TL;DR — The main steering gear must move the rudder 35°-to-30° in no more than 28 seconds at maximum ahead service speed; the auxiliary must move it 15°-to-15° in no more than 60 seconds at half speed or 7 knots, whichever is greater. Both systems must be separate and independent so that failure of one cannot render the other inoperative.
What the Rule Says
Scope of Part 58
Title 46 CFR Part 58 governs the design and construction of main and auxiliary machinery installed on vessels 46 CFR §58.01-1. Within that part, Subpart 58.25 addresses steering gear specifically, and Subpart 58.30 addresses fluid power transmission and control systems that serve steering apparatus and a range of other critical shipboard equipment 46 CFR §58.30-1.
Definitions You Must Know
The regulations draw sharp distinctions between terms that exam questions routinely conflate 46 CFR §58.25-5:
Steering gear (complete system) — all machinery, power actuating systems, control systems, and ancillary equipment necessary for moving the rudder.
Main steering gear — the machinery, power actuating systems, and means of applying torque to the rudder stock (tiller or quadrant) necessary for steering in normal service.
Auxiliary steering gear — equipment, other than any part of the main steering gear, necessary to steer the vessel in case of failure of the main steering gear. A tiller, quadrant, or other component serving the same purpose is explicitly excluded from this definition.
Power actuating system — the hydraulic equipment that applies torque to the rudder stock, including rudder actuators, steering-gear power units, and all pipes, valves, fittings, linkages, and cables transmitting power to the actuators.
Control system — the equipment by which orders for rudder movement are transmitted from the pilothouse to the steering-gear power units, including transmitters, receivers, feedback devices, hydraulic servo-control pumps, hunting gear, and all associated gearing, piping, shafting, cables, and circuitry.
Full followup control — closed-loop (feedback) control that relates helm position to a specific rudder angle, automatically stopping the rudder when the selected angle is reached.
Maximum ahead service speed — the greatest speed the vessel is designed to maintain in service at sea at the deepest loadline draft.
Maximum astern speed — the speed estimated to be attainable at maximum designed power astern at the deepest loadline draft.
Quick-acting valve — a ball, plug, spool, or similar valve with a handle connected for quick manual operation.
General Requirements for Steering Gear
Every self-propelled vessel must carry both a main steering gear and an auxiliary steering gear, arranged so that failure of one will not render the other inoperative and so that transfer from main to auxiliary can be effected quickly . Steering gear must be separate and independent of all other shipboard systems, with three narrow exceptions: electrical switchboards from which they are powered, automatic pilots and similar navigational equipment, and propulsion machinery in an integrated propulsion-and-steering system . No thruster may count as part of a vessel's required steering capability unless the vessel has an integrated propulsion-and-steering system .
On oceangoing vessels required to have power-operated steering gear (except tank vessels subject to §58.25-85(e)), arrangements must be provided for steadying the rudder both in an emergency and during a shift from one steering gear to another. On hydraulic steering gear, a suitable arrangement of stop valves in the main piping is an acceptable means of accomplishing this .
Performance Standards — Main Steering Gear
The main steering gear and rudder stock must 46 CFR §58.25-10:
1. Be of adequate strength and capable of steering the vessel at maximum ahead service speed. 2. Move the rudder from 35° on either side to 35° on the other at maximum ahead service speed and deepest loadline draft, and from 35° on either side to 30° on the other in not more than 28 seconds under the same conditions. 3. Be power-operated when necessary to meet the 28-second standard, or when the rudder stock diameter exceeds 12 centimeters (4.7 inches) in way of the tiller (excluding ice-strengthening). 4. Be designed so as not to be damaged at maximum astern speed — though this need not be proved by trials at maximum astern speed and maximum rudder angle.
Performance Standards — Auxiliary Steering Gear
The auxiliary steering gear must :
1. Be of adequate strength and capable of steering the vessel at navigable speed, and be capable of being brought speedily into action in an emergency. 2. Move the rudder from 15° on either side to 15° on the other in not more than 60 seconds with the vessel at its deepest loadline draft and running at one-half maximum ahead service speed or 7 knots, whichever is greater. 3. Be power-operated when necessary to meet the 60-second standard, or when the rudder stock diameter exceeds 23 centimeters (9 inches) in way of the tiller (excluding ice-strengthening).
No auxiliary steering gear is required on a double-ended ferryboat with independent main steering gear fitted at each end .
When Auxiliary Gear May Be Omitted
When the main steering gear includes two or more identical power units, no auxiliary steering gear need be fitted, provided :
- On a passenger vessel: the main gear can meet the 28-second standard with any one power unit not operating.
- On a cargo vessel: the main gear can meet the 28-second standard with all power units operating.
- For installations completed on or after September 1, 1984 (international voyages) or after June 9, 1995 (any vessel): after a single failure in the hydraulic piping or in one power unit, the defect can be isolated so that steering capability is maintained or speedily regained in less than ten minutes.
Vessels of 70,000 gross tons or over must have two or more identical power units in the main steering gear .
Steering-Gear Control Systems
Every power-driven steering-gear system must have at least one steering-gear control system 46 CFR §58.25-70. Key requirements:
- The main steering gear must be operable from the pilothouse and must provide full followup control. Supplementary non-followup control may also be provided .
- The pilothouse transfer switch must be operated by one lever, must pass through "off" when transferring between control systems, and must prevent more than one control system from being energized at a time. Switches for each control system must be in separate enclosures or separated by fire-resistant barriers .
