Warning systems in the cockpit
| System | Function | Minimum requirement |
|---|---|---|
| Stall warning | Audible and/or visual warning shortly before stall speed | CS-23.207: warning must activate between stall speed and stall speed + 10 KIAS (typically via a flag or pressure port on the wing leading edge) |
| Gear warning (retractable types) | Audible warning on power reduction without gear extended | CS-23.729 |
| Master caution / warning (complex types) | Aggregate annunciator for several subsystems | CS-23.1322 |
Stall warner — purpose
The stall warning serves to warn the pilot of imminent flow separation due to an excessive angle of attack:
- Flow separation occurs at high AoA (above critical AoA, typically 15-18°).
- Consequence: lift loss, possible spin, possible crash.
- The stall warner gives the pilot an audible (beeper, horn) and/or visual (lamp) warning before the real stall — typically 5-10 KIAS above Vs.
→ Function: pilot reacts by lowering the nose (reducing AoA) and possibly adding power.
Operational limits — markings
Operational limits are usually marked by a red line on instrument displays. Examples:
- Vne on the ASI: red line as the not-to-exceed maximum speed.
- Maximum RPM on the tachometer: red line.
- Maximum CHT on the CHT gauge: red line.
- Maximum oil pressure: red line.
→ The pilot must never exceed a red-line value — risk of structural or engine damage.
Warning-light colour coding
Cockpit warning lights follow standardised colour coding per CS-25.1322 and EASA AMC:
| Colour | Meaning | Pilot action |
|---|---|---|
| Red | WARNING — immediate action required — life- or aircraft-threatening | Act immediately (e.g. engine fire, low oil pressure) |
| Amber / yellow | CAUTION — attention needed, action likely | Monitor, prepare to act |
| Green | OK / status (e.g. gear down, generator OK) | No action |
| White / blue | Informative (e.g. switch state) | No action |
→ Warning lights in the cockpit that require immediate action by the pilot are red. Examples:
- Engine fire warning (flashing red).
- Low oil pressure (red).
- Bus voltage loss in critical situations.
CO detector
Cabin heat in piston-engine aircraft typically works via an exhaust muff (heat exchanger around the exhaust). A cracked exhaust can introduce carbon monoxide (CO) into the cabin — invisible, odourless, lethal.
Recommended: an electronic CO detector in the pilot's field of view. Some states/operations require it (check national rules). Classic card-type CO indicators with colour change are less reliable.
Recording / data recorders
In light PPL trainers not generally required (FDR / CVR per Regulation 965/2012 apply only above certain weights or for commercial operations). Some modern glass cockpits record flight parameters internally — see AFM supplements.
Colour coding of warning lights*.*