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Home › Navigation › BNWAS and Anti-Collision Alert Systems
Operational guide · Safety & equipment

BNWAS and Anti-Collision Alert Systems

BNWAS monitors watch activity and calls assistance if the OOW does not respond. It must operate whenever the ship is underway at sea; MSC.1/Circ.1474 advises against using the automatic mode linked to autopilot.

BNWASSOLAS V/19anti-collision alertwatchkeeping

Operational Explanation

MSC.128(75) describes three modes, but subsequent MSC.1/Circ.1474 states that Automatic, if available, should not be used: it can disable BNWAS when automatic steering is disengaged. Use Manual ON to keep it operational underway at sea. Mode and dormant-period controls remain protected and restricted to the master. IMO MSC.1/Circ.1474.

Regulatory Reference

SOLAS V/19: BNWAS operational whenever the ship is under way at sea. MSC.128(75): modes, dormant period, alarm sequence, reset, security and malfunctions.

BNWAS and collision alerts have different functions. BNWAS escalates calls when no reset occurs; it does not calculate collision risk or replace lookout, a fit watch or COLREG assessment. Resetting alone does not establish that the traffic situation is safe. IMO MSC.128(75): purpose and operation.

Scope of Application

Ships subject to the carriage requirement under relevant dates and thresholds. A full-sequence test is ship procedure/good practice where prescribed, not a universal IMO periodicity.

Procedure / How to Complete It

  1. Verify Manual ON underway at sea; do not rely on autopilot or track-control activation.
  2. The Master sets/protects mode and dormant period under the SMS and conditions.
  3. Test sequence, reset points and remote alarms under maker, PMS/SMS and statutory instructions.
  4. Do not simulate main-power failure unless procedure and maker authorise it.
  5. Record tests, defects, isolation and corrective action under the ship's system.

Practical Example

Autopilot disengaged does not mean BNWAS is not required: when under way at sea the system must be operational in the appropriate mode.

What Typically Goes Wrong

Presenting under way and autopilot as alternative triggers or inventing a uniform IMO periodicity for end-to-end/power-failure tests.

Common Mistakes Mistake Library

MistakeConsequenceHow to Avoid It
Presenting under way and autopilot as alternative triggers or inventing a uniform IMO periodicity for end-to-end/power-failure tests.Incorrect operational decision or regulatory statusUse the primary reference and ship-specific procedure

What the PSCO Checks

Operational status under way, access security, dormant setting, alarm sequence, reset locations, records and defect management.

Operational Tips

Preparation checklist

FAQ

Does automatic mode mean BNWAS is needed only with autopilot?
No. It must operate underway at sea even with manual steering. MSC.1/Circ.1474 advises that Automatic, if available, should not be used; use Manual ON.
Is there one IMO periodic test for every ship?
No. Method and frequency follow maker, PMS/SMS and applicable statutory instructions.
Who controls mode and dormant period?
The Master through protected access.

Related Topics

WatchkeepingBridge Resource Management

Last substantive revision of this page: 15 September 2026 · page fingerprint c892b8a3a76c