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The next generation of loading computer has arrived

By Markus Tompuri, Senior Technical Consultant, NAPA Safety Solutions, NAPA Ltd.

There are currently four types of stability software, all of which have varying levels of capability.

Type 1 has software that only calculates intact stability.

Type 2 can calculate intact stability and check damage stability based on a limit curve (e.g. for vessels applicable to SOLAS Part B-1 damage stability calculations).

Type 3 calculates intact and damage stability by direct application of pre-programmed damage cases by reference to the relevant Conventions and/or Codes for each loading condition.

Type 4 is the most advanced of them all. It calculates damage stability associated with an actual loading condition and/or actual flooding cases, by using the direct application of user or sensor defined damage to enable a safe return to port (SRtP).

Since the start of 2020, all passenger-carrying newbuildings have been required to have a Type 4 Loading Computer installed. Passenger ships constructed before 1 January 2014 must also comply with this requirement no later than the first renewal survey after 1 January 2025.

What’s changed?

Loading computers are one of the best ways to make cargo loading and ship performance more efficient and reduce vessel risk. For these reasons, bridge officers have come to rely heavily on them and it is, therefore, necessary for their specifications and capabilities to be regularly reviewed and – where necessary – revised and upgraded.

The Type 4 loading computer has been developed to enhance safety in flooding emergencies and to provide the master with more information for safe return to port. There is a multitude of changes in Type 4 loading computer, with the majority being in the damage stability module. Below are the three most significant:

1. Automatic damage detection and watertight doors – Loading computer is using a detailed 3D model of the ship with also the internal arrangement modelled. When the ship is fitted with flooding level sensors the flooded compartments are detected automatically in the loading computer. Maintaining the ships’ watertight subdivision is critical for the safety of operation. If a watertight door is detected in the damaged compartment, then the system automatically prompts the user to add the adjacent compartments to the damage.

2. Damage stability criteria – Every modern passenger vessel was designed with compliance to the SOLAS probabilistic damage stability requirements. To assess the severity of the damage case a set of criteria are used based on the survivability factor in SOLAS. These criteria enable the user to gain a clearer understanding of the damage case. The system also calculates the immersion angle of escape routes.

3. Approval of damage stability functions – Because the requirements from SOLAS – via IACS – have been implemented in class rules, damage stability functions and calculation results with the loading computer are now subject to class approval. For older ships, this will also mean that stability and strength calculations also require class approval.

Effectively Managing Your Ships’ Stability

Stability management is a core component of passenger vessel operations, and the NAPA Loading Computer originated from the collaboration with key stakeholders across the passenger sector. NAPA Loading Computer undertakes a wide range of calculations related to hydrostatics, intact stability, and ship longitudinal strength to optimize vessel load while minimizing stress and safety risk.

Today it’s the most trusted stability solution for passenger vessels, and since its launch in 1993, NAPA Loading Computer has become the industry benchmark for integrated decision support. NAPA Loading Computer Type 4 is Safe Return to Port (SRtP) and IACS Type 4 compliant. It is also compliant with all the relevant IMO Circulars (MSC.1/Circ.1400, and MSC.1/Circ.1532-Rev.1., MSC.1/Circ.1589)

NAPA Loading Computer is currently used by almost all the major cruise lines, as well as the ferry, RoRo, RoPax, StoRo, and LoLo operators. In recent months this has included Kvarken Link, Windstar Cruises, and all nine Carnival Cruise line brands. In total, NAPA Loading Computer is installed onboard more than 2,000 ships across the global commercial and passenger fleet and is approved by all major class societies.

Ships should always be loaded with a keen consideration for the vessel’s longitudinal strength. If you load in the wrong sequence or unevenly, you can structurally damage a ship. If this happens frequently, there is a substantial risk to the seaworthiness of that vessel.

To ensure that best practice is followed, and in line with the newly enforceable regulation, NAPA will now only deliver Type 4 compliant software for passenger ships. We believe that this will make a major difference to passenger and crew safety on ferries, cruise liners, and other similar ships. Not least because it was given the master of each ship a clear sense of whether or not they can make a safe return to port.

If you are operating a passenger ship built before 2014, you must have your vessel upgraded at the latest by their first renewal survey after 1 January 2025.

To learn more about what this will mean for your ships, you can contact me at, or on LinkedIn.

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