BD Deck Officer Class 2 (Chief Mate) cheat sheet

Mercator: departure (nm) = DLong (minutes) × cos mean latitude; rhumb-line distance along a meridian equals DLat in minutes.

Great-circle distance: cos D = sin φ1 sin φ2 + cos φ1 cos φ2 cos Δλ; initial course from sin C = cos φ2 sin Δλ / sin D.

Amplitude: sin A = sin δ / cos φ; amplitude is named east for rising and west for setting, with north or south according to declination.

Sextant altitude correction: Ho = Hs + IC + dip + refraction ± semi-diameter + parallax; intercept a = Ho − Hc, drawn toward if Ho is greater.

Tide prediction by rule of twelfths: within a six-hour rise or fall, increments are 1/12, 2/12, 3/12, 3/12, 2/12, and 1/12 of range.

Passage planning stages: appraisal, planning, execution, monitoring; each leg requires no-go areas, abort points, UKC, and contingency anchorages.

Cocked-hat fix: random errors produce a triangle whose centre is the likely position; a constant offset indicates systematic error such as compass or index error.

ECDIS route check: safety contour must exceed maximum draught plus UKC; XTD must keep the ship clear of charted obstructions and no-go areas.

Stowage factor (m³/t) = cargo volume / cargo mass; broken stowage (%) = (available volume − occupied volume) / available volume × 100.

Draft survey displacement is corrected for density (× ρ actual / 1.025), trim by LCF, and deductibles such as ballast, fresh water, and constants.

Cargo sweat forms when warm moist air meets a cold cargo surface; ship sweat forms when moist hold air meets cold ship structure; dew-point control prevents both.

IMDG segregation: codes 1–4 mean away from, separated from, separated by one hold or compartment, and separated by two; class compatibility is checked before stowage.

Grain stability depends on angle of repose, filling of holds, trimming, and the Grain Code allowable heel; a slack hold permits grain shift and list.

Reefer carriage requires set-point temperature, fresh-air exchange, pre-cooling, and continuous recording; cargo temperature must be within the agreed range before loading.

Timber deck cargo increases KG and absorbs water; lashings and stanchions must be checked, and stability must account for water absorption and ice accretion.

A clean bill of lading states cargo received in apparent good order; a claused bill records damage or shortage and affects documentary credit acceptance.

GM = KM − KG; righting lever GZ = GM sin θ for small angles; righting moment = Δ × GZ.

Free-surface correction FSC = FSM / Δ; corrected GM = GM solid − FSC; a slack tank therefore reduces metacentric height.

Angle of loll occurs with negative GM: GZ is zero at loll, the ship is unstable upright, and lowering weights or filling low tanks can restore positive GM.

List from an off-centre weight: tan θ = transverse moment / (Δ × GM); trim = (LCG − LCB) / MCTC, with MCTC in tonne-metres per centimetre.

Damage stability: lost-buoyancy method treats flooding as increased displacement; added-weight method adds floodwater as a weight; permeability reduces reserve buoyancy.

SOLAS requires a collision bulkhead located between 0.05L and 0.08L from the forward perpendicular; double bottoms, cofferdams, and watertight subdivision limit progressive flooding.

Inclining experiment determines lightship KG from known shifting weights and measured heel; KM is taken from hydrostatics, giving GM = KM − KG.

Floodable length is the maximum length of a compartment that can flood without submerging the margin line; it sets the permissible compartment length.

STCW rest hours: at least 10 hours in any 24 and 77 hours in any 7 days; rest may be split into no more than two periods, one at least 6 hours, with interval between consecutive rest periods not more than 14 hours.

MLC 2006 limits work to 14 hours per 24 and 72 per 7, or rest to 10 per 24 and 77 per 7; records must be maintained.

SOLAS requires on-board familiarization before assignment and periodic abandon-ship and fire drills; training and drill records are entered in the official logbook.

Enclosed-space entry requires risk assessment, atmosphere testing for oxygen, hydrocarbons, H2S and CO, a permit, a standby person, and rescue equipment.

Risk assessment uses likelihood × severity; controls follow the hierarchy of elimination, substitution, engineering, administrative, and PPE.

Pilot exchange covers course, speed, draught, manoeuvring characteristics, tugs, berthing plan, and emergency contingencies.

Bridge team: master retains overall responsibility; OOW monitors position and traffic; helmsman and lookout report directly; closed-loop communication confirms orders.

ISPS security levels: level 1 normal, level 2 heightened, level 3 exceptional; ship security plan and SSO implement measures.

UNCLOS: territorial sea 12 nm, contiguous zone 24 nm, exclusive economic zone 200 nm, all measured from baselines; innocent passage applies in the territorial sea.

COLREGS Rule 5 requires a proper lookout by sight and hearing and all available means; Rule 6 requires safe speed; Rule 7 defines risk of collision.

MARPOL Annex I oil, II noxious liquid, III harmful substances, IV sewage, V garbage, VI air pollution; discharge rules vary by annex and special area.

