Ice and Rain Protection, Fire and Smoke Protection
Ice protection
Ice protection is either anti-icing (preventing ice) or de-icing (removing ice). Thermal anti-icing uses bleed air through piccolo tubes in the wing leading edge and engine intakes; electrical heating is used for pitot tubes, static ports, TKS weeping wings and propeller blades. Pneumatic de-icing boots inflate to crack ice off. Ice detectors alert the crew; the trap is that anti-ice systems have limits - some cannot keep up with severe icing, and engine bleed demand reduces performance. Protected areas are usually the leading edges and intakes; unprotected areas can accumulate ice and cause handling changes.
Rain protection
Rain removal uses windscreen wipers, rain repellent, or bleed-air blowers that create a high-velocity air film. Windshield heating prevents fogging and ice and is also a structural consideration (heated windshields are laminated).
Fire and smoke detection
Engine fire detection uses continuous-loop detectors (e.g. Kidde) or thermocouples; a loop responds to overheat or fire, and the fire handle shuts off fuel, bleed air and hydraulics and arms the extinguisher. Cargo and lavatory smoke detectors are photoelectric or ionisation types. Fire extinguishing agents are halon (or replacements) for engines and cargo; the agent displaces oxygen and interrupts the chain reaction.
Traps
Confusing the fire warning with the overheat warning; the fire handle does more than discharge the bottle. Another trap is that a detector loop failure can cause a false fire warning, and the system may have dual loops for redundancy. Also, smoke in the cabin requires establishing the source and using smoke removal, not simply opening the outflow valve without considering pressurisation.
Worked example
If an engine fire loop is tested and shows a fault, the correct action is to treat the system as inoperative and follow the MEL, not to assume a fire exists. Rule of thumb: a fire warning requires immediate action; an overheat warning allows a more measured response.