Airworthiness Directive · Amendment 39-15491 · Air Tractor, Inc. Models AT-300, AT-301, AT-302, AT-400, and AT-400A Airplanes
Air Tractor, Inc. Models AT-300, AT-301, AT-302, AT-400, and AT-400A Airplanes
This AD applies to the following airplanes that are certificated in any category:
(1) Models AT-300, AT-301, AT-302, and AT-400A airplanes, all serial numbers, that have aluminum spar caps;
(2) Models AT-400 airplanes, serial numbers 400-0244 through 400-0415, that have aluminum spar caps; and
(3) Models AT-300 and AT-301 airplanes, all serial numbers that have aluminum spar caps and are or have been converted to turbine power.
The FAA is adopting a new airworthiness directive (AD) to supersede AD 2003-06-01, which applies to all Air Tractor, Inc. (Air Tractor) Models AT-300, AT-301, AT-302, and AT-400A airplanes that have aluminum spar caps; certain Air Tractor Models AT-400 airplanes that have aluminum spar caps; and all Models AT-300 and AT-301 airplanes that have aluminum spar caps and are or have been converted to turbine power. AD 2003-06-01 requires replacing the wing spar lower caps at a specified safe life limit; allows extending the safe life limit on certain airplanes if a wing lower spar cap splice rework is done; allows a limited time of continued operation beyond the safe life limit provided parts are ordered, the replacement is scheduled, and repetitive inspections reveal no cracks; and requires a report of any cracks found during any inspection to the FAA. This AD results from a recent report of cracks found on a Model AT-301 airplane at hours below the modification time specified in AD 2003-06-01. Consequently, this AD retains the wing spar lower cap replacement and reporting requirements from AD 2003-06-01 and adds a repetitive eddy-current inspection. We are issuing this AD to detect and correct cracks in the wing centerline splice joint. If not detected and corrected, these cracks could result in the wing separating from the airplane during flight.
To address this problem, you must do the following, unless already done:
(1) For all affected airplanes without steel web plates, part numbers (P/N) 20990-1 or 20990-2, or steel spar caps installed, eddy-current inspect the left and right wing spar lower cap outboard holes for cracks following Snow Engineering Co. Process Specification #197, revised June 4, 2002. Do the inspections at the following compliance times:
| Affected airplanes | Initial compliance time | Repetitive compliance time |
|---|---|---|
| (i) For all airplanes | Initially inspect upon reaching 3,500 total hours time-in-service (TIS) on the wing spar lower cap or within the next 10 hours TIS after May 8, 2008 (the effective date of this AD), whichever occurs later | Repetitively inspect thereafter at intervals not to exceed 450 hours TIS until the wing spar center splice joint modification or the required wing spar lower cap replacement. After each replacement, initially inspect upon reaching 3,500 total hours TIS on either wing spar lower cap, and repetitively inspect thereafter at intervals not to exceed 450 hours TIS until the wing spar center splice joint modification or the required wing spar lower cap replacement. |
| (ii) Airplanes that have had an eddy-current inspection done on the wing spar lower cap within the last 450 hours TIS before the effective date of this AD | You may take credit for that inspection. Continue with the required repetitive inspection intervals | Repetitively inspect thereafter at intervals not-to-exceed 450 hours TIS from the time of the last inspection until the wing spar center splice joint modification or the required wing spar lower cap replacement. After each replacement, initially inspect upon reaching 3,500 total hours TIS on either wing spar lower cap, and repetitively inspect thereafter at intervals not to exceed 450 hours TIS until the wing spar center splice joint modification or the required wing spar lower cap replacement. |
(2) For all affected Models AT-300 and AT-301 airplanes with reciprocating engines, the 450-hour repetitive inspections required in this AD are terminated after the wing spar center splice joint modification is incorporated in accordance with paragraph (g) of this AD or when the wing lower spar caps are replaced. The replacement specified in paragraph (f)(2) of this AD is still applicable.
(3) If cracks are found during any inspection required in paragraphs (e)(1)(i), (e)(1)(ii), or (g)(2) of this AD, replace the wing lower spar cap before further flight.
