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UNCLASSIFIED
MINISTRY OF NATIONAL DEFENCE
PORTUGUESE NAVY
SHIP MANAGEMENT
BUILDING DEPARTMENT
- SHIPBUILDING DIVISION
STABILITY CRITERIA FOR THE BUS AND
UAM'S OF THE PORTUGUESE NAVY
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ITDINAV 802
-MINISTRY OF NATIONAL DEFENCE PORTUGUESE NAVY
SHIP MANAGEMENT
BUILDING DEPARTMENT
- SHIPBUILDING DIVISION
STABILITY CRITERIA FOR THE PORTUGUESE NAVY'S BUS AND UAMS
ITDINAV 802(A)
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ITDINAV 802
SHIP MANAGEMENT
BUILDING DEPARTMENT
- SHIPBUILDING DIVISION
Lisbon, 16th September 1996
LETTER FROM PROMULGATION
1. ITDINAV 802 is an unclassified publication.
2. Extracts from this publication may be made without the permission of the
promulgating authority.
3. ITDINAV 802 was prepared by the Shipbuilding Division, Buildings Department,
Ship Directorate
4. This revision of ITDINAV 802 repeals the previous version of 10 March 1996.
THE DIRECTOR OF SHIPS
Manuel Beirão Martins Guerreiro
CMG ECN
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LIST OF DISTRIBUTION
INTERNAL:
Research
Logistics Information
Construction Department, Shipbuilding
Department1 copy
Department1 copy
Maintenance Department1 copy
Division2 copies
EXTERNAL:
Arsenal do
Alfeite3 copies
Transport Directorate1 copy
Navy1 copy
Naval School1 copy
Squadron1 copy
Ocean Escort Squadron1 copy
Division1 copy
Flotilla1 copy
Fault Clearance School1 copy
Institute1 copy
Material Services1 copy
Directorate General of the
Patrol
Navy Staff - 4th
G2EA /
Hydrographic
Superintendence of
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CHANGE LOG
IDENTIFICATION OF THE
CHANGE OR CORRECTION
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DATE ON WHICH IT
WAS CARRIED
OUT
IV
WHO CARRIED IT OUT
(SIGNATURE, RANK, UNIT)
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REFERENCES
1. Sarchin, T.H. and Goldberg, L.L., (1962), Stability and Buoyancy Criteria for
U.S. Naval Surface Ships, Transactions SNAME, SNAME
2. Design Data Sheet DDS079-1, (1975), Stability and Buoyancy of U.S. Naval
Surface Ships, Department of the Navy, Naval Ship Engineering Centre, USA
3. Naval Engineering Standard NES109, (1989), Issue 3, Stability Standards for
Surface Ships, Sea Systems Controllerate, Procurement Executive, MoD,
Foxhill, Bath, United Kingdom
4. ITESTMAT 801, (1990),
Definition of the fluctuation bands of the BU's and
Navy UAM's, Studies Office, Directorate-General of Naval Material
5. SOLAS, (1986), International Convention for the Safety of Life at Sea,
International Maritime Organization, London
6. Resolution A.749(18), (1993), Code on Intact Stability for all Types of Ships
Covered by IMO Instruments, International Maritime Organization, London
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ITDINAV 802
INDEX
Letter of promulgation
II
Distribution list
III
Recording of amendments
IV
References
V
Index
VI
Section 1 - General Provisions
1.1
1.1. Introduction
1.1
1.2. Growth margin policy
1.2
Section 2 - Scope
2.1
2.1. Definition of the classes and categories of ships
2.1
2.2. Definition of the application of the criteria
2.2
Section 3 - Common calculation methodologies and definition of
3.1
loading conditions
3.1. Common calculation methodologies
3.1
3.1.1. Correction of liquid mirrors in tanks
3.1
3.1.2. Determining the centroid of the sail area
3.2
3.2. Definition of loading conditions
3.4
3.2.1. Light condition
3.4
3.2.2. Minimum port displacement (Light Harbour condition)
3.5
3.2.3. Minimum operating displacement (Light Seagoing condition)
3.6
3.2.4. Loaded displacement (Deep condition)
3.8
3.2.5. Unballasted laden voyage from port
3.9
3.2.6. Ballast shift on departure from port
3.11
3.2.7. Displacement with cargo, without ballast on arrival at port
3.13
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3.2.8. Ballast shifting on arrival at port
3.15
Section 4 - Intact Stability Criterion for Warships
4.1
4.1. Requirements of the intact righting lever bend
4.1
4.2. Stability under wind
4.2
4.2.1. Definition of conditions
4.2
4.2.2. Determination of the inclining arm
4.3
4.2.3. Criterion
4.6
4.3. Stability under ice and wind
4.6
4.3.1. Definition of conditions
4.6
4.3.2. Criterion
4.7
4.4. Yawing stability at high speeds
4.8
4.4.1. Definition of conditions
4.8
4.4.2. Determination of the tilting moment
4.8
4.4.3. Criterion
4.9
4.5. Stability under lifting and transshipment of heavy loads
4.10
4.5.1. Definition of conditions
4.10
4.5.2. Determination of the tilting moment
4.11
4.5.3. Criterion
4.11
4.6. Stability when moving the trim to an edge
4.12
4.6.1. Definition of conditions
4.12
4.6.2. Determination of the tilting moment
4.13
4.6.3. Criterion
4.13
4.7. Stability in port
4.14
4.7.1. Definition of conditions
4.14
4.7.2. Criterion
4.14
4.8. Stability during docking
4.15
4.8.1. Definition of conditions
4.15
4.8.2. Criterion
4.15
Section 5 - Damage stability criteria for warships
5.1
5.1. Definition of conditions
5.1
5.1.1. Watertight subdivision criteria
5.1
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5.1.2. Extent of damage to living works
5.2
5.1.2.1. Longitudinal extension
5.2
5.1.2.2. Transverse extension
5.2
5.1.2.3. Vertical Extension
5.3
5.1.3. Loading conditions considered
5.3
5.1.4. Permeability of flooded compartments
5.4
5.2. Straightening and tilting arm (wind) bends at fault
5.4
5.3. Criterion
5.5
Section 6 - Intact Stability Criterion for Auxiliary Ships and
6.1
UAM's
6.1. Definition of conditions
6.1
6.2. Requirements of the intact righting lever bend
6.1
6.3. Stability under wind
6.4
6.3.1. Definition of conditions
6.4
6.3.2. Determining the inclination arms
6.4
6.3.3. Criterion
6.8
6.4 Stability under wind and ice
6.8
6.4.1. Definition of conditions
6.8
6.4.2. Criterion
6.9
6.5. Yawing stability at high speeds
6.9
6.5.1. Definition of conditions
6.9
6.5.2. Determining the tilting moment
6.10
6.5.3. Criterion
6.11
6.6. Stability under crowding of the trim on one edge
6.11
6.6.1. Definition of conditions
6.11
6.6.2. Determination of the tilting moment
6.12
6.6.3. Criterion
6.12
6.7. Stability during docking
6.13
6.7.1 Definition of conditions
6.13
6.7.2. Criterion
6.13
Section 7. - Damage stability criteria for auxiliary vessels
7.1
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and UAM's
7.1. Definition of conditions
7.1
7.1.1. Watertight subdivision criteria
7.1
7.1.2. Extent of damage to living works
7.2
7.1.2.1. Longitudinal extension
7.2
7.1.2.2. Transverse extension
7.3
7.1.2.3. Vertical Extension
7.3
7.1.2.4. Minor Damages
7.3
7.1.3. Loading conditions considered
7.4
7.1.4 Permeability of flooded compartments
7.4
7.2. Breakdown of straightening and tilting arm curves
7.5
7.2.1. Crowding of passengers on one side
7.5
7.2.2. Simultaneous launching of all loaded life-saving appliances on one
7.5
side
7.2.3. Wind pressure
7.6
7.3. Criterion
7.6
Section 8. - Stability Criteria for Tugs (Not available)
---
Section 9. - Stability Criteria for Floating Dock
9.1.
9.1 Definition of conditions
9.1.
9.2 Criteria
9.1.
Section 10 - Stability Criteria for Small Craft (Not available)
---
Section 11. - Stability Criterion for Sailboats (Not available)
---
Section 12 - Stability Criteria for Support Vessels
---
Beaconing (Not available)
Section 13. - Intact and Faulty Stability Criteria for
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Barges and pontoons
13.1. Intact stability for barges and pontoons
13.1
13.1.1. Definition of conditions
13.1
13.1.2. Criterion
13.2
13.2. Damage stability for barges and pontoons
13.3
13.2.1. Definition of conditions
13.3
13.2.2. Criterion
13.3
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1. GENERAL PROVISIONS
1.1. Introduction
The publication of the present stability criteria aims to define the basic stability
requirements to which the Portuguese Navy's surface units and UAM's must obey.
Any multi-hull, aerostatically or hydrodynamically sustained vessels, or
exceptional cases of monohulls, which due to their operational nature may require a
specific and detailed stability analysis, shall be investigated separately, considering the
most unfavourable circumstances, the stability criteria being defined on a case-by-case
basis. For example, catamarans, "Small Waterplane Twin Hulls" (SWATH's), trimarans,
hydrofoils, and surface effect ships (SES's) are considered to be multi-hull, aerostatically
or hydrodynamically sustained ships.
Regardless of the stability criteria, the designer must use engineering judgement
to assess whether the ship has adequate stability or not. It must be emphasised that the
verifications and criteria defined herein represent the minimum acceptable. Any
additional verifications should be made whenever deemed appropriate, as the specific
characteristics of each ship should be taken into account. As mentioned in the previous
paragraph, the criteria have been defined for monohulls, and may not be appropriate for
multihulls, aerostatic or hydrodynamic lift ships.
The use of computer programmes to assist in stability analysis should be preceded
or followed by a check on their validity and capacity, particularly if they have not been
previously approved.
1.2. Margin policy of growth
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In the case of new designs, the stability criteria shall be met in full at the end of
construction without any operational limitations such as net loading restrictions. The
intact and damage stability criteria have to be met including an allowance for the weight
increase that is likely to occur before the next stability verification of the ship and an
allowance for the vertical variation of the centre of gravity (CG). In the absence of
concrete elements about the magnitude of this weight increase, the following values
should be used:
• Warships (for every 10 years)
5% increase in loaded displacement;
3% increase in VCG height in the light displacement condition.
• Auxiliary and passenger ships (for every 12 years)
3% increase in light displacement;
3% increase in VCG height in the light displacement condition.
• Other supply vessels operating in coastal waters or in port
(for every 20 years)
5% increase in light displacement;
3% increase in VCG height in the light displacement condition.
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2. FIELD OF APPLICATION
2.1. Definition of the classes and categories of ships
For the definition of the criteria to be applied, it is considered that surface vessels
are divided into two classes, and within these into several categories, namely:
1 - Naval Units (BU's)
A - Oceanic
A.1. - Ships expected to suffer all the direct effects of extreme
conditions (e.g. tropical cyclones). This category includes ships
moving as part of amphibious and assault forces.
A.2. Ships expected to avoid the direct effects of extreme
conditions (e.g. tropical cyclones).
B - Coastal
B.1. Ships expected to suffer all the direct effects of extreme
conditions (e.g. tropical cyclones).
B.2. Ships that are expected to avoid the direct effects of extreme
conditions (e.g. tropical cyclones), but remain at sea in all other
weather states.
B.3. Ships that will berth in protected harbours or anchorages if
winds in excess of Force 8 are forecast, and harbour craft.
2 - Navy Auxiliary Units (UAM's)
A - All, with the exception of the cases listed under B.
B - Special Cases
B.1. Tugboats
B.2. Floating Docks
B.3. Small craft (including lifeboats)
B.4. Sailboats
B.5. Buoyage Support Vessels
B.6. Barges and pontoons
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2.2. Definition of the application of the criteria
Sections 1, 2, and 3 of the publication apply to all types of surface vessels (except
sailing ships), with regard to general definitions, the distribution of vessels by class, and
the definition of loading conditions.
Sections 4 and 5 apply to all categories of warships, including ocean-going and
coastal. Ocean warships (Category A.1.) are defined as all corvettes, frigates, destroyers,
cruisers and battleships. Other ships such as platforms for air operations (e.g. aircraft
carriers, helicopter carriers), amphibious and assault ships (e.g. LHA, LPD) are also
included in this category. In the specific case of the MP, to date, and by way of example,
the following classes of ships are considered to be included in this category:
• FFAH's "Vasco da Gama
• FF's "Comandante João Belo
• FC's "Baptista de Andrade
• FC's "João Coutinho
Coastal warships (Category B.2.) are defined as all patrol vessels, dive support
vessels, mine action vessels and landing craft. In the specific case of the MP, at present,
and by way of example, the following classes of ships are considered included in this
category:
• PC's "Cacine"
• Limpopo CP's
• MCMV "Ribeira Grande
• LDG's "Bombarda
Coastal warships (Category B.3.) are defined as all surveillance craft. In the
specific case of the MP, at present, and as an example, the following classes of vessels are
considered included in this category:
• FPB "Argos"
• FPB "D.Aleixo"
• FPB "Andorinha" (Swallow)
Sections 6 and 7 apply to all categories of auxiliary vessels, namely ocean-going,
coastal and port-based, and all Category A UAMs. Auxiliary ships include refuellers and
hydrographic ships. In the specific case of MP, at present, and as an example, the
following units are considered to be included in the category of auxiliary vessels:
• NRP "Bérrio
• NRP "Almeida Carvalho
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• NRP "Andromeda
Section 8 applies to all BUs and UAMs that are designed specifically for the
purpose of towing, whether or not this is their primary function.
Section 9 applies only to floating docks.
Section 10 applies to all small craft. Lifeboats are considered included within this
criterion.
Section 11 applies specifically to all sailing vessels. At present, and by way of
example, the following units are encompassed within this criterion:
• NE "Sagres".
• UAM "Creoula"
• NE "Polar"
• NE "Vega"
Section 12 applies to all vessels carrying out buoyage support activities. At
present, and by way of example, the following units are encompassed within this
criterion:
• NRP "Schultz Xavier
• UAM "Guide"
Section 13 applies to all UAM's which are used as barges for
cargo transport or as floating mooring pontoons.
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3.
ITDINAV 802
METHODOLOGIES OF
DEFINITION
CALCULATION METHODS COMMON
E
OF LOADING CONDITIONS
3.1. Common calculation methodologies
3.1.1. Correction of liquid mirrors on tanks
The initial metacentric height (GM) and the righting lever curves should be
corrected, taking into account the effect of the liquid mirrors on the tanks, according to
the following assumptions:
• Tanks assumed to be partially filled should be those which produce the greatest
liquid mirror effect (Mfs ) at a heeling angle of 30° when they are at 50% of
their total capacity.
• The values of Mfs for each tank can be obtained from the formula:
M fs 
where
Mfs - is the momentum of the liquid mirror at any angle of heel, in ton.meter;
v - is the total capacity of the tank, in cubic metres;
b - is the maximum mouth of the tank, in metres;
- is the specific weight of the liquid contained in the tank, in cubic metres.tonne;
v
- is the total fineness coefficient of the tank, defined by ;
blh
h - is the maximum height of the tank, in metres;
- is the heeling angle, in degrees;
l - is the maximum length of the tank, in metres;
k - is the dimensionless coefficient to be determined from the following formulas,
based on the value of
b
h
:


