GMA OOW Deck cheat sheet

Meridional parts: MP = 7915.7 × log10[tan(45° + Lat/2)], with Lat in degrees; Mercator sailing uses ΔMP and DLong to derive course and distance.

Plane sailing: departure = distance × sin(course) and DLat = distance × cos(course); for short legs convert departure to DLong using DLong = departure / cos(mean latitude).

Great circle initial course from A to B: tan(C) = sin(DLong) / [cos(LatA)·tan(LatB) − sin(LatA)·cos(DLong)], quadrant resolved from the sign of DLong and relative latitudes.

Great circle distance: cos(D) = sin(LatA)·sin(LatB) + cos(LatA)·cos(LatB)·cos(DLong); vertex latitude satisfies cos(LatV) = cos(LatA)·sin(initial course).

Amplitude at rising/setting: sin(amplitude) = sin(declination) / cos(latitude); amplitude is measured from the observer's prime vertical, named E or W of N/S.

Azimuth by ABC tables: A = tan(Lat)/tan(P), B = tan(Dec)/sin(P), C = A ± B, then tan(azimuth) = 1/(C·cos(Lat)); P is the local hour angle.

Running fix: advance the earlier position line by the true course and speed over the interval, then transfer the line parallel to itself; the fix is where it cuts the later position line.

Set and drift from two fixes: compare the DR position with the observed fix, then divide the displacement vector by the elapsed time to get rate and direction of the current.

Radar collision avoidance: a steady relative bearing with decreasing range indicates a risk of collision; a relative plot with constant bearing and constant range indicates a stationary target.

Beaufort scale anchors: force 0 under 1 knot, force 5 = 17–21 knots, force 8 = 34–40 knots (gale), force 10 = 48–55 knots (storm), force 12 = 64 knots and above (hurricane).

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

In a Northern Hemisphere depression, surface winds circulate anticlockwise and converge inward; in a Southern Hemisphere depression they circulate clockwise and converge inward.

Tropical revolving storm warning signs: falling pressure of about 1 hPa per hour or more, heavy swell from the storm direction, and cirrus followed by altostratus and cumulonimbus.

Fog formation: radiation fog needs clear skies, light wind, and high relative humidity; advection fog forms when warm moist air moves over a cold surface and is common in sea areas with cold currents.

Local winds: sea breeze blows from sea to land by day (land heats faster); land breeze blows from land to sea at night; both are driven by differential heating.

Frontal systems: a cold front typically produces a narrow band of heavy showers and squalls with a sharp pressure rise and wind veer after passage; a warm front produces steady rain and poor visibility.

In the Northern Hemisphere, a mid-latitude depression's warm sector is bounded by the warm front ahead and the cold front behind, with the wind veering as the cold front passes.

Pressure tendency: a falling barometer that then steadies or rises indicates a passing low; a rapid fall of more than 3 hPa in 3 hours signals a deepening system.

Archimedes' principle: a floating body displaces a weight of water equal to its own weight; displacement (Δ) = length × breadth × draught × block coefficient × water density.

Initial stability: GM = KM − KG; positive GM means the ship returns to upright, negative GM means it capsizes, and GM is measured in metres.

Righting lever: GZ = GM × sin(θ) for small angles; the curve of statical stability plots GZ against heel, and GZ maximum is typically near 30–40 degrees.

Free surface effect: FSC = (i × ρ) / Δ, where i is the second moment of area of the free surface; subdivision into tanks reduces i and hence the loss of GM.

Angle of loll: a ship with negative GM lies at an angle where GZ = 0; it must be corrected by lowering G (filling low tanks) rather than by adding weight high up.

Load line marks: the Summer load line is the reference; Winter is 50 mm below Summer, Tropical 1/48 of the Summer draught above, and Fresh Water allowance = Δ / (4 × TPC).

TPC = (waterplane area × water density) / 100; it gives the tonnes needed to change the mean draught by 1 cm.

Bulkhead and structural terms: collision bulkhead is located not less than 5% of the ship's length from the forward perpendicular; a transverse bulkhead provides subdivision and limits flooding.