(f) Replace each wing lower spar cap in accordance with the applicable maintenance manual, as follows:
| Affected airplanes | Initial replacement compliance time | Repetitive replacement/inspection compliance time |
|---|---|---|
| (1) For all affected Models AT-300 and AT-301 airplanes with reciprocating engines and that do not incorporate the wing spar center splice joint modification | Upon reaching 5,000 total hours TIS on either wing spar lower cap or within the next 25 hours TIS after April 4, 2003 (the effective date of AD 2003-06-01), whichever occurs later | Replace each time the safe life limit of 5,000 total hours TIS on either wing spar lower cap is reached. After each replacement, inspect as specified in paragraph (e)(1) of this AD until the wing spar center splice joint modification or the required wing spar lower cap replacement. |
| (2) For all affected Models AT-300 and AT-301 airplanes with reciprocating engines that do incorporate the wing spar center splice joint modification done in accordance paragraph (g) of this AD | Upon reaching the safe life limit of 7,000 total hours TIS on either wing spar lower cap or within the next 25 hours TIS after April 4, 2003 (the effective date of AD 2003-06-01), whichever occurs later | Replace each time the safe life limit of 7,000 total hours TIS on either wing spar lower cap is reached. After each replacement, inspect as specified in paragraph (e)(1) of this AD until the wing spar center splice joint modification or the required wing spar lower cap replacement. |
| (3) For all affected AT-302, AT-400, and AT-400A airplanes with aluminum spar caps; and all affected Models AT-300 and AT-301 airplanes with aluminum spar caps that are or have ever been converted to turbine power | Upon reaching 4,450 total hours TIS on either wing spar lower cap or within the next 25 hours TIS after April 4, 2003 (the effective date of AD 2003-06-01), whichever occurs later | Replace each time the safe life limit of 4,450 total hours TIS on the wing spar lower cap is reached. After each replacement inspect as specified in paragraph (e)(1) of this AD until the required wing spar lower cap replacement. |
(g) For airplanes specified in paragraph (f)(1) of this AD, you may extend the safe life limit of the wing spar lower cap to 7,000 hours TIS by incorporating the wing spar center splice joint modification following the procedures in Snow Engineering Co. Service Letter #55, revised October 23, 2002; or Snow Engineering Co. Service Letter #55, revised October 4, 2004, with the following requirements:
(1) This modification must be done no earlier than 4,600 total hours TIS on the wing spar lower cap and no later than 5,000 total hours TIS on the wing spar lower cap.
(2) Immediately before incorporating the modification, you must do an eddy-current inspection for cracks following Snow Engineering Co. Process Specification #197, revised June 4, 2002.
(3) After each replacement, inspect as specified in paragraph (e)(1) of this AD until the wing spar center splice joint modification or the required wing spar lower cap replacement.
(h) Eddy-current inspections required by this AD must be done by one of the following:
(1) A level 2 or 3 inspector certified in eddy-current inspection using the guidelines established by the American Society for Nondestructive Testing or NAS 410; or
(2) A person authorized to perform AD maintenance work and who has completed and passed the Air Tractor, Inc. training course on eddy-current inspection on wing lower spar caps.
Note 1: We are not retaining from AD 2003-06-01 the provision to allow a limited time of continued operation beyond the safe life limit provided parts are ordered, the replacement is scheduled, and repetitive inspections reveal no cracks. That provision was put in AD 2003-06-01 to prevent airplanes from being inadvertently grounded if parts were not available. If parts availability were to ever become a problem in the future, the owner/operator could request an alternative method of compliance following the procedures in 14 CFR 39.19 and this AD.
(i) Report the results of any inspection required by this AD where cracks are found to the FAA.
(1) Submit this report within 10 days after the inspection.
(2) Use the form (Figure 1 of this AD) and submit it to FAA, Fort Worth Airplane Certification Office (ACO), 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: (817) 222-5156; facsimile: (817) 222-5960.
(3) The Office of Management and Budget (OMB) approved the information collection requirements contained in this regulation under the provisions of the Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and assigned OMB Control Number 2120-0056.
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.
