AD/B737/113 Amdt 1 Rudder Power Control Unit Replacement (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/B737/113 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 737 Series Aeroplanes

AD/B737/113 Amdt 1 Rudder Power Control Unit Replacement 10/2005

Applicability:

Model 737 series aeroplanes, having a main rudder power control unit (PCU) and vernier control rod bolts that are identified in Boeing Alert Service Bulletin (ASB) 737-27A1202 Revision 2, dated August 7, 1997.

Requirement:

1.    Perform the test requirements of Part I of the Accomplishment Instructions of Boeing ASB 737-27A1202.

2.    Replace the rudder PCU in accordance with Part II of the Accomplishment Instructions of Boeing ASB 737-27A1202.

3.    Replace the dual servo valve and a bolt in the PCU in accordance with Part III of the Accomplishment Instructions of Boeing ASB 737-27A1202.

4.    Replace the vernier control rod and two dual load path bolts in accordance with Part IV of the Accomplishment Instructions of Boeing ASB 737-27A1202.

5.    Replace two nutplates on the control rod in accordance with Part V of the Accomplishment Instructions of Boeing ASB 737-27A1202.

Accomplishment of the requirements of AD/B737/201 (FAA AD 2002-20-07) constitutes terminating action for the requirements of this Directive.

Note 1:  Some aircraft may already meet some of the requirements of Boeing ASB 737-27A1202 through compliance with previous CASA ADs (B737/79 and B737/99), however, these aircraft may still require on-going inspections and/or component replacement dependent on the scope of previous actions completed.  This directive supersedes AD/B737/79 & AD/B737/99.  Pending the cancellation of ADs B737/79 & 99, compliance with this directive can be considered as achieving compliance with ADs/B737/79 & 99.

Note 2:  FAA ADs 97-14-04, 96-23-51 and 94-01-07 all refer to inspection, test and replacement actions on Boeing 737 rudder systems and are all referenced in Boeing ASB 737-27A1202.

Compliance:

1.    To be completed every “A” check and every time a PCU is replaced.

2.    Within 24 months after 26 February 1998.

3.    Within 24 months after 26 February 1998.

4.    Within 24 months after 26 February 1998.

5.    Within 24 months after 26 February 1998.

The compliance times remain unchanged by this issue.

This Amendment becomes effective on 29 September 2005.

Background:

This AD makes compliance with a Boeing ASB mandatory.  The Boeing ASB gives instructions to ensure that the secondary servo slide in the dual servo valve of the rudder PCU operates correctly.  The ASB also requires the replacement of the vernier control rod and two dual loadpath bolts in the rudder PCU assembly.  The eventual aim of the ASB is to have all rudder PCUs replaced with a modified item which is not prone to jamming.

Previous Boeing Service Bulletins and FAA ADs had addressed some of the problems identified with the rudder control system, but this latest bulletin incorporates a comprehensive test, inspection and component replacement procedure which overcomes the possible effects of a jam in the secondary slide of the rudder PCU assembly.

Amendment 2 is issued in response to FAA AD 2002-20-07, which requires incorporation of a new rudder control system; which when incorporated, supersedes the requirements of AD 97-14-04, the Requirement document of this Directive.

David Punshon
Delegate of the Civil Aviation Safety Authority

19 August 2005