7.5.1 Except as provided in paragraph 7.5.18,
units should be provided with a main steering gear and an auxiliary
steering gear to the satisfaction of the Administration. The main
steering gear and the auxiliary steering gear should be so arranged
that a single failure in one of them so far as is reasonable and practicable
will not render the other one inoperative.
7.5.2 The main steering gear should be of adequate
strength and sufficient to steer the unit at maximum service speed
and this should be demonstrated. The main steering gear and rudder
stock should be so designed that they will not be damaged at maximum
astern speed but this design requirement need not be proved by trials
at maximum astern speed and maximum rudder angle.
7.5.3 The main steering gear should, with the
unit at its deepest seagoing draught, be capable of putting the rudder
over from 35° on one side to 35° on the other side with the
unit running ahead at maximum service speed. The rudder should be
capable of being put over from 35° on either side to 30° on
the other side in not more than 28 s, under the same conditions.
7.5.4 The main steering gear should be operated
by power where necessary to fulfil the provisions of paragraph 7.5.3
and in any case in which the Administration would require a rudder
stock of over 120 mm diameter in way of the tiller.
7.5.5 The main steering gear power unit or units
should be arranged to start automatically when power is restored after
a power failure.
7.5.6 The auxiliary steering gear should be of
adequate strength and sufficient to steer the unit at navigable speed
and capable of being brought speedily into action in an emergency.
7.5.7 The auxiliary steering gear should be capable
of putting the rudder over from 15° on one side to 15° on
the other side in not more than 60 s with the unit at its deepest
seagoing draught while running at one half of its maximum speed ahead
or seven knots, whichever is the greater.
7.5.8 The auxiliary steering gear should be operated
by power where necessary to fulfil the provisions of paragraph 7.5.7,
and in any case in which the Administration would require a rudder
stock of over 230 mm diameter in way of the tiller.
7.5.9 Where the main steering gear comprises two
or more identical power units an auxiliary steering gear need not
be fitted if the main steering gear is capable of operating the rudder
in accordance with the provisions of paragraph 7.5.3 while operating
with all power units. As far as is reasonable and practicable the
main steering gear should be so arranged that a single failure in
its piping or in one of the power units will not impair the integrity
of the remaining part of the steering gear.
7.5.10 Control of the main steering gear should
be provided both on the navigating bridge and in the steering gear
compartment. If the steering gear control system which provides for
control from the navigating bridge is electric, it should be supplied
from the steering gear power circuit from a point within the steering
gear compartment.
7.5.11 When the main steering gear is arranged
according to paragraph 7.5.9 two independent control systems should
be provided, each of which can be operated from the navigating bridge.
Where the control system comprises a hydraulic telemeter, the Administration
may waive the provisions for a second independent control system.
7.5.12 Where the auxiliary steering gear is power
operated, it should be provided with a control system operated from
the navigating bridge and this should be independent of the control
system for the main steering gear.
7.5.13 Means should be provided in the steering
gear compartment to disconnect the steering gear control system from
the power circuit.
7.5.14 A means of communication should be provided
between the navigating bridge and:
7.5.15 The exact angular position of the rudder,
if power operated, should be indicated on the navigating bridge. The
rudder angle indication should be independent of the steering gear
control system.
7.5.16 The angular position of the rudder should
be recognizable in the steering gear compartment.
7.5.17 An alternative power supply, sufficient
at least to supply a steering gear power unit which complies with
the provisions of paragraph 7.5.7 and also its associated control
system and the rudder angle indicator, should be provided, automatically,
within 45 s, either from the emergency source of electrical power
or from another independent source of power located in the steering
gear compartment. This independent source of power should be used
only for this purpose and should have a capacity sufficient for 10
min of continuous operation.
7.5.18 Where a non-conventional rudder is installed,
or where a unit is steered by means other than a rudder, the Administration
should give special consideration to the steering system so as to
ensure that an acceptable degree of reliability and effectiveness,
which is based on paragraph 7.5.1, is provided.