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co


si

ta


1

tan2 
2
co
2


b
,

cot 2

h
,
b
h
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• Small tanks meeting the condition
vb
0.01 m
min
where
min
- is the minimum displacement of the ship, in tons.
using a value of k corresponding to 30º, should not be included in the
calculations;
• The residual liquid in the empty tanks should not be accounted for in
the calculations.
3.1.2. Determination of the centroid of the area
The determination of the vertical position of the centroid of the ship's sail area should
be carried out in accordance with the following procedure:
• Consider the longitudinal profile of the ship, from the waterline (corresponding
to the loading condition considered) to the top of the highest mast, dividing it
into n bands parallel to the waterline with a height of 1 metre (in the case of
areas of substantially irregular geometry, the height of these bands may be
reduced to 0.5 m to improve the accuracy of the calculation);
• Determine the sail area of each of the n lanes of the ship's longitudinal profile,
An ;
• In practical terms, the centroid height of each strip, zn , should be assumed to
be approximately located at half height, except in exceptional cases of areas
with irregular geometry where the determination of the centroid height of the
strip considered should be made in an exact manner;
• The vertical position of the centroid of the ship's sail area, hAV , is obtained
from
n
hAV i 1
Ai
. zi
n
Ai
i1
where
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Ai - is the area of each of the horizontal strips considered;
zi - is the height above the reference considered (usually the water line) of each of the
horizontal strips considered;
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3.2. Definition of the conditions of loading
3.2.1. Light displacement (Light condition)
The light displacement condition is defined as corresponding to the complete ship
with all her effects, including spares and tools, with liquids in the piping impossible to
pump, but without fuel, fresh water, lubricating oil, ammunition, provisions and
consumable materials in the respective bunkers, air, cargo, passengers, crew and baggage.
In this condition of loading the tanks, storerooms, and other items shall be as described in
detail in Tables 3.1.
Tank/Circuit
Load
Fuel, reserve
Fuel, plywood
Fuel, service
Fuel, cargo
Empty
Empty
Service level
Empty
Food water, main
Water feeding, auxiliaries
Water food, reserve
Water feeding, recovery
95%
95%
Empty
Empty
Aviation fuel, reserve
Empty
Lubricating oil, spare
Lubricating oil, service
Lubricating oil, drain
Empty
Service level
Empty
Freshwater
Empty
Miscellaneous, purges
Empty
Ballast
Empty
Circuits, Freshwater
Circuits, Sea water
Circuits, Miscellaneous
100%
100%
Service level
Table 3.1. - Definition of net loads in the light displacement condition
3.2.2. Minimum port displacement (Light Harbour condition)
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The minimum displacement in port condition is defined as adding to the light
displacement condition, the weights relating to the complete crew and their baggage, and
to the percentages of the capacity of the ballast, fuel, lubricating oil, fresh water and
consumable tanks necessary to assure the minimum requirements demanded by the
stability criteria. Passengers, cargo, aircraft and ammunition may be included in the
weights to be added, or not, adopting the condition that results in the most penalizing
situation in terms of stability. In this loading condition the tanks, storages, and other
items shall be as described in detail in Tables 3.2 and 3.3.
Tank/Circuit
Load
Fuel, reserve
Fuel, plywood
Fuel, service
Fuel, cargo
CN
CN
Service level
CN
Food water, main
Water feeding, auxiliaries
Water food, reserve
Water feeding, recovery
95%
95%
CN
CN
Aviation fuel, reserve
CN
Lubricating oil, spare
Lubricating oil, service
Lubricating oil, drain
95%
Service level
Empty
Freshwater
CN
Miscellaneous, purges
Empty
Ballast
CN
Circuits, Freshwater
Circuits, Sea water
Circuits, Miscellaneous
100%
100%
Service level
CN - As required by the liquid loading conditions to satisfy the stability criterion.
Table 3.2. - Definition of net loads in the minimum port displacement condition
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Stores/Miscellaneous
Load
Equipment bunkers
50%
Food Stores
10%
Various
Aircraft on board
PC
Assault group personnel
Vehicle assault group
Ammunition assault group
Ammunition
PC
PC
PC
PC
Trim
100%
PC - The worst case scenario is considered
Table 3.3. - Definition of solid loads in the minimum port displacement condition
3.2.3. Minimum operating displacement (Light Seagoing condition)
The minimum operational displacement condition is defined as adding to the light
displacement condition, the weights relating to the complete garrison and respective
baggage, 95% of the ballast tank capacity, and the percentages of the fuel, lubricating oil,
fresh water and consumable tank capacity necessary (and not less than 10%) to ensure the
minimum requirements demanded by the stability criterion. Passengers, cargo, aircraft
and ammunition may be included in the weights to be added, or not, adopting the
condition that results in the most penalizing situation in terms of stability. In this loading
condition, tanks, storages, and other items should be as described in detail in Tables 3.4
and 3.5.
Tank/Circuit
Load
Fuel, reserve
Fuel, plywood
Fuel, service
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100% (comb.)
Service level
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Fuel, cargo
CN
Food water, main
Water feeding, auxiliaries
Water food, reserve
Water feeding, recovery
95%
95%
CN
CN
Aviation fuel, reserve
CN
Lubricating oil, spare
Lubricating oil, service
Lubricating oil, drain
95%
Service level
Empty
Freshwater
CN
Miscellaneous, purges
Empty
Ballast
95%
Circuits, Freshwater
Circuits, Sea water
Circuits, Miscellaneous
100%
100%
Service level
CN - As required by the liquid loading conditions to satisfy the stability criterion.
Table 3.4. - Definition of net loads in the minimum operational displacement condition
Stores/Miscellaneous
Load
Equipment bunkers
50%
Food Stores
10%
Various
Aircraft on board
PC
Assault group personnel
Vehicle assault group
Ammunition assault group
Ammunition
PC
PC
PC
PC
Trim
100%
PC - The worst case scenario is considered
Table 3.5. - Definition of solid loads in the condition of minimum operational displacement
3.2.4. Displacement loaded (Deep condition)
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The laden condition is defined as adding to the light displacement condition, the
weights relating to 95% of the fresh water tanks capacity, 95% of the fuel and lubricating
oil tanks capacity, the total capacity of provisions, ammunition, and consumable materials
in the respective stores, cargo, passengers and also the weight of the complete garrison
and their baggage. In this loading condition the tanks, storerooms and other items shall be
as described in detail in Tables 3.6 and 3.7.
Tank/Circuit
Load
Fuel, reserve
Fuel, plywood
Fuel, service
Fuel, cargo
95%
100% (comb.)
Service level
95%
Food water, main
Water feeding, auxiliaries
Water food, reserve
Water feeding, recovery
95%
95%
95%
95%
Aviation fuel, reserve
95%
Lubricating oil, spare
Lubricating oil, service
Lubricating oil, drain
95%
Service level
95%
Freshwater
95%
Miscellaneous, purges
Empty
Ballast
Empty
Circuits, Freshwater
Circuits, Sea water
Circuits, Miscellaneous
100%
100%
Service level
Table 3.6. - Definition of net loads in the loaded displacement condition
Stores/Miscellaneous
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Load
Equipment bunkers
100%
Food Stores
100%
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Various
Aircraft on board
100%
Assault group personnel
Vehicle assault group
Ammunition assault group
100%
100%
100%
Ammunition
100%
Trim
100%
PC - The worst case scenario is considered
Table 3.7. - Definition of solid loads in the loaded displacement condition
3.2.5. Shipment with cargo, without ballast, departing from port
The laden, unballasted sailing condition at port departure applies only to
Auxiliary Ships and UAM's, and is defined as adding to the light sailing condition, the
weights of all homogeneously distributed cargo, 95% of the fresh water tanks capacity,
95% of the fuel and lubricating oil tanks capacity, total capacity of provisions and
consumables in the respective stores, passengers and also the weight of the complete
garrison and respective luggage. In this loading condition the tanks, storerooms and other
items shall be as described in detail in Tables 3.8 and 3.9.
Tank/Circuit
Load
Fuel, reserve
UNCLASSIFIED
95%
9
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ITDINAV 802
Fuel, plywood
Fuel, service
100% (comb.)
Service level
Food water, main
Water feeding, auxiliaries
Water food, reserve
Water feeding, recovery
95%
95%
95%
95%
Aviation fuel, reserve
95%
Lubricating oil, spare
Lubricating oil, service
Lubricating oil, drain
95%
Service level
95%
Freshwater
95%
Miscellaneous, purges
Empty
Ballast
Empty
Load
100%
Circuits, Freshwater
Circuits, Sea water
Circuits, Miscellaneous
100%
100%
Service level
Table 3.8. - Definition of net loads in the laden, unballasted, displacement condition at departure
port
Stores/Miscellaneous
Load
Load
100%
Equipment bunkers
100%
Food Stores
100%
Various
Aircraft on board
UNCLASSIFIED
100%
10
ORIGINAL
(Blank verso)
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ITDINAV 802
Assault group personnel
Ammunition assault group
100%
100%
Ammunition
100%
Passengers
100%
Trim
100%
Table 3.9. - Definition of the solid loads in the laden, unballasted, displacement condition at departure
port
3.2.6. Ballast shift at departure from port
Ballasted sailing condition at port departure applies only to Auxiliary Ships and
UAM's and is defined as adding to the light load condition the weights relating to the
liquid ballast necessary to meet the requirements of stability and structural integrity, 95%
of the capacity of the fresh water tanks, 95% of the capacity of the fuel and lubricating oil
tanks, the total capacity of provisions and consumables in the respective stores,
passengers and also the weight of the complete crew and their baggage. In this loading
condition the tanks, storerooms and other items shall be as described in detail in Tables
3.10 and 3.11.
Tank/Circuit
Load
Fuel, reserve
Fuel, plywood
Fuel, service
UNCLASSIFIED
95%
100% (comb.)
Service level
11
ORIGINAL
(Blank verso)
UNCLASSIFIED
ITDINAV 802
Food water, main
Water feeding, auxiliaries
Water food, reserve
Water feeding, recovery
95%
95%
95%
95%
Aviation fuel, reserve
95%
Lubricating oil, spare
Lubricating oil, service
Lubricating oil, drain
95%
Service level
95%
Freshwater
95%
Miscellaneous, purges
Empty
Ballast
CN
Load
Empty
Circuits, Freshwater
Circuits, Sea water
Circuits, Miscellaneous
100%
100%
Service level
CN - As required by the liquid loading conditions to satisfy the stability criterion
Table 3.10. - Definition of net loads in ballast displacement condition at port departure
Stores/Miscellaneous
Load
Load
Empty
Equipment bunkers
100%
Food Stores
100%
Various
Aircraft on board
UNCLASSIFIED
100%
12
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ITDINAV 802
Assault group personnel
Ammunition assault group
100%
100%
Ammunition
100%
Passengers
100%
Trim
100%
Table 3.11. - Definition of solid cargoes in ballast displacement condition at port departure
3.2.7. Shifting with cargo, without ballast on arrival at port
The laden, unballasted condition on arrival in port applies only to UAM's and
Auxiliary Ships and is defined as adding to the light displacement condition, the weights
of all homogeneously distributed cargo, 10% of the fresh water tanks capacity, 10% of
the fuel and lubricating oil tanks capacity, 10% of the total capacity of provisions and
consumable materials in the respective storerooms, passengers and also the weight of the
complete crew and respective luggage. In this loading condition the tanks, storerooms and
other items shall be as described in detail in Tables 3.12 and 3.13.
Tank/Circuit
Load
Fuel, reserve
Fuel, plywood
Fuel, service
UNCLASSIFIED
10%
100% (comb.)
Service level
13
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(Blank verso)
UNCLASSIFIED
ITDINAV 802
Food water, main
Water feeding, auxiliaries
Water food, reserve
Water feeding, recovery
95%
95%
10%
95%
Aviation fuel, reserve
95%
Lubricating oil, spare
Lubricating oil, service
Lubricating oil, drain
10%
Service level
95%
Freshwater
10%
Miscellaneous, purges
Empty
Ballast
Empty
Load
100%
Circuits, Freshwater
Circuits, Sea water
Circuits, Miscellaneous
100%
100%
Service level
Table 3.12 - Definition of net loads in the loaded displacement condition, without ballast, at
arrival in port
Stores/Miscellaneous
Load
Load
100%
Equipment bunkers
100%
Food Stores
10%
Various
UNCLASSIFIED
Aircraft on board
100%
Assault group personnel
Ammunition assault group
100%
100%
Ammunition
100%
14
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Passengers
100%
Trim
100%
Table 3.13. - Definition of the solid loads in the loaded, unballasted, on arrival displacement condition
to the port
3.2.8. Ballast shifting on arrival at port
Ballast sailing condition on arrival in port applies only to Auxiliary Ships and
UAM's, and is defined as adding to the light sailing condition, the weights relating to the
ballast necessary to comply with the stability and structural integrity requirements, 10%
of the fresh water tanks capacity, 10% of the fuel and lubricating oil tanks capacity, 10%
of the total capacity of provisions and consumable materials in the respective stores,
passengers and also the weight corresponding to the complete garrison and respective
luggage. In this loading condition the tanks, storerooms and other items shall be as
described in detail in Tables 3.14 and 3.15.
Tank/Circuit
Load
Fuel, reserve
Fuel, plywood
Fuel, service
10%
100% (comb.)
Service level
Food water, main
Water feeding, auxiliaries
Water food, reserve
Water feeding, recovery
UNCLASSIFIED
95%
95%
10%
95%
15
ORIGINAL
(Blank verso)
UNCLASSIFIED
ITDINAV 802
Aviation fuel, reserve
95%
Lubricating oil, spare
Lubricating oil, service
Lubricating oil, drain
10%
Service level
95%
Freshwater
10%
Miscellaneous, purges
Empty
Ballast
CN
Load
Empty
Circuits, Freshwater
Circuits, Sea water
Circuits, Miscellaneous
100%
100%
Service level
CN - As required by the liquid loading conditions to satisfy the stability criterion
Table 3.14. - Definition of net loads in ballast displacement condition on arrival at the port
Stores/Miscellaneous
Load
Load
0%
Equipment bunkers
100%
Food Stores
10%
Various
UNCLASSIFIED
Aircraft on board
100%
Assault group personnel
Ammunition assault group
100%
100%
Ammunition
100%
Passengers
100%
16
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Trim
100%
Table 3.15. - Definition of solid cargoes in ballast displacement condition on arrival at the port
UNCLASSIFIED
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4. INTACT STABILITY CRITERION FOR WARSHIPS
4.1. Requirements of the straightening arm bend intact
The righting lever curve (GZ) should meet minimum requirements in order to
verify that its shape falls within certain pre-set limits, and thus ensure that the ship will
have the majority of the stabilising power between 0 and  .
GZ
0.3m
30º
40º
57.3º
Heeling angle (degrees)
Fig. 4.1. - Definition of the righting lever curve (GZ)
Thus, the following conditions must be met:
• The righting lever curve should end at the angle where uncontrollable flooding
occurs due to the ingress of water through permanent openings in the structure.
Examples of such structural openings are the cases of main engine intake and
exhaust ducts, engine room fan intakes and discharges, etc.
• The straightening arm curve shall comply with the criteria specified in Table
4.1.
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Area under the GZ curve from 0 to 
Area under the GZ curve from 0 to 
Area under the GZ curve from  to 
Maximum GZ
Angle of maximum GZ
GM corrected for net mirror effect
Angle of zero stability
0.08 m.rad
0.133 m.rad
0.048 m.rad
0.3 m

