265
1 INTRODUCTION
Under provisions of international law and
humanitarianconsiderations,shipmastersareobliged
to assist others indistressatseawhenever they can
safelydoso.Thespecificobligationsarisingfromthe
internationalconventions:
International Convention on Marine Search and
Rescue;
Regulation V/10 of the International Convention
forthesafetyofLifeatSea,SOLAS1974.
In 1998, based on the above regulations, the
International Aeronautical and Maritime Search and
Rescue Manual for Mobile Facilities (IAMSAR 2005)
wasdeveloped.Allofficersmustbefamiliarwithits
contents and be regularly trained. The ma
nual is
intended to be carried aboard every bridge. It
contains the standard methods and procedures for
searching, and principles of cooperation and
coordination in various circumstances. However, in
thestressfulsituationscommonlyencounteredduring
SAR action, it would be useful to provide a ship’s
masterwithmoremoderntoolsfordecision‐ma
king.
This could be, for example, a simple algorithm that
youcoulduseinconjunctionwiththeavailabledata
todevelopanSARactionplan.
2 THESARACTIONALGORITHM
The proposed algorithm is a tool whose task is to
integrate one different sources of information. The
finaleffectshouldbethemostoptimalsearchscheme.
Input items can be dividedint
o two groups. The
first are individual manoeuvring characteristics and
bathymetricinformationobtainedfromECDIS.
Thesecondgrouparethevariableelements.These
arethehydro‐meteorologicalconditionsprevailingin
thearea;
Theobservedwind speedanddirection.Thiscan
beestimatedbyobservationwhenapproachingthe
placeofaction;
Thetotalwatercurrents– thesevalues areinthe
database or ECDIS (Electronic Chart Display and
Information System), or provided on traditional
navigationmaps;
For search action to be effective there must be a
pre‐planned search pattern. It will be necessary to
establishthestartingpointoftheactionorgeographic
referencesfortheareatobesearched.Thefollowing
fact
orsshouldbeconsidered:
An Adaptation of an Algorithm of Search and Rescue
Operations to Ship Manoeuvrability
L.Kasyk&K.Pleskacz
M
aritimeUniversityofSzczecin,Poland
ABSTRACT:Thisarticlepresentsanoverviewofanalgorithmtofacilitateactionwhen planningsearchand
rescueoperations,takingintoaccountactualhydro‐meteorologicalconditionsandthemaneuverabilityofships
involvedinthesearch.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 9
Number 2
June 2015
DOI:10.12716/1001.09.02.15
266
The reported position and time of the SAR
incident;
Thetypeofsearchobject;
Personinwater–notdriftinginthewind,only
incurrents;
Life raft – the drift depends on the use of a
ballast system or drogue. Several types of life
raftshouldbeconsidered(e.g.for4,6,15and
25persons);
Boats–differentsizes(e.g.<5,7,12,and24m);
Others.
The maximum speed at which the search vessel
can proceed to the reference point in the current
hydro‐meteorologicalconditions.ʺ
Thedatumpositionisfoundbymovingfromthe
incident position or last computed datum position,
using the drift distance in the drift direction and
plottingtheresultingpositionon
asuitablechart.The
typeofobjectwilldeterminethetotaldrift.Valuesfor
different kinds of search object, depending on wind
speeds, are given in the form of graphs in the
IAMSARmanual.
Figure1.TheSARactionalgorithm
Note that the algorithm works with the ECDIS
system and very easily takes into account tidal
currents,whosestrengthanddirectionvaryaccording
tothedateandtime oftheincidentandduration of
therescueoperation.
3 INFLUENCEOFHYDRO‐METEOROLOGICAL
CONDITIONSONTHEPLANNINGOFSAR
ACTION
Because the
impact of hydro‐meteorological
conditionsandship maneuverability aresimilar,the
ExpandingSquareSearchmethodwillbediscussedin
detailasageneralprincipleforallthreemethods.
Using the algorithm in accordance with the
guidelinesoftheIAMSARmanual,wederive:
ThesearchstartpointandETAatthispoint;
Themostprobablesearcharea;
The first search leg, which is usually oriented
directlyintothewind;
The recommended track spacing for merchant
vessels.
