Section 4 Performance

4.1.1 Main and auxiliary steering gear for rudder-type steering systems are to meet the performance requirements in Vol 2, Pt 6, Ch 1, 4.2 Performance requirements for rudder-type steering systems. Steering performance on ships fitted with podded propulsion systems is to comply with Vol 2, Pt 4, Ch 4, 5.6 Steering system in addition to the requirements of this Chapter, as applicable. Steering performance on ships fitted with steerable water jet systems is to comply with Vol 2, Pt 4, Ch 2, 3.7 Nozzle/steering systems in addition to the requirements of this Chapter, as applicable. Steering performance on ships fitted with azimuth thruster systems is to comply with Vol 2, Pt 4, Ch 3, 4.2 Azimuth thrusters in addition to the requirements of this Chapter, as applicable.

4.1.2 Unless the main steering arrangements for ship directional control comprise two or more identical power units, in accordance with Vol 2, Pt 6, Ch 1, 4.2 Performance requirements for rudder-type steering systems 4.2.1, every ship is to be provided with main steering arrangements, or two or more identical steering actuating systems, and auxiliary steering arrangements in accordance with the requirements of the Rules. The main and auxiliary steering arrangements are to be so arranged that the failure of one of them will not render the other one inoperative.

4.1.3 Main and auxiliary steering gear power units are to be:

1. Arranged to re-start automatically when power is restored after power failure.

2. Capable of being brought into operation from each steering position. In the event of a power failure to any one of the steering gear power units, an audible and visual alarm is to be given at each steering position.

3. Arranged so that transfer between units can be readily effected.

4.1.4 Where the steering arrangements are such that more than one power or control system can be simultaneously operated, the risk of hydraulic locking caused by a single failure is to be considered.

4.1.5 A means of communication is to be provided between the navigating bridge and the steering gear compartment.

4.1.6 Steering gear, other than of the hydraulic type, will be accepted provided the standards are considered equivalent to the requirements of this Section.

4.1.7 Manually operated gears are only acceptable when the operation does not require an effort exceeding 16 kg under normal conditions.

4.2.1 The main steering gear is to be:

1. Of adequate strength and capable of putting the rudder over from 35° on one side to 35° on the other side with the ship at its deep operational draught and running ahead at maximum ahead service speed and under the same conditions, from 35° on either side to 30° on the other side in not more than 28 seconds, which shall be demonstrated in accordance with Vol 2, Pt 1, Ch 3, 16.4 Testing;

2. Operated by power where necessary to meet the requirements of Vol 2, Pt 6, Ch 1, 4.2 Performance requirements for rudder-type steering systems 4.2.1.(a) and in any case when the Rules excluding strengthening for navigation in ice, require a rudder stock over 120 mm diameter in way of the tiller; and

3. So designed that they will not be damaged at maximum astern speed; however, this design requirement need not be proved by trials at maximum astern speed and maximum rudder angle.

4.2.2 The auxiliary steering gear is to be:

1. Capable of steering the ship at navigable speed and of being brought speedily into action in an emergency; and

2. Of adequate strength and capable of putting the rudder over from 15° on one side to 15° on the other side in not more than 60 seconds with the ship at its deep operational draught and running ahead at one half of the maximum ahead service speed or 7 knots, whichever is the greater; and

3. Operated by power where necessary to meet the requirements of Vol 2, Pt 6, Ch 1, 4.2 Performance requirements for rudder-type steering systems 4.2.2.(b) and in any case when the Rules, excluding strengthening for navigation in ice, require a rudder stock over 230 mm diameter in way of the tiller.

4.3.1 Power-operated steering gears are to be provided with positive arrangements, such as limit switches, for stopping the gear before the rudder stops are reached. These arrangements are to be synchronised with the gear itself and not with the steering gear control.