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Proposed Rule

Airworthiness Directives; Air Tractor, Inc. Models AT-501, AT-502, AT-502A, AT-502B, and AT-503A Airplanes

Document Details

Information about this document as published in the Federal Register.

Published Document

This document has been published in the Federal Register. Use the PDF linked in the document sidebar for the official electronic format.

Start Preamble

AGENCY:

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

ACTION:

Supplemental notice of proposed rulemaking (NPRM); reopening of the comment period.

SUMMARY:

The FAA proposes to revise an earlier proposed airworthiness directive (AD) that applies to certain Air Tractor, Inc. (Air Tractor) Models AT-502, AT-502A, AT-502B, and AT-503A airplanes, which proposes to supersede AD 2002-26-05. AD 2002-26-05 lowers the safe life for the wing lower spar caps for Models AT-502, AT-502A, AT-502B, and AT-503A airplanes and those that incorporate or have incorporated Marburger Enterprises, Inc. (Marburger) winglets. AD 2002-26-05 also requires you to eddy-current inspect the wing lower spar caps immediately before modifying to correct any crack in a bolt hole before it extends to the modified center section of the wing and report the results of the inspection to the FAA if cracks are found. AD 2002-11-05 R1 currently requires similar action on Model AT-501 airplanes. Since issuing the earlier NPRM, we determined that Model AT-501 airplanes should be added to the Applicability section of this proposed AD and that this proposed AD should also supersede AD 2002-11-05 R1. We have revised the alternative method of compliance (AMOC) to include inspection procedures for airplanes that have or have had Marburger winglets installed. We have also updated the safe life of the replacement and new production spar cap based on additional data we have received from the manufacturer. Since these actions impose an additional burden over that proposed in the earlier NPRM, we are reopening the comment period to allow the public the chance to comment on these additional actions.

DATES:

We must receive any comments on this proposed AD by October 10, 2006.

ADDRESSES:

Use one of the following addresses to comments on this proposed 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 20590-0001.
  • Fax: (202) 493-2251.
  • 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.

For service information identified in this proposed AD, contact Air Tractor, Incorporated, P.O. Box 485, Olney, Texas 76374; or Marburger Enterprises, Inc., 1227 Hillcourt, Williston, North Dakota 58801; telephone: (800) 893-1420 or (701) 774-0230; facsimile: (701) 572-2602.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

Direct all questions to:

  • For the airplanes that do not incorporate and never have incorporated Marburger Enterprises, Inc. winglets: Rob Romero, Aerospace Engineer, FAA, Fort Worth Airplane Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: (817) 222-5102; facsimile: (817) 222-5960; e-mail: robert.a.romero@faa.gov; 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: (562) 627-5228; facsimile: (562) 627-5210.
End Further Info End Preamble Start Supplemental Information

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments regarding this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include the docket number, “FAA-2004-19961; Directorate Identifier 2004-CE-48-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive concerning this proposed AD.

Discussion

Prior to issuing this supplemental notice of proposed rulemaking (NPRM), 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 certain Air Tractor Models AT-502, AT-502A, AT-502B, and AT-503A airplanes. That proposal was published in the Federal Register as an NPRM on February 9, 2005 (70 FR 6786). The NPRM proposed to supersede AD 2002-26-05 with a new AD that would retain the actions required in AD 2002-26-05, add additional airplanes to the applicability, and incorporate an AMOC to the actions retained from AD 2002-26-05.

AD 2002-26-05, Amendment 39-12991 (68 FR 18, January 2, 2003), currently applies to certain Air Tractor Models AT-502, AT-502A, AT-502B, and AT-503A airplanes. AD 2002-26-05 supersedes AD 2002-11-03 and requires the following:

  • Maintaining the original requirements from AD 2002-11-03 for a lowered safe life, inspection, replacement/modification, and if cracks are found, reporting the results to the FAA;
  • Further lowering the safe life for the wing lower spar cap established in AD 2002-11-03 for Models AT-502, AT-502B, and AT-503A airplanes; and
  • Expanding the applicability of Models AT-502A and AT-502B airplanes to account for future manufactured airplanes.

With this supplemental NPRM we are also proposing to supersede AD 2002-11-05 R1, Amendment 39-14564 (71 FR 19629, April 17, 2006), which currently applies to certain Air Tractor Model AT-501 airplanes. We issued AD 2002-11-05 R1 to revise AD 2002-11-05 to remove AT-400 series and Models AT-802 and AT-802A airplanes from the applicability because separate AD actions were issued for those airplanes. Start Printed Page 45458AD 2002-11-05 R1 retains the actions required in AD 2002-11-05 for Model AT-501 airplanes.

