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Purpose designed by Navitron Systems Limited for professionally operated ocean going commercial vessels of all types from typically 1800 to 20,000 gross registered tonnes, the Navitron NT991G MK2 is a powerfully equipped and technologically advanced Autopilot which is ‘Wheelmarked’ in accordance with MED 96/98/EC and Fully Type Approved to latest IMO and ISO specifications. Also Russian Maritime Register of Shipping (RMRS) and Morsviazsputnik approved, multi waypoint track steer facilities are included for use with ‘Heading to Steer’ data received from ECDIS etc.
A fully Type Approved installation programmable Autopilot for Gyro based vessels from 1800 to approximately 20,000 gross registered tonnes.
Fully programmable to provide optimum installation flexibility and final seagoing performance commensurate with the turn rates and inertia levels of larger vessels, the NT991G MK2 Autopilot is also simple to operate via a traditionally marked rotary Heading selector backed up by CANCEL and CONFIRM keys to preclude accidental course changes as required by Type Approval regulations.
Programmable Rate of Turn (ROT) allows the maximum safe ROT to be set by the operator and can be used in conjunction with automatic waypoint steering data received from ECDIS when operating in the ‘track’ mode.
The control unit is suitable for console or bracket mounting in bridge or wheelhouse locations. Standard system supply also comprises a Mag Heading Sensor Coil and Rudder Reference Unit for installation to low voltage solenoid operated (11-40Vdc / 5A max) hydraulic steering systems. An optional high voltage (110/220Vac/dc) is also available.
A second Mag input facility is provided to accept NMEA heading data from a proprietary source and dual Gyro input ports are standard to accept NMEA and/or 1:1 isolated Synchro heading data.
Where Step by Step, M-type or non 1:1 Synchro ratios are involved, a Fully Type Approved Gyro interface (type NT925HDI) is available. Similarly, fully Type Approved Analogue and Dual Steering Interfaces are available for Azimuth propulsion units and Dual rudder systems respectively. (See Interface types NT990ASI and NT990DSI).
Optional Equipment
| Parameter | Specification |
| Supply Voltage Range | $11\text{V DC}$ to $40\text{V DC}$ (Main power supply with internal failure monitoring) |
| Power Consumption | $2.5\text{W}$ @ $24\text{V DC}$ ($8.1\text{W}$ max with full panel illumination) |
| Solenoid Drive Outputs | Solid-state switching outputs ($11\text{–}40\text{V DC}$, $5\text{A}$ max rating) |
| Switching Polarity | Selectable Common $+VE$ or $-VE$ |
| Optional Drive Modules | Dual solenoid or dual channel analogue output ($\pm 10\text{V DC}$) cards |
| Display Panel | Red illuminated control panel with digital heading/ROT display & bargraph rudder angle display |
| Interface Type | Supported Protocol / Signal | Resolution |
| Mag Heading Input 1 | Direct Navitron Sensor Coil (HSC1 or HSC2) |
$0.25^\circ$ |
| Mag Heading Input 2 | NMEA 0183 ($xxHDM, $xxHDG, $xxHCC, $xxHDT) |
$0.1^\circ$ |
| Gyro Heading Input 1 | Isolated 1:1 Synchro (with $400\text{Hz}$ excitation from autopilot) | $0.25^\circ$ |
| Gyro Heading Input 2 | NMEA 0183 ($xxHDT, $xxHDM, $xxHDG, $xxHCC) |
$0.1^\circ$ |
| Track Steering Input | NMEA 0183 ($xxHTC, $xxHSC, $xxAPB) via Plotter / ECDIS |
— |
| Follow-Up Rate | Minimum $30^\circ/\text{sec}$ for all heading input types |
| Output Type | Configurable Formats & Sentences |
| NMEA 0183 Output |
Isolated RS-422 interface • Heading: • Status / VDR: • Selectable Update Rates: $1\text{Hz}$, $10\text{Hz}$, or $20\text{Hz}$ |
| Furuno Format | Selectable $5\text{Hz}$ or $40\text{Hz}$ update rate ($0.166^\circ$ or $0.1^\circ$ resolution, $5\text{V}$/$12\text{V DC}$) |
| Step-by-Step | Selectable $3$, $6$, $12$, or $24$ steps per degree ($5\text{V DC}$ signal) |
| Navitron Serial Data | Dedicated data line to Navitron digital repeaters / remote displays |
| Parameter | Specification |
| Steering Intelligence | Full P.I.D. steering algorithm with AutoTrim (automatic permanent helm) |
| Steering Modes | AUTO (Heading Control), STBY (Manual Helm), TRACK (ECDIS Waypoint Steering), DODGE |
| Operator Controls | Rotary Course Setter, Yaw, Rudder Ratio, Counter Rudder, Rudder Limit, Turn Rate (ROT), Mode & Gyro/Mag Selectors |
| Automatic Stability | Dynamic compensation for rudder speed variations / two-speed rudder systems |
| Panel Alarms | Power Fail, Off-Course, Steering System Fail, Rudder Limit, Heading Input Fail, Turn Rate Limit (includes Alarm Test facility) |
| Rudder Feedback Unit | Heavy-duty potentiometric reference unit (NT920RTU / NT990RTU) |
| Parameter | Specification |
| Control Unit Dimensions | $297\text{ mm (W)} \times 176\text{ mm (H)} \times 110\text{ mm (D)}$ |
| Weight | Approx. $3.3\text{ kg}$ |
| Operating Temperature | $-20^\circ\text{C}$ to $+60^\circ\text{C}$ |
| Compass Safe Distance | $0.6\text{ m}$ |
| Standard Scope of Supply | NT991G MK2 Control Unit, Mag Heading Sensor Coil, and Rudder Reference Unit |
Manufacturer Part Number: NT991G-MK2
Country of Origin: United Kingdom (UK)
MED Module B Approval: Fully Type Approved (Wheelmarked / Notified Body 0191)
Target Vessels: Commercially operated ocean-going vessels, workboats, and tugs from $1,800\text{ GRT}$ to $30,000\text{ GRT}$
IMO & ISO Compliance: IMO Res. A.694(17), MSC.191(79), ISO 11674, ISO 16329, IEC 60945, IEC 61162
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