MLC 2006 covers seafarer employment agreements, wages, hours, repatriation, accommodation, food, medical care, and complaint procedures.

Hague-Visby Rules: carrier must exercise due diligence to make ship seaworthy and properly crew, equip and supply; liability limits and exclusions apply.

Bill of lading functions: receipt for goods, evidence of contract of carriage, and document of title; a clean B/L has no adverse cargo remarks.

General average: intentional sacrifice or extraordinary expenditure for common safety is shared by cargo, ship, and freight according to York-Antwerp Rules.

Salvage under 1989 Convention: reward based on salved value, danger, success, and efforts; LOF is a no-cure-no-pay salvage agreement.

Fire tetrahedron: fuel, oxygen, heat, and chain reaction; removing any side extinguishes combustion.

Fire classes: A solids, B flammable liquids, C gases, D metals, F cooking oils; water is unsuitable for B, C, D, and F risks unless tested.

Fixed CO2 system: release into a closed space, seal openings, account for all persons, and do not re-enter until atmosphere tested and space ventilated.

Boundary cooling limits spread by cooling adjacent bulkheads; closing fire doors, dampers, and vents isolates the fire and limits oxygen.

Lifeboat capacity and embarkation: each side must accommodate all persons; drills include abandon-ship signals, muster, launch, and recovery procedures.

GMDSS distress: EPIRB 406 MHz, SART 9 GHz, DSC alert on Ch 70, then voice Mayday on Ch 16; false alerts must be cancelled with authorities.

Man overboard: immediate helm response, release lifebuoy with light or smoke, post lookout, and execute Williamson or Anderson turn as appropriate.

Emergency generator and emergency fire pump must be tested; fire control plan shows compartments, controls, and access; emergency lighting and escape routes marked.

GMDSS sea areas: A1 within VHF DSC coverage, A2 within MF DSC, A3 within Inmarsat coverage, A4 outside A1–A3; carriage requirements depend on area.

DSC distress alert on VHF Ch 70 includes ship identity and position; follow with radiotelephony Mayday on Ch 16 and await acknowledgement.

NAVTEX broadcasts maritime safety information on 518 kHz in English; 490 kHz and 4209.5 kHz are used for national languages and HF.

EPIRB transmits on 406 MHz to COSPAS-SARSAT; SART responds on 9 GHz radar; AIS transmits identity, position, course, speed, and static data.

ECDIS uses ENC in S-57 format and S-63 encryption; safety contour, safety depth, and anti-grounding alarms must be set for the ship's draught.

ECDIS route check includes leg validity, XTD, safety contour, isolated dangers, and alarm settings; an independent backup arrangement is required.

AIS can be a collision-avoidance aid but does not replace radar or visual lookout; target data may be delayed or inaccurate.

LRIT transmits ship identity and position to authorities at intervals; it is separate from AIS and is not used for collision avoidance.

Beaufort scale describes wind by speed and sea state; significant wave height is the mean of the highest one-third of waves.

Buys Ballot's law: in the Northern Hemisphere, with back to wind, low pressure lies to the left; in the Southern Hemisphere, low pressure lies to the right.

In a Northern Hemisphere depression, winds circulate anticlockwise and converge; fronts bring rapid wind shifts, pressure changes, and precipitation.

Spring tides occur near new and full moon (syzygy); neap tides near quadrature; tidal range is greatest at springs.

Radiation fog forms over land at night under clear skies and light wind; advection fog forms when warm moist air moves over a cold surface.

Tropical cyclone safe semicircle: in the Northern Hemisphere it is the left side of the track; in the Southern Hemisphere it is the right side.

Ekman transport: wind-driven surface water moves about 45° to the right of wind in the Northern Hemisphere and 45° left in the Southern Hemisphere.

Squall: sudden increase in wind speed, often with rain and temperature drop; reduce sail or adjust course to limit heel and damage.

OOW must maintain position fixes, monitor traffic and weather, and ensure the bridge is manned; the master is called when in doubt or when conditions deteriorate.

Closed-loop communication: sender gives order, receiver repeats it, sender confirms; this reduces misunderstanding on the bridge.

Pivot point: under ahead power it lies near the bow; under astern power near the stern; turn rate and advance/transfer describe manoeuvring response.

Squat increases in shallow water and at higher speed; it reduces under-keel clearance and may cause trim change, especially in wide shallow channels.

Bank effect: suction toward the nearer bank and bow cushion can cause sheering; speed reduction and keeping to the centre reduce risk in narrow channels.

Anchor scope: use about 5–7 times water depth in chain for normal holding; scope is increased in strong wind or current and dragging is checked by bearings.

COLREGS avoiding action: early and substantial, crossing ahead, and monitoring until the other vessel is past and clear.

Interaction between ships: passing vessels experience suction and repulsion; speed reduction and greater lateral clearance reduce interaction effects.