Documentation of HSC operational performance and limitations – The regulatory regime and practical application

Documentation of HSC Operational

The regulation regime and practical

Performance and Limitations.

application.

Principal Research Eng. Per Werenskioldl, Senior Research Eng. Dariusz E. Fathil, Senior Research Eng. Egil Jullumstr@l

Since 1998 the HSC Code has been mandatoq for operation of high-speed craft on international routes. The Code is also widely applied directly as regional and national regulations. A revised Code will enter into force on 1. July 2002, including modi$cations re[ated to documentation of craft operational performance and limitations, in particular to make the Code suitable from the ISM Code viewpoint. According to reports from the indust~ it seems that different practices are being established as to what is acceptable for both documentation of craft performance and onboard application of operational information. The main objective related to the required documentation is for the guidance of the master to enable the craft to be operated safely. A Nordic HSC safety study shows that oflicers stress the importance of having suitable and readily available crafi pe~ormance abta. This paper attempts to interpret the alternatives for pe~ormance documentation as described in the Code, and to describe the available relevant documentation methods, including a summary of characteristic HSC limiting operational criteria. The paper intends to make the master, the operator and the authorities aware of the technology and methods that is available for assessing high-speed crafi pe~ormance and also to develop an understanding for the naval architect to appreciate the needs of a master to have ail relevant operational and safety information.

1 INTRODUCTION

The intent of this paper is to:

describe and interpret for the builders, naval architects,

and operators the regulatory issues related to

documentation of HSC performance as considered in the revised HSC Code,

describe for the masters and operators the performance information that is assumed to be readily available in craft and route manuals for onboard guidance,

give examples of craft performance documentation as developed in co-operation with masters.

It is hoped that it will initiate a basis for dialogue among regulators, builders, naval architects, operators and masters, by which constructive co-operation will lead towards even more knowledgeable and safer HSC operation.

Section 2 discusses the recent HSC Code revision work and the authors’ interpretation of the documentation process required by the Code. Section 3 describes the alternative methods for documentation of HSC operational performance and limitations. Section 4 intends to present a practical

overview of the documentation required, alternative

assessment methods and some relevant performance criteria.

Section 5 presents examples of HSC performance

information as developed in co-operation with operators and

masters, and the alternative use of instrumentation and

guidance systems is discussed.

2 HSC CODE - REVISION WORK

The Design and Equipment (DE) Sub- Committee held its forty – second session in March 1999. Some intersessional work is still needed, however it has been decided that the revised Code should be considered and approved by MSC 72 in June 2000 and that the new HSC Code would enter into force on 1. July 2002, if MSC 72 so determines.

At DE 42 proposal amendments were made to

modify provisions of the Code related to documentation of

operational performance and limitations, in particular to

make the Code suitable from the ISM Code viewpoint.

It is assumed that the Administration has two main

objectives for requiring documentation of high -speed craft performance:

i)

2)

to assess and certify the general operational and safety characteristics of the craft design in accordance with the HSC Safety Certificate, and

to control and certify the basis for safe operation of the craft in the actual route in accordance ‘with the HSC Code and as a part of the SMS (Safety Management System) process.

It is not possible to document all essential operational and safety limitations before a new high-speed craft design enters into service. This is due to variable factors like

specific type and detailed design, specific wave and

environmental conditions and control, steering and handling of the craft.

According to reports from the industry it seems that

different practices are being established as to what is

acceptable for both documentation of craft performance and

‘ Norwegian Marine Technology Research Institute (MARINTEK), Norway

onboard application of operational and safety information. The proposal for amendments to the HSC Code intended to clarify the objectives and procedures for documentation of craft performance of high-speed craft. The amendments were discussed based on the following assumptions:

The HSC Safety Certificate and the information

contained in the Craft Operating Manual should be

based on an initial documentation of the new craft

according to defined procedures in normal operating conditions up to levels of the worst intended condition and in prescribed failure conditions. Predictions, model test, trials and combinations of such should be used for documentation. The limiting sea states and speed related to structural classification of the craft design should also be included.

The information contained in the Route Operating

Manual should be based on verification of craft

performance and operating limitations as documented

initially. The Route Operating Manual should be

amended following specific experience from the

operation of the craft in the actual route and taking into account the operating procedures applied in addition to the part of shipboard management system (ISM) a.o.

dealing with reporting, operational experiences and

updating procedures.