Shear force and bending moment: still water bending depends on the distribution of weight versus buoyancy along the hull; hogging means excess buoyancy amidships, sagging means excess weight amidships.

IMDG segregation codes: 1 = away from, 2 = separated from, 3 = separated by one compartment or hold, 4 = separated by two, and X = no general segregation required.

Dangerous goods class numbers: 1 explosives, 2 gases, 3 flammable liquids, 4 flammable solids, 5 oxidizers, 6 toxic, 7 radioactive, 8 corrosives, 9 miscellaneous.

Cargo sweat and ship sweat: cargo sweat forms when warm moist air meets a cold cargo surface; ventilation is stopped when the dew point of outside air is higher than the cargo temperature.

Draft survey: cargo weight = (displacement at final draught − displacement at initial draught), corrected for density, ballast, fuel, and fresh water changes.

Stowage factor: the volume in cubic metres occupied by one tonne of cargo; for a given hold, maximum cargo weight = hold volume / stowage factor.

Lashing calculations: the breaking strength of lashing wire must exceed the calculated load by a safety factor; MSL (maximum securing load) is generally taken as 50% of breaking strength for wire.

Timber deck cargo must be stowed and secured per the Timber Deck Cargo Code; the ship may then be assigned a timber load line allowing deeper loading.

Container stowage: heavier containers are stowed low and near the centre to reduce GM, and lashings must be checked for racking and racking forces before departure.

Grain cargo: the Grain Code requires the heeling moment to be limited and the cargo to be trimmed; a grain stability booklet must be on board and calculations completed before loading.

STCW rest hours: minimum 10 hours of rest in any 24-hour period and 77 hours in any 7-day period; rest may be divided into no more than two periods, one of at least 6 hours.

Watchkeeping: the OOW must not leave the bridge unattended; a lookout must be maintained at all times, and the OOW is responsible for the safe navigation of the ship.

Muster list: every crew member is assigned a station; the list must be posted, and drills must be conducted at intervals not exceeding one month for abandon-ship and fire drills.

Fatigue management: maximum continuous watch is generally 4 hours on watch followed by 8 hours off in a three-watch system; records must be kept and available for inspection.

Bridge resource management: closed-loop communication requires the receiver to repeat back an order, and the OOW must challenge unclear or unsafe instructions.

Port state control: the ship may be detained for deficiencies that make it unseaworthy; the master must ensure certificates are valid and the ship is fit for the voyage.

Ship's certificates: Safety Management Certificate (SMC) and Document of Compliance (DOC) under ISM; the DOC is issued to the company, the SMC to the ship.

Safety committee: must meet at intervals not exceeding one month, and minutes must be recorded and made available; the master chairs or delegates the chair.

Handover of watch: the relieving OOW must be given the ship's position, course, speed, traffic, and any hazards before formally taking over the watch.

Four-stroke cycle: induction, compression, power, exhaust; the two-stroke cycle completes in one revolution and uses scavenging ports and an exhaust valve.

Diesel engine starting: compressed air at about 25–30 bar is admitted to the cylinders to turn the engine; the air bottles must be kept charged for emergency starting.

Fuel oil system: heavy fuel oil must be heated to about 100–130 °C for atomization; the viscosity at injection should be about 12–15 cSt.

Cooling water: jacket cooling water is kept at about 70–85 °C to limit thermal stress and prevent corrosion; a high-temperature alarm indicates a cooling fault.

Steering gear: SOLAS requires the main steering gear to be capable of putting the rudder from 35° on one side to 35° on the other in not more than 28 seconds at maximum ahead service speed.

Emergency steering: must be tested at least every three months, and the emergency steering drill must be practised; the changeover procedure must be posted.

Bilge and ballast systems: the OOW must know the location of bilge suctions and valves; a high-level bilge alarm in a machinery space must be tested regularly.

Oily water separator: discharge must not exceed 15 ppm; the 15 ppm alarm and automatic stopping device must be operational, and the Oil Record Book must be completed.

Pump and valve operation: a centrifugal pump must be primed before starting; a positive displacement pump must never be run against a closed discharge valve.

