TECHNICAL SPECIFICATION • SIMRAD NAVICO GROUP
GC80 (STANDARD IMO) • GC85 (HSC 70 KTS)
DP-READY • MAINTENANCE-FREE SEALED GYRO
The Simrad GC80 and GC85 MK2 Gyro Compass systems represent industry-leading marine heading reference solutions engineered for both standard commercial vessels and High-Speed Craft (HSC). Employing advanced sealed gyrosphere technology, the GC80/85 series delivers exceptional heading accuracy, dynamic stability, and low lifecycle operating costs with zero annual oil servicing required. The system is universally trusted across offshore supply vessels, dynamic positioning (DP2/DP3) platforms, commercial merchant fleets, and fast passenger ferries.
Up to 75°/sec
30,000h Calc. (>70,000h Obs.)
Up to 70 Knots (GC85)
Simrad GC80 / GC85 MK2 Series
Engineered for 24/7 Harsh Maritime & Offshore Service
A wide range of control units enables custom configurations for new shipbuilding or practical retrofits. Heading distribution supports NMEA/IEC serial channels, classic 24V step outputs, and analog Rate-of-Turn (ROT) lines without secondary converter boxes:
- Maintenance-Free Sealed Gyro: No annual fluid changes or routine top-ups required.
- Dynamic Positioning (DP) Optimization: Fast follow-up and ultra-low noise drift make it the premier choice for offshore DP systems.
- Flexible Control Enclosures: Compact, Expanded, and Dual Control Unit topologies.
- GC50 Replacement Path: The legacy GC50 is discontinued; GC80/85 MK2 provides the seamless modern replacement.
Notice Regarding Legacy Simrad GC50 Systems:
Please note that the Simrad GC50 Gyro Compass is officially obsolete and no longer manufactured. Vessels operating older GC50 units can directly retrofit to the Simrad GC80 MK2 Compact or Expanded system, utilizing existing repeater cables, step lines, and NMEA listeners with minimal bridge alteration. Seanav Marine provides complete turn-key GC50-to-GC80 changeover services globally.
1. System Architecture & Control Unit Topologies
The Simrad GC80 and GC85 MK2 systems are modularized into two primary assemblies: the Master Compass and the Control Unit. Depending on bridge redundancy criteria, vessel class, and repeater count, three control unit variants are available:
Compact Control Unit MK2
Engineered for standard merchant cargo vessels, coastal tankers, and workboats requiring basic serial and step distribution in a compact console space.
- Complete Unit P/N:
000-15036-001 - Full System Kit:
000-15567-001 - Power Input Fuse: F101 (6.3A)
- IEC 61162 / NMEA serial data outputs
Expanded Control Unit MK2
Designed for vessels requiring numerous heading repeaters, wing azimuth dials, autopilot steering, ECDIS, radar sync, and analog ROT drives.
- Complete Unit P/N:
000-15037-001 - Full System Kit:
000-15568-001 - Up to 10 repeater drive lines (F1–F10, 1A fuses)
- Supports analog ROT and high-speed step outputs
Dual Control Unit MK2
Integrates two independent master compasses (GC80 + GC80 or GC80 + GC85) with automatic failover switching, meeting SOLAS dual gyro carriage criteria.
- Complete Unit P/N:
000-15038-001 - Seamless automatic / manual gyro changeover
- Direct feed to Dynamic Positioning (DP) consoles
- Independent power supply redundancy
2. Critical Spare Parts: Sensitive Elements & Installation Tool
The sensitive element (gyrosphere) is the hermetically sealed heart of the Simrad gyrocompass. While the GC80 and GC85 share the same exterior housing and control architecture, their sensitive elements are distinct and must never be interchanged:
| Component Description | Simrad Part Number | Application & Operational Notes | Replacement Frequency |
|---|---|---|---|
| GC80 Sensitive Element | 44174027 | Standard commercial merchant vessels conforming to IMO A.424(XI). Sealed fluid damping; low-RPM rotor. | 4–8 Years (30k–70k hrs) |
| GC85 Sensitive Element | 44170728 | High-Speed Craft (HSC up to 70 knots) compliant with IMO A.821(19). High follow-up responsiveness. | 4–8 Years (30k–70k hrs) |
| OEM Service Tool | 44174449 | Mandatory installation tool. Required for extracting and safely seating the sensitive element without damaging the suspension torsion wire. | Reusable Service Tool |
Do not install a GC80 element (44174027) into a GC85 master compass or vice-versa. The GC85 sensitive element has specific dynamic damping parameters tuned to track vessel turn rates up to 70 knots. Utilizing the special OEM Service Tool (44174449) is strictly required during replacement to prevent torsion wire stress and ensure accurate centering.
