Airworthiness Directive · Amendment 39-14798 · Air Tractor, Inc. Model AT-602 Airplanes
Air Tractor, Inc. Model AT-602 Airplanes
This AD affects Model AT-602 airplanes, all serial numbers beginning with 602-0337, that are certificated in any category.
The FAA adopts a new airworthiness directive (AD) for all Air Tractor, Inc. (Air Tractor) Model AT-602 airplanes. This AD requires you to repetitively inspect (using the eddy current method) the wing center splice joint two outboard fastener holes on both of the wing main spar lower caps for fatigue cracking; repair or replace any wing main spar lower cap where fatigue cracking is found; and report any fatigue cracking found. This AD results from fatigue cracking at the wing center splice joint outboard fastener hole in one of the wing main spar lower caps. We are issuing this AD to detect and correct cracks in the wing main spar lower cap, which could result in failure of the spar cap and lead to wing separation and loss of control of the airplane.
To address the problem, do the following:
(1) Before doing the initial eddy current inspection required in paragraph (e)(2) of this AD, gain access for the inspection by cutting inspection holes, modifying the vent tube, and installing cover plates; unless already done. Follow Snow Engineering Co. Service Letter #204, revised March 26, 2001, Drawing titled “602 Spar Inspection Holes and Vent Tube Mod.,” dated November 13, 2003.
(2) Eddy current inspect the wing center splice joint outboard two fastener holes in both the right and left wing main spar lower caps for cracks. Follow Snow Engineering Co. Process Specification #197, Revised June 4, 2002. For the following airplanes, use the wing spar lower cap hours time-in-service (TIS) schedule below in Table 1 of this AD to do the initial and repetitive inspections:
| Serial Nos. | Condition | Initially inspect | Repetitively inspect thereafter at the following intervals |
|---|---|---|---|
| (i) 602-0337 through 602-0584 | As manufactured | Upon accumulating 2,000 hours TIS or within 50 hours TIS after December 14, 2006 (the effective date of this AD), whichever occurs later, unless already done | 1,000 hours TIS. |
| (ii) 602-0337 through 602-0584 | Modified with cold-worked fastener holes following Snow Engineering Co. Service Letter #244, dated April 25, 2005 | If performing the cold-working procedure in Service Letter #244, it includes the eddy current inspection | 2,000 hours TIS. |
(3) Do an eddy current inspection as part of the cold working procedure in Service Letter #244, dated April 25, 2005, even if the wing spar was previously inspected.
(4) One of the following must do the inspection:
(i) 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
(ii) 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.
(f) For the airplanes listed in paragraph (e)(2) of this AD, as terminating action for the inspection requirements, you may modify your wing by installing part number (P/N) 20996-2 steel web plate and P/N 20985-1/2 8-bolt splice blocks following Snow Engineering Co. Drawing 20998, Revision B, dated September 28, 2004, and cold work the lower spar cap two outboard fastener holes at the wing center section splice connection following Snow Engineering Co. Service Letter #240, dated September 30, 2004.
(g) For all affected airplanes listed in paragraph (e)(2) of this AD, repair or replace any cracked spar cap before further flight. For repair or replacement, do one of the following:
(1) For cracks that can be removed by performing the terminating action listed in paragraph (f) of this AD above, perform the actions in paragraph (f) of this AD.
(2) For cracks that can not be removed by performing the terminating action in paragraph (f) of this AD, you must replace the lower spar caps and associated parts listed in paragraph (h) of this AD before continued flight.
(h) For all Model AT-602 airplanes, upon accumulating 6,500 hours TIS on the wing spar lower caps or within the next 50 hours TIS after December 14, 2006 (the effective date of this AD), whichever occurs later, replace the wing lower spar caps, splice blocks and hardware, wing attach angles and hardware, and install the steel web plate, P/N 20996-2, if not already installed, following Snow Engineering Co. Drawing 20776, Sheet 2, Revision A, dated August 30, 2004. Compliance with this paragraph terminates the inspection requirements of paragraph (e)(2) of this AD.
(i) Report any cracks you find within 10 days after the cracks are found or within 10 days after December 14, 2006 (the effective date of this AD), whichever occurs later. Include in your report the airplane serial number, airplane TIS, wing spar cap TIS, crack location and size, corrective action taken, and a point of contact name and phone number. Send your report to Andrew McAnaul, Aerospace Engineer, ASW-150 (c/o MIDO-43), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; telephone: (210) 308-3365; facsimile: (210) 308-3370. 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 and those following sections) 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.
Aircraft
