Manning compliance, certificate validity, contract pressure, relief logistics and rest-hour exposure — the four constraints that decide whether a vessel can sail.
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A vessel can be perfectly maintained, perfectly bunkered, and perfectly certified, and still not be allowed to sail. Crew is the binding constraint that catches everything else flat-footed.Four conditions must hold simultaneously:
Constraint
Failure mode
Minimum safe manning
Rank slot empty or under-rank → vessel non-compliant
Certificate validity
Officer’s CoC / GMDSS / medical lapsed → cannot sail in role
Contract pressure
Officer past contract end with no relief → MLC fatigue concern
Rest hours
Sustained breach → SMS deficiency, PSC exposure
Pass any three and fail one — the vessel still doesn’t sail. The pipeline tracks all four on a rolling basis and surfaces the constraint that’s about to bite first.
The vessel’s certificate of minimum safe manning lists exact rank-slot requirements:
1 Master
1 Chief Officer
1 Second Officer
1 Third Officer
1 Chief Engineer
1 Second Engineer
1 Third Engineer
1 Fourth Engineer
1 Electrical Officer (where required)
N ratings (Bosun, ABs, OS, oilers, motorman, etc.)
The pipeline cross-checks the current roster against the manning certificate. A rank-slot empty or filled by an under-ranked officer triggers a manning shortfall. Every shortfall is severity CRITICAL — a vessel sailing under-manned is both non-compliant and operationally fragile.
Certificate of Competency (CoC) — the rank licence, flag-issued
GMDSS — Global Maritime Distress & Safety System (deck officers)
STCW endorsements — by vessel type (tanker, gas, chemical, polar)
Medical fitness — typically annual or biennial
Vaccination records — yellow fever, COVID, others depending on trade
Travel documents — passport, seamen’s book, visas
For each, the same expiry-window logic the certificates pipeline uses:Δdays=Dexpiry−Dtoday
Window
Action
Already expired
Officer must not sail — escalate immediately
0–30 days
Renewal urgent — coordinate with crewing
31–90 days
Renewal in planning
Beyond 90 days
Routine
Crew-certificate renewals are paperwork-bound — they take weeks of administration and depend on physical presence for medicals. A certificate at 30 days that hasn’t started the renewal process is already late.
Each officer has a contract length and a sign-on date. The contract end date is fixed; the relief is what has to happen on or before it.Officer state by contract:
State
Condition
On contract
Sign-on date set, contract end in future, relief planned or being planned
Approaching
Contract end within 30 days, relief plan should exist
Over-contract (with relief plan)
Contract end past, relief logistics in motion
Over-contract (no relief plan)
MLC fatigue concern — escalate
An officer over-contract by more than 30 days with no relief plan is the textbook MLC-fatigue exposure: the officer’s contract has lapsed, the union may file, the flag may investigate, and the vessel’s compliance posture deteriorates.
Once a relief is planned, the logistics get specific:
Visa — does the joining officer have the destination-country visa, and how long does it take to obtain?
Travel — flights from the officer’s home country to the join port; layovers and transit visas
Quarantine — destination-country quarantine if required
Medical — current and valid; if expired during travel, may not be allowed to board
Crew change-friendly port — not every port allows crew changes; the relief may need to be re-routed
Each of these has a lead-time. The pipeline computes:Trelief_critical=max(tvisa,ttravel,tquarantine,tmedical)Compared against the time to the next crew-change-eligible port:Slack=Tport−Trelief_criticalNegative slack means the relief can’t make the planned port — needs re-routing or earlier port stop.
Maritime Labour Convention rest-hour requirements:Hrest≥10 h in any 24 h windowHrest≥77 h in any 7-day windowThe 24-hour rest may be split into a maximum of two periods, one of which must be at least 6 hours, with no more than 14 hours between consecutive rest periods.A breach is logged whenever an officer’s rest record violates either constraint. Repeated breaches across a crew indicate fatigue risk and SMS-deficiency exposure during the next PSC inspection.The pipeline aggregates rest-hour breaches per officer per month and flags:
def relief_slack(officer, next_port, today): """How much margin between when we need the relief and when we can have it.""" contract_end = officer["contract_end"] # Critical-path lead time for the relief lead_visa = officer["replacement"]["visa_lead_days"] lead_travel = officer["replacement"]["travel_lead_days"] lead_quarantine = officer["replacement"]["quarantine_days"] lead_medical = officer["replacement"]["medical_lead_days"] relief_critical = max(lead_visa, lead_travel, lead_quarantine, lead_medical) days_to_port = (next_port["eta"] - today).days days_to_contract = (contract_end - today).days # Negative means we won't make it return min(days_to_port, days_to_contract) - relief_critical
A negative slack triggers a relief-routing review — sometimes a relief that can’t make Singapore can make Colombo a few days earlier.
Engineering issues can usually be fixed with parts and time. Documentation issues can be fixed with paperwork. Crew issues hit a wall the moment the vessel reaches port — if the relief isn’t there, the vessel doesn’t sail. The pipeline runs continuously because a 30-day window can collapse to zero with one cancelled flight or one delayed visa.
The single highest-leverage data point in crew management is the relief plan. A vessel with every officer on contract and every certificate valid still has zero margin if no reliefs are planned for the upcoming contract end dates. The pipeline reports relief planning status as a first-class metric, not as a footnote.