An overview of the regulatory documentation process, as interpreted by the authors is presented in Figure 1.

, ... ..—... . .—..——_____.. . . 1] Initial Docurnentatlon : ●Prdof Compknti (17.2) \ ●@aft ~. WSISJ81 (17.2.1) I - .....4. ... ... .... . Puli+aelo Trlete ●FeiluraCandbns (A8)

●Worst IntandadCond. (?VIC) Pasa. Safaty (A#)

●%. ~~6 and CkISS inb. as appika~e (17.2.1) Abmattw (M) Vafitidon ofWlc * MathameUeSISlmulattona ●Modalteata _I &..--___.. : Purpoaa ~ •HSC~te AknaUva (17.1) -——— ——— ..- —.... __.. ●MeasurementSyatam ~ ●GUfdSIKWCI#I ~. Maw

WIC andFailureEventa (Standardto be devabpad)

e

:-H-

I

;Pwpose Aaemanv9 (17.1) ~ ●GuidancwRoutaOP. Manual ●InatnananlSy31em

mm u~ OnlineCha& ot Performance ; ●oparaaonelPmcedma (Sbndafd b ba dedopad)

Figure 1. Overview of the high-speed crajl pe~ormance documentation process (as interpreted by the authors).

3 DOCUMENTATION OF HSC PERFORMANCE

Assessment Methods

Ship performance should be quantified according to specific operational or mission requirements, either related to human

factors, specific mission or cargo or ship safety and

survivability. Any ship performance assessment

methodology shall include:

● _{Definition of environmental conditions}

w Ship configuration and ship performance

documentation

● _{Definition of criteria for performance limitations}

The methods which can be applied to assess the

seakeeping and safety performance of a vessel are shown in Figure 2. Assessment methods must be suited for the purpose and must be able to deal with the actual design details available at the different stages of the project. For this reason, methods applied in the early stages will normally be based on computer tools, which can be further verified by model tests at later stages. Since the cost of design changes

will increase as the design progresses, it is of great

importance to apply these tools wisely at the preliminary design. The costs related to documentation of performance

and improvement of design increase significantly when

moving towards right in the figure below.

Computations Theseakwplng charwe+lslms

01 me v,wel are calculated using wmputar program.

I

Model Teata

A scaled mcdel of Ihe vessel is built n“d tested 1“ aWW*

b.wn m different sea states

I

7

Full Scale Triala

The veseel is laded afiw II is built to dawmn. ,t* se.keeping chru.eta rmtms

Figure 2. Main categories of methods to assess seakeeping performance.

Direct Computations SeakeeDing

In applying direct computations there are a variety of classes of different software to calculate the motions of the vessel. The distinct difference between time-domain and frequency-domain codes should be noted.

In thefrequency domain, all the motions are treated

as sinusoidal oscillations about an equilibrium position. For this reason, frequency-domain computations can only treat

linear problems (or at least linearized problems). In these

codes, typical computations include performing calculations for a set of frequencies in regular waves. These results are

then treated statistically, by combining them with wave

spectra describing the distribution of wave energy on

different wave frequencies in a sea state, and scatter

diagrams, describing the annual or seasonal composition of sea-states for a sea area.

In the time domain codes, a simulation in time is

performed, and time series of the vessel responses are

written. Time domain computations offer the possibility to add non-linear characteristics of the vessel, and simulation of vessel motions in irregular short- or long-crested seas can be

performed. Time domain codes can also be used for simulation of specific operations or manoeuvring of a vessel.

Within these two main categories, there are several variations in theoretical formulations. For high speed vessels, there exists 2D strip theories (Salvesen, Tuck & Faltinsen (1970)), 2 %-D high speed strip theories (Faltinsen & Zhao (1991)), and 3D theories. Figure 3 shows approximately the valid speed range for the different theories. These theories again may be linear, partly- or fully-nonlinear.

‘“

F-’””*

0:4 F.

Ii 2’0 3’0 io V[knots) for Lpp.100m

Figure 3. Valid range for different calculation methods.

