AD/B767/234 Cargo Compartment Fire Extinguishing System Time Delay Relays (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 767 Series Aeroplanes

AD/B767/234 Cargo Compartment Fire
Extinguishing System - Time Delay Relays 2/2008

Applicability:	Model 767-200, 767-300 and 767-300F series aeroplanes as identified in Boeing Special Attention Service Bulletin (SASB) 767-26-0131, dated 24 July 2006.
Requirement:	1.    Carry out general visual inspection, in accordance with SASB 767-26-0131 of part number (P/N) TDH6103-1804 time delay relay (K826) in the main equipment centre to determine if the relay was manufactured during a certain date range.
2.    If, as a result of the Requirement 1 inspection, a relay manufactured during the date range specified in the SASB is found, replace the relay with a relay that was not manufactured during the specified date range, or with a relay that has been tested by the supplier and found to be unaffected by thermal expansion, in accordance with the SASB.
3.    Time delay relay, P/N TDH6103-1804, may not be installed on any aeroplane as a replacement spare, if the relay has a date code between 0000 and 0343 and does not have an additional date code with the letter "T.''
Later revisions of the above SASB, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2007-23-08, are considered acceptable for compliance with the equivalent Requirements of this Directive.
Note:  FAA AD 2007-23-08 Amdt 12524 refers.
Compliance:	For Requirement 1 - Within 24 months after the effective date of this Directive.
For Requirement 2 - Within 30 days after finding a relay manufactured during the date range specified in the ASAB.
For Requirement 3 - As of the effective date of this Directive
This Airworthiness Directive becomes effective on 14 February 2008.

Background:

The FAA has advised of a report indicating that failure of a time delay relay in the electrical load management system (ELMS) panel of a Boeing Model 777 led to testing of other time delay relays at Boeing and at the supplier.  Similar relays are also used in the cargo fire suppression system controlling when the secondary fire bottles discharge.

This Directive is issued to ensure there is sufficient fire suppressant to control a cargo fire if the aeroplane is more than the relay delay time from a suitable airport, which could result in an uncontrollable fire in the cargo compartment.  The Directive requires an inspection to determine the date code of the time delay relay for the cargo fire suppression system and, if necessary, replacing of the relay.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

10 December 2007