Ice, Rain and Environmental Protection
Anti-icing and de-icing
Anti-icing prevents ice formation (thermal bleed air on wings and engine inlets, electrical heater mats on small aircraft); de-icing removes ice already formed (pneumatic boots, weeping alcohol). Know which surfaces are protected: wing leading edges, tail leading edges (sometimes not protected - a trap), propeller blades, engine intakes, pitot heads, static ports, and windscreens. Ice detector systems may be automatic or manual.
Rain and pitot/static protection
Windscreens use electrical heating or hot air for demisting and rain removal; wipers are mechanical. Pitot tubes are electrically heated and static ports may be heated; blockage causes airspeed or altitude errors. Traps: a blocked pitot with open static behaves like an altimeter (airspeed rises in climb, falls in descent); a blocked static causes errors in both airspeed and altitude indications.
Worked example and rule
Worked example: in icing conditions the airspeed indicator reads low and the altimeter is steady. Reasoning: suspect a blocked pitot (airspeed unreliable) with static still open, so altitude remains valid. The rule of thumb: with a suspected pitot blockage, use pitch and power, and cross-check with GPS ground speed and attitude; do not chase the airspeed indicator.