This chapter has been developed on the assumption that the fitting and operation of
stabilization systems is most applicable to the ground effect mode. Where a craft is
fitted with hydrodynamic stabilization control systems within the meaning of chapter 16
of the 2000 HSC Code, that system should comply with the requirements of that Code.
Where conflict exists between the aerodynamic meaning of terms used in this chapter and
the marine terminology used elsewhere in these Guidelines, the aerodynamic meaning is
intended to be followed.
15.1 Definitions
15.1.1 Stabilization system is a system intended to stabilize the main parameters
of the craft's attitude: roll, flight trim, pitch, heading and altitude and control the
craft's motions: roll, pitch, yaw and heave. This term excludes devices not associated
with the safe operation of the craft. The main elements of a stabilization system may
include the following:
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.1 devices such as rudders, foils, flaps, skirts, fans, tilting and steerable
propellers, pumps for moving fluids;
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.2 power drives actuating stabilization devices; and
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.3 stabilization equipment for accumulating and processing data for making
decisions and giving commands such as sensors, logic processors and automatic
safety control.
15.1.2 Stabilization device means a device listed in 15.1.1.1 with the aid of
which forces for controlling the craft's attitude are generated.
15.1.3 Automatic safety control is a logic unit for processing data and making
decisions to put the craft into the displacement or other safe mode if a condition
impairing safety arises.
15.1.4 Automatic control system is a system which enables the craft's heading
and/or altitude to be maintained without operator input.
15.2 General Requirements
15.2.1 Stabilization systems should be so designed that, in case of failure or
malfunctioning of any one of the stabilization devices or equipment, it would be
possible either to ensure maintaining the main parameters of the craft's motion within
safe limits with the aid of working stabilization devices or to put the craft into the
displacement or other safe mode.
15.2.2 In case of failure of any automatic equipment or stabilization device, or of its
power drive, the parameters of craft motion should remain within safe limits.
15.2.3 Craft fitted with an automatic stabilization system should be provided with an
automatic safety control unless the redundancy in the system provides equivalent safety.
Where an automatic safety control is fitted, provision should be made to override it and
to cancel the override from the main operating station.
15.2.4 The parameters and the levels at which any automatic safety control activates to
decrease speed and put the craft safely in the displacement or other safe mode should
take account of the demonstrated safe values of altitude, roll, flight trim, pitch, yaw
and associated accelerations appropriate to the particular craft and service; also to
the possible consequences of power failure for propulsion, lift or stabilization
devices.
15.2.5 The parameters and the degree of stabilization of the craft provided by an
automatic stabilization system should be demonstrated to be satisfactory, having regard
to the purpose and service conditions of the craft.
15.2.6 The SSA specified in part C should include analysis of any stabilization system
applying to the craft. Such analysis should be implemented by systematic process to
secure sufficient reliability.
15.3 Longitudinal and Height Control Systems
15.3.1 Craft fitted with an automatic stabilization system should be provided with an
automatic safety control unless the redundancy arrangements are such that this control
is not required by 15.2.3. Foreseeable malfunctions should have only minor effects on
automatic control system operation and should be capable of being readily counteracted
by the operating crew.
15.3.2 The parameters and levels at which any automatic safety control activates to
decrease speed and put the craft safely into the displacement or other safe mode should
take account of the safety levels and of the safe values of motions appropriate to the
particular craft and service.
15.4 Demonstrations
15.4.1 The limits of safe use of any of the stabilization control system devices should
be based on demonstrations and a verification process in accordance with chapter 16 and
annex 8.
15.4.2 Demonstration in accordance with chapter 16 and annex 8 should determine any
adverse effects upon safe operation of the craft in the event of an uncontrollable total
deflection of any one control device. Any limitation on the operation of the craft as
may be necessary to ensure that the redundancy or safeguards in the systems provide
equivalent safety should be included in the craft operating manual.