0.3 m
as large as
possible
( minimum
allowable in
design)
Table 4.1. - Criteria for the straightening arm curve
4.2. Stability under wind
4.2.1. Definition of conditions
It is assumed that crosswind and port-to-stern swing occur simultaneously. For
conventional ships (monohulls) a maximum port-to-stern roll angle of 25 degrees is
assumed.
The nominal wind speeds to be used are dependent on the ship category,
dependent on its application, as defined by Table 4.2.
Minimum wind speed for
design purposes (knots)
Vessel Category
UNCLASSIFIED
2
Minimum wind speed for
vessels with at least 5
years in service
(us)
ORIGINAL
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A - OCEANIC
A.1. Ships expected to suffer all the direct
effects of extreme conditions (e.g.
tropical cyclones). This category includes
ships which travel
integrated into amphibious and assault
forces
A.2. ships expected to avoid the
direct effects of extreme conditions (e.g.
tropical cyclones).
B - COASTAL
B.1. Ships expected to suffer all direct
effects of extreme conditions
(e.g. tropical cyclones).
B.2. vessels expected to avoid the direct
effects of extreme conditions (e.g.
tropical cyclones) but remaining at sea in
all other
weather states.
B.3. ships which will berth in sheltered
harbours or anchorages if winds in excess
of force 8 are expected, and
harbour craft
C - PORTO
C.1 All vessels
100
90
80
70
100
90
80
70
60
50
60
50
Table 4.2. - Nominal wind speeds
4.2.2. Determination of the inclining arm
The heeling arm due to the crosswind effect shall be determined as follows:
• Consider the longitudinal profile of the ship, from the waterline to the top of
the highest mast, dividing it into n bands parallel to the waterline with a height
of 1 metre (in the case of areas of substantially irregular geometry, the height
of these bands may be reduced to 0.5 m to improve the accuracy of the
calculation);
• Determine the sail area of each of the lanes of the ship's longitudinal profile,
and calculate the vertical position of the centroid of the ship's sail area
according to the procedure defined in 3.1.2;
• Determine the pressure exerted by the wind on each of the tracks (Pi ), using
the following expression:
Pi
UNCLASSIFIED
V2
C2g i
3
ORIGINAL
(Blank verso)
UNCLASSIFIED
ITDINAV 802
where
C - dimensionless coefficient for each type of ship. If not known, it is reasonable to
assume the expression based on the average value of C, i.e. Pi .0195.Vi 2
- air density, 1,025 kg/m ;3
g - acceleration of gravity, 9.81 m/s ;2
Vi - wind speed, knots. The nominal wind speed is assumed to occur 10 metres
above the water surface. The actual wind speed at different elevations above the
waterline shall be determined from Fig.4.2.
• Calculate the inclining arm due to the wind, using the expression:
L cos 2n
 Arm
Pi Ai
1000. i 1
where
Pi - total wind pressure in each longitudinal strip, kg/m2 ;
Ai - sail area of each longitudinal strip, m ;2
L-
defined arm between the points of midship draught to the centroid of the
ship's sailing area, as shown in Fig.4.3, m;
V - nominal wind speed, knots;
-displacement of the ship, t.
-angle of adornment, degrees;
UNCLASSIFIED
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30
25
Elevation (m)
20
Nomin.Sp al
eed
15
50
60
70
80
90
100
10
5
0
0
20
40
60
Wind speed (knots)
80
100
120
Fig. 4.2. - Wind speed variation with elevation above water surface
WIND
L
d
d/2
d = draught
Fig. 4.3. - Definition of the wind tilt arm
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4.2.3. Criterion
Based on Fig.4.4. the criteria to be met is as follows:
• The heeling angle due to the direct action of crosswind () shall not exceed 30
degrees.
• The ratio between disturbing (A2 ) and stabilising (A1 ) energy should be A1 >
1.4 A2
• The GZ value at point C shall not exceed 60% of the maximum GZ value.
GZ
Straightening arm intact
C
Tilting arm
wind
A1
A2
Angle of ornament
Uncontrollable flood angle
25º
Fig. 4.4. - Righting lever curves (GZ) and tilting moment due to
crosswind
4.3. Stability under ice and wind
4.3.1. Definition of conditions
It is assumed that icing and strong wind occur simultaneously. Stability conditions
under icing are defined as follows:
• Uniform distribution of 150 mm thickness of ice on all exposed floors, decks
and ruffs. The density of the ice should be assumed to be 950 kg/m .3
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• The weight and position of the centre of gravity (LCG, VCG, and TCG) of the
ice mass considered shall be taken into account in the calculations for
determining the righting lever curve.
• The heeling arm due to wind shall be calculated ignoring the effect of the
added area due to ice thickness but including the effect of the weight of ice on
the displacement of the ship.
• The inclination arm due to wind shall be determined as defined in 4.2.2.
• The wind slope arm calculation shall be based on a nominal wind speed equal
to 70% of the value specified in Table 4.2.
4.3.2. Criterion
Based on Fig.4.5. the criteria to be met is as follows:
• The heeling angle due to the joint action of ice and wind () should not exceed
30 degrees.
• The GZ value at point C shall not exceed 60% of the maximum GZ value.
• The ratio between disturbing (A2 ) and stabilising (A1 ) energy should be A1
> 1.4 A2
• The areas under the righting lever curve, corrected for uniform distribution
of 150 mm ice thickness, the metacentric height (GM) values, and the
maximum righting lever shall be in accordance with that specified in Table
4.3.
Area under the GZ curve from 0 to 
Area under the GZ curve from 0 to 
Area under the GZ curve from  to 
Maximum GZ
Angle of maximum GZ
GM corrected for net mirror effect
0.051 m.rad
0.085 m.rad
0.03 m.rad
0.24 m

