Rolls-royce Helicon X3 P&T Control System

 Pitch Control:

The function of the pitch controller is to move the propeller blades in accordance to the control lever order. The actuator unit represents the interface between the remote control and the main servo system, which performs the actual positioning of the blades.

1.1 Normal Control

 The output from the pitch controller is computed on the basis of the input signals from pitch lever and the actuator position feedback. Lever and feedback signals are scaled and checked against adjustable limits, with corresponding alarm for exceeding the normal range. 

The levers have one set of adjustments (minimum, zero and maximum) for each manoeuvre station. Multiple sets of feedback adjustments (minimum, zero and maximum) are available for various engine power take-outs. In combined mode the lever signal is modified in a Combinator program, see chapter Pitch and RPM Combinatory (combined Control).

1.2 Backup Control 

The Backup Control system consists of closed loop control identical to the Normal Control system. The Backup Control is a separate system, and is independent of the Normal Control system. A system failure in the Normal Control system will automatically switch to and engage the Backup Control. 

Lever order signals and feedback are monitored and verified against adjustable alarm limits. If the signals exceed the limits this will release an alarm to the alarm plant and both visual and audible system failure alarm will be actuated at the manoeuvre stations.

.1.3 Backup Control Operation

 If a failure occurs on important parts of the Normal Control for the Pitch, Azimuth or RPM Control function, the control will automatically be switched over to the Backup Control system. A system failure audible and visible alarm will be activated on each of the control panels. 

The thruster control will continue to follow the lever in command and transfer is done by using the common in command buttons. The command can be transferred between all bridge position and the bridge control levers will continue to work as in normal control. 

A failure that occurs on important parts of the Backup Control for the Pitch, Azimuth or RPM Control function will not affect the Normal Control system. If a system failure occurs on the Backup Control an audible and visible alarm will be activated on each of the control panels.

.1.4 Backup Control Limitations 

The Backup Control system has only interface to the control levers. The Backup Control system does not have interface to External Control systems like Dynamic positioning systems, Joysticks or Autopilots.

1.5 Pitch Indication 

The Pitch Indication system is independent of the Normal Pitch Control system by means of separate transmitters and electronic circuits. The pitch indicators are connected in series and are driven from the Backup Control system.

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