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AD/B737/228 Amdt 1 - Honeywell Start Converter Unit

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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/B737/228 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/B737/228 Amdt 1
Honeywell Start Converter Unit
Model 737-600, -700, -700C, -800, and -900 series aeroplanes, equipped with start converter units (SCU) having Honeywell part number (P/N) 1151858- 241, Series 1 through 9 inclusive, or P/N 1152426-245, Series 1 through 6 inclusive.

Replace the SCU of the auxiliary power unit (APU) located in the electrical and electronics (E/E) compartment in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, Federal Aviation Administration (FAA) of the United States.
Boeing 737-600/700/800/900 Maintenance Manual, Chapter 49-41-61, dated 5 June 1998; and Aircraft Maintenance Manual, Chapter 49-41-61, dated 10 October 2003, are approved methods of compliance with this Requirement.  Replace the applicable SCU listed in the "Existing Honeywell P/N" column below, with the corresponding SCU listed in the "Replacement Honeywell P/N" column below, as follows.

Existing Honeywell P/N
1151858-241, of any series 1 through 9 inclusive
1152426-245, of any series 1 through 6 inclusive
Replacement Honeywell P/N
1151858-241, series 10 or
1151858-241, series 11 or
1151858-241, series 12
1152426-245, series 7 or
1152426-245, series 8 or
1152466-250, series 1 or
1152466-250, series 2 or
1152466-250, series 3 or
1152466-250, series 4

Note:  FAA AD 2004-10-10 Amdt 39-13640 refers.

Remains unchanged as within 36 months after 5 August 2004.

This Amendment becomes effective on 27 July 2012.

This amendment updates the list of approved APU SCU that may be fitted to these aircraft in accordance with United States Federal Aviation Authority approved Alternate Method Of Compliance 130S-04-314.
The original effective date and compliance time remains unchanged.
The original issue of this Airworthiness Directive became effective on 5 August 2004.
The original Directive required replacement of the APU SCU, located in the E/E compartment, with a new or modified SCU.  This action is necessary to prevent overheating of the electrical connector of the SCU, which could create an ignition source and possible fire in the E/E compartment and cause damage to certain electrical wire bundles on the E2-2 shelf.  Such damage could result in loss of power from the APU generator, failure of electrically powered aeroplane systems, and consequent reduction in the ability of the flight crew to control the aeroplane in certain adverse operating conditions.

Peter Nikolic
Delegate of the Civil Aviation Safety Authority
24 July 2012