The following is a list of ADs that have been issued to date that are related to the wing spar inspection and safe life on Air Tractor airplanes:

AD No.Affected air tractor model airplanesStatus
2000-14-51AT-501, AT-502, and AT-502ASuperseded by AD 2001-10-04.
2001-10-04AT-400, AT-500, and AT-800 SeriesRevised by AD 2001-10-04 R1.
2001-10-04 R1AT-400, AT-500, and AT-800 SeriesSuperseded by AD 2002-11-05.
2002-11-05AT-400, AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-802, and AT-802ARevised by AD 2002-11-05 R1.
2002-13-02AT-300, AT-301, AT-302, AT-400, and AT-400A AirplanesSuperseded by AD 2003-06-01.
2002-11-03AT-502, AT-502A, AT-502B, and AT-503ASuperseded by AD 2002-26-05.
2002-26-05AT-502, AT-502A, AT-502B, and AT-503ACurrent.
2003-06-01AT-300, AT-301, AT-302, AT-400, and AT-400ACurrent.
2002-11-05 R1AT-501Current.
2006-08-08AT-400, AT-401, AT-401B, AT-402, AT-402A, and AT-402BCurrent.
2006-08-09AT-802 and AT-802ACurrent.

You may view these ADs at the following Internet Web site addresses: http://www.airweb.faa.gov/​Regulatory_​and_​Guidance_​Library/​rgAD.nsf/​MainFrame?​OpenFrameSet or http://www.gpoaccess.gov/​fr/​index.html.

Comments

We provided the public the opportunity to participate in developing the proposed AD on Air Tractor Models AT-502, AT-502A, AT-502B, and AT-503A airplanes. The following presents the comments received on this earlier proposed AD and FAA's response to each comment:

Comment Issue No. 1: Allow Repetitive Inspection and an Upper Life Limit on the New Cap

Lewis Air Service states there is a need to incorporate an alternative solution that includes repetitive inspections and an upper life limit on the new cap. Based on the way the NPRM is currently written, the commenter believes the low cap replacement time is too burdensome and not cost effective.

Although we agree that repetitive inspections may reduce the economic impact and minimize the risk of reduced agricultural production, this will not meet the safety intent of this proposed AD. We determined that reliance on critical repetitive inspections carries an unnecessary safety risk when parts replacement or modifications exist. In determining what inspections are critical, the FAA considers (1) the safety consequences of the airplane if the known problem is not detected by the inspection; (2) the reliability of the inspection, such as the probability of not detecting the known problem; (3) whether the inspection area is difficult to access; and (4) the possibility of damage to an adjacent structure as a result of the problem.

Since the initial publication of the earlier proposed AD, Air Tractor has completed fatigue testing on the replacement spar cap. The life of the cap has been updated in this proposed AD to reflect the results of this testing and subsequent analysis.

We are not changing this proposed AD based on this comment but are changing it based on new data from the manufacturer.

Comment Issue No. 2: Proposed AD Is Not Necessary

M&M Air Service states that they operate eight different Air Tractor airplanes and to date have not found any cracks. The commenter indicates that the proposed rulemaking is confusing, not cost beneficial, and excessive.

Based on these comments, we infer that the commenter wants the NPRM withdrawn.

We do not agree with the commenter. Fatigue analysis/testing/fleet history shows that the wing spar will crack and fail over time. The commenter's airplanes not cracking to date does not prevent the unsafe condition from developing on the commenter's airplanes or other airplanes of the same type design in the future.

To date, we have received over 50 reports of cracked spar caps on AT-502 series airplanes and one report of complete wing separation. We realize that there are many different wing configurations in-service on these airplanes and each has different requirements. However, analysis shows that the airplane could fail in the affected area based on the design and normal utilization of the type design airplanes.

We are not changing this proposed AD based on this comment.

Comment Issue No. 3: Compliance Time To Accommodate Flying Schedules

The National Agricultural Aviation Association requests the FAA consider the flying schedules of the airplanes and accommodate a program that can be done during the off-season. The commenter suggests the FAA allow repetitive inspections until an ultimate solution is reached, assuming no cracks are found.

We have considered the importance of the financial and operational impact this proposed rulemaking may have on owners and operators and, in this specific case, aerial application businesses. This proposed AD uses inspections to manage the safety of the wing centerline joint instead of reducing the compliance times for replacing parts. However, this approach cannot be used indefinitely. Extending the service life of fatigue-critical, primary structure areas requires not only ensuring the safety of the area being inspected or modified, but also ensuring the safety of the complete structure when extending the service life.

Fatigue analysis shows that the safe life is the solution to the unsafe condition, not repetitive inspections over the life of the airplane. For eligible airplanes, we are providing an AMOC that provides an aggressive repetitive inspection program until 8,000 hours time-in-service (TIS), provided no cracks are found.

The FAA has shown a history of accommodating flying schedules through AMOCs on previous ADs for this subject. We will continue to consider AMOCs provided they maintain a level of safety acceptable to the FAA.

For the replacement spar cap, we have received new data that justifies a much higher safe life than was previously published in the NPRM. Start Printed Page 45459

We are not changing this proposed AD based on this comment.

