Sea Trials and Performance Testing

Sea trials are the structured set of performance tests carried out at sea to verify that a newly built or substantially modified vessel meets its design specification, its contractual obligations to the owner, and the regulatory requirements of the flag state and classification society. A trial failure at the contracted speed point costs a builder roughly $50,000 to$200,000 per day in delay liquidated damages plus the costs of a repeat trial and potentially a dry-dock correction, which is why the speed-power prediction and the trial programme design are treated as critical path items from the keel-laying stage.

This article covers the full trial programme: the categories of event in a newbuilding programme, the ISO 15016:2015 methodology for correcting raw speed-trial data to ideal conditions, the EEDI verification procedure under MARPOL Annex VI Regulation 20, the IMO MSC.137(76) manoeuvring criteria and how each trial is conducted, the endurance and machinery trials, the noise survey per IMO Resolution MSC.337(91), and the ISO 19030:2016 framework for monitoring hull and propeller performance in service. Companion calculations are available at Voyage Speed and Power Fit, Hull ISO 19030 Performance, Turning Circle Advance, Stopping Distance, Zig-Zag Overshoot, EEDI Attained, and EEXI Attained. The related articles Engine Sea Trial Procedures and Marine Engine Performance Monitoring cover the propulsion-plant side of the same event and should be read alongside this article.

Trial event types in a newbuilding programme

A newbuilding contract typically defines five classes of sea trial event, each serving a different purpose.

The builder’s trial takes place before any owner involvement. The yard uses it to verify that all systems function, clear defects from the harbour-acceptance test, and establish the actual power-speed relationship before committing to the formal contractual trial. Owner representatives may observe, but no results from this event are contractually binding.

The gas trial applies to LNG carriers, LPG carriers, and vessels with gas-fuelled propulsion. It is conducted after the cargo containment system or fuel gas supply system is first loaded and verifies cargo handling, emergency shutdown sequences, and dual-fuel propulsion behaviour at operating conditions. Typically this requires 48 to 72 hours at sea and a crew with gas-training certification. The trial is witnessed by class and the flag state administration.

The contractual (pre-delivery) sea trial is the binding event. The owner’s superintendent and technical manager, class surveyors from at least one society, flag state inspectors where the flag requires, and the yard’s trial team all attend. The trial programme is fixed in the shipbuilding contract and deviations require written agreement. Results are signed by both parties; they determine contract acceptance and trigger any speed-bonus or liquidated-damages provisions. For a Panamax bulk carrier, that bonus-malus band is typically plus or minus 0.25 knots at the specified power, representing millions of dollars of charter value over a 25-year life.

A repeat trial is scheduled when the contractual trial reveals a deficiency, most commonly a shortfall in corrected speed. The repeat covers only the deficient items or the full powering sequence, depending on contract language. Repeat-trial costs generally fall on the yard.

A post-delivery performance trial, where contracted, occurs 6 to 12 months after delivery, with the hull in a defined fouling condition, to confirm that the guaranteed performance band is being met in service.

Harbour acceptance test and sea acceptance test

Before the formal contractual sea trial, most shipbuilding programmes run two intermediate events: the harbour acceptance test (HAT) and the sea acceptance test (SAT). The distinction matters for both the yard’s quality process and the owner’s inspection rights.

The HAT, sometimes called the quay trial or dock trial, is conducted with the vessel secured alongside or in a dry dock, either immediately before flooding and undocking or within the first hours after the vessel is waterborne. Its purpose is to verify that each individual system functions to design specification before the ship leaves the relative safety of the yard environment. Engine room auxiliaries, bridge control systems, fire detection and suppression, watertight door operation, GMDSS radio equipment, lifeboat release mechanisms, bilge pump capacity, and steering gear response to bridge commands are all tested under controlled conditions where remedial work is straightforward. A typical HAT programme for a Panamax bulk carrier runs 3 to 5 days and generates a defect list that the yard is contractually required to clear before the SAT.

The SAT is the first full-power run with the vessel at sea, normally at anchor or at slow speed away from the berth. Its scope is narrower than the contractual acceptance trial: the SAT verifies that the propulsion plant reaches design RPM, that all bridge control positions function at sea speed, and that the navigational instruments give consistent readings. It is the builder’s internal check that nothing was overlooked during the HAT. Owner representatives typically attend the SAT but the results are not contractually binding unless the contract explicitly provides for SAT acceptance milestones.

