Safety Investigation Report 2018:1 Factual Information/1.6/1.6.8 Aircraft Systems/9
SAFETY INVESTIGATION REPORT MH370 (9M-MRO)
9) Airplane Information Management System
The Airplane Information Management System (AIMS) collects and calculates large quantities of data. The AIMS manages this data for several integrated avionics systems. These systems are the:
- Primary display system (PDS)
- Central maintenance computing system (CMCS)
- Airplane condition monitoring system (ACMS)
- Flight data recorder system (FDRS)
- Data communication management system (DCMS) - including ACARS datalink
- Flight management computing system (FMCS)
- Thrust management computing system (TMCS)
The AIMS has software functions that do the calculation for each of these avionics systems. The AIMS supplies one other software function that many aircraft systems use. It is the data conversion gateway function (DCGF).
The AIMS has two cabinets, for redundancy, which do the calculations for other avionic systems. The Left cabinet is located in the forward rack of the Main Equipment Centre (MEC) while the Right cabinet is located in rear rack of the MEC. To do these calculations, each AIMS cabinet has the following:
The IOMs and CPMs are considered Line Replaceable Modules (LRM). The IOM transfers data between the software functions in the AIMS CPMs and external signal sources. The CPMs supply the software and hardware to do the calculations for several avionic systems. The software is called functions. To keep a necessary separation between the functions, each function is partitioned. The partitions permit multiple functions to use the same hardware and be in the same CPM.
The Left AIMS cabinet gets electrical power from the 28V DC Capt Flight Instrument bus and the 28V DC F/O Flight Instrument bus. The Right AIMS cabinet gets electrical power from the 28V DC Left bus and the 28V DC Right bus. Each cabinet receives the power from four 28V DC circuit breakers in the overhead circuit breaker panel. The four 28V DC bus inputs are known as power 1 through power 4. Power 1 and power 2 enter the cabinet through a connector on the left side of the cabinet and therefore they are considered as left power. Power 3 and power 4 enter the cabinet through a connector on the right side of the cabinet and are considered as right power.
Each LRM receives power from four sources, two for main power and two for monitor power. The main circuitry uses the main power. Special circuits that monitor the condition of the power supply in the LRM use the monitor power. The two main and two monitor sources of power for each LRM come from different power sources.
Each AIMS cabinet also receives power through one hot battery bus circuit breaker in the standby power management panel. The connection to the hot battery bus keeps the LRMs internal memories active. The hot battery bus also makes the AIMS cabinet less likely to have faults due to power transients.