ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT

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AUDIO SWITCHING 12.23.20-9

AUDIO SWITCHING

ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT

ELEC DC ESS BUS FAULT  SUBJECT: ATA 23 - LOSS OF DIGITAL AMU IN CASE OF DC ESSENTIAL BUS BAR LOSS 1. PURPOSE  The purpose of this OIT is to inform all Airbus operators using aircraft fitted with TEAM digital AMU of the loss of all audio communications in case of a failure of the DC essential Bus.  All analog AMUs (AMU PN other than the above listed affected PN) are not affected by this issue.  A review of the electrical failure events since A320 entry into service was performed. Events involving DC ESS BUS loss that cannot be recovered before landing remain very remote. As a result, the certification requirements of the digital AMU remain fulfilled.  A FCOM TR has been issued to warn pilot about the loss of communication (Ref.C document)

ELEC DC ESS BUS FAULT  a- An automatic transfer of the AC&DC ESS BUS in case of AC BUS 1 loss: This will allow shortening the 90 to 120 seconds average transfer time to 3 seconds only. Hence, the audio communications will also be recovered within 3 seconds.  b- A manual recovery of the AMU power supply through the audio switch 16RN if DC ESS BUS is permanently lost:  Airbus has developed a modification that consists in installing two electrical relays on AMU power supply bus. These relays are controlled by the audio switch 16RN. In case of DC ESS Bus loss, an ECAM message is triggered (DC ESS BUS FAULT, USE VHF2 OR 3, SELECT AUDIO SWTG) leading the crew to select the audio switch 16RN to either ”First Officer" or "Pilot position". This ensures that the audio function is kept operative thanks to the two relays installed by the modification.

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