MARINTEK in close co-operation with The

Technical University of Norway has developed both 2D and

2Y2D frequency domain (MASHIMO), and time domain

(SIMSHIP) programs’. These programs can be applied for monohulls and multihulls at low, moderate and up to high

speed. In particular, the applications of MASHIMO for

catamarans and monohulls have been verified by

comprehensive model tests in regular and irregular waves using free running models at different headings to the waves.

Typical heave and pitch transfer functions, RAO’S, as

calculated and compared to model measurements are shown in Figures 4-5 and 6-7 for a 110 m monohull and a 40 m catamaran, respectively. 2.5 ~ a 0.5 ---—-–---~——.—_{._ -...__ .———....}.-._ ___ ___ [ 1

‘d

● Model Tests 1 “!!T.!Y .- ——.—. r~ ;-L ~ ---~:i 0.0 —-- -4-—---- - ---—-4--4 2 3 4 5 6

Significant Wave Height (m)

Figure 4. RMS values for 110 m Monohull RMS Pitch: 24 knl Head Seas

IL

—MASHIMO ‘ i 0.05 /----–- ‘-- .-==’”+—-—+===== i

-L-L-l--!

0.00 &L_ 2 3 4 5 6 SignificantWave Height (m)

Figure 5. RA4S values for 110 m Monohull

RMS Pitch: 24 ksd Head Seas

200

‘r-–--l---~---m

::~---

ye-J-o:

$+

_—-.

.—-—

‘

‘-””-n“

~

J

. ModelTests a 0.50 — — MASHIMO ‘-’ [ “0.00 ‘ ——J–” ’ ‘ ‘ – -4 8 12 16 WavePeriod(see)

Figure 6. RAO’s 40 m Catamaran Pitch: 30 kn/ Head Seas

3.00 2.50 2.00 G g 1.50 a a 1.00 0.50 0.00 I I

k

‘1

● ModelTests ~: +— _{— MASHIMO} ~ ● _I 4——— ————--.-———-.—.—.J, ● .+__..._.] — t- --- -—-- I 4 8 12 16 Wavef%riod(see)

Figure 7. RAO’S 40 m Catamaran

Vert. ace. at FP: 30 Im/ Head Seas

2Parts of these programs have also been developed during the Dynamic Analysis Support Systems project under the

An example of results from frequency-domain calculations, using the program MASHIMO is shown below:

. Motion transfer functions in six degrees of freedom

● _{Displacements, velocities and accelerations}

● Relative motion transfer functions

● Motion transfer functions at specified points

● Dynamic global loads

. Short term statistics of the above mentioned

. Long term statistics of the above mentioned

. Operability limiting boundaries

. Percentage operability

Short term statistics of the data from the calculations includes; standard deviations, significant values, expected maximum in a seastate of a given duration, etc. Long term statistics of the data from the calculations can be calculated based on a specified wave/ frequency scatter diagram.

The programs can include the effects from motion

control devices such as active and passive foils (e.g. roll stabilizing fins, T-foils, rudder control) and active or passive roll stabilizing tanks.

Slamming

Bow or wetdeck slamming problems might be of great significance for the HSC design. HSC masters report that slamming is considered, in particular when vibrations or noise influences the comfort of passengers. (Ochi, 1964) formulated a slamming index 20/hr, which can be applied as a reference. However, the definition of “acceptable slam” from the passenger or master point of view might vary

considerably. In both theoretical calculations and in

analysing model test results MARINTEK applies the Ochi slamming index and a ship type dependent panel pressure to assess operating limitations.

The program Slam2D has been developed by

MARINTEK as a part of the DASS-project (Dynamic

Analysis Support Systems). It can be used to predict forces, moments and the pressure distribution on two-dimensional

bodies due to slamming (Zhao & Faltinsen (1993)). The

average pressure over a panel can also be found. The results are given as a function of time.

The program does not require that the hull sections are symmetric. Calculations can be performed on general 2D

hull-sections with some limitations. Slamming forces both

in the horizontal and vertical direction are calculated together with the slamming moment. The section is allowed to have arbitrary vertical, horizontal and rotational velocities, which

may vary with time. It represents the relative velocities

between the cross- section and the fluid. The relative

vertical velocity may also include the effect of forward speed.

The program has recently been extended to deal

with flow separation (Zhao etal (1996)).