Comment Issue No. 4: Lack of Wing Life-Limit Information

Julie Broussard of Lewis Flying and Maintenance Service, Inc., states that she was never informed in writing of a 1,600 hour safe life or replacement life of 8,000 hours TIS for the AT-502 wing. The commenter also urges the FAA to make the manufacturer “fix the wing.”

We issued AD 2002-26-05, Amendment 39-12991 (68 FR 18, January 2, 2003), which applies to Air Tractor Models AT-502, AT-502A, AT-502B, and AT-503A airplanes. That AD lowers the safe life for the wing lower spar caps to 1,650 hours TIS. AD 2002-26-05 supersedes AD 2002-11-03, Amendment 39-12764 (67 FR 38371, June 4, 2002). We also issued Special Airworthiness Information Bulletin (SAIB) CE-05-28, dated January 21, 2005, announcing an AMOC to AD 2002-26-05. The AMOC allows an inspection program instead of the safe life replacement program required by AD 2002-26-05, which allows operation of a modified wing up to 8,000 hours TIS, provided no cracks are found during required inspections.

We are legally bound to notify the public of an AD through publication in the Federal Register. AD 2002-26-05 was published in the Federal Register on January 2, 2003. In the past, we have sent copies of ADs and SAIBs to registered owners of the affected airplanes, which could be a bank or holding company. This may be the reason the commenter did not receive notification of the change in the safe life limit and replacement schedule.

This supplemental NPRM is still only a proposal at this time. The previous NPRM on this subject was published in the Federal Register on February 9, 2005 (70 FR 6786).

We will always encourage modifications that incorporate design changes that make critical parts stronger and safer. However, our responsibility is to address the continued operational safety of the airplane fleet, ensure that current design regulations are met, and correct any unsafe conditions.

Establishing a safe life and an option of an aggressive repetitive inspection schedule until 8,000 hours TIS (provided no cracks are found) meets the FAA's responsibility. Further, the replacement spar cap has been substantiated to a much higher safe life than previously published.

We are not changing this proposed AD based on this comment.

Comment Issue No. 5: New Production Airplanes Have a 27 Percent Increase in Safe Life

The National Transportation Safety Board (NTSB) questions the rationale for new production AT-502B airplanes having a 27 percent increase in the safe life limit on the wing from 1,650 hours TIS to 2,100 hours TIS. The commenter also states a concern for the conservatism in the initial and repetitive inspection program.

Other items of concern to the commenter are:

  • The wording proposed in section (e)(2) of the earlier proposed AD may allow for inspections to continue indefinitely. The commenter states that airplanes using the AMOC who find cracks should report them to the FAA.
  • Airplanes that have been modified with a replacement cap should follow the inspection program for later serial number airplanes.
  • There has been nothing done to address the use of winglets as it applies to inspection intervals.

The safe life for new production AT-502B airplanes was determined as a result of fatigue testing performed by the manufacturer. The initial and repetitive inspection program was based on a thorough damage tolerance analysis using a validated load spectrum and coupon testing.

It should be noted that since publication of the earlier NPRM, the manufacturer has completed more extensive testing, and we are now proposing a safe life for new production AT-502B airplanes that represents much more than the 27 percent increase the commenter states.

We do not agree that paragraph (e)(2) of the previously proposed AD allowed for indefinite inspections. Paragraph (e)(2) of the proposed AD refers to Appendix 2, which has clearly defined upper limits on inspection times (8,000 hours TIS for eligible airplanes).

We agree that any cracks detected should be reported to the FAA. We are retaining the reporting requirement from the earlier NPRM in this proposed AD.

Airplanes with replacement spar caps, as well as new production airplanes, are no longer required to follow an inspection program.

We agree that we did not address an inspection program for airplanes with winglets installed. We are revising this proposed AD to include an AMOC inspection program for airplanes that have or have had winglets installed. Further, this proposed AD states that airplanes with the new or replacement spar caps are not eligible to have the winglet STC installed without proper fatigue substantiation.

Comment Issue No. 6: Include Model AT-501 Airplanes in the Applicability

Leland Snow, President of Air Tractor, Inc., states that Model AT-501 airplanes should be included in the Applicability section and that new airplanes should not have a safe life limit of 3,100 hours TIS.

The commenter states the costs for doing the inspection is too low. The inspection typically costs from $450 to $550. Parts cost for the replacement spar cap is approximately $16,500 plus approximately $16,500 for labor (a total of $33,000).

The commenter also states that winglets should be removed before allowing the AMOC.

We agree with the commenter that Model AT-501 airplanes should be included in the Applicability section. We also agree to update the Cost Impact section. We are revising this proposed AD to include those changes.

We do not agree that airplanes with winglets installed should be excluded from the AMOC. We are adding an AMOC inspection program in this proposed AD to cover airplanes that have winglets installed following Supplemental Type Certificate (STC) SA00490LA.

Comment Issue No. 7: Torsion Loads

John R. Janssen states that torsion loads need to be accounted for to properly address the wing safe life limit for the affected airplanes.