- Each motor controller for a steering gear must be located in the steering-gear compartment. A means of starting and stopping each steering-gear motor must also be in the steering-gear compartment .
- On vessels of 500 gross tons or above, each main and auxiliary steering gear must be operable by controls from the steering-gear compartment, and those controls must not be rendered inoperable by failure of the pilothouse controls .
- When the auxiliary steering gear is power-driven, its control system in the pilothouse must be separate and independent from the main steering gear control system (though the steering wheel or lever need not be duplicated) .
Fluid Power Systems
The fluid power regulations of Subpart 58.30 apply to steering apparatus (main and auxiliary, including bow thruster systems), watertight door operating systems, cargo hatch operating systems, automatic propulsion boiler control systems, starting systems for internal combustion engines used for main propulsion or auxiliary power, centralized control systems, lifeboat handling equipment, controllable pitch propeller systems, all systems containing a pneumatic or hydropneumatic accumulator, and all pneumatic power and control systems with a maximum allowable working pressure exceeding 150 psig, among others .
Inspection Requirements
At each inspection for certification and at each periodic inspection, the marine inspector must test and inspect main propulsion and auxiliary machinery and associated equipment, including fluid control systems, as necessary to verify safe operation. Remote controls for stopping machinery driving forced and induced draft fans, fuel oil transfer pumps, fuel oil unit pumps, and ventilation fans serving machinery and cargo spaces must be tested at each regular inspection for certification and periodic inspection 46 CFR §61.20-3.
Subchapter T Vessels
For vessels subject to 46 CFR Part 182 (Subchapter T), all machinery and equipment must be suitable for the vessel and its intended operation, and must be installed and maintained to afford adequate protection against fire, explosion, machinery failure, and personnel injury 46 CFR §182.100. Auxiliary machinery of the internal combustion piston type must comply with Part 182 provisions; steam or gas turbine auxiliary machinery receives separate consideration under Subchapter F. Heating boilers must be tested or examined every three years 46 CFR §182.310.
Why It Matters on the Exam
Exam questions on this topic almost always test one of three things: (1) the specific rudder-angle and time limits for main versus auxiliary steering gear, (2) the rudder-stock diameter thresholds that trigger mandatory power operation, or (3) the location requirements for motor controllers and local steering-gear controls. The 28-second / 35°-to-30° standard for the main gear and the 60-second / 15°-to-15° standard for the auxiliary gear are the most frequently tested numbers. The 500 GT threshold for mandatory local (steering-gear compartment) controls is also a reliable exam item.
Common Pitfalls
Confusing the angle standards. The main gear must traverse 35°-to-35° (full swing) and 35°-to-30° in 28 seconds. The auxiliary must traverse only 15°-to-15° in 60 seconds. Candidates often mix up which standard applies to which gear.
Misidentifying the speed basis for auxiliary gear. The auxiliary gear performance is measured at one-half maximum ahead service speed or 7 knots, whichever is greater — not simply at half speed.
Assuming a thruster counts as steering. Unless the vessel has an integrated propulsion-and-steering system, no thruster counts toward required steering capability 46 CFR §58.25-5.
Forgetting the rudder-stock diameter thresholds. Power operation of the main gear is required when the stock exceeds 12 cm (4.7 in); for the auxiliary, the threshold is 23 cm (9 in). These are different numbers and both appear on exams.
Placing motor controllers in the pilothouse. Every motor controller for a steering gear must be in the steering-gear compartment, not the pilothouse 46 CFR §58.25-70.
Overlooking the 500 GT local-control requirement. On vessels of 500 GT or above, local controls in the steering-gear compartment must be independent of pilothouse control failures .
Quick Check
What is the maximum time allowed for the main steering gear to move the rudder from 35° on one side to 30° on the other, and under what conditions is this measured?
28 seconds, with the vessel at its deepest loadline draft and running at maximum ahead service speed. 46 CFR §58.25-10
What rudder movement and time limit applies to the auxiliary steering gear?
From 15° on either side to 15° on the other in not more than 60 seconds, with the vessel at its deepest loadline draft and running at one-half maximum ahead service speed or 7 knots, whichever is greater.
At what rudder-stock diameter does power operation of the main steering gear become mandatory?
When the diameter of the rudder stock exceeds 12 centimeters (4.7 inches) in way of the tiller, excluding strengthening for navigation in ice.
Where must each motor controller for a steering gear be located?
In the steering-gear compartment. 46 CFR §58.25-70
On a vessel of 500 gross tons or above, what additional requirement applies to steering-gear controls?
Each main and auxiliary steering gear must be operable by controls from the steering-gear compartment, and those controls must not be rendered inoperable by failure of the controls in the pilothouse.
Under what condition may a vessel omit the auxiliary steering gear entirely?
When the main steering gear includes two or more identical power units and meets the applicable performance criteria (differing for passenger versus cargo vessels), and — for qualifying installations — after a single failure, steering capability can be maintained or speedily regained in less than ten minutes. A double-ended ferryboat with independent main steering gear at each end is also exempt.
What remote-control systems must be tested at each regular inspection for certification and periodic inspection?
Remote controls for stopping machinery driving forced and induced draft fans, fuel oil transfer pumps, fuel oil unit pumps, and fans in ventilation systems serving machinery and cargo spaces. 46 CFR §61.20-3