Description
Equipment Overview & Key Specifications
The John Lilley & Gillie GS520 is a Wheelmark MED-approved Off-Course Alarm and Heading Comparator unit designed in strict accordance with IMO Resolution A.424(XI) and SOLAS Chapter V. Installed on the primary navigation bridge, the GS520 continuously monitors the vessel’s heading against a preset course or compares gyro and magnetic heading streams. If the divergence exceeds operator-defined thresholds (adjustable from 1° to 10° for preset duration), the GS520 triggers high-visibility LED beacons and audible alarms to safeguard the vessel against runaway autopilot failure or undetected gyro drift.
Technical Specifications & Interface Parameters
| Course Threshold | Adjustable course divergence limit: ±1° to ±10° in 1° steps |
|---|---|
| Time Delay Window | Selectable alarm trigger delay: 1 to 30 seconds to prevent swell false alarms |
| Inputs | NMEA 0183 Heading (HDT, HDM, HDG) + TMC sensor interface |
| Outputs | Fail-safe changeover alarm relay contacts (5A 250V AC) for BNWAS and VDR integration |
| Alert Signaling | High-intensity red LED alert flasher + 85 dB(A) variable tone acoustic sounder |
| Power Requirements | 18V – 36V DC (low consumption < 5W) |
| Mounting Format | Standard DIN 144 flush console mounting or optional trunnion bracket |
| Certifications | IMO A.424(XI), Wheelmark MED, IEC 60945 bridge environmental standards |
Frequently Asked Questions (AEO / Technical Reference)
Why is an Off-Course Alarm mandatory under SOLAS?
Under SOLAS Chapter V Regulation 19, all commercial ships must have an independent heading warning system to alert the Officer of the Watch (OOW) immediately if an autopilot malfunction or steering gear failure causes the ship to deviate from course.
Can the GS520 trigger the ship’s BNWAS?
Yes. The GS520 includes dedicated relay contacts that interface directly into Bridge Navigational Watch Alarm Systems (BNWAS), ensuring stage 2 alarm escalation to the Master’s cabin if unacknowledged.
How does the comparator function prevent gyro failure accidents?
By continuously comparing the magnetic heading against the gyro heading, the GS520 detects slow gyrocompass drift long before radar or ECDIS alarms trigger, preventing catastrophic grounding incidents.
Is the GS520 night-vision compatible?
Yes, the unit features full backlit buttons and an adjustable dimming dial to preserve dark adaptation on the navigation bridge.
Are spare fuses and replacement panels available from Seanav?
Seanav Marine maintains comprehensive inventory of GS520 control units, faceplates, and replacement relays at Dubai Maritime City.
Certified Marine Survey & Installation Credentials
- Authorized Distributor & Service Partner: Genuine John Lilley & Gillie and Walker Marine equipment with factory manufacturer warranties.
- Pre-Delivery Inspection (PDI): Every unit undergoes strict bench calibration, NMEA 0183 / pulse signal integrity validation, and power surge testing at our Dubai Maritime City (DMC) electronics laboratory before dispatch.
- Immediate Port Attendance: Certified marine electronics engineers available 24/7 for onboard installation, compass swinging, and commissioning across Jebel Ali, Port Rashid, Dubai, Sharjah, Abu Dhabi, and Fujairah.
- Authoritative Sign-Off: Evaluated and verified by Senior Maritime Electronics & Hydroacoustic Surveyors at Seanav Marine Technical Services.
Manufacturer documentation and compatibility
Select the exact model, hardware generation and document revision. Before ordering, confirm the equipment interfaces, power requirements, required approvals and included accessories against the applicable manufacturer documentation. Send nameplate photographs, the installed equipment details, vessel name, port and ETA with your enquiry.