The two-stage HAT/SAT approach is standard on major building programmes at the three largest commercial shipbuilding nations. The Society of Naval Architects and Marine Engineers (SNAME) Panel SP-7 and the equivalent guidelines from the Classification Society societies set out the minimum test scope for each stage. IACS Unified Requirement Z20 references the HAT as the pre-sea-trial machinery certification event.

The trial condition at which the contractual sea trial runs matters too. Virtually all speed-power contracts specify a “deep-water” condition: water depth must be at least 10 times the ship’s draft ($h/T \geq 10$) and preferably 20 times at the trial location, so that the Lackenby shallow-water correction is negligible. Most contracts also specify that the trial shall be in the fully laden condition at the design draught, or alternatively in a defined ballast condition that the owner and builder agree is representative of the vessel’s common service draught. Running the trial too high in ballast understates resistance and overstates speed; running with more trim than the design trim can affect appendage resistance.

Steering gear trials: SOLAS Chapter II-1 Regulation 29

SOLAS Chapter II-1 Regulation 29 requires that every vessel’s steering gear is tested before departure from any port. The sea trial provides the formal certification baseline for this test. The steering gear trial at sea is distinct from the bridge-to-steering-gear communication check in port; it verifies the actual time-to-hard-over performance and the changeover between the main and auxiliary steering systems under operating conditions.

The standard performance requirement is that the main steering gear shall be capable of putting the rudder from 35 degrees on one side to 35 degrees on the other in not more than 28 seconds, with the vessel at its deepest service draft and running at maximum service speed ahead, or at two-thirds of the maximum continuous rated shaft revolution speed, whichever is the greater. This is the quantitative criterion most often cited as the “35/35/28” rule. At the trial this is measured three times and the average must meet 28 seconds; individual runs must not exceed 30 seconds.

The auxiliary steering gear trial, also required under SOLAS II-1 Regulation 29.14, must demonstrate that the auxiliary system can bring the rudder to 15 degrees from midships in either direction within 60 seconds with the vessel at the design service condition. The changeover time from main to auxiliary must be confirmed, and the steering position on the after steering flat (or emergency steering compartment) must be activated and verified operational.

Class procedures from DNV Rules for Ships Part 4 Chapter 9, Lloyd’s Register Rules and Regulations Part 5 Chapter 2, and Bureau Veritas Rules Part C Chapter 1 all specify that the steering gear certificate is issued only after the sea trial results are signed by the attending surveyor. For vessels subject to IMO Resolution MSC.137(76), the steering gear trial is conducted prior to or during the same sea trial programme as the manoeuvring trials. The rudder response times measured during the crash-stop and zig-zag trials indirectly confirm steering gear performance at speed; the formal 35/35/28 check is a separate low-speed timing run at the nominated approach speed.

Vessels with unconventional steering arrangements, including azipods, cycloidal propellers, and flap rudders, are subject to equivalent tests defined by the class society, since the SOLAS II-1/29 literal text applies to a rudder deflected by a steering gear. IMO MSC/Circ.1102 (2003) provides guidance on how the criterion transfers to non-conventional steering.

Speed trials: the measured-mile and GPS methods

Measuring the speed of a ship precisely is harder than it appears because the vessel is moving through a body of water that is itself moving, and the propulsion resistance changes with wind, waves, temperature, and hull cleanliness. The trial answers the question of what speed-power relationship holds for a clean hull in calm, deep, standard-density seawater.

Two methods are in use. The measured-mile method uses a fixed course of known length, historically one nautical mile but now typically 2 to 3 nautical miles, marked by transit ranges or shore-based laser stations. The vessel runs the course at constant shaft speed or constant power in alternating directions. The traditional measured-mile locations include the Skelmorlie mile in the Firth of Clyde, the Polperro course in the English Channel, the Yoko-Sugishima course off Japan, and several courses off South Korean ports. These sites have precisely surveyed lengths and current-characterization data.

The GPS-based method uses differential GPS or, since about 2010, RTK-GPS with position accuracy better than 0.5 m, to measure speed over ground continuously over a run of 20 to 30 minutes at constant power. GPS trials can be conducted in any suitable open water area and have become the dominant method for large commercial vessels because they avoid the scheduling and tidal constraints of fixed measured-mile sites. ISO 15016:2015 and ITTC Procedure 7.5-04-01-01.1 (2017 revision) standardize both methods and specify the same hierarchy of data corrections.

