MCA Oral Preparation
Module 34 Steering Gear Infographic
Detailed visual study notes for steering gear regulations, control logic, Safematic redundancy, local backup and emergency steering checks.
Module
34
Sections
8
Focus
35-30
Focus
SOLAS II-1
Module purpose
A structured steering gear crib sheet for EOOW, Second and Chief Engineer oral preparation. It links SOLAS II-1 Reg. 29/30 requirements to practical machinery operation, emergency steering and Class-controlled repair decisions.
Navigation
Module 34 • Section 1
1. Steering Gear as a Safety-Critical Closed Loop
System chain
Bridge wheel/tiller/autopilot or DP sends a demanded angle. The control system converts this to pump stroke, valve command or electric steering drive command. Actuators move the rudder or pod. Feedback measures actual angle and stops the command at the demanded angle.
Oral trap
Do not describe only “two rams” or “four rams”. Always include command, control, power, actuator, feedback, indication, alarms, local/emergency operation and remaining capability after failure.
35-30 explanation
The final few degrees approaching set point are controlled by follow-up feedback. Pump stroke/valve command reduces to prevent overshoot and hunting, so SOLAS proves time to 30°, not the deliberately slowed final approach to 35°.
Examiner-safe phrase
“The steering gear is a closed-loop positioning system. The bridge orders an angle, the pump or drive moves the actuator, feedback reduces the command as actual rudder angle approaches demand, and independent indication confirms what the rudder or pod actually did.”
Module 34 • Section 2
2. SOLAS II-1 Regulation 29 - Core Requirements
Main steering
Main steering and rudder: adequate strength, able to steer the ship at maximum ahead service speed, capable of putting the rudder from 35° on one side to 35° on the other, and under the same conditions at deepest seagoing draught from 35° on either side to 30° on the other in not more than 28 s.
Auxiliary steering
Auxiliary steering: adequate strength, capable of steering at navigable speed, brought speedily into action, and capable of putting the rudder from 15° on one side to 15° on the other in not more than 60 s with the ship at deepest seagoing draught and running ahead at one half of maximum ahead service speed or 7 knots, whichever is greater.
Redundancy
Main and auxiliary gear must be arranged so failure of one does not make the other inoperative. Duplicated main gear can be accepted if the capability and single-failure isolation requirements are met.
Module 34 • Section 3
3. System Types - What to Compare
Two-ram hydraulic
Two double-acting rams act on a tiller/crosshead. Discuss duplicated pumps, telemotor/electro-hydraulic control, relief valves, isolations, feedback, ram seals and local steering.
Four-ram hydraulic
Four cylinders act through crossheads on a two-arm tiller. High torque and practical split-system redundancy. Be ready to explain which valves isolate a leaking ram/line and what capability remains.
Rotary vane
Compact gear where oil pressure acts on vanes in a housing to rotate the stock. Advantages: compact, smooth, high torque. Disadvantages: internal leakage and seal repair complexity.
Module 34 • Pump Detail
3A. Swashplate and Hele-Shaw Pumps - How They Control Steering
Swashplate / axial piston pump
A rotating cylinder block carries pistons parallel to the drive shaft. The pistons bear on an angled swashplate, so shaft rotation makes them reciprocate. Changing swashplate angle changes piston stroke and pump delivery. In neutral, zero angle gives no delivery. Tilting the plate in the opposite direction reverses flow.
Hele-Shaw variable-delivery pump
This classic steering pump uses a floating ring or cam ring with radial pistons. When the ring is centred there is no effective piston stroke and the pump is neutral. Offsetting the ring creates piston stroke and delivery; offset in the opposite direction reverses the flow. More offset means greater stroke and more oil delivery.
How steering control is achieved
In both systems the helm order acts through follow-up or hunting gear to stroke the pump. As the rudder stock moves, mechanical or electro-hydraulic feedback progressively destrokes or recentres the pump. This slows the final approach, avoids overshoot and hunting, and holds the rudder at the demanded angle without continuous unnecessary pumping.
