06-3614. Airworthiness Directives; Air Tractor, Inc. Model AT-501 Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule; request for comments.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) to revise AD 2002-11-05, which applies to certain Air Tractor, Inc. (Air Tractor) AT-400 series and Models AT-501, AT-802, and AT-802A airplanes. AD 2002-11-05 establishes a safe life for the wing lower spar cap. Since we issued AD 2002-11-05, we have received reports of cracks found prior to the established safe life on AT-400 series airplanes and on Model AT-802A airplanes. We are issuing separate AD actions for AT-400 series and Models AT-802 and AT-802A airplanes to address the unsafe condition of those airplanes. This AD retains the actions required in AD 2002-11-05 for Model AT-501 airplanes and removes AT-400 series and Models AT-802 and AT-802A airplanes from the applicability of AD 2002-11-05.

DATES:

This AD becomes effective on April 21, 2006.

On June 8, 2001 (66 FR 27014, May 16, 2001), the Director of the Federal Register previously 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; U.S. 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, Incorporated, P.O. Box 485, Olney, Texas 76374; 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-2006-23647; Directorate Identifier 2006-CE-06-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 winglets: John Cecil, Aerospace Engineer, Los Angeles Aircraft Certificate Office, FAA, 3960 Paramount Boulevard, Lakewood, California 90712; telephone: [phone]; facsimile: [phone].

SUPPLEMENTARY INFORMATION:

Discussion

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 recalculated the fatigue life of the wing lower spar cap on Air Tractor AT-400, and AT-500, and AT-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 life 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 safe 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 fire 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 2001-10-04 R1, we received a comment from the National Transportation Safety Board (NTSB) 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 reduce 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 and 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 airplane 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.

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 continues to exist or develop on type design Air Tractor Model AT-501 airplanes. 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 failure of the spar cap and lead to wing separation and loss of control of the airplane.

What does this AD require? This AD revises AD 2002-11-05, Amendment 39-12766 (67 FR 37967, May 31, 2002), with a new AD that retains the actions required in AD 2002-11-05 for Model AT-501 and removes the AT-400 series and Models AT-802 and AT-802A airplanes from the applicability.

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-2006-23647; Directorate Identifier 2006-CE-06-AD” in the subject line of your comments. If you 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 contact 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 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

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. 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-2006-23647; Directorate Identifier 2006-CE-06-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. FAA amends § 39.13 by removing Airworthiness Directive (AD) 2002-11-05, Amendment 39-12766 ( 67 FR 37967, May 31, 2002), and by adding a new AD to read as follows:

2002-11-05-R1 Air Tractor, Inc.: Amendment 39-14564; Docket No. FAA-2006-23647; Directorate Identifier 2006-CE-06-AD.

When Does This AD Become Effective?

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

Are Any Other ADs Affected by This Action?

(b) This AD revises AD 2002-11-05, Amendment 39-12766.

What Airplanes Are Affected by This AD?

(c) This AD applies to Model AT-501 airplanes that are certificated in any category. Use Table 1 in paragraph (c)(1) of this AD for AT-501 airplanes that do not incorporate and never have incorporated Marburger winglets and use Table 2 in paragraph (c)(3) of this AD for AT-501 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 line
AT-501	0002 through 0061	4,531 hours TIS.
AT-501	All beginning with 0062	7,693 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) The following table applies to airplanes that incorporate or have incorporated Marburger winglets. These winglets are installed in accordance with Supplemental Type Certificate (STC) No. SA00490LA. Use the winglet usage factor in Table 2 of this paragraph, the 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-501	0002 through 0061	1.6
AT-501	all serial numbers beginning with 0062	1.6

What Is the Unsafe Condition Presented in This AD?