Double-run mean and current cancellation

The core problem with any speed-over-ground measurement is that tidal current and residual ocean current add to or subtract from the vessel’s speed through water. The double-run mean method solves this at first order.

If the vessel runs on heading $\theta$ and achieves speed-over-ground $V_{SOG,1}$, then reverses to heading $\theta + 180°$ and achieves $V_{SOG,2}$, and if the current vector $V_C$ is constant over the two runs, then:

The current cancels because it adds on one run and subtracts on the other. ISO 15016:2015 requires a minimum of three double runs (six single runs) at each power setting for a full correction set. In practice, for the contractual trial of a large vessel at the design speed point, four double runs (eight single runs) are preferred.

Higher-order current effects, where current changes between runs, require the “mean of means” extension. If $V_{m,j}$ is the mean of double-run pair $j$:

and residual tidal drift across the run set is estimated by fitting a time-series polynomial to successive pair means. Annex D of ISO 15016:2015 gives the full least-squares procedure.

Speed-power curve construction

The trial is conducted at four or five power settings, typically 50%, 75%, 90%, and 100% of the contractual MCR (maximum continuous rating), with some contracts also specifying an economy speed point at 25% MCR. Each setting gives one corrected speed data point after applying all ISO 15016 corrections. The resulting pairs $(P_i, V_{s,i})$ are fitted to a cubic curve:

where $a$ is the ship’s resistance constant and $V_s$ is speed through water. Deviations from the cubic fit greater than 2% at any setting trigger investigation before the trial result is accepted. The companion calculator at Voyage Speed and Power Fit applies this curve to voyage planning.

ISO 15016:2015: correction hierarchy for speed trial data

ISO 15016:2015 defines the corrections that must be applied to raw trial data before the speed-power result can be compared with contractual specifications or used for EEDI verification. The corrections are applied in a fixed hierarchy: wind, wave, current, shallow water, displacement, water density, and air density.

Wind resistance correction

Wind exerts an aerodynamic drag force on the above-water structure. The corrected shaft power at calm-wind conditions is:

where $\Delta P_{wind}$ is the power equivalent of the wind-induced resistance increment, calculated from the measured relative wind speed $V_{WR}$ and direction $\psi_{WR}$:

$A_T$ is the transverse projected area above the waterline, and $C_{DA}(\psi_{WR})$ is the directional aerodynamic drag coefficient, which comes from wind-tunnel tests on the vessel’s superstructure model or from the Isherwood regression for conventional hull forms (ITTC 7.5-02-07-02.2). Wind corrections exceeding 2% of total resistance at the trial speed are flagged in the trial report.

Wave-added resistance correction

Short-period waves increase hull resistance through bow-pressure effects and added mass in heave and pitch. ISO 15016:2015 uses the Kwon method for the trial conditions correction, with the Fujii-Takahashi or Jinkine-Ferdinande regression as alternatives. The correction is:

where $H_s$ is significant wave height, $T_z$ is mean zero-crossing period, $L_{pp}$ is length between perpendiculars, $B$ is breadth, and $C_B$ is block coefficient. Trials are typically cancelled if $H_s$ exceeds 1.5 m for vessels under 150 m or 2.0 m for vessels above 250 m. The contractual trial programme specifies the acceptable environmental window.

Shallow-water correction

In water of limited depth $h$ relative to draft $T$, hull resistance increases because of the restricted flow under the keel (the blockage effect) and the wave-speed limitation imposed by the finite water column. Trials should be conducted where the depth ratio $h/T$ exceeds 10; below that threshold, the Lackenby (1963) method quantifies the speed reduction:

where $A_m$ is the midship section area and $g$ is gravitational acceleration. Most major newbuilding anchorages have charted depths exceeding 50 m at the trial locations, making this correction negligible; but for shallow harbours and coastal builders in the Yellow Sea or Gulf of Thailand, it can reach 0.3 to 0.5 knots.

Water temperature and density correction

Propeller thrust and engine fuel consumption both depend on seawater density $\rho$. The standard reference density is 1,025 kg/m³ at 15°C. Power is corrected by:

Air density affects engine charge-air density and therefore combustion efficiency. ISO 15016 applies the engine manufacturer’s correction curve to normalize power output to ISO 3046-1 reference conditions (25°C, 100 kPa, 30% relative humidity).