Examiner-safe swashplate line
“A swashplate pump is a variable-displacement axial piston pump. The swashplate angle controls piston stroke and therefore oil delivery. Follow-up feedback reduces that angle as actual rudder angle approaches the ordered angle, so the rudder slows and stops accurately at the set point.”
Examiner-safe Hele-Shaw line
“A Hele-Shaw pump is a classic variable-delivery steering pump. Offset of the floating ring creates piston stroke and oil flow, while hunting gear and rudder feedback recentre the ring as the rudder reaches the ordered angle. That is how it provides follow-up steering rather than continuous uncontrolled pumping.”
Module 34 • Section 4
4. Azipod / Podded Steering and Local Backup
Thrust-vector steering
The pod rotates the propulsion thrust rather than deflecting a separate rudder. Steering failure can therefore be a propulsion/manoeuvring failure as well as a steering failure.
Local Backup Unit
A stand-alone local HSI provides steering backup non-follow-up control, steering alarm/fault indication, propulsion backup control and propulsion alarm/fault indication. It is for emergency or severe remote-control failure/maintenance.
Local operator rule
Use communication discipline: bridge order, repeat, press/hold correct rotation command, observe mechanical/independent angle, stop at order, report actual angle. Never assume automatic follow-up locally.
Module 34 • Section 5
5. Safematic / Single Failure Philosophy
Objective
Any single failure should be detected and prevented from causing total loss of steering. Failed power unit/drive/pipe section should be tripped, isolated or segregated and steering maintained or speedily regained.
Hydraulic leak route
Inform bridge, start/confirm standby unit, isolate defective section by approved valves, contain oil, monitor level and pressure, reduce speed/helm load and continue with healthy system if capability remains.
Electrical fault route
Confirm bridge alarms, identify affected power/control supply, use alternate control/power route, avoid disabling the healthy system and document fault/repair.
Module 34 • Section 6
6. Protections and Alarms
Hydraulic
Relief valves on isolated pressure sections; oil cleanliness arrangements; low-level alarms; storage tank capacity; pressure/temperature monitoring; filter condition; leakage detection.
Electrical
Power units restart automatically when power is restored; bridge audible/visual alarm for power failure; independent control systems where required; short-circuit protection only on control supply circuits; separation of circuits/cables/pipes.
Indication
Actual rudder angle must be independent of the steering control demand and visible on bridge; actual angle must also be recognisable locally for emergency steering.
Module 34 • Section 7
7. Departure and Emergency Checklist
Before departure
Test both pumps/power units, main and alternative bridge controls, full movement, hard-over alarms/limits as applicable, rudder angle indicators, local control, communications and records.
Emergency steering
Establish bridge-local communication, use repeat-back orders, operate local/non-follow-up control, report actual angle, keep personnel clear of moving rams/tiller and reduce ship speed if required.
Records
Log test time, systems used, faults, corrective actions, personnel and any restriction. Steering defects affecting capability/redundancy require Master/company/Class/Flag route per SMS.
- Both steering pumps/power units running and stopped as required
- Steering from main bridge position and alternative control position
- Full port/starboard movement and matching independent angle indication
- Alarms: power failure, low level/leakage and control supply/fault as fitted
- Bridge - steering flat communications including backup method
- Local/emergency steering control demonstrated and logged
Module 34 • Section 8
8. Damage, Repair and Class Considerations
Feedback or hunting-gear error
Can give wrong amidships or hunting. Verify independent/local angle and only adjust by approved procedure. Retest bridge and local control and log the correction.
Rudder stock/tiller damage
Do not treat structural twist as a routine alignment fault. Reduce load, verify indicators, avoid heavy helm, notify Master and arrange Class-approved inspection/repair.
Drydock links
Rudder drop/jump, carrier bearing wear, pintle clearance, hollow rudder water ingress, tiller/key security and stock alignment all affect steering capability and Class acceptance.