Timed Turns: Instrument Flying Handbook Ch. 7

Handbook Reference

IFH Ch 7

7.timed-turns. Timed Turns

A timed turn is a precision instrument maneuver in which the pilot uses the turn coordinator (or turn-and-slip indicator) and the clock to change heading by a specific number of degrees, without reference to the heading indicator or magnetic compass. Timed turns are a fundamental partial-panel skill, used primarily when the heading indicator has failed or is suspect, when the magnetic compass is unreliable due to acceleration and turning errors, or whenever a pilot needs a precise heading change in turbulent conditions where compass swing makes direct reading impractical.

The technique relies on the calibrated rate of turn produced by the turn coordinator. A standard-rate turn is 3° per second, which results in:

360° in 2 minutes (hence the term "2-minute turn")
180° in 60 seconds
90° in 30 seconds
30° in 10 seconds

A half-standard-rate turn is 1.5° per second and is typically used at higher airspeeds (above approximately 200 knots) or when flying high-performance and transport-category aircraft where standard-rate would require excessive bank.

Calibration check. Before relying on timed turns, the pilot should verify that the turn coordinator is accurate. With wings level and the airplane trimmed, establish a standard-rate turn (miniature airplane wing aligned with the standard-rate index) and time a 360° turn using the heading indicator (assuming it is operational and being used only for the calibration check) or a known visual reference. The turn should require 2 minutes ±a few seconds. If it does not, the pilot must apply a correction factor — for example, if 360° actually requires 1 minute 50 seconds, every commanded interval must be shortened proportionally.

Procedure for a timed turn.

Determine the desired heading change in degrees and compute the required time at standard rate (degrees ÷ 3 = seconds).
Note the second hand position on the clock, or start the elapsed-time function.
Smoothly roll into a coordinated standard-rate turn in the desired direction, using the turn coordinator as the primary bank reference. The ball must remain centered.
Maintain altitude with pitch and power; cross-check the attitude indicator (if available), altimeter, and VSI.
As the calculated time elapses, smoothly roll out wings-level using the turn coordinator. Begin the rollout slightly before the time expires — typically half the bank angle in seconds — to compensate for the rollout arc. For example, with about 15° of bank in a typical light single, lead the rollout by roughly 1–2 seconds.
After rollout, allow the magnetic compass to settle in level, unaccelerated flight, then verify the new heading.

Example. The pilot is heading 090° on partial panel and ATC issues a heading of 150°. The required heading change is 60° to the right.

Time required = 60 ÷ 3 = 20 seconds at standard rate.
Note the sweep second hand at, for instance, the 12 o'clock position.
Roll into a coordinated right standard-rate turn, holding the wing on the index.
Begin rollout at approximately 18 seconds, completing wings-level near 20 seconds.
After 10–15 seconds of straight, level, unaccelerated flight, verify 150° on the magnetic compass.

Common errors.

Improper rate of turn. Holding less than full standard rate produces an undershoot; holding more produces an overshoot. The wing-tip of the miniature airplane must remain precisely on the index.
Uncoordinated turn. A skidding or slipping turn distorts the indicated rate and induces compass errors that complicate the post-turn heading check.
Failure to lead the rollout. Rolling out exactly at the calculated time results in a consistent overshoot equal to roughly half the time spent rolling out.
Altitude excursions. Increased back pressure is required to hold altitude in the turn; failing to add it produces a descent, especially at higher bank angles.
Cross-check breakdown. Fixating on the clock at the expense of the attitude, turn coordinator, and altimeter causes pitch and bank deviations.

Magnetic compass coordination. Although timed turns make the heading indicator unnecessary, the magnetic compass remains the only direct heading reference on partial panel. Because of northerly turning error and acceleration error (ANDS — Accelerate North, Decelerate South), the compass cannot be read accurately during the turn. The pilot uses the timed turn to arrive near the desired heading, then refines the heading in straight-and-level flight using the compass, or by combining timed-turn and compass-turn techniques (UNOS — Undershoot North, Overshoot South) when rolling out on northerly or southerly headings.

Proficiency in timed turns is required during the instrument practical test under partial-panel conditions and is one of the foundational tools that allow continued safe IFR flight after a vacuum or electrical instrument failure.

Oral Exam Questions a DPE Might Ask

Q1How long does it take to turn 90° at standard rate, and how do you know?

30 seconds. A standard-rate turn is 3° per second, so 90° divided by 3°/sec equals 30 seconds. A full 360° turn takes 2 minutes.

Q2Why would you use a timed turn instead of just turning to a heading on the heading indicator?

Timed turns are used on partial panel when the heading indicator has failed or is unreliable, since the magnetic compass cannot be read accurately while turning due to northerly turning and acceleration errors.

Q3How do you verify the turn coordinator is accurate before relying on timed turns?

Establish a standard-rate turn and time a full 360°; it should take approximately 2 minutes. If it doesn't, apply a proportional correction factor to all subsequent timed turns.