Factual Information 2015:1.11 Flight Recorders/1.11.3.1
This page contains an extract from MH370/01/15 Factual Information which accompanied the (first) Interim Statement released by The Malaysian ICAO Annex 13 Safety Investigation Team for MH370 on 8th March 2015.
1.11.3.1 SSFDR ULB Battery Expiry
According to maintenance records, the SSFDR ULB battery expired in December 2012.
There is no evidence to suggest that the SSFDR ULB battery had been replaced before the expiry date. The SSCVR ULB battery however was replaced, as scheduled, with the next expiry in June 2014. There is some extra margin in the design to account for battery life variability and ensure that the unit will meet the minimum requirement. However, once beyond the expiry date, the ULB effectiveness decreases so it may operate, for a reduced time period until it finally discharges. While there is a definite possibility that a ULB, will operate past the expiry date on the device, it is not guaranteed that it will work or that it would meet the 30-day minimum requirement. There is also limited assurance that the nature of the signal (characteristics such as frequency and power) will remain within specification when battery voltage drops below the nominal 30-day level.
Technical Log records showed that the SSFDR (together with the ULB) was replaced on the aircraft on 29 February 2008. Component installation records for the ULB showed that at the time the SSFDR was replaced on aircraft the expiry date for the battery was December 2012.
Interviews were held with the MAS Engineering Technical records staff to determine why the ULB battery was not replaced before the expiry. It was revealed that the Engineering Maintenance System (EMS, a computer system used to track and call out maintenance) was not updated correctly when the SSFDR was replaced on 29 February 2008. The update involves ‘removal’ of the old unit in the system followed by ‘installation’ of the new unit. In this particular instance, although the old unit was ‘removed’, the new unit was inadvertently not ‘installed’ in the system. If the system was updated correctly on the installation, the next due for removal would have been for the replacement of the ULB battery. Since the system was not updated it did not trigger for the removal of the SSFDR for replacement of the ULB battery when it was due. ULB battery replacement is normally done in the workshop by routing the removed SSFDR, together with the ULB, to the workshop. This oversight was not noted until after the disappearance of MH370 when details of the ULBs were requested.
Subsequently, MAS Engineering Technical records carried out a fleet-wide record inspection for the ULBs to ensure all records for other aircraft are updated accordingly.
Source: Malaysian ICAO Annex 13 Safety Investigation Team for MH370, 8 March 2015, Factual Information MH370/01/15
The Factual Information was updated in 2018 by the Safety Investigation Report MH370/01/2018 which added new content but did not include all of the previous data.