Engine instrumentation, indication and fire protection
Engine instrumentation, indication and fire protection
This section covers the gauges and sensors that show engine health and the systems that detect and suppress fire. The exam tests instrument interpretation and fire-protection logic.
Core rules and concepts
- Tachometer, manifold-pressure gauge, oil pressure/temperature, CHT, EGT, fuel flow and carburettor temperature are the core indications. Each gauge depends on a sensor, wiring and correct calibration.
- EGT probes are placed on exhaust stacks; a single cold cylinder can indicate ignition, fuel or compression trouble. CHT indicates cooling adequacy and is more directly related to cylinder damage than oil temperature.
- Fire detection may use spot detectors or a continuous loop; a fire warning requires confirmation and prompt shutdown, fuel shutoff and extinguisher use.
- Fire protection includes detection, warning, extinguishing and isolation. Never reset or ignore a fire warning in flight.
Worked example
During a run-up, one EGT remains much lower than the others while the engine runs roughly. The mechanic checks the spark plug, ignition lead and fuel nozzle for that cylinder. A cold EGT with a rough engine points to a dead cylinder, not a gauge error, so the run-up is stopped and the fault is corrected.
Traps
Do not treat a gauge reading as a sensor reading without checking wiring; do not ignore a fire warning because the gauge looks normal; and do not confuse CHT limits with oil-temperature limits.