CaptainSandL
14th Nov 2004, 17:15
I was discussing the flat/failed battery in-flight with someone recently that seemed to raise more questions than we could answer. These were our conclusions:
Identification:
A flat battery will probably be noticed by an IRS DC FAIL light on the classics, since there is no failed battery light. There is a BAT DISCHARGE on the NG’s but the QRH does not give much help other than to say that you have 60 mins of standby power, which we knew anyway. Clocks will stop.
Consequences:
The hot battery bus would become unpowered so you would lose all fire protection, hence the APU if running would auto shutdown!
The QRH does not have a failed battery checklist (although BAT DISCHARGE is close). Surely if the above consequences are correct it should be in the QRH, perhaps with a recommendation to land at the nearest suitable airport.
Other things to throw into the melting pot include the clocks, they would also lose power so would you lose time data in the FMC? Will this be the case for both classics & NG’s since the NG FMC gets its time data from the GPS? What will losing time data do to VNAV & LNAV?
Why doesn’t the battery charger (NG) hold up the voltage to all the various battery busses when the battery has failed and if the Main Battery fails will the Aux Battery continue to power the batt busses as normal?
Any answers or experiences would be most enlightening.
S & L
Identification:
A flat battery will probably be noticed by an IRS DC FAIL light on the classics, since there is no failed battery light. There is a BAT DISCHARGE on the NG’s but the QRH does not give much help other than to say that you have 60 mins of standby power, which we knew anyway. Clocks will stop.
Consequences:
The hot battery bus would become unpowered so you would lose all fire protection, hence the APU if running would auto shutdown!
The QRH does not have a failed battery checklist (although BAT DISCHARGE is close). Surely if the above consequences are correct it should be in the QRH, perhaps with a recommendation to land at the nearest suitable airport.
Other things to throw into the melting pot include the clocks, they would also lose power so would you lose time data in the FMC? Will this be the case for both classics & NG’s since the NG FMC gets its time data from the GPS? What will losing time data do to VNAV & LNAV?
Why doesn’t the battery charger (NG) hold up the voltage to all the various battery busses when the battery has failed and if the Main Battery fails will the Aux Battery continue to power the batt busses as normal?
Any answers or experiences would be most enlightening.
S & L