3. Printed Circuit Board (PCB / PWB) Assemblies & Field Modules
The electronic circuits of the Simrad GC80/85 are split between the Master Compass and the Control Unit. Internal boards within the Control Unit are factory integrated and calibrated as complete unit assemblies:
| PCB Designation | Simrad Part Number | Alternate OEM Reference | Location & Function |
|---|---|---|---|
| MCC PCB (Master Compass Control) | 44142313 | 10189501 02 | Located inside Master Compass. Controls sensitive element rotation, horizontal centering, and follow-up servo loops. |
| Inverter PCB Module | 44141760 | 10169537 | Located inside Master Compass. Drives the 3-phase high-frequency rotor motor within the gyrosphere. |
| Compact Control Unit MK2 Assembly | 000-15036-001 | Complete Control Unit | Complete factory unit with CPU, power supply, and display. Internal boards are replaced as an entire assembly. |
| Expanded Control Unit MK2 Assembly | 000-15037-001 | Complete Control Unit | Includes high-capacity multi-channel repeater buffer boards, step drivers, and analog ROT output circuits. |
| Dual Control Unit MK2 Assembly | 000-15038-001 | Complete Control Unit | Dual gyro integration console with automatic switchover relays, redundant CPU controllers, and DP monitoring ports. |
4. Complete System Unit & Kit Part Numbers (MK2)
For new installations, major refits, or replacing damaged complete assemblies, reference the official Simrad Navico MK2 catalog part numbers:
| System / Unit Description | Catalog Part Number | Legacy / Alternative P/N | Scope of Supply |
|---|---|---|---|
| GC80 Master Compass (Unit) | 27102169 | 27101674 | Stand-alone master compass enclosure with gimbal support ring (sensitive element ordered separately). |
| GC85 Master Compass (Unit) | 27101682 | HSC Master Enclosure | High-Speed Craft master compass enclosure tuned for high turn-rate dynamics. |
| GC80 Compact Gyro System MK2 (Full Kit) | 000-15567-001 | MK2 Complete System | Includes GC80 Master Compass, Compact Control Unit MK2, manuals, and standard installation materials. |
| GC80 Expanded Gyro System MK2 (Full Kit) | 000-15568-001 | MK2 Complete System | Includes GC80 Master Compass, Expanded Control Unit MK2 with high-capacity repeater buffers. |
| GC85 Compact Gyro System MK2 (Full Kit) | 000-15570-001 | HSC Complete Kit | Includes GC85 HSC Master Compass, Compact Control Unit MK2, tailored for fast craft installations. |
5. Fuses, Power Supply Ratings & Consumables
Always install the exact specified fuse ratings to protect sensitive microprocessor inverter boards and power conditioning circuits from surge damage:
| Circuit Location | Fuse Designation | Current Rating | Protected Subsystem |
|---|---|---|---|
| Master Compass Enclosure | Fuse F1 | 12A | Located in front panel fuse holder; protects internal rotor inverter feed. |
| Power Supply Unit (PSU) | Fuse F201 | 6.3A | Main 110/220V AC power input supply circuit. |
| Power Supply Unit (PSU) | Fuse F202 | 20A | Emergency 24V DC battery backup power input circuit. |
| Control Unit (Internal) | Fuse F101 | 6.3A | Main internal DC bus input protection. |
| Expanded Unit Repeater Lines | Fuses F1 through F10 | 1A Each | Individual stepper repeater lines; protects against cable shorts on bridge wings. |
6. Cables, Mounting Accessories & Installation Kits
Pre-fabricated factory extension cables ensure signal integrity between the master compass and console-mounted control panels without ground-loop interference:
| Accessory / Cable Description | Simrad Part Number | Application Details |
|---|---|---|
| Flush Mount Kit | 27101757 | Mounting bracket and bezel hardware for flush console installation of the Control Panel. |
| Extension Cable (5 Meter) | 44170736 | Standard length interconnect cable linking Master Compass to Control Unit. |
| Extension Cable (10 Meter) | 44170744 | Intermediate length interconnect cable for consoles positioned further from gyro room. |
| Extension Cable (15 Meter) | 44170751 | Long-run shielded interconnect cable for lower-deck gyro rooms or large bridge decks. |
7. Maintenance Lifecycle, Settling Time & Operational Reality
The defining engineering achievement of the Simrad GC80/85 is its sealed sensitive element:
- No Annual Fluid Servicing: Unlike older traditional gyrocompasses (such as Yokogawa CMZ700 or Sperry MK37) that demand annual fluid replacement, support liquid top-up, and slip-ring brush replacement, the GC80/85 element is completely sealed. There is no oil to measure, change, or spill.