0.15 m
Table 4.3. - Criterion for the straightening arm curve, with the combined effects of icing and
wind
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ITDINAV 802
GZ
Corrected straightening arm due
to distribution of 150 mm ice
thickness
C
Tilting arm
wind
A1
Angle of
ornament
A2
Uncontrollable flood angle
25º
Fig. 4.5. - Righting lever (GZ) curves and tilting moment due to ice
accumulation and crosswind
4.4. Yawing stability at high speeds
4.4.1. Definition of conditions
The ship is assumed to heel solely due to the action of centrifugal force arising
from high speed yaw. The assumed heeling angle does not reflect the transient behaviour
of the ship at the beginning and at the end of the heeling but when stabilised during the
heeling.
4.4.2. Determination of the inclining moment
The centrifugal force acting on a ship during a heel is expressed as
by:
 Force
wher
e
1000. V 2
gR
- displacement of the ship, t;
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ORIGINAL
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ITDINAV 802
V - linear speed of the ship during the yaw, m/s;
g-
acceleration of gravity, 9.81 m/s ;2
R - radius of gyration of the ship, m. For calculation purposes it is reasonable to assume that
R is approximately half the tactical diameter.
The heeling arm used in conjunction with the centrifugal force referred to above is
defined as the distance between the centre of gravity of the ship and the centre of lateral
resistance of the live works. This arm is a function of the cosine of the heeling angle. The
vertical position of the centre of lateral resistance of the live works is assumed at middraught.
 Arm
V2 a
co
gR
wher
e
a-
vertical distance between the centre of gravity of the ship and the centre of lateral
resistance, defined at moulded draught, with the ship unnumbered, m;
-angle of adornment, degrees.
4.4.3. Criterion
Based on Fig.4.6. the criteria to be met is as follows:
• The stabilised heeling angle due to the action of centrifugal force during
turning should not exceed 15 degrees.
• The stabilising power reserve (A) shall be greater than 40% of the total area
under the righting lever curve A > 0.4 AT , measured to the uncontrollable
flood angle.
• The GZ value at point C shall not exceed 60% of the maximum GZ value.
UNCLASSIFIED
9
ORIGINAL
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UNCLASSIFIED
ITDINAV 802
GZ
Tilting arm due to
the swerve at high speed
Straightening arm intact
C
A
15º
Angle of ornament
Uncontrollable flood
angle
Fig. 4.6. - Straightening arm curves (GZ) and tilting moment due to
yaw at high speed
4.5. Stability under lifting and transshipment of heavy loads
4.5.1. Definition of conditions
Lifting heavy loads is a particularly critical case in small ships, which for
whatever reason have to lift and load/unload weights. This operation has two
simultaneous consequences in terms of the vessel's transverse stability:
• The lifting (and possibly adding, in case of loading) of weight, acting on the
boom end of the lifting equipment/system, raises the ship's centre of gravity,
thus decreasing its righting lever;
• The transshipment of the cargo away from the ship's centreline generates a
heeling moment that will cause the ship to heel.
All possible positions of the lifting equipment/system should be considered in
this analysis.
4.5.2. Determination of the tilting moment
UNCLASSIFIED
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ITDINAV 802
For the application of the criterion, the righting lever curve is modified by
correcting the vertical position of the centre of gravity (VCG) and the displacement of the
ship, in order to quantify the effect of the weight addition considered at the place where it
will be stowed.
The slope arm curve is calculated using the expression:
wa  d 
 Arm
where
w - weight of the load, t;
a-
transverse distance from the centre line to the boom tip of the
lifting equipment/system, m;
d-
height of the lifting point above deck where cargo will be stowed, m;
- displacement, including the addition of the displaced load (w), t;
-angle of adornment, degrees.
4.5.3. Criterion
Based on Fig.4.7. the criteria to be met is as follows:
• The stabilised heeling angle due to the action of the tilting moment caused by
lifting and transferring weights should not exceed 15 degrees.
• The stabilising power reserve (A) shall be greater than 40% of the total area
under the righting lever curve A > 0.4 AT , measured to the uncontrollable
flood angle.
• The GZ value at point C shall not exceed 60% of the maximum GZ value.
• If the vessel lifts weights at sea for relatively long periods of time, the heeling
arms have to be added due to the combined effects of port-to-stern swing and
moderate wind (on the opposite side of the ship from which the cargo is lifted).
UNCLASSIFIED
11
ORIGINAL
(Blank verso)
UNCLASSIFIED
ITDINAV 802
GZ
Intact straightening arm corrected for
KG change
Tilting arm
C
A
15º
Angle of ornament
Uncontrollable flood
angle
Fig. 4.7. - Curves of righting lever (GZ) and tilting moment due to
lifting and transshipment of heavy loads
4.6. Stability under crowding of the trim on one edge
4.6.1. Definition of conditions
The movement of personnel is likely to have a major effect on the transverse
stability of small vessels carrying a relatively large number of persons on board. The
concentration of personnel on one side may produce a heeling moment such that it results
in a significant reduction in the ship's dynamic stability.
It is considered for all purposes that:
• each person occupies an available deck area equal to 0.2 m ;2
• each person has an average weight of 75 kg, not including any type of
equipment. The addition of the weight of equipment carried must be
analysed separately and in detail on a case-by-case basis.
4.6.2. Determination of the tilting moment
UNCLASSIFIED
12
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ITDINAV 802
The inclining arm produced by the transverse movement of the staff is determined
by the expression
Inclination arm
wa 
where
w - weight of personnel moved, t;
a-
transverse distance from the ship's centreline to the centre of gravity of the personnel
moved, m;
- displacement, t;
-angle of adornment, degrees.
4.6.3. Criterion
Based on Fig.4.8. the criteria to be met is as follows:
• The stabilised heeling angle due to personnel moving to an edge should not
exceed 15 degrees.
• The stabilising power reserve (A) shall be greater than 40% of the total area
under the righting lever curve A > 0.4 AT , measured to the uncontrollable
flood angle.
• The GZ value at point C shall not exceed 60% of the maximum GZ value.
UNCLASSIFIED
13
ORIGINAL
(Blank verso)
UNCLASSIFIED
ITDINAV 802
GZ
Inclining arm due to side
loading (crowding of
personnel)
Straightening arm intact
C
A
15º
Angle of ornament
Uncontrollable flood
angle
Fig. 4.8. - Straightening arm curves (GZ) and tilting moment due to
crowding of personnel at an edge
4.7. Stability in port
4.7.1. Definition of conditions
It is considered that the weather conditions in port are substantially reduced, so
that the port-to-ship balance is considered negligible, and the ship is subjected only to the
action of the wind. For all purposes it is assumed that the nominal wind speed to be
applied to the various cases is defined in Table 4.2.
The determination of the heeling moment shall be done as specified in 4.2.2.
4.7.2. Criterion
The criteria to be met are as follows:
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14
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ITDINAV 802
• The stabilised heeling angle due to the heeling moment generated by crosswind
with speed as defined in 4.7.1. shall not exceed 7 degrees.
• The corrected metacentric height should not be less than 0.15 m.
4.8. Stability during docking
4.8.1. Definition of conditions
In terms of transverse stability, the critical condition during docking occurs just
before the ship touches the blocks, where the load exerted on the ship is maximum.
The loading condition of the ship while docking is usually defined through a
docking plan. However, if this does not exist, a trim of 0.3 metres astern should be
assumed for all purposes, or a higher value if the ship cannot achieve this trim.
4.8.2. Criterion
The criteria to be met are as follows:
• The corrected metacentric height should always be positive throughout the
docking process.
UNCLASSIFIED
15
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ITDINAV 802
5. DAMAGE STABILITY CRITERION FOR WARSHIPS
5.1. Definition of conditions
The following are defined as failure situations to be considered in this criterion:
1. Structural damage resulting in flooding due to:
• Collision with the bottom resulting in moderate flooding;
• Bow thrust;
• Collision or impact with the bottom resulting in major flooding;
• Explosion by enemy action resulting in major flooding.
2. Flooding caused by:
• Crosswinds combined with port-starboard swing;
• Progressive flooding (circuit breakers, etc.);
• Fire fighting inside the ship.
The main idea behind this criterion is to ensure the survival of the ship, not
