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Fresh Water Allowance (FWA)

Loadline draft shift allowed when moving from sea water to fresh water. Loadline Convention: FWA (mm) = Δ / (4·TPC).

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Formula, assumptions, and limits

FWA (mm)=Δ4TPC\text{FWA (mm)} = \frac{\Delta}{4 \cdot \text{TPC}}
SymbolMeaningUnit
Δ\DeltaSummer-load displacementt
TPCTPCTonnes per centimetre at SLWLt/cm
FWAFWAFresh water allowancemm

Source: IMO ICLL 1966; Derrett & Barrass Ch.8

In short

Compute Loadline FWA from displacement and TPC.

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