. Process Specification #197, page 1, revised June 4, 2002, pages 2 through 4, dated February 23, 2001, and page 5, dated May 3, 2002; and Snow Engineering Co. Service Letter #202, page 3, dated October 16, 2000. The Director of the Federal Register approved the incorporation by reference of this service information following 5 U.S.C. 552(a) and 1 CFR part 51. To get a copy of this service information, contact Air Tractor, Incorporated, P.O. Box 485, Olney, Texas 76374; telephone: [phone]; facsimile: [phone]; or Marburger Enterprises, Inc., 1227 Hillcourt, Williston, North Dakota 58801; telephone: [phone] or [phone]; facsimile: [phone]. To review copies of this service information, go to the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, go to: http://www.archives.gov/​federal_​register/​code_​of_​federal_​regulations/​ibr_​locations.html or call [phone]. To view the AD docket, go to the Docket Management Facility; US Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590-001 or on the Internet at http://dms.dot.gov. The docket number is FAA-2006-23646; Directorate Identifier 2006-CE-05-AD.

Appendix 1 To AD 2006-08-08

The following provides procedures for determining the safe life for those Models AT-401, AT-401B, AT-402, AT-402A, and AT-402B airplanes that incorporate or have incorporated Marburger winglets. These winglets are installed following Supplemental Type Certificate (STC) No. SA009490LA.

What if I removed the Marburger winglets prior to further flight after the effective date of this AD or prior to the effective date of this AD?

1. Review your airplane's logbook to determine your airplane's time in service (TIS) with winglets installed per Marburger STC No. SA00940LA. This includes all time spent with the winglets currently installed and any previous installations where the winglet was installed and later removed.

Example:

A review of your airplane's logbook shows that you have accumulated 350 hours TIS since incorporating the Marburger STC. Further review of the airplane's logbook shows that a previous owner had installed the STC and later removed the winglets after accumulating 150 hours TIS. Therefore, your airplane's TIS with the winglets installed is 500 hours.

If you determine that the winglet STC has never been incorporated on your airplane, then your safe life is presented in paragraph (c)(1) of this AD. Any future winglet installation will be subject to a reduced safe life per these instructions.

2. Determine your airplane's unmodified safe life from paragraph (c)(1) of this AD.

Example:

Your airplane is a Model AT-401B, serial number 1022. From paragraph (c)(1) of this AD, the unmodified safe life of your airplane is 7,777 hours TIS.

All examples from hereon will be based on the Model AT-401B, serial number 1022 airplane.

3. Determine the winglet usage factor from paragraph (c)(4) of this AD.

Example:

Again, your airplane is a Model AT-401B, serial number 1022. From paragraph (c)(4) of this AD, your winglet usage factor is 1.1.

4. Adjust the winglet TIS to account for the winglet usage factor. Multiply the winglet TIS (result of Step 1 above) by the winglet usage factor (result of Step 3 above).

Example:

Winglet TIS is 500 hours X a winglet usage factor of 1.1. The adjusted winglet TIS is 550 hours.

5. Calculate the winglet usage penalty. Subtract the winglet TIS (result of Step 1 above) from the adjusted winglet TIS (result of Step 4 above).

Example:

Adjusted winglet TIS−the winglet TIS−winglet usage penalty.

(550 hours)−(500 hours TIS) = (50 hours TIS).

6. Adjust the safe life of your airplane to account for winglet usage. Subtract the winglet usage penalty (result of Step 5 above) result from the unmodified safe life from paragraph (c)(1) of this AD (result of Step 2 above.).

Example:

 

Unmodified safe life−winglet usage penalty = adjusted safe life.

(7,777 hours TIS)−(50 hours TIS) = (7,727 hours TIS).

7. If you remove the winglets from your airplane before further flight or no longer have the winglets installed on your airplane, the safe life of your airplane is the adjusted safe life (result of Step 6 above). Enter this number in paragraph (e)(1) of this AD and the airplane logbook.

What if I have the Marburger winglet installed as of the effective date of this AD and plan to operate my airplane without removing the winglet?

1. Review your airplane's logbook to determine your airplane's TIS without the winglets installed.

Example:

A review of your airplane's logbook shows that you have accumulated 1,500 hours TIS, including 500 hours with the Marburger winglets installed. Therefore, your airplane's TIS without the winglets installed is 1,000 hours.