- Observed Mean Time To Failure (MTTF): Navico calculates theoretical MTTF at 30,000 operational hours. In field operational data gathered across global commercial fleets, observed MTTF frequently surpasses 70,000 hours (approx. 8 years) under clean, temperature-regulated gyro room conditions.
- Settling Period: Settles fully within 3 to 4 hours without latitude/speed preset assistance, and faster when initial heading is pre-aligned. Settling error remains below ±0.3°.
- 4 to 8 Year Replacement Milestone: When the sensitive element reaches end-of-life (indicated by rotor vibration, increased settling error, or bearing drift), it is replaced as a clean plug-and-play assembly utilizing tool
44174449without stripping gimbal mechanical assemblies.
8. Frequently Asked Questions (FAQ) • Simrad GC80/85
1. What is the fundamental difference between the Simrad GC80 and GC85?
The GC80 is tailored for standard commercial vessels compliant with IMO A.424(XI) and ISO 8728 up to standard merchant speeds. The GC85 is engineered specifically for High-Speed Craft (HSC) up to 70 knots conforming to IMO A.821(19) and ISO 16328 HSC, featuring the specialized sensitive element 44170728 tuned for rapid azimuth dynamics.
2. Does the Simrad GC80 really require no annual servicing?
Yes. The sensitive element contains a factory-sealed fluid chamber. There are no annual oil renewals, carbon brushes, or supporting fluid top-ups required. Routine annual inspection focuses purely on verifying power supply voltages, inspecting terminal tightness, checking cooling fan operation, and validating heading repeater sync.
3. Can the GC80/85 replace an obsolete Simrad GC50?
Yes. Since the Simrad GC50 is obsolete, the GC80 MK2 Compact or Expanded system is the authorized direct upgrade platform. It seamlessly links to existing bridge repeaters and navigation equipment.
4. Why is service tool 44174449 strictly required for sensitive element replacement?
The sensitive element is suspended on high-precision torsion wires. Attempting to lift or insert the gyrosphere manually without tool 44174449 will almost certainly bend the gimbal pivots or snap the suspension wires, resulting in catastrophic equipment failure.
5. Why is the Simrad GC80 so popular on Dynamic Positioning (DP) vessels?
DP systems require heading references with exceptionally low noise, high update frequencies, and reliable multi-gyro redundancy. The GC80 Dual Control Unit MK2 (000-15038-001) provides seamless auto-transfer, independent power isolation, and direct integration with Kongsberg, Converteam, and other leading DP consoles.
Get Simrad GC80/85 Genuine Spares & Port Service
Seanav Marine stocks genuine Simrad GC80/85 MK2 sensitive elements (44174027 & 44170728), replacement MCC PCBs (44142313), Inverter modules (44141760), complete control units, and certified overhaul service across UAE, India, Oman, Egypt, Singapore, and global ports.
Seanav Marine Technical Operations Desk
Reviewed by Lead Marine Electronics Engineer & Gyrocompass Specialists • Dubai Maritime City (UAE) & Mumbai (India) • Verified Marine Heading Reference Standard.
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