AD/B717/25 Power Conversion Distribution Unit (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (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 717 Series Aeroplanes

AD/B717/25 Power Coversion Distribution Unit 11/2007

Applicability:	Model 717-200 aeroplanes.
Requirement:	1.    Inspect the power conversion distribution units (PCDU) to determine its part number.  A review of aeroplane maintenance records is acceptable in lieu of this inspection if the part number can be conclusively determined from that review.  If the PCDU part number is 762904E or higher, no further work is required by this Directive.
2.    If, as a result of the Requirement 1 inspection, it is determined that the PCDU part number is below 762904E, carry out the following:
a.     Modify the PCDU in accordance with Boeing Alert Service Bulletin (ASB) 717-24A0028, Revision 1, dated 20 December 2005.
Note 1:  A modification accomplished before the effective date of this Directive in accordance with Boeing ASB 717-24A0028, dated 24 November 2004, is acceptable for compliance with Requirement 2.a.
Note 2:  Boeing ASB 717-24A0028 refers to Hamilton Sundstrand Service Bulletin 40EGS22P-24-10, Revision 1, dated 11 May 2005, as an additional source of service information for the modification.
b.    Accomplish the applicable actions specified in Table 1.

Table 1

Do the following:

In accordance with Hamilton Sundstrand Service Bulletin (SB):

Rework the transformer rectifier unit assembly (TRU)

Rework the W3 wiring harness assembly to install direct lead wires to the TRU

Add a ground wire to the TRU transformer

Add an insulated spacer to the PCDU top cover

40EGS22P-24-3, dated 30 June 2000

Install new PCDU 186 firmware

40EGS22P-24-4, Revision 1, dated 2 January 2002

Install new PCDU 186 firmware

40EGS22P-24-6, dated 25 July 2002

Modify the top cover of the PCDU

40EGS22P-24-7, dated 3 September 2003

Modify printed wiring board (PWB) assemblies A4 and A5

Check and apply torque seal to fasteners on the TRU assembly and to PCDU internal fasteners, as applicable

40EGS22P-24-8, dated 4 September 2003

Modify PWB assembly A4

40EGS22P-24-9, dated 19 November 2003

Later revisions of the above SBs, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2007-19-03 are considered acceptable for compliance with the equivalent Requirements of this Directive.

Note 3:  FAA AD 2007-19-03 Amdt 39-15193 refers.

Compliance:

For Requirements 1 and 2.a. - Within 20 months after the effective date of this Directive.

For Requirement 2.b. - Before or concurrently with the Requirement 2.a. modification.

This Airworthiness Directive becomes effective on 25 October 2007.
Background:	The United States Federal Aviation Administration (FAA) has advised that they have received reports of failed PCDUs, the loss of an electrical bus, together with the presence of a strong electrical burning odour in the flight deck and forward cabin.
This Directive requires the inspection of the PCDU to determine its part number and, if necessary, the modification of certain PCDUs.  The Directive is issued to prevent the loss of an electrical bus due to PCDU failure which could result in the loss of all flight displays for an unacceptable time period together with a consequent emergency landing.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

14 September 2007