Probabilistic damage stability for passenger ships—the p-factor illusion and reality

Vassalos, Dracos and Mujeeb-Ahmed, M. P. and Paterson, Donald and Mauro, Francesco and Conti, Fabien (2022) Probabilistic damage stability for passenger ships—the p-factor illusion and reality. Journal of Marine Science and Engineering, 10 (3). 348. ISSN 2077-1312 (

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The paper complements an earlier publication by the authors addressing the probability of survival in the IMO framework for damage stability assessment, the s-factor. The focus here is on the probability of occurrence of a certain damage scenario (breach), conditional on its dimensions and location (centre and port or starboard side), the p-factor. Pertinent assumptions and limitations are explained, following its evolution for specific application to passenger ships. Attempts to provide analytical descriptions of the damage breach distributions as tetrahedra shapes positioned along the ship length whilst accounting for changes in ship geometry, structural arrangements, and subdivision for consumption by the wider profession has led to misconceptions and misunderstandings of what exactly the p-factor is in the context of probabilistic damage stability calculations. This is evidenced by the fact that the same original damage breach distributions, derived in Project HARDER, based on largely cargo ships with the age spread over the last three decades of the previous century, are still being used today for all ship types, including modern passenger ships. Filling this gap, a new database for passenger ships developed in the EC-funded Project FLARE, is briefly presented, leading to new damage breach distributions specifically for passenger ships. It is believed that this paper will throw considerable light in enhancing understanding on the p-factor, which has been cluttered with unnecessary complexity from the outset.


Vassalos, Dracos ORCID logoORCID:, Mujeeb-Ahmed, M. P., Paterson, Donald, Mauro, Francesco ORCID logoORCID: and Conti, Fabien;