necessarily to maintain its fighting capacity.
5.1.1. Watertight compartmentalisation criterion
The basis for determining the extent of flooding is the length of hull damaged
(open to the sea) at any point along the ship's length, resulting from enemy action or
collision. In small ships, however, and due t o practical limitations, the criterion is based
on the number of flooded watertight compartments. For calculation purposes, the length
of the ship should be referred to its value between perpendiculars.
The watertight subdivision criteria should ensure that:
UNCLASSIFIED
1
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ITDINAV 802
• Vessels of less than 30 metres in length shall be able to withstand at least one
main watertight compartment flooding;
• Ships between 30 and 92 metres in length shall be able to withstand, as a
minimum, the flooding of any two adjacent main watertight compartments;
• Ships over 92 metres in length shall withstand swift flooding due to an opening
in the hull located anywhere along the length of the ship, equal in length to
15% of the length of the ship;
5.1.2. Extent of damage to living works
5.1.2.1. Longitudinal extension
In cases where the watertight subdivision is based on the number of flooded
compartments, the longitudinal extent of flooding is defined by the position of the
transverse watertight bulkheads bounding those compartments.
In cases where watertight subdivision is based on the length of hull open to the
sea, the longitudinal extent of flooding is defined by the position of watertight transverse
bulkheads immediately forward and aft of the hull opening boundaries.
5.1.2.2. Transverse extension
The maximum extent of transverse flooding is defined by the resultant damage in
transverse penetration up to the margin line, but not affecting any longitudinal
watertight bulkhead located on the margin line.
A lower transverse penetration should be assumed where this results in a flooding
situation that is more damaging in terms of stability.
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ITDINAV 802
5.1.2.3. Vertical Extension
It is assumed that all decks and platforms are not watertight, as this results in the
most adverse situation due to flooding on upper decks, the effect of liquid mirrors, and
the possibility of asymmetric flooding occurring.
All decks and platforms located in the damaged area of the hull are also assumed
to be damaged, and therefore not watertight.
In the case of damage to the double bottom, two cases could result, which should
be considered:
• The flooding of low-lying areas of the ship could increase stability;
• The eventual asymmetric flooding decreases stability;
Regarding the vertical extent of damage to the double bottom, the worst case
should be assumed.
5.1.3. Loading conditions considered
The loading conditions to be considered in the damage stability assessment are as
follows:
• Displacement loaded
• Minimum operating displacement
These conditions are defined in accordance with Section 3.
5.1.4. Permeability of flooded compartments
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For the purposes of calculating the volumes of water admitted into the flooded
compartments, the permeability values of the compartments, defined in accordance with
Table 5.1, shall be considered.
Permeability
Displacement
Operative
loaded
shift
minimum
0.95
0.95
0.95
0.95
0.90
0.90
0.90
0.90
0.90
0.90
0.85
0.85
0.80 a 0.90
0.95
0.60
0.95
0.60
0.95
0.80
0.95
0.80
0.95
0.70
0.95
0.60 a 0.80
0.95
0.65
0.65
0.85
0.85
0.97
0.97
Compartment Type
Housing
Central, Communications, Operations
Canteen
Pump rooms
Rudder engine housing
Auxiliary engine rooms
Paióis
Ammunition bunkers artillery
Portable armouries
Rocket/missile emplacements
Kitchens, pantries
Torpedo bunkers
Load
Paiol moorings
Main engine room
Cofferdams and other empty spaces
Table 5.1. - Average permeability of compartments
5.2. Straightening and tilting arm (wind) bends at fault
The ship's righting lever is to be re-calculated for each case of damage, taking into
account the losses of buoyancy inherent to flooded compartments, also accounting for the
effect of liquid mirrors and open sea communications where applicable. In addition the
righting lever curve is to be corrected by 0,05across to account for unknown
asymmetrical flooding or cross motion of unpeeled cargo during heeling.
The wind slope arm shall be determined according to the procedure described in
Section 4, paragraph 4.2.2. using a nominal wind speed defined as follows:
• From the curve in Fig.5.1. for displacements up to 5000 tons;
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• By the expression V 22.5 .15
for displacements greater than
5000 tonnes.
34
Rated wind speed (knots)
32
30
28
26
24
22
20
0
1000
2000
3000
4000
5000
Intact displacement (tonnes)
Fig.5.1 - Rated wind speed for damage stability for ships of less than 5000 tons displacement
5.3. Criterion
Based on Fig.5.3. the criteria to be met is as follows:
• The static, or band, heel angle, defined by point B, due to the damage sustained
shall not exceed 15 degrees;
• The ratio between disturbing (A2 ) and stabilising (A1 ) energy should be A1 >
1.4 A ;2
• The stabilising energy (A1 ) should be greater than the value defined in Fig.5.2.
• The value of GZ at point C shall not exceed 60% of the maximum value of GZ,
the latter being defined by the righting lever to 45° or the angle of
uncontrollable flooding, whichever is the lesser;
• The fall should be less than is necessary to cause uncontrollable flooding
through permanent openings;
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• The longitudinal metacentric height should be positive, i.e. GML >0.
Required stabilising area (m.degrees)
1,6
1,4
1,2
Displacement
up to 5000 t
1
0,8
Displacement
between 5000
and
50000 t
0,6
0,4
0,2
0
0
1
2
3
4
5
Displacement (tx103 )
(tx104 )
Fig.5.2 - Stabilising area (A1 ) required for damage stability
GZ
Corrected straightening
arm in malfunction
15º
A1
Tilting wind
arm
C
A2
Band
Angle of ornament
B
45º or angle of
uncontrollable flooding
Adornment
Reach
Fig.5.3 - Straightening and tilting arm bend due to damage and crosswind
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6. INTACT STABILITY CRITERION FOR AUXILIARY VESSELS
AND UAM'S
6.1. Definition of conditions
This applies to all ships and crafts, classified as Category A. Auxiliary or
UAM's as defined in Section 2, with length between perpendiculars equal to or greater
than 24 metres.
6.2. Requirements of the straightening arm curve intact
The form of the righting lever curve (GZ) should meet minimum requirements to
ensure that the ship will have the majority of the stabilising power between 0 and
 .
GZ
0.15m
30º
40º
57.3º
Heeling angle (degrees)
Fig. 6.1. - Definition of the righting lever curve (GZ)
Thus, the following conditions must be met:
• The straightening arm curve should end at the angle where uncontrollable
flooding occurs due to water entering through permanent openings in the
structure. Examples of these structural openings are
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of the inlet and outlet ducts of main engines, engine room ventilators, etc.
• The straightening arm curve shall comply with the criteria specified in Table
6.1.
Area under the GZ curve from 0 to 
Area under the GZ curve from 0 to  *.
Area under the GZ curve from  to  *.
Maximum GZ
Angle of maximum GZ
GM corrected for net mirror effect
Angle of zero stability
0.055 m.rad
0.09 m.rad
0.03 m.rad
0.2 m
 (never <
25º)
0.15 m
as large as
possible
*- The area under the righting lever curve should be determined to either 40° or the uncontrollable flood angle, whichever is the
lesser.
Table 6.1. - Criteria for the straightening arm curve
6.3. Stability under wind
6.3.1. Definition of conditions
This criterion shall be applied to all ships and crafts with a length of more
than 24 metres, for all loading conditions, in the intact condition. The conditions of
application of the criterion are defined sequentially by:
1. It is assumed that crosswind and port-to-stern swing occur simultaneously;
2. It is assumed that the ship is subjected to a constant wind pressure acting
perpendicular to the median plane of the ship, generating a constant heeling
arm, designated lw1 . ;
3. The ship is assumed to experience a leeward heeling angle (1 ) due to wave
action, defined from the static heeling angle (0 ) due to wind action as
described in paragraph 2;
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4. The uncontrollable flooding angle is defined by2 ;
5. The ship is subjected to the action of an additional pressure due to the gust of
wind, which results in a heeling arm of the gust of wind lw2 . ;
6. The effect of liquid mirrors shall be accounted for under all conditions
analysed, in accordance with the procedure set out in Section 3.
6.3.2. Determining the inclination arms
The effect of crosswind should be determined as follows:
• The inclination arms lw1 and lw2 are constant for all heeling angles and
are respectively defined, in metres, by the expressions:
l PEACE