EEDI verification at sea trial

MARPOL Annex VI Regulation 20 requires the attained EEDI to be verified by calculation from trial data before the International Energy Efficiency Certificate is issued. The attained EEDI formula for a single-engine, single-propeller vessel is:

where $P_{ME}$ is shaft power at 75% of the contractual rated MCR, corrected to ISO 15016 ideal conditions; $C_{F,ME}$ is the CO₂ emission factor for the fuel type (3.1144 t CO₂/t for HFO, 3.0660 for MDO); $SFC_{ME}$ is the certified specific fuel consumption at 75% MCR in g/kWh from the engine’s NOx Technical File (EIAPP certificate); $P_{AE}$ is the auxiliary power demand at the EEDI design draught; $W$ is the ship’s deadweight or gross tonnage capacity parameter; and $V_{ref}$ is the ISO 15016-corrected trial speed at 75% MCR.

The result must not exceed the required EEDI from Regulation 21:

where $EEDI_{ref}(W)$ is the ship-type reference line value and $X$ is the phase-factor reduction percentage (Phase 1, 2, or 3 depending on contract date and ship type). The companion calculators at EEDI Attained and EEDI Required implement Regulation 21 in full, including the phase factor table from IMO MEPC.1/Circ.795. For existing ships subject to EEXI under Regulation 23, see EEXI Attained.

The verification survey is conducted by the flag administration or a Recognized Organization (RO) acting on its behalf. The survey verifies: the engine NOx Technical File and EIAPP certificate; the trim and draught at trial; the ISO 15016 correction calculations; the computed attained EEDI against the required value. A shortfall triggers an engine power limitation (EPL) or a shaft power limitation (ShaPoLi) before re-survey. The EEXI EPL and ShaPoLi article covers the power-limitation options.

Manoeuvring trials: IMO MSC.137(76) criteria

IMO Resolution MSC.137(76), adopted in December 2002 and applicable to all ships of 100 m or more in length plus chemical tankers and gas carriers regardless of length, defines five quantitative criteria that must be met at the SOLAS sea trial. Compliance is verified under SOLAS Chapter II-1 Regulation 29, and the results are recorded in the Manoeuvring Booklet retained on board under SOLAS Chapter V Regulation 28.

“Ship lengths” in the table means the ship’s length between perpendiculars, $L_{pp}$.

Turning circle trial

The turning circle test is run at the vessel’s approach speed (typically full sea speed) with full rudder (35 degrees on most vessels; 45 degrees on vessels with high-lift rudders). The vessel is held on the initial heading until speed and heading rate are steady, then the rudder is put hard over and held for 540 degrees of heading change (one-and-a-half full turns). The trial is run in both port and starboard directions and in sufficient water depth (at least 2.5 times the draft) to exclude bottom effects.

The key parameters are advance (forward distance from rudder execute to 90-degree heading change), transfer (lateral distance at 90-degree change), tactical diameter (diameter of the turn at 180-degree change), and steady turning radius. Advance and tactical diameter are the MSC.137(76) criteria. Most cargo ships achieve tactical diameters of 3.5 to 4.8 $L_{pp}$ at 35-degree full-rudder. The companion calculator Turning Circle Advance and Turning Circle Tactical Diameter implement the standard parameter extraction.

Zig-zag trial

The 10/10 zig-zag (Kempf manoeuvre, named after G. Kempf who standardized it in the 1930s) tests the vessel’s yaw-checking and course-keeping ability. The procedure: vessel steady at approach speed on a fixed heading, rudder put 10 degrees to starboard, held until heading changes 10 degrees starboard of the initial heading, then rudder put 10 degrees to port and held until heading reaches 10 degrees port of the initial, then starboard again. The run continues for three to five rudder reversals.

The first overshoot angle is the amount by which the heading swings past the 10-degree check heading before the rudder effect from the opposite-helm application arrests the swing. For a 300-metre container ship, a first overshoot of 8 degrees is typical; 12 degrees would fail the MSC.137(76) criterion. A 20/20 zig-zag is also conducted for some vessel types to check response at larger amplitudes. The Zig-Zag Overshoot calculator computes the first and second overshoot angles from the measured heading time-history, and Nomoto K index and Nomoto T index characterise the linear manoeuvring response underlying the zig-zag behaviour.

Crash stop

The crash stop measures the track reach under emergency full-astern propulsion from full ahead speed. The vessel accelerates to full trial speed on a straight heading, then receives an all-back-full telegraph order. For a twin-screw vessel the procedure is similar but both shafts reverse simultaneously.

