AD/B747/299 Amdt 2 Yaw Damper Actuator (Cth)
AIRWORTHINESS DIRECTIVE
On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/B747/299 Amdt 1 and issues the following AD under subregulation 39.001(1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
Boeing 747 Series Aeroplanes
| AD/B747/299 Amdt 2 | Yaw Damper Actuator | 8/2008 |
Applicability: | Model 747-400, -400D, and -400F series aircraft, as identified in Boeing Alert Service Bulletin 747-27A2479, dated 8 November 2007, or later FAA approved revision. |
Requirement: | Action in accordance with the technical requirements of FAA AD 2008-13-03 Amdt 39-15566. |
Compliance: | As specified in the Requirement document, with a revised effective date of |
| This Amendment becomes effective on 31 July 2008. | |
Background: | The original issue of this Airworthiness Directive required an ultrasonic inspection of the yaw damper portion of the upper and lower rudder power control modules main manifold for cracking. Such cracking, unless detected and corrected, could result in an uncommanded left rudder hardover, consequent increased pilot workload, and possible runway departure upon landing. Amendment 1 expanded the applicability and discontinued certain requirements of the previous Airworthiness Directive. Amendment 2 is issued in response to a new FAA AD, which was prompted by additional reports of failure or cracking of the power control module manifold in the area of the yaw damper cavity endcap at intervals well below the initial inspection threshold of the existing AD. This amendment limits applicability, reduces initial inspection threshold and repetitive interval, and requires installation of a secondary retention device for the yaw damper modulating piston. |
| The original issue of this Airworthiness Directive became effective on |
David Villiers
Delegate of the Civil Aviation Safety Authority
20 June 2008
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