Manoeuvring

The mathematical model and computer program SIMAN calculates standard manoeuvres as defined by IMO, and the results can be compared to standard criteria. SIMAN is primarily intended for use in the early stage of the design of a new ship. The program has been tested against a number of full-scale trials and has proved to be accurate for a large range of hull forms, including high-speed mono-hulls. All

versions of SIMAN run under Windows.

m-Calculations are made in the time domain and this makes it easy to perform real time simulations with either automatic or manual control. A combination of simulation software and electronic charts is developed for onboard or onshore use as a planning and decision support system for

ship handling. A combination of simulation software,

electronic chart and 3D visual presentation constitute a ship

simulator of sufficient realism to be used for feasibility

studies concerning operation of ships. This tool has been

developed by MARINTEK and can also be used for

acquainting ship officers with the handling characteristics of a new ship or with the navigation in a new area of operation. Combination of model tests and theoretical calculations The combined use of theoretical tools and model tests has become more and more common and is a cost-effective way

of performing seakeeping studies. The model tests are

performed in order to study limiting or critical operational features, and to calibrate and adjust the theoretical models. Additional wave and route conditions and operability can then be studied with calibrated numerical models.

Model Tests

Seakeeping calculations provide a good starting point in the

design process. There are, however, still areas where

numerical methods are not adequate. Examples of this are

strongly non-linear phenomenon like controllability,

broaching, green water on deck and wetdeck slamming. For seakeeping tests, the recommended procedure is to use free running models with tuned autopilots. With a free running model, it is possible to conduct more realistic tests in

all wave headings. In addition to the standard motion

measurements, analysis of broaching, dynamic stability,

slamming and green water on deck can be undertaken. The cost of model tests is usually more expensive than computer calculations. Thus, test conditions like waves, headings and speeds should be selected carefully, in order to calibrate the computer model and analyse critical non-linear response.

MARINTEK offers highly specialised and cost-effective testing facilities and techniques for accurate testing and prediction of performance, manoeuvring, seakeeping and safety of high-speed craft.

In particular MARINTEKs Ocean Basin has

dimensions 80x 50 m with an adjustable depth of O to 10 m, wave generating capacity of maximum wave height of 1.0 m and significant wave height of 0.5 m. The Ocean Basin fast carriage system follows the free running models at any heading to the waves. Both Towing Tank and Ocean Basin test facilities enable use of light free-running models with comprehensive instrumentation and use of active auto-pilot and regulation systems.

With improved tracking of models via

dGPS-systems, outdoor sea tests have become more practical over the last few years. Onboard systems are performing as well as indoor laboratory equipment, and wave buoys or wave sensors accurately describe the environment the models are exposed to. The control systems applied are similar to those used in the laboratories. Fast transformation of data from onboard computers to main computers onshore give direct control of results from tests.

Typical high-speed craft model tests are: Towin~ Tank:

● _{Seakeeping tests in head and following seas with or}

without motion damping systems (free running model).

● Dynamic stability tests.

● Resistance tests (towed model).

● Propulsion tests.

Ocean Basin (free runnimz models):

● Seakeeping tests (all headings), with or without motion

damping systems.

● Controllability and broaching tests.

● Maneuvering tests (turning circle, Zigzag, and spiral

tests).

● HSC Code failure tests.

● Wash tests (towed or propelled model).

. Shallow water maneuvering.

. Shallow water resistance (towed model).

O~en sea models:

. Seakeeping tests all headings, with or without motion

damping systems

. Controllability and broaching tests.

. Maneuvering tests.

. Failure tests (in calm water and waves).

Full-Scale Tests

As shown in Figure 1, the intention of the HSC Code

requirements for craft performance documentation is two-fold:

1) Initial documentation for certification purposes and

2) Verification of craft performance for ISM (Safety

Management System) - update of operational manual and operational control procedures.

The initial documentation should be supplied by the

shipbuilder to:

the Flag State Administration for craft certification

purposes - according to the Code requirements

the operator for acceptance - according to the contract and performance specifications.

In addition, it is required that the operator ensures

verification of craft performance relating to operational

limitations be included in the Route Operational Manual and crew education/ training system.