For a large slow-speed two-stroke main engine, the reversal sequence takes 15 to 30 seconds from telegraph order to engine running astern at starting power. The total stopping sequence involves engine reversal, shaft deceleration, and the hydrodynamic braking effect of the reversing propeller. Track reach for a loaded Panamax bulk carrier of 225 m $L_{pp}$ typically falls between 10 and 13 ship lengths under the standard crash-stop procedure. The Stopping Distance calculator applies the ITTC stopping-distance model with ship-specific resistance and propeller parameters. A dedicated crash-stop calc is at Crash Stop.

The crash stop is hard on the propulsion system. Reversing a large two-stroke main engine from full ahead applies high thermal and mechanical stress. The trial is therefore conducted only as required; it’s not repeated without strong justification, and the planned number of stops (one per direction as a rule, one to two per full trial) is negotiated in the trial programme.

Spiral and pull-out tests

MSC.137(76) does not mandate the spiral test or pull-out test, but class society procedures and the ITTC recommended procedure 7.5-02-06-02 (Captive model tests, manoeuvring) list them as supplementary tests for inherently unstable vessels. The spiral test detects course instability by holding successive rudder angles and recording equilibrium yaw rate; a non-monotonic curve indicates a dynamically unstable vessel that cannot maintain a straight course without active helm correction. Highly loaded VLCC tankers can be mildly unstable at full load.

Endurance trial and machinery certification

The endurance trial is a continuous run at the declared MCR for 4 to 6 hours, with all plant items operating in their design configuration and all redundancy systems tested in turn. The engineering team measures shaft power by torsion meter and, on modern vessels, by shaft power meter (optical or strain-gauge type), fuel mass flow by Coriolis meters with independent cross-check from tank gauge surveys, and lubricating oil and cooling water flow rates.

The certified Specific Fuel Consumption (SFC or SFOC) from the endurance trial is the primary contractual output. It is corrected to ISO 3046-1 standard conditions and recorded in the engine’s NOx Technical File as the EIAPP-certified value for EEDI purposes. A 1% drift upward in SFOC over time adds roughly 1.7 to 2.1 g CO₂/kWh to the operational energy efficiency indicator, which is why marine engine performance monitoring tracks the SFC trend against the trial baseline throughout the vessel’s life. The Engine SFOC Sensitivity to Air Temperature calculator shows how ambient conditions shift apparent SFOC if uncorrected.

The endurance trial also certifies:

• Propulsion redundancy: each shaft line tested independently where applicable.
• Bow thruster output and endurance at maximum rated power.
• Emergency generator start and load-pickup to full essential load within 45 seconds, per SOLAS II-1 Regulation 44.
• Steering gear change-over between main and auxiliary unit, and tiller engagement, per SOLAS II-1 Regulation 29 (the same regulation that requires manoeuvring compliance).
• Anchor windlass holding, lowering, and retrieval tests per class rules. The holding power of the bower anchor relative to vessel size can be estimated using Anchor Holding Power.

Noise and vibration surveys

IMO Resolution MSC.337(91), adopted in 2012 and effective from 1 July 2014, sets noise-level limits on board ships. It is the first binding international noise standard for merchant ships and applies to all ships of 1,600 GT or more contracted for construction on or after 1 July 2014.

The noise survey at sea trial measures A-weighted continuous sound levels ($L_{Aeq}$) in decibels at specified locations across the vessel. The MSC.337(91) limits are:

• Engine room and machinery spaces: 110 dB(A)
• Navigation bridge (underway): 65 dB(A)
• Radio room: 60 dB(A)
• Officers’ cabins: 60 dB(A)
• Crew recreation rooms: 65 dB(A)

The survey is conducted by an independent acoustics surveyor approved by class, with the vessel at full sea speed in conditions where ambient noise does not corrupt the measurement. Compartments exceeding the limits require correction before delivery, which typically means additional acoustic treatment to bulkheads, machinery mounts, or vent ducting.

Vibration surveys (whole-body vibration per ISO 6954:2000) are conducted concurrently for crew spaces and bridge, checking that propeller-induced vibration frequencies do not coincide with structural resonances. The Ship Vibration article covers the propeller-blade-rate and hull-girder resonance mechanisms in detail.

Bollard pull trial

The bollard pull trial applies specifically to tugs and anchor-handling vessels and is covered by IACS Recommendation No. 16 and individual class society procedural notes (DNV, Lloyd’s Register, Bureau Veritas). The trial measures static thrust at maximum continuous engine output with the tug’s propulsion pulled against a fixed quay bollard.

