Gyro Magnetic Compass
Gyro-Magnetic Compass (also known as the Flux Gate Compass System).
🧭 1️⃣ What It Is
A Gyro-Magnetic Compass combines:
- a Gyroscope → for stability (reduces turning and acceleration errors), and
- a Magnetic Sensor (Flux Valve) → for direction reference to Earth’s magnetic field.
Together, they give a stable, accurate heading display without the lag and errors of a simple magnetic compass.
⚙️ 2️⃣ Main Components (and Their Roles)
| Component | Function | Simplified Explanation |
|---|---|---|
| Flux Valve (Flux Gate Sensor) | Senses Earth’s magnetic field direction | Like an electronic magnetic compass, remotely located (often in the fin or wingtip) to avoid magnetic interference. |
| Horizontal Gyro | Provides stability | Keeps the heading steady and smooth during maneuvers. |
| Heading Indicator (HSI / Directional Gyro) | Displays the current heading | What the pilot actually sees on the panel. |
| Slaving Amplifier (Error Detector + Amplifier) | Compares gyro heading to magnetic heading | Detects difference (drift) between gyro and magnetic reference and produces a correction signal. |
| Synchronizing (Torque) Motor | Corrects gyro drift | Applies a torque to realign the gyro heading with the magnetic heading. |
🔁 3️⃣ How It Works (Step-by-Step)
Flux Valve
- Measures the Earth’s magnetic field and produces an AC signal that represents magnetic north.
- This is your true magnetic reference.
Error Detection (Slaving / Precession Amplifier)
- Compares the flux valve signal (magnetic heading) with the gyro’s current heading.
- If they disagree, an error signal is generated.
Amplification and Phase Detection
- The AC error signal is amplified and phase-checked to determine which way the gyro must precess.
Torque Motor (Synchronizing Motor)
- Receives the DC correction signal and precesses the gyro to reduce the heading difference.
Recheck and Repeat
- The process continues until the gyro heading matches the magnetic field direction — at which point the system is synchronized.
🧠 4️⃣ Easy Memory Trick: “FEAT”
👉 F E A T = Flux valve → Error detector → Amplifier → Torque motor
That’s the correction cycle:
F → E → A → T
↓ ↓ ↓ ↓
Flux Valve → detects drift → Amplifies signal → Applies torque to gyro
This keeps the gyro heading “slaved” (automatically aligned) to the magnetic heading.
✈️ 5️⃣ Types of Operation
| Mode | Description |
|---|---|
| Slaved mode | The gyro is automatically corrected (normal mode of operation). |
| Free gyro mode | Pilot manually resets heading — used if the flux valve or slaving system fails. |
💬 6️⃣ Summary in Plain English
The Gyro-Magnetic Compass combines a stable gyro with a magnetic sensor (flux valve). The flux valve senses true magnetic north, the gyro keeps the heading steady, and the slaving system (FEAT) automatically corrects any drift so that your displayed heading always matches the Earth’s magnetic field.