AD/AT/19 Amdt 1 - Flap System Overrun Prevention (Cth)

COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES

Airtractor AT-300, 400 and 500 Series Aeroplanes

AD/AT/19 Amdt 1

Flap System Overrun Prevention 3/99

Applicability: Models AT-300, AT-301, AT-302, AT-400, AT-400A, AT-401, AT-401A, AT-401B, AT-402, AT-402A, and AT-402B aircraft, serial numbers 300-0001 through 401B- 1063; and, models AT-501, AT-502, AT-502A, AT-502B, and AT-503A aircraft, serial numbers 502-0001 through 502B-0500; that do not have a part number (P/N) 70975-1 flap actuator overtravel stop installed in accordance with the Rework Instructions section of Snow Engineering Co. Service Letter 165, dated May 15, 1998.

Requirement: Replace the existing flap actuator overtravel stop with a new one of improved design, P/N 70975-1. Accomplish this replacement in accordance with the Rework Instructions section of Snow Engineering Co. Service Letter 165.

Note: FAA AD 98-25-01 Amdt 39-10922 refers.

Compliance: Unless already accomplished, within 50 hours time in service after 25 March 1999.

This Amendment becomes effective on 25 March 1999.

Background: Investigations have shown that it is possible for the flap control system to overrun through disengagement of the flap actuator overtravel nut. As a result of this overrun it is possible for the flap control pushrod to interfere with the aileron control pushrod to the extent that aileron control is lost. A modification introduced a new overtravel stop with improved security to prevent flap actuator overrun.

Amendment 1 is issued in response to a new FAA AD which was prompted by reports of the flap actuator jackscrew breaking through the roll pin hole on three of the affected aircraft that were already in compliance with Snow Service Letter 140, Revised (FAA AD 96-23-19). This Directive requires installation of a new improved overtravel stop that is secured to the jackscrew by a welding method.