We agree with the commenter that the torsion load is a contributing factor to the fatigue life of the wings, as are all the other loads (ground, gust, maneuver, etc.). These loads have been accounted for in the load spectrum that was used in developing the inspection program and the life of the new/replacement spar cap.

We are not changing this proposed AD based on this comment.

Comment Issue No. 8: Marburger Winglets

Lewis Broussard, Owner, Lewis Flying and Maintenance Service, Inc., states that installing Marburger Enterprise, Inc. winglets increases the safe life of the wing.

We do not agree with the commenter. We have data that shows adding winglets increases the operating stresses at the wing root and consequently leads to a reduced safe life.

We are not changing this proposed AD based on this comment.

Comment Issue No. 9: AMOC Should Apply to Airplanes With Winglets

Rick Marburger of Marburger Enterprises, Inc., states that airplanes Start Printed Page 45460with winglets installed should be included in the AMOC repetitive inspection program.

We agree with the commenter. We included procedures in the AMOC repetitive inspection program to address airplanes that have or have had winglets installed.

We are revising this proposed AD to incorporate this change.

Comment Issue No. 10: Unfair Safe Life Limit for the New Spar Cap

Tom Miller of Ingalls Aerial Sprayers, Inc., states the safe life limit of 3,100 hours TIS for the new/replacement spar cap is unfair. Numerous other commenters have similar concerns. The commenters state the new design should be given a safe life limit that is equivalent to the old design, which is 8,000 hours TIS.

We agree with the commenters. The 3,100-hour TIS safe life limit was based on data submitted by Air Tractor and approved by the FAA. However, since the earlier proposed AD was published, Air Tractor began a new test program using a recently validated load spectrum to determine a new safe life for this design configuration. That testing has been completed and the new safe life limit is being published in this proposed AD.

We are revising this proposed AD to incorporate this change.

Relevant Service Information

The following service information from AD 2002-11-05 R1 and the previous NPRM are still valid for this supplemental NPRM:

  • Snow Engineering Drawing Number 21050;
  • Snow Engineering Service Letters #197 or #205, both revised March 26, 2001; and
  • Snow Engineering Service Letter #244, dated April 25, 2005.

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

FAA's Determination and Requirements of This Proposed AD

Since issuing the earlier NPRM, we determined that Model AT-501 airplanes should be added to the Applicability section. We also developed an AMOC to the requirements of AD 2002-26-05 for airplanes that have or have had winglets installed. We are extending the safe life for new production airplanes and replacement spar caps.

After examining the circumstances and reviewing all available information related to the incidents described above, we have determined that:

  • The unsafe condition referenced in this document exists or could develop on other Air Tractor Models AT-501, AT-502, AT-502A, AT-502B, and AT-503A airplanes of the same type design that are on the U.S. registry;
  • We should change this proposed AD to include Model AT-501 airplanes in the Applicability section and revise the AMOC.
  • We should take AD action to correct this unsafe condition.

The Supplemental NPRM

Adding additional models to the Applicability section goes beyond the scope of what was originally proposed in the earlier NPRM. Therefore, we are reopening the comment period and allowing the public the chance to comment.

This proposed AD would supersede AD 2002-26-05 and AD 2002-11-05 R1 with a new AD that would:

  • Retain the actions required in AD 2002-26-05 and AD 2002-11-05 R1;
  • Add additional airplanes to the Applicability section;
  • Incorporate a revised AMOC to include inspection procedures for airplanes that have or have had winglets installed following STC SA00490LA; and
  • Extend the safe life for new production airplanes and replacement spar caps.

The following table summarizes the effects this proposed AD would have on the airplane models affected by this proposed AD:

Model
AT-501• Supersede AD 2002-11-05 R1.
• Retain the safe lives from AD 2002-11-05 R1.
• Provide an AMOC that allows extension of the safe life through an inspection and modification program.
AT-502• Supersede AD 2002-26-05.
• Retain the safe lives from AD 2002-26-05 and add S/Ns to applicability. AD 2002-26-05 provided safe lives for S/Ns 0003 through 0236. Proposed action applies the same safe life to all S/Ns beginning with 0003.
• Provide an AMOC that allows extension of the safe life through an inspection and modification program.
AT-502A• Supersede AD 2002-26-05.
• Retain the safe lives from AD 2002-26-05.
• Provide an AMOC that allows extension of the safe life through an inspection and modification program.
AT-502B• Supersede AD 2002-26-05.
• Retain the safe lives from AD 2002-26-05 for S/Ns 0187 through 0654, except 0643.
• Increase the safe lives beyond those listed in AD 2002-26-05 for S/Ns 0655 and greater, as well as S/N 0643.
• Add requirement to cold work outboard wing center splice block bolt holes in the lower spar cap on S/Ns 0643 and 0655 through 0692.
• Provide an AMOC that allows extension of the safe life through an inspection and modification program for S/Ns 187 through 654, except 643.
AT-503A• Supersede AD 2002-26-05.
• Retain the safe lives from AD 2002-26-05.
• Provide an AMOC that allows extension of the safe life through an inspection and modification program.

