AD 2004-15-15 Airworthiness Directives; Air Tractor, Inc. Models AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, AT-503A, 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:   Model Serial Nos. AT-401, AT-401B, AT-402, AT-402A, and AT-402B 0716 through 1144 AT-501, AT-502, AT-502A, AT-502B, and AT-503A 0037 through 0658 AT-602 0337 through 0664 AT-802 and AT-802A 0001 through 0139

(e) To address this problem, you must inspect the upper longeron and upper diagonal tube (as applicable) on the left hand side of the fuselage frame just forward of the vertical fin front spar attachment for cracks at the times specified below. You must also replace and modify any cracked upper and diagonal longerons (as applicable) found during any inspection required by this AD before further flight after the inspection in which cracks are found.   Affected models and serial nos. Inspection compliance times Procedures (1) AT-401, AT-401B, serial numbers (S/Ns) 0716 through 1144 Initially inspect upon the accumulation of 1,250 total hours time-in-service (TIS) or within the next 100 hours TIS after September 7, 2004 (the effective date of this AD), whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper and diagonal longerons are replaced and modified. Replacing and modifying the upper and diagonal longerons is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #218A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #218B, dated November 10, 2003. (2) AT-402, AT-402A, and AT-402B, S/Ns 0716 through 1144 Initially inspect upon the accumulation of 1,250 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper and diagonal longerons are replaced and modified. Replacing and modifying the upper and diagonal longerons is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #218A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #218B, dated November 10, 2003. (3) AT-501, AT-502, AT-502B, and AT-503A, S/Ns 0037 through 0658 Initially inspect upon the accumulation of 4,800 total hours TIS or within the next 100 hours TIS after September 7, 2004 (the effective date of this AD), whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #195B, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #195A, revised November 10, 2003. (4)AT-502A, S/Ns 0037 through 0658 Initially inspect upon the accumulation of 2,800 total hours TIS or within the next 100 hours TIS after September 7, 2004 (the effective date of this AD), whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #195B, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #195A, revised November 10, 2003. (5) AT-602, S/Ns 0337 through 0661 Initially inspect upon the accumulation of 700 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #213A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #213B, revised November 10, 2003. (6) AT-602, S/Ns 0662 through 0664 Initially inspect upon the accumulation of 1,750 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #213A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #213B, revised November 10, 2003. (7) AT-802 and AT-802A, S/Ns 0001 through 0004 and 0012 through 0118 Initially inspect upon the accumulation of 250 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #217A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #217B, revised November 10, 2003. (8) AT-802 and AT-802A, S/Ns 0005 through 0011 Initially inspect upon the accumulation of 900 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #217A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #217B, revised November 10, 2003. (9) AT-802 and AT-802A, S/Ns 0119 through 0139 Initially inspect upon the accumulation of 1,750 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD Inspect following Snow Engineering Co. Service Letter #217A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #217B, revised November 10, 2003. (f) You may replace and modify the upper and diagonal longeron (as applicable) at any time as a terminating action for the repetitive inspection requirement in this AD. However, you must replace and modify the upper and diagonal longeron (as applicable) before further flight after any inspection in which cracks are found.

(d) This AD is the result of reports of cracks in the aft fuselage upper longeron, originally detected as excessive movement in the empennage due to the loss of fuselage torsional rigidity. The actions specified in this AD are intended to detect and correct cracks in the upper aft longeron, which could cause the fuselage to fail. Such failure could result in loss of control of the airplane.

(b) This AD supersedes AD 2002-19-10.