There is RAT for Blue electric pump and PTU between G and Y EDPs and also electric pump for Yellow. The ECAM philosophy for the use of redundancy is same. They are only available if the main pump produces low pressure. They are to be switched off if the low pressure is due to reservoir low level and the system is lost. In case of reservoir overheat or reservoir air low pressure they are switched off till the condition disappears and then an attempt is suggested to recover the system.
The general logic is G and Y are main systems so their loss the system tries to recover, subject to conditions mentioned above automatically through PTU. In case PTU has a problem Yellow services are recovered through Yellow electric pump. Green having too many services is only recoverable through PTU. If not then services are lost. In case of single hydraulic B failure, since it doesn't have many services and the complications of unretractable RAT it's not recovered through RAT but taken as lost. Only in case of dual hydraulic failure ECAM tells you to recover the B through RAT. to bring it to single failure.
Last edited by vilas; 22nd Sep 2021 at 10:33.