AD 2005-13-12 Airworthiness Directives; Air Tractor, Inc. Models AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-402, AT-602, AT-802, and AT-802A Airplanes

(c) This AD affects the following airplane models and serial numbers that are certificated in any category:   Models Serial Nos. AT-300, AT-301, AT-302, AT-400, and AT-400A All serial numbers. AT-401/AT-402 All through 401-0700. AT-602 All through 602-0695 that have any 7/16-inch eyebolt (part number (P/N) AN47-22A) installed; all beginning with 602-0703; and all that have any 9/16-inch eyebolt (P/N 30774-1) installed. AT-802 and AT-802A All through 802A-0188 that have any 7/16-inch eyebolt (P/N AN47-30A) installed; all beginning with 802A-0189; and all that have any 9/16-inch eyebolt (P/N 30775-1) installed.

(e) To address this problem, you must do the following:   Actions Compliance Procedures (1) Tighten the four eyebolts that attach the front and rear spar of the horizontal stabilizer to the respective stabilizer strut using the torque values referenced in Snow Engineering Co. Service Letter #129, revised October 21, 2004 Within the next 100 hours time-in-service (TIS) or 12 calendar months after August 5, 2005 (the effective date of this AD), whichever occurs first, unless already done. Repetitively tighten thereafter at every 12 calendar months after the date of the initial tightening to the specified torque Follow Snow Engineering Co. Service Letter #129, Issued September 26, 1994, Revised October 21, 2004. (2) Repetitively replace any eyebolts that attach the front and rear spar of the horizontal stabilizer to the respective stabilizer strut Initially replace upon accumulating the applicable number of hours TIS referenced in Snow Engineering Co. Service Letter #129, revised October 21, 2004, or within 50 hours TIS after August 5, 2005 (the effective date of this AD), whichever occurs later. Replace repetitively thereafter at the intervals referenced in Snow Engineering Co. Service Letter #129, revised October 21, 2004 Follow Snow Engineering Co. Service Letter #129, Issued September 26, 1994, Revised October 21, 2004. (3) For Model AT-602 airplanes through serial number 602-0695 and AT-802, and 802A airplanes through serial number 802A-0188: As an alternative in order to use the increased replacement compliance times in paragraph (e)(2) of this AD, you may replace the steel brace assembly inside the stabilizer with a new steel brace assembly with larger bushings, and (i) For the Model AT-602 airplane: replace any 7/16-inch eyebolt with the 9/16-inch eyebolt (P/N 30774-1) (ii) For the Model AT-802 and AT-802A airplanes: replace any 7/16-inch eyebolt with the 9/16-inch eyebolt (P/N 30775-1) At any time after August 5, 2005 (the effective of this AD). Use the applicable time in Snow Engineering Co. Service Letter #129A, dated August 7, 2004. The repetitive replacement of paragraph (e)(2) of this AD is still required Follow Snow Engineering Co. Service Letter #129A, Dated August 7, 2004. (4) Do not install any 5/16-inch eyebolt (P/N AN44-17A or AN44-21A), 7/16-inch eyebolt (AN47-22A or AN47-30A), or 9/16-inch eyebolt (P/N 30774-1 or 30775-1) that exceeds the corresponding cumulative hours TIS specified in paragraphs (e)(2) or (e)(3) of this AD As of August 5, 2005 (the effective date of this AD) Not Applicable.

(d) This AD is the result of reports of failures of the subject eyebolt. The actions specified in this AD are intended to detect, correct, and prevent future fatigue failure in any eyebolt that attaches the front and rear spar of the horizontal stabilizer to the respective stabilizer strut. Failure of the eyebolt could lead to an abrupt change or complete loss of pitch control and/or the airplane departing from controlled flight.

(b) None.