The procedural requirements:

• Tow wire minimum length: 3 times the tug’s length.
• Water depth: minimum 2 times the tug’s draft.
• Current at the trial site: maximum 0.5 knots.
• Wind: maximum Beaufort 4 at the tug’s bow.
• Duration for continuous bollard pull average: minimum 5 minutes at full power, with readings at 10-second intervals.
• Maximum bollard pull: the 30-second average of the highest sustained thrust.

The certified values are: continuous bollard pull (CBP) in tonnes and maximum bollard pull (MBP) where specified. For ASD (azimuthing stern drive) tugs, pull values are measured at full ahead and full astern, because the astern pull is often 15 to 25% lower than ahead pull due to the nozzle-duct arrangement. The Tug Bollard Pull Selection and Offshore AHTS Bollard Pull calculators match required pull to vessel capability. Full background on bollard pull and tug performance is at Tug Operations and Bollard Pull.

Trial documentation and certification

The sea trial produces a structured set of documents, each with a defined regulatory or contractual function.

The Speed Trial Certificate, signed by the builder, the owner’s representative, and the attending class surveyor, certifies the corrected trial speed at each power setting and the correction methodology used. It is the primary commercial document for the vessel’s speed warranty under any subsequent time charter party. The speed warranty clause and the related on-hire speed-consumption guarantee are discussed in Charter Party Speed and Consumption Warranties.

The Manoeuvring Booklet, class-certified, contains all MSC.137(76) trial results in IMO-specified format. It is required to be retained on board under SOLAS Chapter V Regulation 28. The Pilot Card and Wheelhouse Poster, derived from the same data, are displayed on the bridge for use by pilots and watch officers. See Pilotage Operations for how pilots use this data in port approach.

The International Energy Efficiency Certificate (IEEC), issued by the flag administration or its RO after reviewing the EEDI verification calculation, confirms that the attained EEDI does not exceed the required EEDI. Without the IEEC, the vessel cannot trade internationally under MARPOL Annex VI. An EEDI Technical File documenting the calculation inputs is retained on board.

The Specific Fuel Consumption Certificate, derived from the endurance trial mass-flow data, records the ISO 3046-corrected SFC at full MCR and at 75% MCR. It feeds the EIAPP and EEDI Technical File.

The Class Certificate of Trial, issued by the attending classification society, confirms that the trial programme was conducted per class rules and that the vessel is fit for service in the certified notation.

ISO 19030:2016: in-service hull and propeller performance

Once the vessel enters service, the ISO 15016-corrected trial data forms the performance reference state (PRS) against which degradation is measured. ISO 19030:2016 (Ships and marine technology, Measurement of changes in hull and propeller performance) defines the monitoring methodology and three indicators of performance change.

The three ISO 19030 indicators

The speed loss indicator ($\Delta V_s$) measures the reduction in speed at constant shaft power compared to the PRS, after correcting for environmental conditions using the same ISO 15016 hierarchy:

A negative $\Delta V_s$ (speed reduction at constant power) indicates hull fouling, propeller fouling, or propeller damage. For a large bulk carrier, $\Delta V_s$ of 0.5 knots corresponds to roughly 12 to 18% additional fuel consumption to maintain the charter-party speed. The hull performance calculator at Hull Performance Speed Loss ISO 19030 implements this indicator.

The power increase indicator ($\Delta P_{shaft}$) measures the extra shaft power required to maintain the PRS speed:

The shaft power factor (SPF) normalizes power increase against the PRS to give a dimensionless degradation ratio. Values above 1.15 (15% power increase) typically justify a hull cleaning. The Hull ISO 19030 calculator computes SPF from noon-report data.

Environmental data filtering

ISO 19030 requires the same environmental corrections as ISO 15016, but applied continuously to noon-report or high-frequency log data rather than to controlled trial runs. The standard defines minimum data quality thresholds: significant wave height below 2.5 m, Beaufort wind below 5, and water depth above 15 times the draft. Voyage segments outside these thresholds are excluded from the performance database. This filtering requirement means that full ocean crossings on the North Atlantic in winter contribute few usable data points, while coastal runs in benign conditions contribute many.

The comparison of ISO 19030 indicators over time directly informs dry-docking schedules, hull coating selection, and in-water cleaning decisions. The Slow Steaming and CII article discusses how speed reduction interacts with the hull-fouling power penalty and the CII calculation.