1
lw2 1.5lw1
where
P - lateral pressure due to wind, which should be defined by
P 504 N / m2 . Ships with restrictions in their operational use may adopt
values lower than those stipulated above;
A - projected side area of the ship and deck cargo above the margin line
water, in m ;2
Z - vertical distance between the centre of the area A and the centre of the
line. As an approximation, it is feasible to assume that the centre of the
carina is at half the average immersion of the ship;
- displacement in the ship, in t;
g - acceleration of gravity, g 9.81 m / s2 .
• The swing angle (1 ), expressed in degrees, should be determined as
follows:
1
109kX 1 X 2
where
lo
l
X1 - Factor defined by Table 6.2; X2
- Factor defined by Table 6.3; k Factor defined as follows:
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Ships with a bilge bend
rounded, without sway barbets or
keels
Ships with a tapered bilge curve
Vessels with seabass and/or swing
keel
k = 1.0
k = 0.7
Table 6.4.
r - Defined by the expression r .
OG
0.6

;
OG - Distance between the waterline and the centre of gravity, in metres
(+ if the GC is above, - if the GC is below the waterline, respectively);
d - average immersion of the ship, in meters;
s - Factor defined by Table 6.5.
T - Ship's rocking period, in seconds. It should be estimated through the
expression:
2

0.

0.



0.

