FAA Sport Pilot Airplane (SPA)Aircraft Performance and SystemsMedium
A pilot is flying straight and level on a heading of north in the Northern Hemisphere and begins a coordinated turn toward east. During the initial part of the turn, the magnetic compass will
- Aremain fixed on north until the turn is complete
- Bimmediately and accurately indicate the turn toward east
- Cindicate a greater rate of turn than is actually occurring
- Dbriefly indicate a turn in the opposite direction, toward west
Show answer & explanationAnswer & explanation
Correct answer: D. briefly indicate a turn in the opposite direction, toward west
Magnetic dip causes the compass card to swing opposite the direction of turn when starting from a northerly heading in the Northern Hemisphere. This is remembered by the mnemonic UNOS: Undershoot North, Overshoot South. The compass will lag and briefly show a turn toward west before catching up to indicate the actual eastward turn.
Why the other options are wrong
- A. The compass does move, but initially in the wrong direction due to turning error.
- B. The compass is not instantaneously accurate during turns due to magnetic dip errors.
- C. This describes overshoot, which occurs when turning from a southerly heading, not northerly.
Compass Turning Error (UNOS)
Due to magnetic dip, a magnetic compass gives erroneous indications during turns, especially near north and south headings in the Northern Hemisphere.
- UNOS: Undershoot North, Overshoot South
- Turning from north shows an initial turn opposite actual direction
- Turning from south shows an exaggerated turn indication
- Error is greatest near N/S headings and least near E/W headings
Memory trick: UNOS: Undershoot North, Overshoot South