Maintenance · 4 minute read
Autopilot heading error diagnosis
Investigate autopilot heading errors methodically: compare references, check data sources, note magnetic interference and record when the error occurs.
An unexpected heading display does not automatically mean the drive is steering badly. First distinguish a heading-reference problem from a boat that is failing to hold its target. Compare like with like, record the conditions and avoid recalibrating repeatedly before understanding the symptom.
Key facts
- Distinguish
- Heading from course over ground
- Compare
- The same magnetic or true reference
- Inspect
- Selected heading source
- Record
- When the discrepancy changes
Distinguish magnetic heading, true heading and course over ground
Heading describes where the bow points; course over ground describes movement across the earth. Tide and leeway can make them differ without a fault. At low speed, some position-derived course readings may also be unsuitable as a heading comparison.
Check whether displays use true or magnetic values and whether you are looking at the same selected source. Write down the labels, not only the numbers. A disagreement between different references can be mistaken for poor calibration.
Check new equipment for magnetic interference
Think about new speakers, tools, spare anchors, wiring or equipment near the heading sensor. Movable objects can create intermittent symptoms. Compare the current arrangement with installation photographs and the manufacturer’s separation guidance.
Do not move or recalibrate the sensor while relying on it to steer. Return to a safe operating arrangement and involve the installer when relocation is needed. The sensor’s mounting and orientation are part of the commissioned system.
Check the autopilot heading data source
A network may contain more than one heading source. Record which one the pilot and plotter are using and whether selection changes after startup. A replacement display or software update can make source configuration worth rechecking.
Use the equipment’s documented source-selection process. Do not disconnect network devices at random. A diagram and clear fault record help a technician find conflicting or missing data without creating additional faults.
Record when autopilot heading errors occur
Record whether the discrepancy stays constant, changes with direction, appears when equipment is switched on, or follows a particular sea state. Include actual observations and relevant alarms. Patterns are more diagnostic than an estimate made from memory.
If the boat is physically steering unexpectedly, take manual control using the supported procedure and assess navigation first. Troubleshooting should happen only when steering and lookout can be maintained safely.
Retest heading data after correcting the fault
After a documented correction, repeat the relevant checks and compare with the baseline. Follow manufacturer commissioning instructions if calibration or sensor position has changed. Record final sources and settings for the next service visit.
Do not use software offsets to conceal an unexplained changing error. A consistent alignment correction and intermittent interference are different problems and need different responses.
Questions
Frequently asked
Should heading equal GPS course?
Not necessarily. Current and leeway can make the direction of travel differ from the direction the bow points.
Can stored metal affect the sensor?
It can, depending on location and equipment. Check the manufacturer’s installation guidance and what has changed nearby.
Will a compass offset fix every error?
No. An offset cannot resolve a changing interference or source-selection problem. Establish the cause first.
When should I stop using the pilot?
Take over when steering or data is unreliable and manage navigation first. Resume only after the fault is understood and the system is appropriately verified.
Practise autopilot operation with an instructor
Habits are learned at the helm with someone watching. The training section explains what a good instructor covers and where to find one in your state.