Costs of Compliance

We estimate that this proposed AD affects approximately 500 airplanes in the U.S. registry.

We estimate the following costs to do each proposed inspection:Start Printed Page 45461

Labor costParts costTotal cost per airplaneTotal cost on U.S. operators
8 work-hours × $80 per hour = $640No parts required for inspection$640$640 × 500 = $320,000.

We estimate the following costs to do the proposed modification:

Labor costParts costTotal cost per airplaneTotal cost on U.S. operators
120 work-hours × $80 per hour = $9,600Approximately $3,700$9,600 + $3,700 = $13,300$13,300 × 500 = $6,650,000.00.

We estimate the following costs to do the proposed replacement:

Labor costParts costTotal cost per airplaneTotal cost on U.S. operators
254 work-hours × $80 per hour = $20,320Approximately $16,500$20,320 + $16,500 = $36,820$36,820 × 500 = $18,410,000.00.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify that the proposed regulation:

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 regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket.

Examining This Proposed AD Docket

You may examine the AD docket that contains the proposed AD, the regulatory evaluation, any comments received, and other information on the Internet at http://dms.dot.gov;​ or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone (800) 647-5227) is located at the street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

Start List of Subjects

List of Subjects in 14 CFR Part 39

End List of Subjects

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 14 CFR part 39 as follows:

Start Part

PART 39—AIRWORTHINESS DIRECTIVES

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

Start Authority

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

End Authority
[Amended]

2. FAA amends § 39.13 by removing Airworthiness Directive (AD) 2002-26-05, Amendment 39-12991 (68 FR 18, January 2, 2003) and AD 2002-11-05 R1, Amendment 39-14564 (71 FR 19628, April 17, 2006), and by adding a new AD to read as follows:

Air Tractor, Inc.: Docket No. FAA-2004-19961; Directorate Identifier 2004-CE-48-AD.

Comment Due Date

(a) We must receive comments on this proposed airworthiness directive (AD) by October 10, 2006.

Affected AD

(b) This AD supersedes AD 2002-26-05, Amendment 39-12991, and AD 2002-11-05 R1, Amendment 39-14564.

Applicability

(c) This AD applies to certain Models AT-501, AT-502, AT-502A, AT-502B, and AT-503A airplanes. Use Table 1 in paragraph (c)(1) of this AD for airplanes that do not incorporate and never have incorporated Marburger Enterprises, Inc. (Marburger) winglets. Use Table 2 in paragraph (c)(4) of this AD for certain AT-500 series airplanes that incorporate or have incorporated Marburger winglets.

(1) The following table applies to airplanes (certificated in any category) 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: Start Printed Page 45462

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

ModelSerial Nos.Wing lower spar cap safe life
AT-5010002 through 00614,531 hours TIS.
AT-501All serial numbers beginning with 00627,693 hours TIS.
AT-502All serial numbers beginning with 00031,650 hours TIS.
AT-502AAll serial numbers beginning with 01581,650 hours TIS.
AT-502B0187 through 0654, except 06431,650 hours TIS.
AT-502B0643, and 0655 through 06929,000 hours TIS.
AT-502B0693 through 07019,500 hours TIS.
AT-502BAll serial numbers beginning with 07029,800 hours TIS.
AT-503AAll serial numbers beginning with 00671,650 hours TIS.

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

(3) Airplanes that have been modified to install lower spar caps, part numbers (P/N) 21058-1 and 21058-2, should use a safe life of 9,800 hours TIS.

(4) The following table applies to airplanes (certificated in any category) that incorporate or have incorporated Marburger winglets. These winglets are installed following Supplemental Type Certificate (STC) 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 Installed Following STC SA00490LA

ModelSerial Nos.Winglet usage factor
AT-5010002 through 00611.6
AT-501All serial numbers beginning with 00621.6
AT-5020003 through 02361.6
AT-502A0158 through 02381.6
AT-502AAll serial numbers beginning with 02391.2
AT-502BAll serial numbers beginning with 01871.2

(5) Model AT-502B airplanes, S/N 0643, all S/Ns beginning with 0655, and all other airplanes that have been modified with replacement spar caps, P/N 21058-1 and P/N 21058-2, are not eligible to have STC SA00490LA installed without additional fatigue data being provided to the FAA at the address in paragraph (f) of this AD.

Unsafe Condition

(d) This AD is the result of service reports and analysis done on wing lower spar caps of Air Tractor, Inc. airplanes. The actions specified by 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.

