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The multiplex umbilical cables provided the electrical power and
communication to the pods. The electrical power originated from power and
communication cabinets located on the surface. The cabinet has a dedicated
uninterruptable power supply that provided electrical power to subsea systems
for a minimum of two hours if main power from the rig was interrupted or
removed. There were control panels on the rig that would allow the rig crew to
send emergency disconnect commands to the subsea equipment. The commands
were transferred to the BOP stack through control pods that were connected to
the rig by multiplex umbilical cables.
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D. Automatic Mode Function (“Deadman”)

The automatic mode function (“AMF”) or “deadman” system is designed
to close the BSR in the event that the LMRP suffers the loss of electrical power,
the loss of fiber‐optic communication with the rig, and the loss of hydraulic
pressure from the rig. The accumulator bottles located on the lower BOP stack
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provided the hydraulic power for the AMF. The step‐by‐step AMF sequence
for the Deepwater Horizon is in Appendix H.

The AMF relied upon two redundant control pods – a blue pod and a
yellow pod. Under normal operations, the pods were powered through AC
cables from the surface. In the event of a loss of power from the surface, the
power supply for each of the control pods was maintained through batteries
located in the subsea electronics module (“SEM”) in the multiplex section of each
pod. The pods were located on opposite sides of the LMRP. Each functioned
independently and each had its own power supply and batteries. Each pod
included solenoid valves, which were devices that opened and closed in
response to electrical signals. The solenoids were designed to communicate with
the BOP elements and trigger the delivery of 4,000 psi closing pressure to the
BSRs through the dedicated accumulator bottles located on the lower BOP stack.

E. Autoshear Function

The autoshear function is designed to close the BSR in the event of an
unplanned disconnect of the LMRP from the lower BOP stack. A poppet valve

333 Id.
334 Id. The AMF is usually designed for events such as the riser parting. If the riser parts at the
lower flex joint or some other part of the riser system, the AMF sequence is designed to activate
to seal the well.

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