(d) This AD is the result of service reports and analysis done on wing lower spar caps of Air Tractor airplanes. The actions specified in this AD are intended to prevent fatigue cracks from occurring 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 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) To address this problem, you must do the following:

Table 3.—Actions/Compliance/Procedures

Actions	Compliance	Procedures
(1) Modify the applicable aircraft records as follows to show the reduced safe life for the wing lower spar cap (use the information from table in paragraph (c)(1) of this AD and utilize the information in paragraph (c)(3) of this AD and the Appendix to this AD, as applicable). (i) Incorporate the following into the Aircraft Logbook “In accordance with AD 2002-11-05, the wing lower spar cap is life limited to ___.” Insert the applicable safe life number from the applicable tables in paragraphs (c)(1) and (c)(3) of this AD and the Appendix of this AD. (ii) If, as of the time of the logbook entry requirement of paragraph (e)(1) of this AD, your airplane is over or within 10 hours of the safe life, an additional 10 hours TIS after July 12, 2002 (the effective date of this AD) is allowed to do the replacement.	Do the logbook entry within the next 10 hours TIS after July 12, 2002 (the effective date of AD 2002-11-05), unless already done. The logbook language is referenced as AD 2002-11-05 instead of AD 2002-2002-11-05 R1 to maintain continuity and to assure that no additional action is necessary.	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 as specified in paragraphs (e)(1) of this AD. Make an entry into the aircraft records showing compliance with this portion of the following section 43.9 of the Federal Aviation Regulations (14 CFR 43.9). Do the replacement when the safe life is reached following Snow Engineering Service Letters #197 or #205, both revised March 26, 2001, as applicable. The owner/operator may not do the replacement unless he/she holds the proper mechanic authorization.
(2) If you have ordered parts from the factory when it is time to replace the wing lower spar cap (as required when you reach the established safe life), but the parts are not available, you may eddy-current inspect the wing lower spar cap. These inspections are allowed until one of the following occurs, at which time the replacement must be done: (i) Crack(s) is/are found; (ii) Parts become available from the manufacturer; or (iii) Not more than three inspections or 1,200 hours TIS go by: the first inspection would have to be done upon accumulating the safe life; the second inspection would have to be done within 400 hours TIS after accumulating the safe life; the third inspection would have to be done 400 hours TIS after the second inspection; and the replacement would have to be done within 400 hours TIS after the third inspection (maximum elapsed time would be 1,200 hours TIS).	Inspect before further flight after ordering the parts and thereafter at intervals not to exceed 400 hours TIS until one of the criteria in paragraphs (e)(2)(i), (e)(2)(ii), and (e)(2)(iii) of this AD is met.	Following the procedures in Snow Engineering Service Letter #197, pages 1 and 2, revised March 26, 2001, and page 3, dated June 13, 2000; and Snow Engineering Service Letter #205, pages 1, 2, and 4, revised March 26, 2001, and page 3, dated October 25, 2000 as applicable.
(3) Eddy-current inspect the wing lower spar cap in order to detect any crack before it extends to the modified center section of the wing and repair that crack or replace the wing section. The inspection must be done by one of the following: (i) 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 (ii) A person authorized to perform AD work who has completed and passed the Air Tractor, Inc. training course on Eddy Current Inspection on wing lower spar caps.	Immediately before the replacement/modification required when you reach the new safe life. For airplanes that had this replacement done in accordance with either AD 2001-10-04 or AD 2001-10-04 R1, do this inspection and any necessary corrective action within the next 400 hours TIS after July 12, 2002 (the effective date of AD 2002-11-05), unless already done (have the mechanic who did the work mark the logbook accordingly).	Following the procedures in Snow Engineering Service Letter #197, pages 1 and 2, revised March 26, 2001, and page 3, dated June 13, 2000; and Snow Engineering Service Letter #205, pages 1, 2, and 4, revised March 26, 2001, and page 3, dated October 25, 2000, as applicable.

May I Request an Alternative Method of Compliance (AMOC)?

(f) The Manager, Fort Worth or Los Angeles Airplane Certification Office (ACO), as applicable, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19.

(1) For information on any already approved AMOCs or for information pertaining to this AD, contact:

(i) 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, Fort Worth, Texas 76193-0150; telephone: [phone]; facsimile: [phone]; and

(ii) 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].

(2) AMOCs approved for AD 2001-10-04 and/or AD 2000-14-51 are not considered approved for this AD.

(3) AMOCs approved for AD 2001-10-04 R1 for the Model AT-501 airplanes are considered approved for this AD.