Compliance

(e) To address this problem, you must do the following:

ActionsComplianceProcedures
(1) For all affected airplanes: Modify the applicable airplane records (logbook) as follows to show the reduced safe life for the wing lower spar cap (use the information from Table 1 in paragraph (c)(1), Table 2 in paragraph (c)(4), and Appendix 1 of this AD, as applicable):  (i) Incorporate the following into the airplane logbook “In accordance with AD **-**-** (AD 2002-26-05 or AD 2002-11-05, as applicable) 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)(4) of this AD and Appendix 1 of this AD  (ii) If, as of the time of the logbook entry requirement of paragraph (e)(1)(i) of this AD, your airplane is over or within 50 hours of the safe life, an additional 50 hours TIS after the effective date of this AD is allowed to do the replacementFor airplanes previously affected by AD 2002-26-05: Do the logbook entry within the next 10 hours TIS after January 15, 2003 (the effective date of AD 2002-26-05). For airplanes not previously affected by AD 2002-26-05: Do the logbook entry within the next 10 hours TIS after the effective date of this AD, unless already done. The logbook language for AT-501 airplanes is referenced as AD 2002-11-05 instead of AD 2002-11-05 R1 to maintain continuity and assures no further action is necessaryAirplane Records Modification: 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 airplane records as specified in paragraph (e)(1) of this AD. Make an entry into the airplane records showing compliance with this portion of the AD in accordance with section 43.9 of the Federal Aviation Regulations (14 CFR 43.9). Spar Cap Replacement: Do the replacement when the safe life is reached following Snow Engineering Drawing Number 21050, Snow Engineering Service Letters #197 or #205, both revised March 26, 2001, as applicable. The owner/operator may not do the spar cap modification/replacement, unless he/she holds the proper mechanic authorization.
Start Printed Page 45463
(2) For all affected airplanes: To extend the safe life of the wing lower spar cap, 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 ADInspection schedule included as part of the alternative method of compliance (AMOC) in Appendix 2 to this ADProcedures included as part of the AMOC in Appendix 2 to this AD.
(3) For all affected airplanes: Report to the FAA any cracks detected as the result of each inspection required by paragraph (e)(2) of this AD on the form in Figure 1 of this AD. 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 2120-0056Only if cracks are found, send the report within 10 days after the inspection required in paragraph (e)(2) of this ADSend the form (Figure 1 of this AD) to FAA, Fort Worth Airplane Certification Office, Attn: Rob Romero, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: (817) 222-5102; facsimile: (817) 222-5960.
(4) For Model AT-502B airplanes, S/Ns 502B-0643, and 502B-0655 through 502B-0692: Cold work the left-hand and right-hand two outboard wing center splice block bolt holes (4 total) in the lower spar capBefore accumulating 2,000 hours TIS or within the next 100 hours TIS after the effective date of this AD, whichever occurs laterFollowing Snow Engineering Service Letter #244, dated April 25, 2005.
(5) For all affected airplanes: Airplanes that have the two-part modification done following the applicable service bulletins (Snow Engineering Service Letters #197 or #205, both revised March 26, 2001; or Snow Engineering Service Letter #244, dated April 25, 2005), but have over-sized outboard bolt holes at the splice block, must obtain an AMOC from FAA as specified in paragraph (f) of this AD to determine applicable inspection intervalsNot applicable.Not applicable.
Start Printed Page 45464

Alternative Methods of Compliance (AMOC)

(f) The Manager, Fort Worth or Los Angeles Airplane Certification Office (ACO), as applicable (see paragraphs (f)(1)(i) and (f)(2)(ii) of this AD below for specific contacts), 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, contact:

(i) For the airplanes that do not incorporate and never have incorporated Marburger Enterprises, Inc. winglets: Rob Romero, Aerospace Engineer, FAA, Fort Worth Airplane Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: (817) 222-5102; facsimile: (817) 222-5960; e-mail: robert.a.romero@faa.gov.

(ii) For airplanes that incorporate or have incorporated Marburger Enterprises, Inc. winglets: John Cecil, Aerospace Engineer, Los Angeles Aircraft Certification Office, FAA, Start Printed Page 454653960 Paramount Boulevard, Lakewood, California 90712; telephone: (562) 627-5228; facsimile: (562) 627-5210.

(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, AD 2002-11-03, AD 2002-11-05, AD 2002-11-05 R1, or AD 2002-26-05 are considered approved for this AD.

Special Flight Permit

(g) Under 14 CFR part 39.23, we are limiting the special flight permits for this AD by the following conditions:

(1) Operate only 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.

Related Information

(h) To get copies of the documents referenced in this AD, contact Air Tractor, Incorporated, P.O. Box 485, Olney, Texas 76374; or Marburger Enterprises, Inc., 1227 Hillcourt, Williston, North Dakota 58801. 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, or on the Internet at http://dms.dot.gov. The docket number is FAA-2004-19961.

Appendix 1 to Docket No. FAA-2004-19961

The following provides procedures for determining the safe life for those Models AT-501, AT-502, AT-502A, and AT-502B airplanes that incorporate or have incorporated Marburger Enterprises, Inc. (Marburger) winglets. These winglets are installed in accordance with Supplemental Type Certificate (STC) No. SA00490LA.

