Essential bus procedure

[astaib]

Hello,

Just a short question because I'm not sure to understand very well what is written in the AFM about the use of the essential bus.

Can you tell me what is the procedure about the essential bus?

1/ Is it only in case of the alternator is not charging anymore?
2/ Do I have to shut down something before switching on the essential bus?
3/ Is there any breaker to trip?
4/ How long is the essential bus autonomy? 30 minutes?
5/ What are the instruments powered by the essential bus?
...

Thanks for your help.

Arnaud.

[Rich]

Section 3.7.2 seems to cover this subject quite completely, at least in the latest release of the POH. You might check you've got the most current one.

The only caveat I would add is that you really do NOT have to use the essential bus in the event of alternator failure. You could just choose to turn off this and that more selectively.

[astaib]

Hi,

Thank you.

If I understood correctly:
-Alternator failure: no bus essential, just immediate landing
-Electrical failure: bus essential ON, immediate landing

Thank you.

[Rich]

Let me be more clear.

The essential bus is a short-cut to limit potential current draw for alternator failure. But there are still uncertainties. An example is pitot heat - you still are in control whether it's drawing amps or not. And using it cuts off things you may want, such as #2 navcom and the audio panel.

Electrical system failure is a whole other ball game. It depends on what failed and its consequences. You might have no electrical power whatsoever available. Could be an electrical fire. The essential bus deal is not really designed for dealing with this.

Both scenarios do call for expeditious landing, the second more so, even to the point of maybe an off-field precautionary landing.

[astaib]

thanks for this explanation.

Arnaud.