Figure2. Diagram ofExpandingSquareSearchtaking into
accountthehydro‐meteorologicalconditions
[source:simulatorTRANSASECDIS3000‐i]
The database of ENC (Electronic Navigational
Chart,partofECDIS)maps,andtheElectronicChart
Display and Information System provide full
information about the currents, allowing more
accurate navigation. The transformation of the
standard method using an algorithm that calculates
the impact of hydro‐meteorological conditions gives
some interesting results. The
solid line in Fig. 2
indicatesthesearchmethodassuming:
noimpactofhydro‐meteorologicalconditions;
thedistancefromthepresentshippositionto the
searchstartpointis33NM;
the search object is a six‐person life raft with
drogue;
theship’smaximumspeedis10kn;
visibilityis5NM;
thesearchareaislimitedtoasquarewithsidesof
10NM.
Thealgorithmusedtosimulatetheformingpartof
TRANSAS ECDIS 3000‐i takes into account the drift
direction and speed, and the maneuvering speed of
the ship. In the following simulation additional
parameterstothestandard
searchareassumed:
Driftis180º/1kn;
Themaneuveringspeedoftheshipis8kn.
267
We get a new method of exploration marked by
thedottedlineinFig.2:
Anewsearchstartpoint(1);
New waypoints (2–10), courses and distance in
eachleg.
Bycomparingthetwo diagrams, we canseethat
the actual search area is very different from the
diagramwithoutadditionaldata.Thecommonareais
asearchareaoflessthan50percent.
The analyzed algorithm takes into account
some
hydro‐meteorological parameters but does not
include ship maneuverability (except for
maneuveringspeed).
4 INFLUENCEOFSHIPMANOEUVRABILITYON
THEPLANNINGOFSARACTION
Eachshiphasindividualmaneuveringcharacteristics.
Differences may evenoccuramong sister ships – let
alone vessels of various types, sizes, construction –
caused by, for
example, the location of
superstructuresalongthehullresultinginadifferent
reactiontoasidewind.Inaddition,issuescomewith
driveandcontrol:thetypesandnumberofrudders,
propellers, additional equipment (e.g. thrusters).
Additionally, a ship with a classic right‐ ‐handed
propeller will be maneuvered differently from
one
witharight‐handedpitchpropeller.Therefore,itwill
turntotherightortotheleftdifferently.Theturning
circleisalsodependentonvariablessuchasloading
conditionsandrudderangle.
According to international regulations contained
in resolution A.751(18), 1993, Interim Standards for
ShipManeuverability,eachshipwith
alengthof100
m or more, as well as chemical tankers and LPG
tankers built after 1994, must have certain
maneuvering standards. In practice, maneuvering
standards are known to all ships, as they allow for
safeoperation.
From the point of view of course alterations
duringSARaction,in
additiontomaneuveringspeed,
the only significant parameter that should be
consideredisturningability. Accordingto therules,
the turning ability of the ship is considered
satisfactory if the advance does not exceed 4.5 ship
lengths,andthetacticaldiameterdoesnotexceedfive
shiplengths,bothtotheright
orleft,atarudderangle
of35degrees.
Inthecaseofashipoflength200m,thediameter
of the acceptable theoretical turning circle is thus
approximately 800–1000m. In the case of a specific
vessel(e.g.typeB517/2),theminimumturningcircle
diameterisapproximately
600m,whichcorresponds
to three ship lengths. However, it should be noted
that this is the diameter of the fixed turning circle,
which is measured in a situation when the ship is
alreadymoving inacircle.Iftheshiphastochange
coursebyapproximately90degreesfromits
position
when moving along a fixed course, this is a very
important parameter defined as advance. This
describesthedistanceavesselwillcontinuetotravel
ahead on her original course while engaged in a
turningmaneuver.It is measuredfromthat pointat
which the rudder is placed hard
over, to when the
vessel arrives on a new course 90degrees from the
original.
After the rudder is turned, a ship does not
immediately adopt a circular, due to the inertia
related to the mass of the vessel. The ship makes
additionalheadwayuntilitadoptsacircularcourse
in
apredetermineddirection(Fig.3).
Figure3.Shipmanoeuvringparameters
[source:http://www.titanicology.com]
DisregardingadvanceduringanSAR actionmay
resultintwoproblems,particularlyinthefirstlegsof
thespiral.
Thefirstproblemisthattheshipwillnotbeable
to physically perform the maneuver. The calculated
routebetweentwowaypointswillbetooshortforthe
executionoftwochanges
ofcourse(Fig.4).
Figure3.Theplacewheretheexecutionofthe next course
alterationisimpossible
[source:simulatorTRANSASECDIS3000‐i]