Propeller performance monitoring

ISO 19030 Part 2 (ISO 19030-2:2016) distinguishes between hull fouling and propeller fouling by measuring propeller rotational efficiency separately. A reduction in propeller open-water efficiency $\eta_0$ at constant advance coefficient $J$ indicates propeller surface degradation; a reduction in $V_s$ at constant $P_{shaft}$ with stable $\eta_0$ points to hull resistance increase. The distinction matters because propeller polishing is a 4 to 8 hour in-water operation costing roughly $15,000 to$25,000, whereas hull cleaning requires a dedicated port call or dry-dock.

Contractual speed and consumption guarantees

The sea trial result is the point of origin for the owner’s commercial rights throughout the vessel’s life. Under most standard-form shipbuilding contracts (SAJ, BIMCO Newbuildcon), the builder guarantees:

1. A contracted speed at a specified draught, trim, and power setting in calm weather and deep water.
2. A maximum fuel consumption at the same conditions.
3. Sometimes a minimum bollard pull (for tugs) or a minimum cargo system throughput rate (for tankers or LNG vessels).

The tolerance band is typically 0.25 to 0.5 knots on speed and 3% on fuel consumption. Breach outside the tolerance triggers a liquidated damages per-fraction-of-knot schedule that can amount to several million dollars over the life of the vessel. The Off-Hire and Performance Claims article describes how trial-certified performance baselines carry over into charterparty disputes.

Limitations of the trial measurement

Sea trial measurements have documented sources of error that practitioners should be aware of when interpreting results.

The ISO 15016 wind correction relies on aerodynamic drag coefficients from model tests or the Isherwood regression, both of which carry uncertainties of 10 to 15% for unusual superstructure arrangements. For vessels with large deck cargo, windmill installations, or crane structures, purpose-built wind-tunnel models are strongly advisable.

The wave-added resistance correction in ISO 15016 is based on wave-spectrum calculations that assume a fully-developed JONSWAP or P-M sea state. Swell from distant storms that is not locally wind-generated can add resistance without a corresponding local wave-height reading, leading to under-correction.

Current corrections using the double-run mean assume that current is spatially and temporally uniform over the trial site. In areas with strong tidal eddies or stratified flow (common in Norwegian fjords, Korean straits, and estuarine anchorages), the actual current field can vary 0.2 to 0.5 knots across a 3-nautical-mile run, biasing the mean. The ITTC 2017 procedure recommends running the speed trial outside tidal strength periods and in open water away from headlands.

The SFOC value used in the EEDI calculation comes from the engine’s NOx Technical File, certified on the engine test bed at the manufacturer’s facility. On the test bed, the engine typically operates with slightly different injection timing, sea water temperature, and back pressure than on the installed vessel. Differences of 1 to 3 g/kWh between test-bed SFOC and in-service SFOC are documented in the literature; the EEDI calculation uses the test-bed value, not the in-service value.

Post-trial hull fouling starts from the moment the vessel is launched. For vessels with long fitting-out periods, 4 to 6 months of exposure at the dock before the contractual trial means the trial is not conducted on a fully clean hull. Some contracts allow a fouling correction; others accept the launch-to-trial interval as part of the builder’s responsibility and require antifouling paint applied within a defined period before the trial.

In-service ISO 19030 monitoring is only as good as the noon-report data quality. Manual fuel readings, uncalibrated flow meters, and estimated speed-over-ground from chart positions rather than GPS create scatter that obscures real performance trends. Vessels equipped with continuous shaft power meters (torsion meters) and GPS track recorders produce ISO 19030 datasets an order of magnitude more useful than those relying on end-of-voyage summary entries.

Classification surveyor and flag state roles at trials

The sea trial is a certification event for three distinct authorities, and each has a specific role that cannot be performed by the others.

The classification society surveyor attends the contractual trial as the technical certifying authority. The surveyor verifies that the trial programme was conducted in accordance with the applicable class rules and that the results support the class notation being assigned. For a vessel classed with Lloyd’s Register under the Maltese cross notation, for example, LR’s ship survey and construction procedure requires the attending surveyor to witness the steering gear timing, confirm the manoeuvring booklet entries against the observed trial results, sign the speed trial certificate, and issue the Class Certificate of Survey. The class surveyor does not sign off on behalf of the flag state; that authority belongs to the Administration.

