Question 1

You are on safety inspection. Your examiner asks you to explain the hydrostatic release unit on the liferaft canister and when servicing is required.

Accepted Answer

The Hydrostatic Release Unit (HRU) is a pressure-activated device that automatically releases the liferaft from its cradle when submerged to a depth of 1.5-4 metres. It cuts the lashing (weak link) allowing the liferaft to float free and inflate via a painter line connection to a lifeline. The HRU must be serviced annually by an approved service station (except where a 30-month HRU approval exists). The liferaft itself must be serviced at intervals not exceeding 12 months at an approved service station. The date of next service is marked on the canister. An expired HRU or service date is a serious deficiency. SOLAS III Reg 20 / LSA Code Chapter 4: inflatable liferafts require servicing at intervals not exceeding 12 months, at an approved and certified service station. The HRU is a critical component — it provides the automatic float-free release that means the liferaft can survive a rapid sinking. The weak link (breaking load 2.2-4.4 kN) ensures the painter line breaks if the vessel sinks faster than the liferaft can float free, preventing the liferaft from being dragged down. Without a functioning HRU, the liferaft will not release automatically. The 30-month approval for certain HRUs is an IMO-approved alternative to the 12-month requirement — the HRU type approval certificate specifies which interval applies. In practice PSC inspects service dates at every inspection — an overdue service is among the most common LSA deficiencies cited.

Question 2

Your examiner asks: "What must be shown on the muster list, and where must it be posted?" Give the SOLAS Chapter III requirements.

Accepted Answer

SOLAS III Reg 37: the muster list must show: each crew member's emergency station; duties assigned (firefighting, survival craft, medical); lifeboat or liferaft assigned; signals for mustering; instructions for passengers. Posted in conspicuous locations including the bridge, engine room, and crew accommodation. The muster list must be updated after any change in crew and before departure. Each crew member must be instructed in emergency duties before departure on first voyage. SOLAS III Reg 37 requires the muster list before departure on a voyage. SOLAS III Reg 19 requires: abandon ship drill within 24 hours of departure (new crew); monthly abandon ship drill for all crew; weekly testing of general emergency alarm. The emergency duties must be simple enough that crew can carry them out without reference to the list under stress. Key OOW point: the "person in charge" of each survival craft must be a certificated officer or seafarer — not any crew member. The Emergency Squad (for firefighting, damage control) must be identified by name. An unmaintained or out-of-date muster list is a PSC deficiency and may indicate deeper SMS failures. In practice examiners ask OOW candidates to describe their own emergency duties from the muster list — they expect a specific, practised answer.

Question 3

Your examiner asks: "Describe the types of EPIRB carried on SOLAS vessels, how they activate, and what happens when one activates." Give a complete answer.

Accepted Answer

Category I EPIRB: float-free, auto-activating when submerged to 1-4m depth; also manual activation. Category II EPIRB: manual activation only (bracket-mounted). Both transmit on 406 MHz (digital distress alert with MMSI/vessel identity to Cospas-Sarsat) and 121.5 MHz (homing). On activation: the 406 MHz signal is received by Cospas-Sarsat satellites, decoded, and passed to an LEUT (Local User Terminal), then to an MCC (Mission Control Centre), then to an RCC (Rescue Coordination Centre) which initiates SAR. Position accuracy: Doppler shift gives approx 5km; if GNSS-linked EPIRB, position accuracy is within 100m. SOLAS IV requires carriage of at least one float-free Category I EPIRB per vessel on international voyages. The 406 MHz transmission is the primary signal — it carries the vessel's unique 15-hex identification code (linked to the MMSI in the GMDSS registration database). The 121.5 MHz is the secondary homing frequency used by SAR aircraft and vessels. GNSS-integrated EPIRBs provide a position within the first transmission. The EPIRB must be registered with the flag state — an unregistered EPIRB wastes SAR resources. SOLAS also requires a SART (Search and Rescue Transponder) or AIS-SART for each survival craft. The Louisa SY30 case (MAIB 17/2017) where the Coastguard could not locate a vessel partly because of EPIRB terminology confusion demonstrates why OOWs must know the full activation and response chain.