DC BUS 3 failure

[19AB67 16]

Hi folks, 

just after reaching TOC of my flight QFA9001 YMML to SBGL (T/O with 183 tons of fuel..., 14h38m estimated block time), VH-OEI suffered a bunch of EICAS messages: 

    OUTFLOW VLV R, RUD RATIO SNGL, >NO LAND 3, BRAKE LIMITER, ANTISKID, TEMP ZONE, >TRIM AIR OFF

and the status page added some...

   RECIRC FAN UPR R/L, HYDIM 2

1. Upsss... looks like I have to dump lots of fuel and return to MEL..., right? 

Checking (cough cheating by ) the Aircraft Failures page I found that 'solely' DC BUS 3 has kissed 'Goodbye'. 

2. How realistic is that error? Has anybody experienced it? 

3. How come that this does not show up in EICAS? 

4. What would be broken causing this error message? Obviously nothing we can by-pass or feed by the other power source on board of my ship...

5. I assume any of the DC BUS x failures triggers an emergency landing, correct? 

Thanks in advance. 

[Captain Kevin 586]

What does the FCOM tell you to do.

[19AB67 16]

1 minute ago, Captain Kevin said:

What does the FCOM tell you to do.

Hi Kevin. 

The QRH does not mention DC BUS at all, only AC BUS. 

The FCOM gives some information about the DC BUS system, but no advice in case of failure. 

[downscc 1,327]

2 hours ago, 19AB67 said:

Hi Kevin. 

The QRH does not mention DC BUS at all, only AC BUS. 

The FCOM gives some information about the DC BUS system, but no advice in case of failure. 

The QRH does have steps to follow for each individual alarm that is annunciated.  You first fly the airplane, then follow QRH and then communicate on company channel to get advice/recommendations.  There are four DC buses each fed by a separate T/R from an AC bus, and there is no way to replaced a T/R unit in the air so you basically deal with the individual issues and press on or go home.

[Qavion2 39]

28 minutes ago, downscc said:

There are four DC buses each fed by a separate T/R from an AC bus, and there is no way to replaced a T/R unit in the air so you basically deal with the individual issues and press on or go home.

Unless there is a short (or something similar) on Bus 3, the DC Bus tie system should provide power to DC Bus 3 (from the other DC Busses). The DC Bus Ties are normally closed. I'm guessing there is a short on the bus, otherwise you would not see all these messages.

It's interesting to compare the messages generated in PSX compared to PMDG. It would take a few days to figure out the differences.

EQUIP COOLING, >FMC MESSAGE, >NO AUTOLAND (shortly followed by an A/P disconnect - I selected another A/P), >JETT NOZZLE L, FUEL PUMP 2 FWD, FUEL PUMP 3 AFT, >DATALINK LOST, HYD PRESS DEM 3, AUTOBRAKES, SPEEDBRAKE AUTO, >FUEL JETT A, RUD RATIO SNG and a bucketload of Status Messages. Other oddities: Indications for all fuel pump pressures disappeared. All MCP switch engage lights failed to illuminate (although the switches seemed to work).  Unfortunately, there are a lot of annunciator lights powered by DC Bus 3, so you may not get a good indication of what's going on. The JETT NOZZLE L message may be appearing because the associated valve position logic computer card is unpowered (?) not because the valve is in the wrong position. I don't know why the TRIM AIR message isn't present in PSX. I'll ask the programmer.

In PMDG, I'm not sure if the BRAKE LIMITER Advisory message should be there. This message appears if more than two limiters are faulty on one wheel bogey. DC Bus #3 powers one brake limiters on each bogey.

 

Cheers

JHW

[19AB67 16]

Dan and JHW, thanks for your advice.