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SESK: Stuff Everyone Should Know · sesk.info/pilot-heading-indicator-drift

Why must a basic heading indicator be realigned with the magnetic compass?

Gyroscopic precession makes it drift.

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  1. Precession makes it drift ✔
  2. Static pressure makes it lag
  3. Pitot pressure makes it lead

Why: Friction causes the gyro heading display to creep from its set position. Periodic compass comparison and realignment keep the indication useful.

Huh, didn't know that: A magnetically slaved heading system usually corrects itself without manual realignment.

The dad joke
The heading indicator drifted because it needed a little direction in life.
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References

Answer: Precession makes it drift. Friction causes the gyro heading display to creep from its set position. Periodic compass comparison and realignment keep the indication useful.

  1. Pilot's Handbook of Aeronautical Knowledge Chapter 8 www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/phak/10_phak_ch8.pdf
    Because of precession caused by friction, the heading indicator creeps or drifts from its set position.
    Checked 2026-10-09.

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