1 EXT Power and Syncronizing Bus SSB

[fsam]

Hello Hardy, one short question if I connect for example left external power only with all engines running and IDG's on syncronizing bus, GCB's engine 1 and 2 opens but SSB is still closed meaning external power and IDG 3 and 4 supplying the syncronizing bus, same behaviour if I have only the right external power connected then engines 3 and 4 GCB's opens but SSB stays closed too. In my understanding of the system the SSB should open since no permanent paralleling of IDG and external power is allowed. If I connect both external power or using APU power everything works fine. Can you check, I have all faults set to none and tried several times. Thank you
Ralf

[Hardy Heinlin]

Hi Ralf,

thanks for the hint. I just checked the update history. This is a bug introduced with update 10.1.1 by this modification:

1.1.091. BCU logic: When just one EXT PWR is AVAIL and just one APU GEN is ON, and the EXT PWR is on the one side of the SSB and the APU GEN on the other, then setting that EXT PWR to ON will no longer open the SSB but instead disconnect that other APU GEN (when two EXT PWR are AVAIL, the logic works as usual and this modification is not applied).

I'll try to fix it in version 10.29.


Regards,

|-|ardy

[fsam]

Hello Hardy thanks for your fast respond, one additional idea regarding single external power, if IDG's supplying power and APU is not running and single external power will be connected and switched on this source will take over the whole network and causes the BCU 1 and 2 to open all GCB's and closing the SSB. If both external power lines are connected with IDG's running and APU off, the external power connect side will open the GCB's and the SSB too, but this works very well. Please check also the situation during engine start with only one external power connected (and APU off), here the first IDG with closed GCB will take over the whole network.
Best regards
Ralf

[Hardy Heinlin]

Hi Ralf.

In my understanding of the system the SSB should open since no permanent paralleling of IDG and external power is allowed.

I agree: Permanent paralleling of IDG and external power is not allowed.

However, re "SSB should open" I disagree because in our scenario the opposite EXT PWR is not available. I think, in this case, instead of opening the SSB, the four GCBs should open. Here's a quote from a maintenance book:

When external power is applied to an airplane being powered by IDGs on both sides of the synch bus and both external power sources are available, the SSB is tripped first, followed by the adjacent GCBs. If opposite external power is not available, the SSB is not tripped, but the four GCBs are.

Cheers,

|-|ardy

[fsam]

Hello Hardy, you are right SSB stay closed and all GCB opens in case of single external power activation.
However I'm glad to have such a outstanding simulater for home-use - and trying to use two external power connections all the time to avoid confusion...
Best regards
Ralf

[Hardy Heinlin]

Thanks for the compliment :-) By the way, I just implemented the single-EXT logic in the single-APU case as well. I guess nobody has noticed this detail so far because for the single-APU case you need to trip an APU field with that toggle switch on the overhead maintenance panel which no pilot has ever touched probably -- neither in PSX nor on the real ship.

to avoid confusion...

Don't you use APU power on the real aircraft after landing before you change to EXT power at the gate? Do you sometimes connect external power while the engines are running, and never start the APU?


Cheers,

|-|ardy

[John H Watson]

Don't you use APU power on the real aircraft after landing before you change to EXT power at the gate? Do you sometimes connect external power while the engines are running, and never start the APU?

Some airlines have at least trialled this, but it seems pointless. You're not saving fuel because the engines are running longer (while external power is being connected). You're also slowing down the disembarkation, unloading, etc and impeding traffic on roads behind the aircraft. Whilst you may save on APU hours and start cycles, it's a selfish procedure.

Of course, when the APU is U/S, it has to be done.

[fsam]

Hello Hardy, in former times I heard the statement external power should be used since the airlines have already paid for. But I know the case without APU operation is mostly the case if  APU or APU GEN are INOP, regarding the GCB and the GCR switches I have an idea of it (resetting the field relay inside the GCU) but it seems to be a very special case, also glad to see this in the simulation. So at the end, my question for single external power feeding was more theoretical than is will be used during normal operation.
Best redgards
Ralf

[Hardy Heinlin]

The SSB logic is now modified in PSX 10.29:

http://aerowinx.com/board/index.php?topic=4191.0


Regards,

|-|ardy

[fsam]

Hello Hardy, this was fast, I have tried in several conditions, one single source is providing electrical power as expected, thanks for the quick solution.
Best regards
Ralf