GM
GM - Metacentric height corrected for the effect of the liquid mirrors, in
metres;
Ak - total area of the rattles, or area of the lateral projection of the swing
keel, or the sum of these areas, in square metres;
CB - Total fineness coefficient of the carine;
B - breadth of the ship, in metres;
L - length of the ship on the waterline, metres.
B/d
X1
B/d
X1
2.4
1.0
3.0
0.90
2.5
0.98
3.1
0.88
2.6
0.96
3.2
0.86
2.7
0.95
3.3
0.84
2.8
0.93
3.4
0.82
2.9
0.91
3.5
0.80
Table 6.2. - Values of factor X1
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CB
X2
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.82
0.89
0.95
0.97
1.0
Table 6.3. - Values of factor X2
100. A .
k
L. B
k
0
1.0
1.5
2.0
2.5
3.0
3.5
4.0
1.0
0.98
0.95
0.88
0.79
0.74
0.72
0.70
Table 6.4. - Values of the k
T
s
6
7
8
12
14
16
18
20
0.100
0.098
0.093
0.065
0.053
0.044
0.038
0.035
Table 6.5. - Values of the factor s
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GZ
B
1
lw2
lw1
A
0
2
C
Heeling angle (degrees)
Fig. 6.2 - Curves of the righting lever (GZ) and tilting moment
due to wind
6.3.3. Criterion
Based on Fig.6.2. the criteria to be met is as follows:
• The heeling angle due to direct wind action ( ) should not exceed 16 degrees
or 80% of the edge dip angle, whichever is smaller.
• The ratio of disturbing (A) and stabilising (B) energy should be
BeA.
6.4. Stability in wind and ice
6.4.1. Definition of conditions
All ships or vessels operating in areas where ice accumulation is likely to occur,
adversely affecting stability, the loading conditions analysed should also include
accounting for the effects of ice accumulation.
The effects of ice accumulation should be defined as follows:
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• 30 kg of ice per square metre on exposed horizontal areas of decks and
walkways (corresponding to a uniformly distributed thickness of 32 mm);
• 7.5 kg of ice per square metre in vertical areas projected from each side of the
vessel above the waterline (corresponding to an evenly distributed thickness of
8 mm);
• The total projected lateral area of the discontinuous surfaces of jibs, bollards,
and rigging of ships without sails and the projected lateral area of other small
objects shall be calculated by increasing the total projected area of those
surfaces assumed to be continuous by 5% and the moments of this area by
10%;
• The density of the ice should be assumed to be 950 kg/m3;
• The wind speed to be considered should be 70% of the value used in 6.4,
w h i c h corresponds to a pressure of 353 N/m2 . The wind slope arm should
be calculated by the same method defined in 6.3.
6.4.2. Criterion
The criteria to be met are as follows:
• The heeling angle due to direct wind action ( ) should not exceed 16 degrees
or 80% of the edge dip angle, whichever is smaller.
• The ratio of disturbing (A) and stabilising (B) energy should be
BeA.
The righting lever curve must comply with the criteria defined in the table
below:
Area under the GZ curve from 0 to 
Area under the GZ curve from 0 to  *.
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0.051 m.rad
0.085 m.rad
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Area under the GZ curve from  to  *.
Maximum GZ
Angle of maximum GZ
GM corrected for net mirror effect
Angle of zero stability
0.03 m.rad
0.24 m
 (never <
25º)
0.15 m
as large as
possible
*- The area under the righting lever curve should be determined to either 40° or the uncontrollable flood angle, whichever is the
lesser.
6.5. Yawing stability at high speeds
6.5.1. Definition of conditions
The ship is assumed to heel solely due to the action of centrifugal force arising
from high speed yaw. The assumed angle of heel does not reflect the transient behaviour
of the ship at the beginning and end of the heeling but rather when stabilised during the
heeling.
6.5.2. Determination of the tilting moment
The heeling moment acting on a ship during a heel is expressed as
by:
M R .02
wher
e

