31 July 2011 C1 CIVIL AVIATION DEPARTMENT HONG KONG ...

CIVIL AVIATION DEPARTMENTHONG KONG, CHINAAirworthiness NoticeNo. 72Issue 231 January 2002SAFETY CRITICAL MAINTENANCE TASKS1 A factor in a serious incident involving an oil leakage on a large twin enginedcommercial air transport aircraft was the failure to re-install the drive cover plate onboth engines following maintenance. The Director-General wishes to highlight thepotential safety benefit where companies choose to apply aspects of Extended RangeTwin Operations (ETOPS) maintenance philosophy to multi-system aircraft in order toavoid the possibility of simultaneous incorrect maintenance on two or more safetycritical systems. In this context, such systems are those which have a fundamentalinfluence upon the safe operation of the aircraft, engines and their systems being a casein point.2 Operators and maintenance organisations should consider the following paragraphswhen planning, and accomplishing scheduled and non-scheduled maintenance tasks onmulti-system aircraft.(a)(b)(c)Arrangements should be made to stagger scheduled maintenance tasks onessential or primary systems such that the accomplishment of similar criticaltasks on two or more systems are segregated. Consideration should be givento introducing procedures that will ensure that such tasks are separated by atleast one flight cycle. Where it is not practical to introduce staggeredmaintenance, inspections and functional checks should be performedindependently to ensure system serviceability.Where it is not practical to introduce staggered maintenance at BaseMaintenance inputs or during rectification of Line or Base defects, the use ofseparate work teams together with the accomplishment of appropriate functionalchecks to verify system serviceability should ensure a similar level of systemintegrity.Procedures should be established to provide maintenance and planningpersonnel with guidance on the identification and accomplishment of safetycritical tasks conducted during scheduled and non-scheduled maintenanceactivities. Routine task documentation should identify those tasks which mayhave a critical effect on safety and should clearly identify the individual stagesof such tasks. Maintenance Programme or Maintenance Schedule basic rulesshould provide the necessary standards to ensure the identification of criticalscheduled maintenance tasks.AN-72 P.131 January 2002