JT/T 258-2021 English PDF (JTT258-2021)

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JT/T 258-2021: Criteria of manoeuvability for transport ship in Yangtze River
JT/T 258-2021
TRANSPORT INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 47.060
CCS U 14
Replacing JT/T 258-2004
Criteria of manoeuvability for transport ship in Yangtze
River
ISSUED ON: JUNE 18, 2021
IMPLEMENTED ON: OCTOBER 01, 2021
Issued by: Ministry of Transport of PRC
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions... 5 
4 Manoeuvability criteria ... 6 
5 Test methods and numerical values ... 8 
Criteria of manoeuvability for transport ship in Yangtze
River
1 Scope
This document specifies the index form and value of the manoeuvability criteria for
transport ships sailing on the main line of the Yangtze River, the principle of criterion
value selection, the test method, the determination of the value.
This document is applicable to transport ships (except high-speed ships), which are
sailing on the main line of the Yangtze River (Yunnan Shuifu to Wusongkou).
2 Normative references
There are no normative references in this document.
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Directional stability
The ability of the ship to automatically stabilize on a new course, without the need
for steering equipment, such as steering and thrusters, after the interference is
eliminated.
3.2
Straight line stability
The ability of the ship, to maintain the ability to navigate in a straight line, without
the need for steering equipment, such as steering and thrusters, after the interference
is eliminated.
3.3
Course-keeping ability
The ability of a ship to maintain its course, by relying on steering equipment, such
as steering and thrusters.
4.1.1.1 The form of the manoeuvability criteria for a motorized single ship includes four
performances: directional stability, course-changing ability, steady-turning ability,
astern stopping ability.
4.1.1.2 The form of the manoeuvability criteria of the fleet includes five performances:
directional stability, course-changing ability, steady-turning ability, astern stopping
ability, astern stability.
4.1.2 The form of directional stability index
In the initial state of constant ship speed AND the heading direction is basically
consistent with the water flow direction, use the course-changing amount (ΔC0) of
sailing for 3 minutes in the state of zero rudder angle OR the average steering angle (δ0)
of maintaining the course for 5 minutes, as the criterion index.
4.1.3 The form of course-changing ability index
In the initial state of constant ship speed and stable heading, the single motor ship shall
be subject to the Z-shaped test, according to the specified rudder angle; use the yawing
index (P') as the criterion index.
In the initial state of constant speed and stable heading, the fleet steers according to the
specified rudder angle AND changes direction by 15°; take the average direction change
angular velocity ( ), from the first move to the direction change of 15°, as the
criterion index.
4.1.4 The form of steady-turning ability index
When the ship is in the state of constant driving, steady speed, full rudder, steady-
turning, in wide and slow-flowing waters, use the ratio ( ) -- of the diameter (D0) of
the arc motion trajectory at the ship's center of gravity TO the length (L) of the ship, --
as the criterion index.
4.1.5 The form of astern stopping ability index
The ship is in a wide, slow-flowing water area, from the state of constant driving at a
steady speed to the state of reversing at 70% of the rated speed of the main engine; take
the ratio -- of the stroke (Ah) to the ship's length ( ), -- from the start of the command
to reverse to the stop of the ship's forward movement, as the criterion index.
4.1.6 The form of astern stability index
When the ship sails downstream, in the initial state of parking at a low speed and the
heading is stable, it drives back and steer the ship in a steady direction for 3 minutes;
5.1.2 Linear stability test or steering stability test
5.1.2.1 Test principle
The ship sails at 0° rudder angle for 3 minutes, to continuously measure the change of
the heading direction. OR keep the heading direction for 5 min, to continuously measure
the change of the steering angle, as relative to time.
5.1.2.2 Test requirements
5.1.2.2.1 The ship test is carried out, in a straight channel, which has smooth water flow
and stable flow velocity. During the test, the forward and reverse wind force shall be
less than Beaufort level 3; the cross wind force shall be less than Beaufort level 2.
5.1.2.2.2 Generally, driving against the current shall prevail. If necessary, two to three
repeated tests can be carried out.
5.1.2.2.3 Before starting the test, the ship is to maintain a constant speed, a stable course,
AND be parallel to the direction of the water flow.
5.1.2.2.4 The difference in rotational speed of each propeller in ships, which have two
or more propellers, is to be less than 1% of the rated rotational speed.
5.1.3 Course-changing ability test
5.1.3.1 Test principle
The motorized single ship and the fleet respectively conduct Z-shaped tests, according
to the specified rudder angle, to completely measure the time-varying curve of the
rudder angle and heading angle, including the overtaking angle, the delay time of
turning, the position of the characteristic point.
5.1.3.2 Test requirements
5.1.3.2.1 The ship test is to be carried out in a wide and straight channel, which has
smooth water flow and stable flow velocity. The wind force during the test shall be less
than Beaufort level 3.
5.1.3.2.2 The test is generally based on reverse current driving. When conditions permit,
it can be tested under two driving conditions: forward and reverse current.
5.1.3.2.3 Before starting the test, the ship is to maintain a constant speed, a stable course,
AND be basically parallel to the direction of the water flow.
5.1.3.2.4 For a motorized single ship, during the test, firstly turn the rudder to +10° and
keep it. When the heading angle changes to +10°, immediately reverse the rudder angle
to -10° and keep it. When the heading angle changes to -10°, turn the rudder to +10°
and keep it. When the heading angle changes to +10°, reverse the rudder angle to -10°
and keep it, until the heading angle change to -10°.
5.1.3.2.5 For the fleet, during the test, firstly turn the rudder to +20° and keep it. When
the heading angle changes to +15°, immediately reverse the rudder angle to -20° and
keep it. When the heading angle changes to -15°, turn the rudder to +20° and keep it.
When the heading angle changes to +15°, reverse the rudder angle to -20° and keep it,
until the heading angle changes to -15°.
5.1.3.2.6 The difference between the rotational speeds of each propeller, in ships which
have two or more propellers, is to be less than 1% of the rated rotational speed.
5.1.4 Turning test
5.1.4.1 Test principle
When the rudder is full, continuously measure the corresponding delay, ship position,
course, ship speed at each moment after each 30° change, in the heading direction of
0°, 10°, 20°, 30°, until 540°.
5.1.4.2 Test requirements
5.1.4.2.1 The ship test is to be carried out in a wide slow-flow area, which has a water
depth greater than 2 times the ship's draught; the wind force during the test is less than
Beaufort level 3.
5.1.4.2.2 The initial speed of each turning test shall be the same, general...