COLREG Rule 13: an overtaking vessel must keep out of the way until finally past and clear; the overtaking vessel is the one approaching from more than 22.5° abaft the beam.

COLREG Rule 14: two power-driven vessels meeting head-on both alter course to starboard and pass port to port.

COLREG Rule 15: crossing vessels - the vessel with the other on her own starboard side must keep out of the way; the stand-on vessel maintains course and speed.

COLREG Rule 19: in restricted visibility, every vessel must proceed at a safe speed and have engines ready for immediate manoeuvre; no stand-on vessel exists.

SOLAS Chapter V: the master must ensure the ship is adequately manned and equipped; the voyage plan must be prepared before departure and monitored throughout.

MARPOL Annex I: oil discharge is prohibited within 50 nautical miles of the nearest land; outside that, discharge is permitted only under the 15 ppm and instantaneous rate conditions.

MARPOL Annex IV: sewage discharge is prohibited within 3 nautical miles of land unless treated by an approved system; untreated discharge is allowed beyond 12 nautical miles.

UNCLOS: the territorial sea extends 12 nautical miles from the baseline; the contiguous zone extends to 24 nm and the exclusive economic zone to 200 nm.

STCW Convention: the OOW certificate requires approved sea service, approved training, and passing the examination; certificates must be revalidated every five years.

Fire triangle: fuel, oxygen, and heat; removing any one side extinguishes the fire. Class A = solids, B = liquids, C = gases, D = metals, and electrical fires.

Firefighting: a CO2 extinguisher is suitable for electrical and liquid fires but must not be used in enclosed spaces where people remain because it displaces oxygen.

Enclosed space entry: the atmosphere must be tested for oxygen (19.5–23.5%), hydrocarbons, and toxic gases before entry; a standby person must remain at the entrance.

Abandon ship: the order is given by the master; the crew mustered at the assembly station proceed to the lifeboat, and the lifeboat is launched with the painter secured until the boat is waterborne.

Man overboard: the immediate actions are to shout 'man overboard', release the lifebuoy with smoke and light, note the position, and commence the Williamson turn or a turn to return.

Emergency position indicating radio beacon (EPIRB) and SART: the EPIRB transmits on 406 MHz to the satellite system; the SART responds on 9 GHz radar and shows a series of dots on the radar display.

Lifeboat drills: must be conducted at intervals not exceeding one month; each lifeboat must be launched and manoeuvred in the water at least once every three months.

First aid: the ABC sequence is airway, breathing, circulation; CPR compressions are given at 100–120 per minute with a depth of 5–6 cm.

Emergency generator: must be tested weekly and be capable of supplying emergency lighting and communications for at least 18 hours.

GMDSS sea areas: A1 within VHF coverage of a coast station, A2 within MF coverage, A3 within Inmarsat coverage, and A4 outside all of these (polar regions).

DSC distress alert: sent on VHF channel 70 or MF/HF 2187.5 kHz; it contains the MMSI, nature of distress, and position, and is followed by a distress call on channel 16 or 2182 kHz.

Distress frequencies: VHF channel 16 (156.8 MHz) for voice, channel 70 for DSC, MF 2182 kHz for voice, and 2187.5 kHz for DSC.

GMDSS equipment by sea area: A1 requires VHF DSC and a SART/EPIRB; A2 adds MF DSC; A3 adds Inmarsat or HF; A4 requires HF for all distress functions.

NAVTEX: broadcasts maritime safety information on 518 kHz (international) and 490 kHz (national) with a range of about 200 nautical miles; messages are received automatically.

EPIRB registration: the 406 MHz EPIRB must be registered with the national authority and the data kept current; it transmits a unique identification and position via the COSPAS-SARSAT system.

Radio watch: VHF channel 16 must be kept on watch continuously; the distress watch on 2182 kHz and DSC 2187.5 kHz is required when the ship is at sea.

Mayday, pan-pan, and securite: Mayday is distress, pan-pan is urgency, and securite is a safety message; each is repeated three times at the start of the transmission.

Battery maintenance: GMDSS batteries must be tested and their capacity verified; the reserve source must be capable of operating the equipment for the required period (typically 6 or 24 hours).