V2
K
0
L


- tilting moment due to yaw, m.t;
- displacement of the ship, t;
V0 - linear speed of the ship during the yaw, m/s;
L - length of the ship, m;
T - average immersion, m;
KG - height of the centre of gravity above the keel, m.
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The heeling arm used in conjunction with the centrifugal force referred to above is
defined as the distance between the centre of gravity of the ship and the centre of lateral
resistance of the live works. This arm is a function of the cosine of the heeling angle. The
vertical position of the centre of lateral resistance of the live works is assumed at middraught.
V2 a
co
gR
 Arm
wher
e
R - radius of gyration of the ship, m. For calculation purposes it is reasonable to assume that R is
approximately half the tactical diameter;
g - acceleration of gravity, g
a-
9.81 m / s2 ;
the vertical distance between the centre of gravity of the ship and the centre of lateral
resistance, defined at moulded draught, with the ship unnumbered, in m, by
a KG
T
2
T - average immersion, m;
-angle of adornment, degrees.
6.5.3. Criterion
Based on Fig.6.3. the criteria to be met is as follows:
• The stabilised heeling angle due to the action of centrifugal force during
turning should not exceed 10 degrees.
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GZ
Tilting arm due to
the swerve at high speed
Straightening arm intact
10º
Angle of ornament
Uncontrollable flood
angle
Fig. 6.3. - Righting lever (GZ) curves and tilting moment due to yaw at
high speed
6.6. Stability under crowding of the trim on one edge
6.6.1. Definition of conditions
The movement of personnel is likely to have a major effect on the transverse
stability of small vessels carrying a relatively large number of persons on board. The
concentration of personnel on one side may produce a heeling moment such that it results
in a significant reduction in the ship's dynamic stability.
It is considered for all purposes that:
• each person occupies an available deck area equal to 0.2 m ;2
• each person has an average weight of 75 kg, not including any type of
equipment. The addition of the weight of equipment carried must be
analysed separately and in detail on a case-by-case basis;
• the height of the centre of gravity of each person should be assumed to
be 1.0m, or 0.3m, depending on whether they are standing or seated,
respectively.
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6.6.2. Determination of the tilting moment
The inclining arm produced by the transverse movement of the staff is determined
by the expression
Inclination arm
wa 
where
w - weight of personnel moved, t;
a-
transverse distance from the ship's centreline to the centre of gravity of the personnel
moved, m;
- displacement, t;
-angle of adornment, degrees.
6.6.3. Criterion
Based on Fig.6.4. the criteria to be met is as follows:
• The stabilised heeling angle due to personnel moving to an edge should
not exceed 10 degrees.
GZ
Inclining arm due to side
loading (crowding of
personnel)
Straightening arm intact
10º
Angle of ornament
Uncontrollable flood
angle
Fig. 6.4. - Straightening arm curves (GZ) and tilting moment due to
crowding of personnel at an edge
6.7. Stability during docking
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6.7.1. Definition of conditions
In terms of transverse stability, the critical condition during docking occurs just
before the ship touches the blocks, where the load exerted on the ship is maximum.
The loading condition of the ship while docking is usually defined through a
docking plan. However, if this does not exist, a trim of 0.3 metres astern should be
assumed for all purposes, or a higher value if the ship cannot achieve this trim.
6.7.2. Criterion
The criteria to be met are as follows:
• The corrected metacentric height should always be positive throughout t h e
docking process.
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ITDINAV 802
CRITERION OF
SHIPS
ESTABILITY CRITERIA AT
EVARIA
FOR
AUXILIARIES AND UAM'S
7.1. Definition of conditions
The following are defined as failure situations to be considered in this criterion:
1. Structural damage resulting in flooding due to:
• Collision with the bottom resulting in moderate flooding;
• Bow thrust;
• Collision or impact with the bottom resulting in major flooding;
• Explosion by enemy action resulting in major flooding.
2. Flooding caused by:
• Crosswinds combined with port-starboard swing;
• Progressive flooding (circuit breakers, etc.);
• Fire fighting inside the ship.
The main idea behind this criterion is to ensure the survival of the vessel.
7.1.1. Watertight compartmentalisation criterion
The basis for determining the extent of flooding is the length of damaged hull
(open to the sea) at any point along the length of the ship, which results from enemy
action or collision. In auxiliary ships and UAM's, the criterion is based on the number of
flooded watertight compartments. For calculation purposes, the length should be referred
to its value between perpendiculars.
Only main transverse bulkheads with a minimum spacing of (3.05 + 0.03L) or
10.65 metres will be considered as watertight boundaries, whichever is less.
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The watertight subdivision criteria should ensure that:
• Ships of less than 75 metres in length should be capable of withstanding
flooding of, as a minimum, one main watertight compartment including the
main engine room;
• Ships between 75 and 200 metres in length shall be able to withstand flooding
of any two adjacent main watertight compartments including an engine room,
or any 3 adjacent compartments excluding engine rooms;
• Ships over 200 metres in length shall withstand rapid flooding due to an
opening in the hull equal to 12.5% of the length of the ship, located at any
point along the length of the ship;
7.1.2. Extent of damage to living works
7.1.2.1. Longitudinal extension
In cases where the watertight subdivision is based on the number of flooded
compartments, the longitudinal extent of flooding is defined by the position of the
transverse watertight bulkheads bounding those compartments.
In cases where watertight subdivision is based on the length of hull open to the
sea, the longitudinal extent of flooding is defined by the position of watertight transverse
bulkheads immediately forward and aft of the hull opening boundaries.
7.1.2.2. Transverse extension
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The maximum extent of transverse flooding is defined by the damage resultant
at transverse penetration up to
1
5
from the ship's mouth, but not affecting it,
any longitudinal watertight bulkhead at the centreline. Less transverse penetration shall
be assumed where this results in flooding that would have a greater impact on stability.
7.1.2.3. Vertical Extension
It is assumed that all decks and platforms are not watertight, as this results in the
most adverse situation due to flooding on upper decks, the effect of liquid mirrors, and
the possibility of asymmetric flooding occurring.
All decks and platforms located in the damaged area of the hull are also assumed
to be damaged, and therefore not watertight.
In the case of damage to the double bottom, two cases could result, which should
be considered:
• The flooding of low-lying areas of the ship could increase stability;
• The eventual asymmetric flooding decreases stability;
Regarding the vertical extent of damage to the double bottom, the worst case
should be assumed.
7.1.2.4. Minor damage
Should any damage less than that specified in paragraphs 7.1.2.1, 7.1.2.2, or
7.1.2.3 result in a more severe situation with respect to heel, loss of metacentric height,
that case shall be assumed.
7.1.3. Loading conditions considered
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The loading conditions to be considered in the damage stability assessment are as
follows:
• Cargo Shipment, without ballast, departing from port
• Ballast shifting at port departure
• Displacement with cargo, without ballast, on arrival at port
• Ballast shifting on arrival at port
These conditions are defined in accordance with Section 3.
7.1.4. Permeability of flooded compartments
For the purpose of calculating the volumes of water admitted into the flooded
compartments, the permeability values of the compartments, defined in accordance with
Table 7.1, shall be considered.
Permeability
Displacement
Operative
loaded
shift
minimum
0.95
0.95
0.95
0.95
0.90
0.90
0.90
0.90
0.90
0.90
0.85
0.85
0.80 a 0.90
0.95
0.60
0.95
0.60
0.95
0.80
0.95
0.80
0.95
0.70
0.95
0.60 a 0.80
0.95
0.65
0.65
0.85
0.85
0.97
0.97
Compartment Type
Housing
Central, Communications, Operations
Canteen
Pump rooms
Rudder engine housing
Auxiliary engine rooms
Paióis
Ammunition bunkers artillery
Portable armouries
Rocket/missile emplacements
Kitchens, pantries
Torpedo bunkers
Load
Paiol moorings
Main engine room
Cofferdams and other empty spaces
Table 7.1. - Average permeability of compartments
7.2. Straightening and tilting arm (wind) bends at fault
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The righting lever in the damaged condition shall be determined by the lost
thrust method accounting for damage as defined in accordance with 7.1.2.
For the purpose of determining the tilting moments, the rules stipulated in the
following paragraphs shall be used.
7.2.1. Crowding of passengers on board
Principles and assumed values for calculation:
• 4 persons per square metre of deck;
• 75 kg weight for each passenger;
• Passengers shall be distributed on the available areas from deck to one side of
the ship on the decks where emergency passenger assembly stations are
situated in such a way that the most adverse heeling moment is produced.
7.2.2. Simultaneous launching of all loaded life-saving appliances
on one side
Assumed calculation principles:
• All life-rafts on the side to which the ship has heeled after having been
damaged should be assumed to be loaded, suspended and ready for lowering;
• Vessels on the opposite side of the heel shall be regarded as standing.
7.2.3. Wind pressure
Principles and assumed values for calculation:
• pressure due to wind, P, equal to 120 N/m ;2
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• the sail area is defined as the projected lateral area above the waterline relating
to the intact condition;
• the wind heeling arm is defined as the vertical distance between the centroid of
the sail area and the point halfway along the mean windward dip of the ship in
the intact condition.
7.3. Criterion
The criteria to be met are as follows:
• The residual straightening arm of the final condition shall have a minimum
range of 15° beyond the angle of equilibrium (band or heel), as shown in
Fig.7.1. If the angle of uncontrollable flooding occurs before the angle of
elimination of the residual straightening arm, then the considered residual
straightening arm curve is truncated at the angle of uncontrollable flooding;
GZ
Leaning arm due to
wind
15º
0
Breakdown of straightening
arm
Angle of
ornament
Fig. 7.1. - Setting the range of the residual straightening arm
curve at malfunction
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• The final condition of the ship after damage, (in case of asymmetric flooding,
after remedial measures have been implemented) should verify the conditions:
In the case of symmetrical flooding there shall be a residual metacentric
height of at least 0.05m, to be calculated by the lost thrust method;
In the case of unsymmetrical flooding, the heeling angle shall not exceed
7° in the case of one flooded compartment, or 12° in the case of two or
more flooded compartments. The heeling angle before remedial action
is taken shall not exceed 15º;
The margin line can never submerge at the end of the flood.
• The area under the righting lever curve shall be at least 0.015 m.rad, measured
from the angle of equilibrium to the lesser of the following angles (as shown in
Fig.7.2.):
uncontrollable flooding angle;
22° (measured from the right ship's position) in the case of one
compartment being flooded, or 27° (measured from the right ship's
position) in the case of the simultaneous flooding of two or more
compartments;
GZ
Leaning arm due to
wind
A>0.015 m.rad
0
0
Breakdown of straightening
arm
+22º 2
Angle of
ornament
Fig. 7.2. - Definition of dynamic damage stability
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ITDINAV 802
• A residual righting lever should be obtained within the range defined by 15°
beyond the balance angle, GZMAX  , such that:
0
0
GZMAX  GZCRIT
0
0
The minimum righting lever, GZCRIT , in metres, is calculated by the formula
Mi
GZ CRIT
0.04
where
- displacement of the ship;
Mi - is the largest of the tilting moments, due to:
Agglomeration of all passengers on board;
Simultaneous launching of all loaded life-saving appliances on one side;
Wind pressure; determined as
defined in 7.2.
• The trim should be less than is necessary to cause uncontrollable flooding
through permanent openings;
• The longitudinal metacentric height should be positive, i.e. GML >0.
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9. STABILITY CRITERIA FOR FLOATING DOCKS
9.1. Definition of conditions
This stability criterion applies to all floating docks as defined in Section 2.
The loading conditions to be considered in the stability assessment are as follows:
• Critical displacement with ship docked;
• Critical dislocation with no ship docked.
The critical displacement is the one corresponding to the critical immersion of the floating
dock.
9.2. Criterion
The criteria to be met are as follows:
• The metacentric height corrected for the effect of the liquid mirrors, the dock
itself and the docked ship, GMF , for the critical mean immersion (when the
water line is between the top and bottom of the piers) should be greater than
1.5 m;
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ITDINAV 802
13. STABILITY CRITERIA FOR BARGES AND PONTOONS
13.1. Intact stability for barges and pontoons
13.1.1. Definition of conditions
The provisions set by this criterion apply to barges and pontoons, which may be
of marine or river application. A vessel will normally be considered as a pontoon or
barge:
• without its own propulsion system;
• unmanned;
• carrying only deck cargo (general cargo, passengers, etc.)
• having a carcase with the following characteristics: CB
0.9 ,
B
.0
T
• no hatches on deck, except for manholes closed with watertight lids.
With regard to stability calculations, the following considerations should be taken
into account:
• Account for water absorption by the deck, and water accumulation on the
cargo and/or deck when calculating the centre of gravity position;
• As far as adornment by the wind is concerned:
1. The wind pressure shall be assumed to be constant, and uniformly
distributed, and shall be considered to act along the length of the
pontoon from the waterline to the maximum height of the load on deck.
The wind pressure to be considered shall be P=0.54 kPa (wind speed 58
knots);
2. The vertical position of the load's centre of gravity should be assumed
to be at mid-height of the load;
3. The windward bias should be considered as defined between the
centroid of the sail area to half of the average barge immersion.
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• In the stability calculations all possible loading conditions must be analysed;
• The angle of uncontrollable flooding should be defined on the basis of existing
permanent openings, excluding all those provided with watertight hatches or
covers, or self-closing tank vents.
13.1.2. Criterion
The criteria to be met are as follows:
• The static heeling angle due to wind pressure shall not exceed the angle
corresponding to half the freeboard of the loading condition considered;
• The minimum range of the righting lever curve should be 20° for barges and
pontoons with a length between perpendiculars of 100 m or less, or 15° for
barges and pontoons with a length of 150 m or more. Interpolated values shall
be used for lengths between 100 and 150 m;
• The metacentric height corrected for the effect of the liquid mirrors shall not be
less than 0.3 m;
• The uncontrollable flooding angle shall not be less than the edge dip angle.
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13.2. Damage stability for barges and pontoons
13.2.1. Definition of conditions
The basis for determining the extent of flooding is the length of damaged hull
(open to the sea) at any point in the ship's length resulting from accident or enemy action.
The criterion is based on the number of flooded watertight compartments.
The watertight subdivision criterion shall ensure that the barges and pontoons
shall be able to withstand at least the flooding of one main watertight compartment.
The longitudinal extent of flooding is defined by the position of the transverse
watertight bulkheads bounding these compartments.
The maximum extent of transverse flooding is defined as damage resulting in
transverse penetration up to the margin line, but not affecting any longitudinal watertight
bulkhead at the margin line. Less transverse penetration shall be assumed where this
results in flooding which has a greater impact on stability.
It is assumed that all decks and platforms are not watertight, as this results in the
most adverse situation due to flooding on upper decks, the effect of liquid mirrors, and
the possibility of asymmetric flooding occurring.
All decks and platforms located in the damaged area of the hull are also assumed
to be damaged, and therefore not watertight.
13.2.2. Criterion
The criteria to be met are as follows:
• The angle of static heel or broken band should not lead to the edge immersion,
or not exceed 10º if no edge immersion occurs;
• The sag produced by the damage should not lead to the immersion of the edge;
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• The damaged metacentric height corrected for the effect of the liquid mirrors
shall not be less than 0.15 m.
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