VDR, an S-VDR, and L-VDR

Learn about the regulations, requirements and differences between each type of Voyage Data Recorders

What is the difference between a VDR, an S-VDR, and an L-VDR

Under regulation 20 of SOLAS chapter V on Voyage Data Recorders (VDR), passenger ships and cargo vessels of 3.000 GT and above constructed on or after July 1, 2002 must carry a VDR, while a Simplified VDR (S-VDR) is accepted for cargo ships of 3.000 GT and above which were built before July 1, 2002.

The main difference in terms of data recording between VDRs and S-VDRs is the range of sensors and systems from which data must be recorded. VDRs are required to record data from a wider range of sensors and systems than S-VDRs.

Both must record certain types of data, including ship's position, speed, heading, audio from the bridge, and other important parameters, however, a VDR must also record data from the ship's radar, including radar images, as well as data from the ship's Automatic Identification System (AIS) and the ship's main and auxiliary engines.

L-VDR’s are not bound by any IMO regulations and are an optional fit for smaller commercial vessels and privately own yachts. They typically record fewer parameters than standard VDR or S-VDR systems, they may have lower storage capacity and will be less expensive overall. However, they still provide valuable information for accident investigation and can help improve maritime safety.

How much storage do I need in my VDR?

That depends on whether the VDR will be used purely to meet the applicable regulations and avoid penalties for non-compliance, or if it will become part of a wider information network that can help drive operational efficiency onboard a vessel and across a fleet.

If the former, then regulations state that a VDR installed before 2014 must record at least 12 hours of voice recordings, but VDRs installed later than 2014 must record 48 hours in total. Because VDRs and S-VDRs will be configured differently on different vessels, it’s impossible to say how much storage is needed in a general sense for all users, however, the most common hard drive size is 32GB.

External hard drives are needed if the sensor data recorded by the VDR also includes CCTV or other sensors that could contribute to a wider approach to optimising operations through cloud-based software for e.g., voyage performance optimisation and fuel reductions. The largest hard drive size offered with Danelec VDRs is7.6TB.

What data must a VDR record?

Data that will provide evidence of the position, movement, physical status, command and control of a vessel over the period leading up to and following an incident. In order to be fully compliant, the VDR must record:


  • Date and time
  • Ship’s position
  • Speed and heading
  • Bridge audio
  • Communication audio (radio)
  • Radar data
  • ECDIS data

VDR only

  • Echo sounder
  • Main alarms
  • Rudder order and response
  • Hull opening (doors) status
  • Watertight and fire door status
  • Speed and acceleration
  • Hull stresses
  • Wind speed and direction
How long does VDR data need to be stored before it can be overwritten?

According to IMO regulations, the recorded data from a VDR must be stored for a minimum of 30 days. This includes all recorded data from the various sensors and systems on the ship, as well as audio recordings from the bridge. The purpose of this requirement is to ensure that in the event of an accident or incident, investigators have access to a comprehensive set of data that can help them understand what happened and why.

However, many VDRs on modern ships are designed to store data for longer periods, such as up to two years, which can provide additional insights for accident investigation and also support broader efforts to improve safety and efficiency in shipping operations.

Where should a VDR be installed on board?

The IMO has issued specific guidelines regarding the installation of VDRs on ships. According to these guidelines, VDRs should be installed in a location that ensures that the recorded data is protected from damage and that the equipment is easily accessible for testing and maintenance. The guidelines specify that:

  • The VDR should be located in a dedicated room or space that is secure and protected from damage.
  • The VDR should be located as close as possible to the ship's centreline in order to minimize the impact of any listing or rolling.
  • The VDR should be located above the waterline and in a position that ensures that the recorded data is protected from heat, cold, vibration, and other environmental factors.
  • The VDR should be located in a position that allows for easy access for testing and maintenance, including the annual performance tests and inspections.
  • The float free capsule should typically be attached to the ship's bridge structure or another suitable location using a hydrostatic release unit that is triggered if the ship sinks.

In addition to these guidelines, the IMO also requires that VDRs are installed in accordance with the manufacturer's instructions and that they are tested and approved by the relevant authorities before being put into service. It's important to follow these guidelines to ensure that the VDR is installed correctly and will function properly in the event of an accident or incident.

What is the mandatory service interval on installed VDRs?

IMO regulations require that VDRs and S-VDRs are tested, inspected, and serviced at specific intervals to ensure that they are functioning properly and recording data accurately. The mandatory service intervals for VDRs and S-VDRs are as follows:

Annual Performance Test: This test is conducted annually to ensure that the VDR or S-VDR is functioning correctly and recording data accurately. The test must be carried out by an approved testing or servicing agent and should be done within three months before or after the anniversary date of the previous test. Remote Pre-annual Performance Tests help to streamline the process and reduce time/costs.

It's worth noting that some VDRs and S-VDRs may require additional maintenance or servicing based on the manufacturer's recommendations or specific operating conditions. It's important to follow these guidelines to ensure that the VDR or S-VDR is always functioning correctly and providing accurate data.

What is Danelec SWAP technology and why do I need it?

Coast Guards won’t let a ship leave port if the VDR is not working, so its important that maintenance and repairs can be done quickly and without hassle. Because servicing and repairing shipboard electronics can be time-consuming and expensive, Danelec SWAP technology automatically saves all system software, configuration, and programming data on a hot-swappable memory card, which can be easily transferred from a defective unit to a new unit. This allows the vessel to have a configured, operational VDR in just hours, while the defective unit can be taken ashore to be fixed without holding the ship up in port.

How is a VDR located and retrieved following the sinking of a vessel?

The VDR recording medium usually consists of two platforms – one fixed and one float-free. Once the float-free capsule is released, it floats to the surface and emits acoustic and visual signals while also transmitting emergency signal with AIS to aid in its recovery. The capsule is typically bright orange or yellow in colour and is designed to be highly visible in the water. However, the float free capsule may not always operate correctly due to damage or if it gets stuck, which means it (or the fixed capsule) must be retrieved from the wreck on the seafloor.

In shallower waters this can be done relatively easily by divers but in deeper waters further from shore, Remotely Operated Vehicles (ROV) and Autonomous Underwater Vehicles (AUV) are used to locate the capsule through video feeds and hydroacoustic instruments such as Side Scan Sonar and Sub-Bottom Profilers. Once the VDR has been located, an ROV with manipulator arms may be used to free it from the wreck and return it to the service.

The entire process is costly and challenging, especially as large ships tend to break up on impact with the seafloor. The El Faro’s VDR float-free capsule for instance, was found hundreds of metres away from the main wreck still attached to one of the ship’s masts.

What certificates must a VDR have to be compliant with regulations?

The IMO states that the VDR system, including all sensors, shall be subjected to an annual performance test. The test shall be conducted by an approved testing or servicing facility to verify the accuracy, duration and recoverability of the recorded data. In addition, tests and inspections shall be conducted to determine the serviceability of all protective enclosures and devices fitted to aid location. A copy of a the certificate of compliance issued by the testing facility, stating the date of compliance and the applicable performance standards, shall be retained on board the ship.

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