Upper overhead maintenance switches

[jgoggi 65]

Hi, yesterday, just out of curiosity, I tried to play with the Flight Control shutoff switches and Split System breaker switch on the upper overhead panel (on the ground), but as I flipped the switches nothing happened (and no EICAS messages at all). Are they functional?

Thanks.

[Jet Tech 31]

Were you on the ground or in Flight?   Maintenance switches are not active inflight

[jgoggi 65]

Hi Paul, I remember being on the ground, anyway it was during a quick general test of the airplane, I will retry tonight. If you say that those switches are functional, then maybe I did something wrong. Thank you!

[Jet Tech 31]

They should be functional,  I will have to go back and recheck them now

[jgoggi 65]

The flight control switches work, while the SSB switch doesn't seem to work, nothing happens in any electrical condition (APU, EXT PWR, engines on), on the ground.

[jgoggi 65]

Any clue about that switch? Thanks.

[Jet Tech 31]

The SSB switch is controlled by the BCU 1 and 2.  It can only be opened or closed manually under very specific circumstances.

From the AOM Vol 2

 

SPLIT SYSTEM BREAKER Switch
Push - (spring-loaded toggle, guarded) opens or closes split system breaker
Note: Operative on ground only.

[jgoggi 65]

It can only be opened or closed manually under very specific circumstances.

 

So maybe this is the key point. Thank you!