2. Determine your airplane's unmodified safe life from paragraph (c)(1) of this AD.

Example:

Your airplane is a Model AT-401B, serial number 1022. From paragraph (c)(1) of this AD, the unmodified safe life of your airplane is 7,777 hours TIS.

All examples from hereon will be based on the Model AT-401B, serial number 1022 airplane.

3. Determine the winglet usage factor from paragraph (c)(4) of this AD.

Example:

Again, your airplane is a Model AT-401B, serial number 1022. From paragraph (c)(4) of this AD, your winglet usage factor is 1.1.

4. Determine the potential winglet TIS. Subtract the TIS without the winglets installed (result of Step 1 above) from the unmodified safe life (result of Step 2 above).

Example:

 

Unmodified safe life−TIS without winglets = Potential winglet TIS.

(7,777 hours TIS)−(1,000 hours TIS) = (6,777 hours TIS).

5. Adjust the potential winglet TIS to account for the winglet usage factor. Divide the potential winglet TIS (result of Step 4 above) by the winglet usage factor (result of Step 3 above).

Example:

 

Potential winglet TIS ÷ Winglet usage factor = Adjusted potential winglet TIS.

(6,777 hours TIS) ÷ (1.1) = (6,155 hours TIS).

6. Calculate the winglet usage penalty. Subtract the adjusted potential winglet TIS (result of Step 5 above) from the potential winglet TIS (result of Step 4 above).

Example:

 

Potential winglet TIS−Adjusted potential winglet TIS = Winglet usage penalty.

(6,777 hours TIS)−(6,155 hours TIS = (622 hours TIS).

7. Adjust the safe life of your airplane to account for the winglet installation. Subtract the winglet usage penalty (result of Step 6 above) from the unmodified safe life from paragraph (c)(1) of this AD (the result of Step 2 above).

Example:

 

Unmodified safe life−Winglet usage penalty = Adjusted safe life.

(7,777 hours TIS)−(622 hours TIS) = (7,155 hours TIS).

8. Enter the adjusted safe life (result of Step 7 above) in paragraph (e)(1) of this AD and the airplane logbook.

What if I install or remove the Marburger winglet from my airplane in the future?

If, at anytime in the future, you install or remove the Marburger winglet STC from your airplane, you must repeat the procedures in this Appendix to determine the airplane's safe life.

Appendix 2—Alternative Method of Compliance (AMOC) To AD 2006-08-08

Optional Inspection Program

For Model AT-402A airplanes, all serial numbers (S/Ns) beginning with 0952, and Model AT-402B airplanes, all S/Ns beginning with 0966, that do not incorporate and never have incorporated Marburger winglets installed following STC No. SA00490LA; you may begin a repetitive inspection interval program as an alternative to the safe life requirement of this AD with the following provisions:

1. Upon accumulating 1,600 hours time-in-service (TIS) or within the next 50 hours TIS after April 21, 2006 (the effective date of AD 2006-08-08), whichever occurs later, eddy-current inspect the outboard two lower spar cap bolt holes following Snow Engineering Process Specification #197, page 1, revised June 4, 2002; pages 2 through 4, dated February 23, 2001; and page 5, dated May 3, 2002. The inspection must be done by one of the following:

a. A Level 2 or Level 3 inspector that is certified for eddy-current inspection using the guidelines established by the American Society for Nondestructive Testing or MIL-STD-410; or

b. A person authorized to do AD work and who has completed and passed the Air Tractor, Inc. training course on Eddy Current Inspection on wing lower spar caps.

2. Repeat these inspections at intervals of (as applicable):

a. 400 hours TIS:

i. Model AT-402A, S/Ns 1021 through 1124

ii. Model AT-402B, S/Ns 1015, and 1021 through 1124

b. 600 hours TIS:

i. Model AT-402A, S/Ns 0952 through 1020

ii. Model AT-402B, S/Ns 0966 through 1020, except 1015

c. 1,000 hours TIS:

i. Model AT-402A, all S/Ns beginning with 1125

ii. Model AT-402B, all S/Ns beginning with 1125

d. If the outboard two lower spar cap bolt holes have been cold worked following Snow Engineering Service Letter #238 or #239, both dated September 30, 2004, then you may double the inspection intervals listed in a., b., and c. above (800 hours TIS, 1,200 hours TIS, or 2,000 hours TIS, as applicable) (See Step 8.-re: mid cycle cold work).

