AHRS and Solid-State Gyros: MEMS Sensors and Attitude/Heading Computation

022-04-06Pablo Asensio Martínez2026-03-271 min

Modern aircraft use solid-state technology to replace mechanical spinning gyroscopes, increasing reliability and accuracy.

AHRS (Attitude and Heading Reference System)

A single unit that computes aircraft attitude (Pitch/Roll) and Heading (Yaw). It typically replaces the separate Attitude Indicator and Directional Gyro.

  • Components:
    • MEMS Gyroscopes (Rate Sensors): Measure angular rate (not position) around 3 axes.
    • Accelerometers: Measure acceleration (gravity) to determine the vertical (Pitch/Roll reference).
    • Magnetometers: Measure the magnetic field to determine Heading (Yaw reference, like a Flux Valve).
  • Integration: A computer integrates the rate data to calculate attitude and uses gravity/magnetic data to correct for drift.

Ring Laser Gyro (RLG)

Used in high-end Inertial Reference Systems (IRS/INS).

  • Principle: Uses two counter-rotating laser beams in a triangular path.
  • Sagnac Effect: When the unit rotates, one beam has a shorter path and the other a longer path, creating a frequency shift.
  • Features: No moving parts, extremely accurate, measure angular rate directly.

Advantages over Mechanical Gyros

  • Reliability: No moving parts (Solid-state).
  • Maintenance: Significantly reduced.
  • Startup: Faster alignment.
  • Output: Digital data easily fed to Glass Cockpit displays (PFD/ND).