The HSC Code describes, in some detail the

requirements and compliance criteria related to the initial documentation (Code-Annex 8). However requirements for restrictions of operation are specified in rather general term as – “particular attention should be paid to the following aspects during normal operation – etc” ($17.5).

MARINTEK performs both standard and specialised

measurements onboard high-speed craft and results are

assessed according to the Code or other relevant criteria.

~ical full-scale test momams might include:

. Seakeeping tests, including controllability and

broaching.

. Maneuvering tests.

● _{Speed tests and shaft power.}

. Fuel consumption and emission.

. Vibrations and noise (dBA).

4 PRACTICAL APPROACH FOR HSC

OPERATIONAL DOCUMENTATION

Except for HSC certification and construction purposes, the

main objective relating to the required documentation of

craft operation and safety is for the guidance of the master.

This objective is clearly stated in the HSC Code $ 18.2:

“The Administration should ensure that the craft is provided

with adequate information and guidance in the form of

manuals to enable the craft to be operated (and maintained) safel y“,

To supply the initial documentation of craft

performance in “worst intended conditions”, performance in failure situations, and to verify operational limitations is normally an extremely complex, time and cost consuming task. As the size of craft varies from 15 m up to above 150 m in length, the total cost-effectiveness and practical value of the initial and the follow-up performance documentation will vary considerably.

Normally neither seakeeping calculations nor model

tests will be conducted for initial performance

documentation of the smaller craft. However, to perform both calculations and seakeeping and manoeuvring model tests can be very cost-effective for novel designs in general and for larger craft in particular. In general verification of operating limitations shall be assessed by adequate full-scale tests, It is vital that the type and number of tests thoroughly reflect the objective in advising the master to operate the craft safely.

Performance characteristics, methods and criteria

for assessment of both initial documentation and for

verification of operational limitations will vary considerably

depending on size and type of craft, route operational

conditions, operator and regulatory criteria. An overview of

the required initial and follow-up performance

documentation is presented in Table 1 and Table 2. Code references, alternative assessment methods and general and proposed specific performance criteria are also described.

5 EXAMPLE PERFORMANCE

DOCUMENTATION FOR ONBOARD

GUIDANCE

The Nordic study “Safety Assessment of HSC Operations” (Havig & Forsman, 1997) showed that the risk to individual passengers on Nordic HSC Passenger/Ro-Ro ferries compare

very favorably with other means of public transport. A

number of safety measures could be introduced, however in order to further improve the safety level. One major safety measure is to improve the documentation of craft operation and safety – and to make this information readily available for onboard guidance. The officers on all craft participating in the study stressed the importance of having suitable and

readily available operation and safety documentation.

However, rather limited information was actually available in the manuals and few systems were implemented either for measuring of performance or for systematic documentation

of operational experiences, as recommended by the ISM

Code.

Specific examples of performance documentation have been presented in the following. The formats and criteria are thoroughly discussed with masters of high-speed ferries,

Maneuvering (calm water) and broaching in stern uperatmg- ‘“ ‘“ “‘ ‘“nmmmons aurmg normal operation“ “ “ “-The revised HSC Code states:

quartering seas

The Code $ 17.5.2 states; “The craft should be controllable and capable of performing the manoeuvres essential to its safe operation up to the critical design conditions”. For

conventional ships certain manoeuvres and criteria have

evolved with experience over time to demonstrate the

efficiency of course-keeping and course-changing elements of control. The important definitive manoeuvres are; turning circle, ZigZag and reversed spiral. A ship’s directional stability can be directly demonstrated by the spiral test. However, directional stability is a not always a necessary ship characteristic for good keeping. Good

course-keeping means ability to maintain a steady course without

excessive rudder activity, particularly under adverse weather

conditions. Thus, course-keeping ability is not indicated

directly by any one definitive trial, and the “safe operation” might have to be demonstrated by additional tests. The problem is clearly shown in the figures below. Figure 8 shows a HSC with good directional stability by an initial spiral test in calm water. Figure 9 shows the same HSC in stern quartering seas revealing broaching and course-keeping

problems with yaw deviations above 25 degrees using

maximum rudder deflection.

