3.1.2 An automatic
and a manual control system are to be provided and arranged to operate
independently, so that failure in one system will not render the other
system inoperative. Arrangements for manual control are to satisfy
the requirements of Pt 7, Ch 4, 2 Class notation DP(CM) when
the automatic system is inoperative.
3.1.3 At least
two position reference systems suitable for the intended service conditions
and incorporating different measurement techniques, are to be provided
and arranged, so that a failure in one system will not render the
other system inoperative. Special consideration will be given where
the use of different techniques would not be practicable during DP
operations.
3.1.4 At least
two heading reference sensors and two wind sensors are to be provided
and arranged, so that a failure of one sensor will not render the
other sensor(s) inoperative.
3.1.5 In the
event of a single failure of a position reference, heading reference,
or wind sensor, the control systems are to continue operating on signals
from the remaining sensors without manual intervention.
3.1.6 The
area of operation is to be adjustable, but is not to exceed the specified
limits based on a percentage of water depth, or as applicable, a defined
absolute or relative surface movement. Arrangements are to be provided
to fix and identify the set point for the area of operation .