If you have removed the Marburger winglets before further flight after the effective date of this AD or before the effective date of this AD, do the following:

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 Table 1 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 Table 1 in paragraph (c)(1) of this AD.

Example: Your airplane is a Model AT-502B, serial number (S/N) 0292. From Table 1 in paragraph (c)(1) of this AD, the unmodified safe-life of your airplane is 1,650 hours TIS.

All examples from hereon will be based on the Model AT-502B, S/N 0292 airplane.

3. Determine the winglet usage factor from Table 2 in paragraph (c)(4) of this AD.

Example: Again, your airplane is a Model AT-502B, S/N 0292. From Table 2 in paragraph (c)(4) of this AD, your winglet usage factor is 1.2.

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 × a winglet usage factor of 1.2. The adjusted winglet TIS is 600 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.

(600 hours TIS) − (500 hours TIS) = (100 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 Table 1 in paragraph (c)(1) of this AD (the result of Step 2 above).

Example:

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

(1,650 hours TIS) − (100 hours TIS) = (1,550 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)(i) of this AD and the airplane logbook.

If you have the Marburger winglets installed as of the effective date of this AD and plan to operate your airplane without removing the winglets, do the following:

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 Table 1 in paragraph (c)(1) of this AD.

Example: Your airplane is a Model AT-502B, S/N 0292. From Table 1 in paragraph (c)(1) of this AD, the unmodified safe life of your airplane is 1,650 hours TIS.

All examples from hereon will be based on the Model AT-502B, S/N 0292 airplane.

3. Determine the winglet usage factor from Table 2 in paragraph (c)(4) of this AD.

Example: Again, your airplane is a Model AT-502B, S/N 0292. From Table 2 in paragraph (c)(4) of this AD, your winglet usage factor is 1.2.

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.

(1,650 hours TIS) − (1,000 hours TIS) = (650 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.

(650 hours TIS) ÷ (1.2) = (541 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.

(650 hours TIS) − (541 hours TIS) = (109 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 Table 1 in paragraph (c)(1) of this AD (the result of Step 2 above).

Example:

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

(1,650 hours TIS) − (109 hours TIS) = (1,541 hours TIS).

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

If you install or remove the Marburger winglets from your airplane in the future, do the following:

If, at anytime in the future, you install or remove the Marburger winglets 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 DOCKET NO. FAA-2004-19961

Optional Inspection Program

For all airplanes listed in this AD; except for Model AT-502B airplanes, serial number (S/N) 0643 and all S/Ns beginning with 0655, and those airplanes that have been modified with the replacement spar caps, part number (P/N) 21058-1 and P/N 21058-2; you may begin a repetitive inspection interval program as an alternative to the safe life requirement of this AD with the following provisions:

For the Model AT-501 airplanes affected by this AD, you may elect to follow this AMOC program and continue to operate your airplane up to 8,000 hours TIS, provided you comply with this AMOC in its entirety. If at the time of the effective date of this AD, you are over 1,600 hours TIS (the time required for the first inspection), you must inspect within 50 hours TIS. If at the time of the Start Printed Page 45466effective date of this AD, you are over 4,000 hours TIS (the time required for 2-part modification), you must have the modification done within 50 hours TIS. If you choose not to follow this inspection program, then you must replace your lower spar caps and associated hardware at the applicable safe life listed in this AD following the procedures in paragraph (e).

For airplanes that do not and never have had Marburger Enterprise, Inc. winglets installed following Supplemental Type Certificate (STC) SA00490LA:

1. Upon accumulating 1,600 hours time-in-service (TIS) or within the next 50 hours TIS after [effective date] (the effective date of AD **-**-**), 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 5, revised 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 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. 800 hours TIS (all S/Ns except as noted in b); or

b. 600 hours TIS (S/Ns 502B-0187 through 502B-0618 that do not have P/N 20998-1/2 web plate installed).

c. If the outboard two lower spar cap bolt holes have been cold worked following Snow Engineering Service Letter #233, dated May 18, 2004, then you may double (1,600 hours TIS or 1,200 hours TIS, as applicable) the inspection interval (See Step 8—re: mid cycle cold work).

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

Following AD **-**-**, 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 {800/600/1,600/1,200, 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. The crack indication goes away by doing the modification following the applicable sheet of Snow Engineering Modification—Wing Centersplice—502, Drawing Number 20989, then you may modify your center splice following Snow Engineering Drawing 20989. After modification, proceed to Step 5.

b. The crack indication does not go away by doing the modification following the applicable sheet of Snow Engineering Modification—Wing Centersplice—502, Drawing Number 20989, 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. For all S/Ns, upon accumulating 4,000 hours TIS, you must:

a. Modify your center splice connection following the applicable sheet of Snow Engineering Modification—Wing Centersplice—502, Drawing Number 20989, unless already done following Snow Engineering Service Letter #197 or #205, both revised March 26, 2001, as applicable. The owners/operator may not do the spar cap modification unless that person holds the proper mechanic authorization. If, as of [effective date] (the effective date of AD **-**-**), your airplane is over or within 50 hours of reaching the 4,000 hour TIS modification requirement, do the modification within the next 50 hours TIS.

b. Before doing the modification, do an eddy-current inspection following Snow Engineering Process Specification #197, page 1, revised June 4, 2002; pages 2 through 5, revised May 3, 2002, unless already done following the applicable Snow Engineering Service Letter #197 or #205, both revised March 26, 2001.