Calm Water Manoeuvring Tests SpiralTeats

[ ‘-+ Yaw Rate

1--- _{/ ~} ~ I

-A- Low Speed Yaw $?— —..- .— .— 2 EL ~ / A z ~P ~ 1 -40 ,0 i o 20 24 is “ r/= Y ‘ / 1 I I I I I I

Ruddar Anala fDea.1

Figure 8. Directional stabili~ in calm water

.— —.. I Soakeephs Test St.m Qu8~rlng Sens 40-,“ ,,: 20. . / / x / —nudd9rM*pq.] 0. -20. . \ / 40,

The route operational manual shall include information of operating limitations, including the worst intended condition (18.2.2.2).

Operating limitation mean the craft limitation with

reference to handling, controllability and performance and the craft operational procedures within which the craft is to operate (1.4.37).

Worst intended conditions means the specified

environmental conditions within which the intention of operation of the craft is provided for in the certification of the craft (1.4.49).

Normal operating conditions are those in which the craft will safely cruise at any heading (A.8.3, 1.1).

The tests and verification process shall document the limiting seas for safe operation of the craft:

- In normal operation at maximum operational speed the accelerations shall not exceed Safety Level 1. The craft operating manual should include detailed description of the effects of speed reduction or change of heading to the waves in order to prevent exceedance (A.8.3.3. 1). - In worst intended conditions, with reduced speed as

necessary, craft shall be safely manoeuvrable and

provide adequate stability in order that the craft can continue safe operation to the nearest place of refuge. - In the worst intended conditions the accelerations shall not exceeding Safety Level 2, nor any levels that could impede the safety of passengers (A.8.3.3.2).

Passerwers shall be reauired to be seated when Safetv Level iis exceeded (A.~.3.3.2).

.

Operating limitations during normal operation are

limited by Safety Level 1 and therefore “passenger health”

conditions. In normal operation, speed reduction an~or

change of heading is acceptable in order to operate within the limiting criteria. Acceptance criteria relating to passenger health are described in Table 1 and Table 2. It should be noted that within (1S0-263 1/1) the health limit with regard to vertical acceleration is of the same general form as the comfort boundaries, but the corresponding levels are twice those of the comfort. In Tables 1 and 2 health criteria are

given for Y2, 1 and 2 hour exposure. Roll and pitch criteria

are related to safe footing.

Figure 10 shows the operating limitations during normal operation for a large catamaran based on a combination of MASHIMO calculations and model tests in head, beam and stern quartering seas. The effects of speed reduction and change of heading are clearly demonstrated. In particular limitations due to transverse accelerations in beam seas and controllability in stern seas was revealed by the free-running model tests. Data from verification tests or experiences on the actual route is yet not available.

s 6s 75 u m

ElnPndTlnm[s]

——.—. ___________..__ ____________ J

Figure 9. Coursekeeping in stern quartering seas

OPERATING LIMITATIONS DURING NORMAL OPERATION

.,.-~&sw.wu@& ~,~a . -+&>Fkf*.>“.:,:,A

+ Pitch< 1.* (R?&) k ...,; .,... ❑ Othac Yaw c 4.@ (RMS) .“ )<:_* ,,

I

Ill

v“’”-’

I

I

II

LIMITING FACTOR

I I I

I

H

I

I

Im ● vet ace Vert: acc TransVaraa am.‘ . .t%& kaaoina Pitch

CG al’s w rdl B

I

I

I HEADING _I 450 _I w I 1350 _I Ie@

Head Sea Baem Saa Fotlowinf

.,, ..,., ,

Figure 10. Example documentation of HSC Operating Limitations

Instrumentation and guidance system

The complexity of providing adequate and readily available An instrumentation and guidance system should

performance information, operation and safety guidance in include the following features:

manuals or by posters is indicated by the exampl~s presented

-above. The practical use of the information is further

hampered by the fact that masters have to consider

significant wave height and heading to fully utilise it

-correctly. Problems to observe and evaluate sea conditions in

general and in night operation in particular are pinpointed by

-all masters. In the revised Code ($17.1) it is stated that

operational information shall be available onboard for

guidance, or the craft shall have an approved instrument system for on-line check of operational performance.

Keeping in mind the main purpose of requiring

documentation of high-speed craft operational and safety

performance, that is to ensure safe operation of the craft in

-the route, -the alternative use of an approved instrumentation

system might be a cost-effective and the most practical

solution for onboard application of the complex information. In particular, as the Administrations should approve adequate systems as a replacement for the follow-up tests and the process for verification of initial documentation.