e. Your logbook entry must include the work done and the inspection intervals that are upcoming, as follows:

“Following AD 2006-08-08, at XXXX (insert hours TIS of the initial pre-modification inspection) hours TIS an eddy-current inspection has been performed. As of now, the safe life listed in the AD no longer applies to this airplane. This airplane must be eddy-current inspected at intervals not to exceed (400/600/800/1,000/1,200/2,000, as applicable) hours TIS. The first of these inspections is due at (insert the total number of hours TIS the first of these inspections is due) hours TIS.''

3. If at any time a crack is found, and:

a. If the crack indication goes away by doing the initial steps of the modification following the applicable sheet of Snow Engineering Co. Drawing Number 20992, then you may continue to modify your wing. After modification, proceed to Step 5.

b. If the crack indication does not go away by doing the initial steps of the modification following the applicable sheet of Snow Engineering Co. Drawing Number 20992, then you must replace all parts and hardware listed in Step 7.

c. Report to the FAA any cracks found using the form in Figure 1 of this AD.

4. Upon accumulating 4,000 hours TIS, you must:

a. Modify your center splice connection following the applicable sheet of Snow Engineering Co. Drawing Number 20992, unless already done. Before doing the modification, do an eddy-current inspection following Snow Engineering Process Specification #197, page 1, revised June 4, 2002; pages 2 through 4, dated February 23, 2001; and page 5, dated May 3, 2002. (See Step 9). If, as of April 21, 2006 (the effective date of AD 2006-08-08), your airplane is over or within 50 hours of reaching the 4,000-hour TIS modification requirement, then you must perform the modification within 50 hours TIS.

b. Your logbook entry must include the work done and the inspection intervals that are upcoming, as follows:

“Following AD 2006-08-08, at XXXX (insert hours TIS of the modification) hours TIS an eddy-current inspection has been performed. As of now, the safe life listed in the AD no longer applies to this airplane. This airplane must be eddy-current inspected at (insert the number of hours TIS at modification plus 1,600 hours TIS) hours TIS.

5. Upon accumulating 1,600 hours TIS after modification, inspect the left-hand and right-hand outboard two lower spar cap bolt holes following Snow Engineering Process Specification #197, page 1, revised June 4, 2002; pages 2 through 4, dated February 23, 2001; and page 5, dated May 3, 2002.

6. Repeat the inspection at intervals of:

a. 1,000 hours TIS; or

b. 2,000 hours TIS if the outboard two lower spar cap bolt holes have been cold worked following Snow Engineering Service Letter #239, dated September 30, 2004 (See Step 8.).

c. Your logbook entry must include the work done and the post-modification inspection intervals that are upcoming, as follows:

“Following AD 2006-08-08, at XXXX (insert hours TIS of the initial post-modification inspection) hours TIS an eddy-current inspection has been performed. As of now, the safe life listed in the AD no longer applies to this airplane. This airplane must be eddy-current inspected at intervals not to exceed (1,000/2,000, as applicable) hours TIS. The first of these inspections is due at (insert the total number of hours TIS the first of these inspections is due) hours TIS.”

d. If at any time a crack is found, then before further flight you must replace the lower spar caps, splice blocks, and wing attach angles and hardware. You must also notify the FAA using the form in Figure 1 of this AD.

7. Upon accumulating 8,000 hours TIS, before further flight you must replace the lower spar caps, splice blocks, and wing attach angles (P/N 20693-1) and associated hardware. No additional time will be authorized for airplanes that are at over 8,000 hours TIS (See Step 9.).

8. If you decide to cold work your bolt holes following Snow Engineering Service Letter #238 or #239, both dated September 30, 2004, at a TIS that does not coincide with a scheduled inspection following this AD, then eddy-current inspect at the time of cold working and then begin the 800/1,200/2000 hour TIS inspection intervals (2 times the intervals listed in Steps 2.a., 2.b., 2.c., and 6.a listed above).

9. If you have modified your airplane before accumulating 4,000 hours TIS, then you may continue to fly your airplane past (modification + 4,000 hours TIS) provided you cut your inspection intervals in half. Make a logbook entry following Step 6.c. to reflect these reduced inspection intervals. Upon accumulating 8,000 hours TIS, you must comply with Step 7 above. See example:

Example:

An AT-402B had the two-part modification installed at 3,000 hours TIS and the bolt holes have not been cold worked.

