Division Airtractor AT-300, 400 and 500 Series Ae - AD/AT/26 - Horizontal Stabiliser Attachment Eyebolts - Airtractor AT-300, 400 and 500 Series Aeroplanes

Airtractor AT-300, 400 and 500 Series Aeroplanes

AD/AT/26	Horizontal Stabiliser Attachment Eyebolts	9/2005

Applicability:	Models AT-300, AT-301, AT-302, AT-400, and AT-400A aircraft; all serial numbers.Model AT-401/AT-402 aircraft, with serial numbers up to and including 401-0700.
Requirement:	1. Tighten the four eyebolts that attach the front and rear spar of the horizontal stabiliser to the respective stabiliser strut using the torque values referenced in Snow Engineering Co. Service Letter (SL) No. 129, revised 21 October 2004.2. Replace eyebolts that attach the front and rear spar of the horizontal stabiliser to the respective stabiliser strut, in accordance with SL No. 129, Issued 26 September 1994, Revised 21 October 2004.Do not install any 5/16-inch eyebolt (part number AN44-17A or AN44-21A), 7/16-inch eyebolt (AN47-22A or AN-47-30A), or 9/16-inch eyebolt (part number 30774-1 or 30775-1) that exceeds the corresponding cumulative hours time in service specified in Requirement 2 of this Directive.Note: FAA AD 2005-13-12 Amdt 39-14149 refers.
Compliance:	1. Within 100 hours time in service or 12 calendar months after 1 September 2005, whichever occurs first, unless already accomplished. Tighten thereafter at intervals not to exceed 12 calendar months.2. Replace initially upon accumulating the applicable number of hours time in service specified in SL No. 129, revised 21 October 2004, or within 50 hours time in service after 1 September 2005, whichever occurs later. Replace thereafter at the intervals specified in SL No. 129, revised 21 October 2004.
	This Airworthiness Directive becomes effective on 1 September 2005.

Background:

The FAA has received numerous reports of failures of horizontal stabiliser attachment eyebolts on AT-301, AT-400, and AT-602 aircraft. Engineering analysis concluded that the eyebolts failed as a result of high cycle, low-nominal stress; and most likely due to the loss of torque during service. Failure of an eyebolt could lead to an abrupt change or complete loss of pitch control and/or aircraft departure from controlled flight.

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David Villiers
Delegate of the Civil Aviation Safety Authority

Airtractor AT-300, 400 and 500 Series AeAirtractor AT-300, 400 and 500 Series Aeroplanes

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