Empirical Earth · Flight & Navigation

Aircraft, gyros & the attitude indicator

The claim

“A level plane would fly off on a tangent; pilots never dip the nose; gyros would drift.”

What is measured

To hold altitude at cruise an airliner keeps pitching its nose down ~8° per hour (v/R) to follow the curve. On a flat plane no such correction would be needed.

What would show this is wrong

aircraft requiring constant nose-down trim to hold altitude, as flying level over a flat plane would demand.

Sources

  1. Ring-laser / fiber-optic gyros & inertial navigation. Sagnac-effect optical gyros; gyrocompass alignment senses Earth rate (15.04°/hr). Standard avionics/IRS references (e.g., Honeywell/Nort link
  2. MEMS vibratory (Coriolis) gyroscopes. Performance grades and bias stability; tactical/consumer applications and GPS aiding. Standard inertial-sensor literature. MEMS gyroscope link
  3. FAA Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25). Attitude indicator operation, gyroscopic instruments, and flight at constant altitude. FAA PHAK link
  4. Schuler tuning: inertial platforms stay level via Earth’s radius. An inertial navigation platform is tuned to a natural period of ~84.4 minutes — that of a pendulum whose length equals Earth link
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