The instrumentation (sensors) should measure relevant

craft characteristics and should be of well proven

commercial types.

The acquisition and analysis system should be

adequately documented and verified by tests.

Limiting criteria for the relevant craft characteristics, human comfort, health and safety levels should be thoroughly assessed by the operator and accepted by the masters.

The operational information should be readily available, preferably of “dead type” being activated manually or as threshold values are exceeded.

A system should be established, within the ISM/Safety Management System, to report operational experiences and allowing for adjustment of both limiting criteria, presentation of information and any active guidance given by the system.

Three levels of instrumentation and guidance systems can be foreseen: 1) 2) 3) 6

The simplest level using three accelerometers in craft center of gravity and presenting information related to

horizontal accelerations (Safety Level 1 and 2) and

vertical acceleration. The system should show actual maximum values and the last (5) minutes predicted RMS-values compared to threshold values. Some active guidance can be presented by this system.

The next level would add measurements of roll, pitch, course and speed. Measured and predicted maximum

and RMS-values would be compared to relevant

comfort, health and safety criteria. By including manual

input of heading to the waves, the information as

presented in Figure 10 will be available and active operational guidance can be given.

The third level guidance system might include a

detection system for the wave condition experienced by the craft at any time, coupled to an analysis and test data system that computes the best heading and speed with

respect to the selected combination of criteria. The

criteria can be any speed loss or craft motion, and also to

some extent criteria for maximum hull loads. The

guidance given by the system should be given not only with respect to the current situation, but might also propose the “best” route further ahead based on stored information of operational area and conditions.

CONCLUSIONS

The IMO code of Safety for High-Speed Craft is mandatory for operation of HSC in international routes. A revised Code including modifications related to the documentation of craft performance and operating limitations will enter into force in July, 2002.

The main objective for requiring comprehensive performance documentation is 1) for craft certification and 2) for the guidance of the shipmaster. The initial documentation

of craft performance for certification purposes shall be

included in the Craft Operating Manual and can be supplied by full-scale tests, model tests and mathematical simulations, or by combination of such. The information contained in the Route Operating Manual should be based on verification of craft performance and operating limitations as experienced in the actual route, also taking into account the operating procedures. The relevant operational and safety information shall be readily available for the master. As an alternative to the comprehensive documentation for the guidance of the master an instrument system for on-line check of operational performance can be applied.

A variety of classes of different software to

calculate the HSC performance are available, as are also model test methods and facilities. It is of great importance to

apply these tools wisely as the stages of design and

construction progresses. As the size of craft, craft

performance and route conditions might vary considerably, the cost-effectiveness and practical value of the initial and follow-up documentation must be considered thoroughly by all parties involved.

According to reports from the industry it seems that

different practices are being established as to what is

acceptable for both documentation of craft performance and onboard application of operational and safety information. Safetv assessment studies show that officers on HSC stress

the importance of having suitable and readily available

information. However, rather limited information is normally available in the craft and route manuals and few systems are implemented either for measuring of performance or for systematic documentation of operational experiences.

An overview of the regulatory documentation

process, as interpreted by the authors is presented. Likewise

the elements of the required initial and follow-up

performance documentation is presented containing Code references, alternative assessment methods, and general and proposed specific performance criteria.

Specific examples of performance documentation are presented, and the complexity of providing adequate and

readily available performance information, operation and

safety guidance is clearly indicated. Keeping in mind the main purpose of requiring operational information, that is to ensure safe operation of the craft in the route, it is concluded that the alternative use of instrumentation system for on-line check of performance could be the most practical and cost-effective approach. 7 1] 2] 3] 4] 5] 6] 7] REFERENCES

Faltinsen, O.M. & Zhao, R., “Numerical predictions of

ship motions at high forward sped”. In Phil. Trans. R. Sot.

Lzmd. A,vol. 334, pp. 241—252, 1991.

Havig, K.M. & Forsman, B., “Nordic Safety Assessment

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I) INITIAL DOCUMENTATION Requirements Method Acceptance Criteria

(Craft Operational Manual) HSC Code Comments, documentation of effects

A) Stomin~ (Calm Water] Code $17.2.1

1- Normal stop from max. speed Annex 8, $4.3 Trials General: Steering control, stopping distance, trim / plough-in effect.

