Airworthiness Directive · Amendment 39-14839 · Air Tractor, Inc. Models AT-501, AT-502, AT-502A, AT-502B, and AT-503A Airplanes
Air Tractor, Inc. Models AT-501, AT-502, AT-502A, AT-502B, and AT-503A Airplanes
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:
| Model | Serial Nos. | Wing lower spar cap safe life |
|---|---|---|
| AT-501 | 0002 through 0061 | 4,531 hours TIS. |
| AT-501 | All serial numbers beginning with 0062 | 7,693 hours TIS. |
| AT-502 | All serial numbers beginning with 0003 | 1,650 hours TIS. |
| AT-502A | All serial numbers beginning with 0158 | 1,650 hours TIS. |
| AT-502B | 0187 through 0654, except 0643 | 1,650 hours TIS. |
| AT-502B | 0643, and 0655 through 0692 | 9,000 hours TIS. |
| AT-502B | 0693 through 0701 | 9,500 hours TIS. |
| AT-502B | All serial numbers beginning with 0702 | 9,800 hours TIS. |
| AT-503A | All serial numbers beginning with 0067 | 1,650 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:
| Model | Serial numbers | Winglet usage factor |
|---|---|---|
| AT-501 | 0002 through 0061 | 1.6 |
| AT-501 | All serial numbers beginning with 0062 | 1.6 |
| AT-502 | 0003 through 0236 | 1.6 |
| AT-502A | 0158 through 0238 | 1.6 |
| AT-502A | All serial numbers beginning with 0239 | 1.2 |
| AT-502B | All serial numbers beginning with 0187 | 1.2 |
(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.
We are adopting a new airworthiness directive (AD) for certain Air Tractor, Inc. Models AT-501, AT-502, AT-502A, AT-502B, and AT-503A airplanes, which supersedes AD 2002- 26-05 and AD 2002-11-05 R1. Since we issued AD 2002-26-05 and AD 2002- 11-05 R1, we determined that additional airplanes should be added to the applicability section and determined the safe life for new production airplanes and replacement spar caps should be extended. We also developed an alternative method of compliance (AMOC) to the requirements of this AD. This AD retains the actions required in AD 2002-26-05 and AD 2002-11-05 R1, adds additional airplanes to the Applicability section, extends the safe life for new production airplanes and replacement spar caps, and incorporates an AMOC. We are issuing this AD 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 could result in failure of the spar cap and lead to wing separation.
To address this problem, you must do the following:
| Actions | Compliance | Procedures |
|---|---|---|
| (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 2006-24-10 (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 replacement. | For 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 January 8, 2007 (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 necessary | Airplane 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. |
| (2) To extend the safe life of the wing lower spar cap for certain airplanes, you may eddy-current inspect and modify the wing lower spar cap. The inspection schedule, modification procedures, and list of eligible airplanes are included in Appendix 2 to this AD | Inspection schedule included as part of the alternative method of compliance (AMOC) in Appendix 2 to this AD | Procedures 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 2120-0056 | Only if cracks are found, send the report within 10 days after the inspection required in paragraph (e)(2) of this AD | Send 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 cap | Before accumulating 2,000 hours TIS or within the next 100 hours TIS after January 8, 2007 (the effective date of this AD), whichever occurs later | Following 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 intervals | Not applicable | Not applicable. |
The aircraft, engines and makers this AD names, by the model designations in its text. A model listed here may still be outside the AD's serial ranges.