(4) AMOCs approved for AD 2002-11-05 for the Model AT-501 airplanes are considered approved for this AD.

Are There Any Additional AMOCs Being Considered for This AD?

(g) The FAA may approve, as an AMOC, inspection of the wing lower spar cap. You must submit the request in accordance with the procedures in paragraph (f) of this AD and adhere to the following:

(1) If you are over or within 10 hours TIS of reaching the safe life used in paragraph (e)(1) of this AD for the wing lower spar cap and you have ordered parts and scheduled a date for the replacement, but having the replacement done on this date grounds the airplane, do the following:

(i) Inspect the wing lower spar cap within 10 hours TIS after approval of the AMOC;

(ii) re-inspect thereafter at intervals not to exceed 400 hours TIS until either cracks are found, the date of the scheduled replacement occurs, or 1,200 hours TIS after the initial inspection are accumulated, whichever occurs first; and

(iii) do the inspections following the procedures in Snow Engineering Service Letter #197, pages 1 and 2, revised March 26, 2001, and page 3, dated June 13, 2000; and Snow Engineering Service Letter #205, pages 1, 2, and 4, revised March 26, 2001, and page 3, dated October 25, 2000, as applicable.

(2) Submit the following to the Fort Worth or Los Angeles ACO, as applicable, using the procedures described in paragraph (f) of this AD:

(i) The airplane model serial number designation, and airplane registration number (N-number);

(ii) the number of hours TIS on the airplane;

(iii) the scheduled date for the replacement; and

(iv) the name and location of the authorized repair shop.

(3) For more information about this issue, contact:

(i) 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, Fort Worth, Texas 76193-0150; telephone: [phone]; facsimile: [phone]; and

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

Special Flight Permit

(h) 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?

(i) You must do the actions required by this AD following the instructions in Snow Engineering Service Letter #197, pages 1 and 2, revised March 26, 2001, and page 3, dated June 13, 2000; and Snow Engineering Service Letter #205, pages 1, 2, and 4, revised March 26, 2001, and page 3, dated October 25, 2000. On June 8, 2001 (66 FR 27014, May 16, 2001), the Director of the Federal Register previously approved this incorporation by reference under 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; 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; U.S. 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-2006-23647; Directorate Identifier 2006-CE-06-AD.

Appendix to AD 2002-11-05 R1

The following provides procedures for determining the safe life for those Model AT-501 airplanes that incorporate or have incorporated Marburger winglets. These winglets are installed in accordance with Supplemental Type Certificate (STC) No. SA00490LA.

1. Review your airplane's logbook to determine your airplane's time in service (TIS) with winglets installed per Marburger STC No. SA00490LA. 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 further winglet installation would be subject to a reduced safe life per these instructions.

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

Example: Your airplane is a Model AT-501, serial number 0100. From paragraph (c)(1) of this AD, the unmodified safe-life of your airplane is 7,693 hours TIS. All examples from hereon will be based on the Model AT-501, serial number 0100 airplane.

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

Example: Again, your airplane is a Model AT-501, serial number 0100. From paragraph (c)(3) of this AD, your winglet usage factor is 1.6.

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

Example: Winglet TIS is 500 hours X a winglet usage factor of 1.6. The adjusted winglet TIS is 800 hours.

Appendix to AD 2002-11-05 R1

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

Example: Adjusted winglet TIS is 800 hours − the winglet TIS of 500 hours. The winglet usage penalty is 300 hours TIS.

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

Example: The unmodified safe life is 7,693 hours TIS − the 300 hours TIS usage penalty = 7,393 hours TIS adjusted safe life.

7. If your remove the winglets from your airplane before further flight or nor longer have the winglets installed on your airplane, the safe life of your airplane is the adjusted safe life (result of 6.). Enter this number in paragraph (e)(1) of this AD and the airplane logbook.

8. If you keep the current winglet installation on your airplane, you must further reduce the safe life by dividing the adjusted safe life (result of 6.) by the winglet usage factor (result of 3.). Record this result in your airplane's logbook.

Example: Adjusted safe life is 7,393 hours ÷ winglet usage factor of 1.6 = 4,621 hours TIS.

9. 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.

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

David R. Showers,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.