How about looking at the Technical side of failures????
I posted previous comment on Composite & Lightening discussion but seems a bit lost there....
Just a few things which are bugging me from what I know about A330s and my experience on them.....
I am MORE interested in that ACARS message.....if that was sent that means there was power available in that system from the BUS2... that means there was full power supply from BUS2 feeding the other electrical buses......
ALSO....IF ACARS were still gathering and sending data about the failures then ACMS/CMC was fully functional, monitoring all the relevant systems and reporting subsequent failures....
Data Transmission
The Data Transmission system comprises:
Aircraft Communications Addressing and Reporting System (ACARS)
The ACARS management unit allows management of the data transmitted to the ground (SDAC, FWC, AIDS, CMS, FMGEC) and entered by the crew. It also allows reception, printing and display of ground messages on the MCDU.
These data are transmitted through the VHF 3 system (or through the SATCOM system if installed).
Gate Link
The system allows a connection between the Aircraft Information Network System (AINS) and the airline ground based information system.
Its description is made in the Description/Operation of the AINS (Ref. 46-11).
Air-to-ground calls
When a call is initiated by an airborne subscriber, the AES sends signals to the GES, using the Rd-Channel. When the GES receives the call request, it assigns a pair of C-Channels, for a voice call, or reserves time on a T-Channel, for long-duration data transmissions. The call can then go through.
The assigned channels are reserved for as long as the call is in progress. The sequence used to initiate the call is automatic and transparent to both the originator and the receiver of the call.
ALSO......looking at the Power distribution schematic of this a/c everything essential is always powered (thats why its called essential)......
Cutting to the chase.....I am looking at these units......
Electrical Contactor Management Unit (ECMU)
The system consists of two separate equipment called ECMU1 and ECMU2.
Their functions are similar but the ECMU1 manages only side 1 contactors and ECMU2 manages only side 2 contactors.
Each ECMU receives the following signals:
-
orders from the GCUs and the GAPCU,
status of the main AC and DC generation contactors,
voltage of the main AC and DC busbars.
The two main functions of the ECMU are:
Operational function:
control of the AC/DC main contactors,
control of the galley shedding,
on ground, control of the transfer between the various electrical power sources (IDG, APU, EXT PWR) in order to avoid any break of power (NBPT),
control of AC/DC ground service busses,
control of Inadvertent Paralleling Trip (IPT).
BITE function
monitor and test the ECMU together with its peripheral circuits,
collect the failures and store the corresponding fault code in the Non Volatile Memory (NVM),
transmit the failure message to the Central Maintenance Computer (CMC) through an ARINC 429 bus.
In addition, in case of ECMU failure, a fault warning message is generated to the Engine/Warning Display (EWD).
Transfer circuit
The Bus Transfer Contactors (BTC)s and the System Isolation Contactor (SIC) are automatically controlled by the ECMUs. They enable supply of all the aircraft electrical network or half of it.
The supply only depends on the availability of one of the five power sources: GEN1, GEN2, APU GEN, EXT PWR A and B.
The control of the BTCs also depends on the availability of these sources and the correct condition of each network.
Operation of BTC1
The BTC1 closes, if no interlock conditions exist on the GCU1:
when the GEN1 is not available, in order to supply the network 1 (AC BUS 1) from another power source (GEN2, APU GEN, EXT PWR A or EXT PWR B),
to supply the network 2 from GEN1 if the GEN2, APU GEN EXT PWR A and EXT PWR B are not available.
Operation of BTC2
The BTC2 closes if no interlock conditions exist on the GCU2:
when the GEN2 is not available in order to supply the network 2 from another power source (GEN1, APU GEN , EXT PWR A or EXT PWR B),
to supply the network 1 from the GEN2 if the GEN1, APU GEN , EXT PWR A and EXT PWR B are not available.
Latching logic of the BTCs
The BTC1 is latched open if a "GLC1 welded" failure or a short circuit not clarified by C/B tripping occurs at level of GEN1 channel.
The same latching logic is used for BTC2.
System Isolation Contactor (SIC)
The SIC closes automatically:
when the GEN2 and EXT PWR A are not available and APU GEN is available in order to supply network 2 from the APU GEN,
when the GEN1 and APU GEN are not available and EXT PWR A is available in order to supply network 1 from the EXT PWR A,
when the GEN2, APU GEN, EXT PWR A are not available and GEN1, is available in order to supply network 2 from the GEN1,
when the GEN1, APU GEN, EXT PWR A are not available and GEN2, is available in order to supply network 1 from the GEN2.
Priority order of power supply
Each network (1 or 2) is supplied in the following priority order:
1XP = IDG1/APU GEN/EXT PWR B/EXT PWR A/IDG2,
2XP = IDG2/EXT PWR A/APU GEN/EXT PWR B/IDG1.
Isolation of the two sides
The isolation of the two sides is possible by action on the BUS TIE pushbutton switch. This control is located on the ELEC control panel 235VU, cockpit overhead panel.
No Break Power Transfer (NBPT)
This function is managed by the ECMUs. It prevents busbar power interruption due to electrical power supply source transfer on ground in normal configuration.
The ECMU receives information from the main AC contactors, each GCU and the GAPCU, to perform this function.
No break power transfer occurrences are permitted between:
any external power and the APU generator,
any IDG and any external power,
any IDG and the APU generator.
Distribution
The alternating current distribution network comprises two independent sections.
Network 1
Network 1 mainly includes the AC BUS 1, the AC ESS BUS and the AC SHED ESS BUS which are three-phase, 115 VAC/400 Hz busses.
The AC BUS 1 supplies the essential busses in parallel. The AC ESS BUS also delivers 26 VAC/400 HZ power supply through a 115/26 VAC transformer.
In the event of the AC BUS 1 loss, the AC ESS BUS and AC SHED ESS BUS are automatically restored by the direct transfer of power supply from the AC BUS 2.
In case of loss of the AC essential busses, FAULT legend on the AC ESS FEED pushbutton switch comes on : this P/BSW enables to transfer the AC essential busses supply from AC BUS 1 to AC BUS 2, in particular when the loss of the AC essential busses normal supply does not result from AC BUS 1 loss.
If there is loss of AC BUS 1 and AC BUS 2 (emergency configuration), the AC ESS BUS and AC SHED ESS BUS are restored via the CSM/G driven by the Green hydraulic power. In case of RAT operation, the AC SHED ESS BUS is automatically shed.
Network 2
Network 2 comprises the AC BUS 2 which is a three-phase, 115 VAC/400 Hz bus.
The AC BUS 2 also delivers 26 VAC/400 Hz power supply through a 115/26 VAC transformer.
I somehow do not agree with so-called assumption of "short circuit" starting this chain of failures.......I think the only way it can be done is by crew intervention (eg turning the wrong BTB p/b off) and stop the serviceable bus feeding the u/s Bus.....which in turn will start the sequence of power failures to these computers......
Still trying to figure out.........any A330/340 guys would like to add????