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

“Following AD **-**-**, at XXXX {insert hours TIS of the modification} hours TIS an eddy-current inspection has been done. 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. For all S/Ns, 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 5, revised May 3, 2002.

6. Repeat the inspection at intervals of:

a. 800 hours TIS; or

b. 1,600 hours TIS if the outboard two lower spar cap bolt holes have been cold worked following Snow Engineering Service Letter #234, dated May 18, 2004 (See Step 8).

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

“This airplane must be eddy-current inspected at intervals not to exceed {800/1,600, 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 a crack is found at any time, 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 or over 8,000 hours TIS (see Step 9).

8. (OPTIONAL): If you decide to cold work your bolt holes following Snow Engineering Service Letter #233 or #234, both dated May 18, 2002, 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 1,600/1,200 hour TIS inspection intervals (2 times the intervals listed in Steps 2.a., 2.b., and 6.a. listed above).

9. (OPTIONAL): If you have modified your airplane in accordance with Step 4 above 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. above to reflect these reduced inspection intervals. Upon accumulating 8,000 hours TIS, you must comply with Step 7 above.

EXAMPLE: An AT-502B airplane 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 TIS.

Inspections would follow at 5,400 hours TIS, 6,200 hours TIS, and 7,000 hours TIS. From Step 6.a. above, this is 800-hour TIS inspection intervals.

Regarding the inspection at 7,000 hours TIS (modification plus 4,000 hours TIS), this relates to the 8,000-hour TIS inspection from Step 7 above, 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 as specified in Step 4 above.

This airplane may continue to fly if inspected again at 7,400 hours TIS and 7,800 hours TIS, which is 400-hour TIS inspection intervals. This 400-hour TIS inspection interval corresponds to Step 9 where you cut your inspection interval from Step 6.a. in half.

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

For airplanes that have or have had Marburger Enterprise, Inc. winglets installed following Supplemental Type Certificate (STC) SA00490LA:

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

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

EXAMPLE: An AT-502 airplane, S/N 502-0200, had winglets installed at 200 hours TIS and removed at 800 hours TIS.

The winglet usage factor is: 1.6

Calculate equivalent hours: 600 hours TIS with winglets X 1.6 = 960 hours TIS

Winglet usage penalty = 960 - 600 = 360

New Step 1 Pre-Modification Initial Inspection Time = 1,600 - 360 = 1,240 hours TIS

Retained Step 2 Pre-Modification Inspection Interval: Since the winglets are removed, the Pre-Modification Inspection Interval remains 800 hours TIS.

New Step 4 Modification time = 4,000 - 360 = 3,640 hours TIS

New Step 5 Post-Modification Initial Inspection time = 3,640 + 1,600 = 5,240 hours TIS.

Retained Step 6 Post-Modification Inspection interval: Since the winglets are removed Start Printed Page 45467the Post-Modification Inspection interval remains at 800/1,600 hours TIS.

New Step 7 replacement time = 8,000 - 360= 7,640 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.d., 4.c., and 6.c.

If you have not removed the winglets, then calculate new, reduced hours for Step 1, 2, 4, 5, 6, and 7 above, as applicable, based on the winglet usage factor listed in Table 2 of paragraph (c)(4) of this AD 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-502B, S/N 502B-0550, that has not had P/N 20998-1/-2 web plate installed and has had winglets on since new.

The winglet usage factor is: 1.2

New Step 1 Pre-modification initial inspection time: 1,600 ÷ ( 1.2 = 1,333 hours TIS.

New Step 2 Pre-modification inspection interval: 600 ÷ ( 1.2 = 500 hours TIS.

New Step 4 Modification time: 4,000 ÷ ( 1.2 = 3,333 hours TIS.

New Step 5 Post-modification initial inspection time: 3,333 + 1,333 (1,600 ÷ (1.2) = 4,666 hours TIS.

New Step 6 Post-modification inspection interval: 800 ÷ (1.2 = 667 hours TIS.

New Step 7 Replacement time: 8,000 ÷ ( 1.2 = 6,667 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.d., 4.c., and 6.c above.

Start Signature

Issued in Kansas City, Missouri, on August 3, 2006.

John R. Colomy,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.

End Signature End Part End Supplemental Information

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BILLING CODE 4910-13-C

[FR Doc. E6-12945 Filed 8-8-06; 8:45 am]

BILLING CODE 4910-13-P