// Time
UTC clocks and indicators
Why the tower runs on UTC, the accuracy CAP 670 requires of the cab clock, and the indicators alongside it: navaid status and the landing clearance indicator.
What it is
- A UTC clock visible from every position, showing hours, minutes and seconds, accurate to ±15 s a day (CAP 670 IAS01.27).
- A navaid serviceability indicator (ATC01.6), and a landing clearance indicator where surveillance radar approaches end under 2 NM (IAS01.36–.39).
How controllers use it
- ATIS broadcasts are coded with the phonetic alphabet, ideally under 30 seconds long, and arriving pilots acknowledge the code (CAP 670 COM05; CAP 493).
UK rules and practice
- Aviation runs on UTC; the local-time readout here is just for convenience.
At Prestwick
- EGPK ATIS is on 121.130.
- Prestwick publishes SRA procedures terminating at 2 NM for RWY 12, 20 and 30 (AIP charts list).
// Through the eras
| Era | Status | Notes |
|---|---|---|
| 1930s–40s | Typical UK practice | A wall clock; RAF watch offices kept GMT. |
| 1950s–60s | Typical UK practice | An electric master-slave clock is typical. |
| 1980s–90s | Typical UK practice | Digital clock displays are typical. |
| Modern | Typical UK practice | A UTC clock visible from every position, ±15 s a day (CAP 670 IAS01.27). |