The first inspection would occur at 4,600 hours TIS. From Step 5, this is modification plus 1,600 hours.

Inspections would follow at 5,600 and 6,600 hours TIS. From Step 6a, this is 1,000-hour TIS inspection intervals.

There is another inspection at 7,000 hours TIS (modification plus 4,000 hours TIS). This relates to the 8,000-hour TIS inspection from Step 7, which is modification plus 4,000 hours TIS, except in this example the modification took place at 3,000 hours TIS instead of 4,000 hours TIS listed in Step 4.

This airplane may continue to fly if inspected again at 7,500 hours TIS, which is 500 hours TIS. This 500-hour time corresponds to Step 9 where you cut your inspection interval from Step 6a in half.

Upon accumulating 8,000 hours TIS (this is the same as Step 7), you must replace the parts listed in Step 7 above.

For Model AT-402A airplanes, al S/N's beginning with 0952, and Model AT-402B airplanes, all S/Ns beginning with 0966, that incorporate or have incorporated Marburger winglets installed following STC No. SA00490LA; you may begin a repetitive inspection interval program as an alternative to the safe life requirement of this AD following the steps above with the following provisions:

If you have removed the winglets, then calculate new, reduced hours for Steps 1, 4, 5, and 7 above, as applicable, based on the winglet usage factor listed in paragraph (c)(4) and Appendix 2 of this AD.

You may repetitively inspect at the same intervals list in Step 2 above provided that you do not re-install the winglets.

Example:

An AT-402B airplane, S/N 1020, had winglets installed at 200 hours TIS and removed at 800 hours TIS.

The winglet usage factor is: 1.1.

Calculate equivalent hours: 600 hours TIS with winglets × 1.1 = 660 hours TIS.

Winglet usage penalty = 660−600 = 60.

New Step 1 Pre-Modification Initial Inspection time = 1,600−60 = 1,540 hours TIS.

Retained Step 2 Pre-Modification Inspection interval: Since the winglets are removed, the Pre-Modification Inspection interval remains at 600 hours TIS.

New Step 4 Modification time = 4,000−60 = 3,940 hours TIS.

New Step 5 Post-Modification Initial Inspection time = 3,940 + 1,600 = 5,540 hours TIS.

Retained Step 6 Post-Modification Inspection interval: Since the winglets are removed the Post-Modification Inspection interval remains at 1,000/2,000 hours TIS.

New Step 7 Replacement time = 8,000−60 = 7,940 hours TIS.

Use the Retained Step 2 interval, the New Step 5 time, and the Retained Step 6 interval to make appropriate logbook entries for the pre- and post-modification intervals, using the format presented in Steps 2.e., 4.b., and 6.c.

If you have not removed the winglets, then calculate new, reduced hours for Steps 1, 2, 4, 5, 6, and 7 above, as applicable, based on the winglet usage factor listed in paragraph (c)(4) and Appendix 2 of this AD.

Repetitively inspect at the appropriate interval listed in the step above divided by the winglet usage factor.

Example:

An AT-402B, S/N 1,000 has had winglets on since new.

The winglet usage factor is: 1.1.

New Step 1 Pre-Modification Initial Inspection time: 1,600 ÷ 1.1 = 1,455 hours TIS.

New Step 2 Pre-Modification Inspection interval: 600 ÷ 1.1 = 545 hours TIS.

New Step 4 Modification time: 4,000 ÷ 1.1 = 3,636 hours TIS.

New Step 5 Post-Modification Initial Inspection time: 3,636 + (1,600 ÷ 1.1) = 5,090 hours TIS.

New Step 6 Post-Modification Inspection interval: 1,000 ÷ 1.1 = 909 hours TIS.

New Step 7 Replacement time: 8,000 ÷ 1.1 = 7,273 hours TIS.

Use the reduced hours you calculate in New Step 2, New Step 5, and New Step 6 to make appropriate logbook entries for the pre- and post-modification inspection intervals, using the format presented in Steps 2.e., 4.b., and 6.c.

Issued in Kansas City, Missouri, on April 10, 2006.

David R. Showers,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.