InstrumentsGyroscopic Instruments
Directional Indicator
The directional indicator is a gyroscopic flight instrument designed to provide stable heading information without the oscillating errors common to a magnetic compass. It must be periodically synchronised with the magnetic compass due to apparent wander and gyroscopic drift. Unlike the magnetic compass, the directional indicator is unaffected by turning and acceleration errors.
Key Points
- •Unaffected by the turning and acceleration errors that affect a magnetic compass.
- •Requires regular synchronisation with the magnetic compass to correct for gyroscopic drift.
- •Subject to <strong>apparent wander</strong>, which is greatest at the poles and zero at the equator.
- •Driven by the vacuum system — a suction failure will cause it to become unreliable over time.
Exam Relevance
Knowing why and how often to align the DI with the magnetic compass is a fundamental navigation and instrument operation concept.
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