2- Emergency stop 1) & 2)< 0.20 g , 3) <0.35 g, “max’’-value her. ace.

3- Crash stop

B) Failure Conditions (Calm Water] Annex 8, $2.1 Trials General: Dec. of stopping distance and her. ace.

1- Total loss of propulsion power ● _{Horizontal ace. e 0.35 g, “max” (Safety Level 2).}

2- Total failure control, one prop. system 3- Involuntary full thrust, one system 4- Failure on directional control system 5- Total loss of electrical power etc.

C) Manoeuvrirw (Calm Water] Annex 8 $3.4.1 Trials General: Safely controllable/manoeuvrable

1- Turning Circle Tests 15° and 30° I-Turning diameter. Her. ace. Level <0.2 g, “max”.

2- Zig-Zag Tests 10/10 and 20/20 2-Yaw-checking ability. Quickness of response

3- Reversed Spiral Tests (30/30) 3- Directional stability characteristics.

D) Seakmimz Performance Annex 8, $3.1-4 General: Tests in two sea conditions, min. head, beam and following

seas. Effects of reduced speeds.

1- Limits for Normal Operational Conditions Trials 1- Moderate degradation of safety (Safety Level 1)

. Horizontal ace.c 0,20 g, “maX”- value.

. Vertical ace. e 0.20 g, RMS (CG)–1/2 h. exposure

( c 0.15& 0.10 g for 1 & 2 hour exposure).

2- Limits for Worst Intended Conditions Trials ● Roll & Pitch e 4.0 & 1.5 degr., RMS

2- Significant degradation of safety (Safety Level 2)

● Horizontal ace. <0.35 g, “max” – value.

● Vertical ace. e (0.25) g, RMS (in CG)

E) Alternative verifkation of ~erformance in Worst Annex 8, $3.2 Model tests and General: Initial doe. in up to worst intended condition might be

Intended Condition (WC). Mathematical impractical or impossible to conduct prior to start of operation.

simulations. Assumed that trial tests for verification of op. limitations is

performed as soon as practical, alternative initial dot. should be accepted.

- Model Tests Model in lab. or in Documentation as in D).

open sea. Two wave conditions, three headings and two speeds.

- Mathematical Calculations combined with Calibrated num. Specified comfort, health and safety criteria (Ref. D). Predictions

adequate model or full-scale test data. program, incl. minimum 7 headings and 2 speeds. Minimum calibration data: one

test data check. wave condition (WC), two headings (head and following) and two

II) VERIFICATION OF PERFORMANCE

(Route Operational Manual)

A) Information included in the Initial Documentation ( I).

B) Onerathw limitations dunn~ normrd operation.

- Test in head to beam seas.

- Tests in stern quarter seas (120-160 deg.)

(Provoking broaching events)

- Tests in following seas (180 deg.)

(Bow diving/plough in)

C) “Dead ShirY’ r)erformance in waves

— Requirements (Ref. HSC Code) Code S 17.2.2 code $17.2.2 Annex 8,53.4.5 Method Trials Trials Trials Alternatives Trials Trials Trials Trials Free drift. Acceptance Criteria

Comments, documentation of effects

● Failure Conditions

● Stopping Tests

● Manoeuvring Tests

● Seakeeping Tests

General: Limitations; handling, controllability and performance taking into account operational procedures.

● ● ● ● ● w ● ● ● * ●

Horizontal ace. <0.20 g, “max”.

Vertical ace. <0,20 g; RMS (CG) – !42h. exposure. (cO.15& 0.10 g for 1 & 2 hour exposure).

Roll c (4.0) deg., RMS. Pitch e (1.5) deg., RIMS. Wet deck slamming.

Steering performance (Yaw deviations and rudder deflections).

Tendencies of broaching/loose of control. Yaw deviations e (20) deg., max-value. Horizontal ace. c 0.20 g,” max”.

Tendencies of bow diving, water on deck. Craft speed = op. speed in specific wave groups.

General: Documentation of drift and motion performance; heading, jpeed, roll, pitch and hor.acc.