clock

Definition

An installed cockpit timepiece displaying hours, minutes, and seconds, used by the pilot to time flight events such as instrument approach segments, holding pattern legs, fuel burn intervals, and dead-reckoning navigation. For helicopter instrument flight under Part 91, a clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation is required equipment.

Plain English

A timing device fitted in the cockpit that shows hours, minutes, and seconds, so the pilot can accurately time things like approach legs and holding turns.

Context Anchor

Seen in aircraft equipment lists and used during instrument flying, especially when a procedure or clearance requires accurate timing.

Derivation

Clock comes from an old word for a bell, because early clocks marked time by ringing. The useful idea for aviation is not the bell, but a dependable device that marks time clearly.

Why Pilots Care

Allows rapid, unambiguous communication of relative bearings during instrument flight when visual references are limited.

Intuition Check

Do not read “clock” here as just any casual time display. In this context, it means a usable aircraft time source that shows hours, minutes, and seconds clearly enough for flight timing.

Example Sentence 1

Crossing the final approach fix, the pilot started the clock to time the descent to the missed approach point.

Example Sentence 2

Scan the nine o'clock position for any rising terrain during the approach.

Definition

A cockpit instrument that displays the current time, typically including hours, minutes, and seconds, and often featuring an elapsed-time function for measuring intervals during flight. Aircraft clocks may be analog or digital and are required equipment for IFR operations under FAR 91.205.

Plain English

A timekeeping device mounted in the cockpit. It shows the time of day and usually has a built-in stopwatch feature so the pilot can time specific events during the flight.

Context Anchor

Seen during cockpit equipment checks, instrument flight planning, fuel timing, and any procedure where the pilot must measure time accurately.

Derivation

Clock comes from an old word meaning “bell.” Early public clocks told time by striking a bell, so the word became tied to timekeeping. In aviation, it keeps that same basic meaning: a device used to know and measure time.

Why Pilots Care

Allows rapid, intuitive description of traffic or landmark positions without needing to use compass degrees.

Intuition Check