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Time for a 180-degree turn on a 4-minute indicator

Aviation Mechanic Airframe (AMA) practice question 1 of 20 on Aircraft Instrument Systems. ACS element AM.II.H.K6 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA turn-and-slip indicator is placarded as a 4-minute turn indicator. With the pointer deflected to the graduation mark, how long does a 180° turn take?

  1. A1 minute, at 3° per second
  2. B4 minutes, the full placarded time
  3. C2 minutes, at 1½° per second
Show the answer and explanation

Correct answer: C. 2 minutes, at 1½° per second

  • A — incorrect Three degrees per second is the standard rate shown by a 2-minute turn indicator, not by one placarded for 4-minute turns.
  • B — incorrect Four minutes is the time for a complete 360° turn at that rate, so half of that circle takes half the time.
  • C — correct A 4-minute indicator shows 1½° per second at the graduation mark, and 180° divided by 1½° per second equals 120 seconds, or 2 minutes.

BACKGROUND

The turn-and-slip indicator combines a gyro-driven turn pointer with an independent slip indicator ball. The turn pointer uses gyroscopic precession: the aircraft's rotation about its vertical axis produces a reaction 90° around the rotor in the direction of spin, tilting the rotor and deflecting the pointer in the direction of turn. Three degrees of turn per second brings an aircraft around 360° in 2 minutes, which is called a standard turn. Faster aircraft often use instruments graduated for 4-minute turns, where alignment with the graduation mark or one pointer width of deflection means 1½° per second and a 360° turn in 4 minutes. The instrument face is customarily placarded to say whether it is a 2-minute or 4-minute indicator.

STUDY TIP

Fix the two rates in mind, 3° per second and 1½° per second, then treat any turn question as simple division of degrees by rate.

KEY POINTS

  • A standard turn is 3° per second, or 360° in 2 minutes.
  • A 4-minute indicator shows 1½° per second at the graduation mark.
  • Turn time equals the degrees of turn divided by the indicated rate.

SOURCES

  • sources/ama-airframe/ch10.txt "Turn-and-Slip Indicator"
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MORE ON AIRCRAFT INSTRUMENT SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.