The flag state Administration, or a Recognised Organisation (RO) authorised under SOLAS Regulation I/6 to act on its behalf, issues the statutory certificates. The International Energy Efficiency Certificate under MARPOL Annex VI Regulation 6 requires the flag’s RO to verify the EEDI calculation independently against the trial data. The Safety Construction Certificate under SOLAS I/12 requires the Administration to be satisfied that all SOLAS requirements have been met, including the manoeuvring compliance under SOLAS II-1/29. For a vessel flagged to a major open registry (Panama, Marshall Islands, Liberia, Bahamas), an RO such as DNV, ABS, or Lloyd’s Register typically holds the authority to act on behalf of the flag and attends the trial in that dual capacity.

The owner’s representative, normally a senior superintendent engineer or a dedicated trials team, attends in a witness and commercial capacity. The owner has no power to refuse class or flag certificates, but has the contractual right to reject the trial result if it falls outside the contracted guarantee band and to withhold acceptance of the vessel. The standard SAJ form contract (Japanese Shipbuilders’ Association Form) and BIMCO NEWBUILDCON both provide for a 30-day rectification period after a failed trial, during which the builder is at risk for all costs.

When multiple class societies are involved, for example when the owner plans to change class after delivery, both societies may attend. The primary attending surveyor is the one assigned to the notation being built; the secondary attends as an observer. This can cause procedural delays if both societies have conflicting test requirements.

Periodic in-service performance testing under SEEMP and ISO 19030

The sea trial establishes a certified performance reference state (PRS). International requirements mandate that this baseline is actively used in service, not filed and forgotten.

MARPOL Annex VI Regulation 22 requires every ship above 5,000 GT to carry a Ship Energy Efficiency Management Plan (SEEMP). The SEEMP framework, described in IMO Resolution MEPC.346(78) (2022) and its predecessors, requires the vessel to monitor and record operational performance data continuously and to compare it against the baseline. Part III of the SEEMP, mandatory from 1 January 2023 for ships subject to the Carbon Intensity Indicator (CII), requires the operator to set an improvement target and to demonstrate a credible pathway to meet it, referencing the operational performance against the trial-certified speed and fuel consumption.

ISO 19030:2016, Parts 1, 2, and 3, specifies the technical method for the in-service comparison. The three-part standard defines: the general principles and data requirements (Part 1); the method for establishing the reference condition from trials and correcting in-service data for environmental factors (Part 2); and the method for determining propeller performance separately from hull resistance (Part 3). The SEEMP framework and ISO 19030 are complementary: SEEMP is the regulatory obligation to monitor; ISO 19030 is the technical standard that tells you how.

In practice, the most rigorous operators run a formal performance test at each drydocking, typically once every 60 months for a vessel on a five-year Special Survey cycle. This drydock entry test is conducted with the hull freshly cleaned and inspected, so it provides a cleaned-hull reference data point that allows the rate of fouling growth between dockings to be quantified. The difference between the ISO 19030 performance at arrival before drydock and at departure after drydock is the fouling penalty accumulated over the service interval.

Some third-party performance monitoring services (conducting continuous shaft power and GPS data logging via onboard hardware) report ISO 19030 SPF values to owners and charterers on a weekly basis. Where a time charter contains a performance warranty clause, these real-time SPF values feed directly into the calculation of any off-hire claim or speed claim. The Off-Hire and Performance Claims article covers the evidentiary weight courts have given to ISO 19030 SPF values in arbitration proceedings.

Related calculators (ls-verified)

• Voyage Speed and Power Fit
• Hull ISO 19030 Performance
• Hull Performance Speed Loss ISO 19030
• Turning Circle Advance
• Turning Circle Tactical and Steady Diameter
• Stopping Distance
• Zig-Zag Overshoot
• Crash Stop
• Zig-Zag 10/10
• Manoeuvring Trial Weather Correction
• Nomoto K Manoeuvring Index
• Nomoto T Manoeuvring Index
• Tug Bollard Pull Selection
• Offshore AHTS Bollard Pull
• EEDI Attained
• EEDI Required
• EEXI Attained
• Anchor Holding Power
• Engine SFOC Sensitivity to Air Temperature

Related wiki articles (ls-verified)

• Engine Sea Trial Procedures
• Marine Engine Performance Monitoring
• Tug Operations and Bollard Pull
• EEXI EPL and ShaPoLi
• What is EEDI
• What is EEXI
• Slow Steaming and CII
• Charter Party Speed and Consumption Warranties
• Off-Hire and Performance Claims
• Time Charter Party
• Classification Society
• SOLAS Convention
• Pilotage Operations
• Ship Vibration
• Ship Resistance and Powering