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When using the magnetic compass in flight, the most accurate heading reading occurs when

Choices

turning at standard rate.
Turning introduces compass errors.
✓ in straight-and-level UNACCELERATED flight on a constant heading.correct
Acceleration on E/W headings causes the compass to swing toward N (ANDS); turning on N/S headings causes lead/lag (UNOS). The magnetic compass is only reliable when straight, level, and unaccelerated. ANDS (Acceleration North, Deceleration South) errors appear on E/W headings during airspeed changes. Turning errors (UNOS) appear when turning to N (undershoot rollout) or S (overshoot). Use the DG/HSI for in-flight turns, then sync to compass when stable.
climbing at Vy.
Climbs change airspeed (acceleration error).
descending at Vno.
Descents accelerate (similar errors).

Why

Acceleration on E/W headings causes the compass to swing toward N (ANDS); turning on N/S headings causes lead/lag (UNOS). The magnetic compass is only reliable when straight, level, and unaccelerated. ANDS (Acceleration North, Deceleration South) errors appear on E/W headings during airspeed changes. Turning errors (UNOS) appear when turning to N (undershoot rollout) or S (overshoot). Use the DG/HSI for in-flight turns, then sync to compass when stable.

FAA source: PHAK Ch 8; PHAK Chapter 8 — Flight Instrumentsbrowse the reference library →

Covered in Supplemental · VIII — Basic Instrument Maneuvers — study the lessons free, then practice with grading and mastery tracking.

Original study question written for this course — representative of FAA knowledge-test topics, not an actual current FAA exam question.