Document ID: chunk:federal_register_of_legislation:F2005L00240:body:0:p2
Version: federal_register_of_legislation:F2005L00240
Segment Type: other
Provision Reference: 
Character Range: 2867–5049

as TRW Systemes Aeronautiques) humidifier, P/N M01AA0101, M01AB0101, M01AB0102 or M01AB0103 is optionally deactivated.
             For Requirement 2 - Before further flight after the functional check and thereafter at intervals not to exceed 36 months unless Lucas (also known as TRW Systemes Aeronautiques) humidifier, P/N M01AA0101, M01AB0101, M01AB0102 or M01AB0103 is optionally deactivated.
             For Requirement 3 - Within 18 months after the effective date of this Directive and thereafter at intervals not to exceed 36 months unless Lucas (also known as TRW Systemes Aeronautiques) humidifier, P/N M01AA0101, M01AB0101, M01AB0102 or M01AB0103 is optionally deactivated.
             For Requirement 4 - Before further flight following the optional deactivation specified in Note 1.
             For Requirement 5.a. - Within 18 months after reactivating the humidifier and thereafter at intervals not to exceed 18 months.
             For Requirement 5.b. - Within 36 months after reactivating the humidifier and thereafter at intervals not to exceed 36 months.
             This Airworthiness Directive becomes effective on 17 March 2005.
Background:  Boeing advised that during routine maintenance checks some engine fire control circuits were found to be faulty due to switch internal continuity failures.  The humidified air being provided by the humidifier was identified as the source of mineral build up on APU and engine fire control switch contacts leading to failure of the switches to discharge fire suppressant in the affected area.  This could result in an uncontrolled fire that could spread to the strut, wing, or aft body of the aeroplane.
             This Directive requires repetitive functional tests and repetitive replacements of the APU and engine fire shutoff switches.  The Directive also provides an optional terminating action for the repetitive functional tests and replacements.

   This action is intended to address the identified unsafe condition by preventing the possibility of mineral build-up on the APU and engine fire shutoff switches.

James Coyne
Delegate of the Civil Aviation Safety Authority

4 February 2005