Ice & Rain Protection
Thermal anti-ice, pneumatic de-ice boots, electrical probe/windshield heating and rain removal.
Ice & rain protection, summary notes
- ANTI-ICING prevents ice forming; DE-ICING lets a little ice build up and then removes it. Wing and engine-cowl leading edges on jets are usually ANTI-iced with hot engine BLEED AIR (thermal); the surfaces are kept above freezing.
- PNEUMATIC BOOTS (mostly on turboprops) are DE-icers: rubber boots on the leading edge inflate to crack off accumulated ice, then deflate, a cyclic system, timed to let ice build before shedding.
- ELECTRICAL heating protects pitot/static probes, angle-of-attack and total-air-temperature probes, windshields, water lines and (via slip rings) propellers; windshields also have anti-ice and demist heating films.
- RAIN removal uses windshield wipers, chemical rain repellent and hydrophobic coatings; ICE DETECTION (probes/sensors) warns the crew or auto-activates protection.
- Fluid (glycol/TKS) systems weep freezing-point depressant through porous panels on some aircraft.
- ⚠ Exam trap: wing/cowl anti-ice normally uses hot BLEED AIR (thermal, prevents ice); pneumatic BOOTS are cyclic DE-icers that inflate to break ice off after it forms; pitot and static probes are ELECTRICALLY heated.
Why are de-icing boots operated in cycles (allowing ice to build up first) rather than continuously?
A de-icing boot works by inflating to crack the ice off its surface. If run continuously with only a thin layer of ice, the ice can form a shell around the inflated boot and merely lift with it, then re-freeze, 'ice bridging'. Allowing a defined thickness to accumulate before a cycle ensures the ice is brittle enough to crack and shed cleanly when the boot inflates.
Ice & rain protection concept map
Ice & Rain Protection
Ice & rain protection quiz
Ice & Rain Protection, quiz
1. Wing and cowl anti-ice on jets usually uses:
Hot engine bleed air (thermal)Pneumatic bootsChemical fluid only2. Anti-icing differs from de-icing in that anti-icing:
Prevents ice formingRemoves ice after it formsOnly detects ice3. Pneumatic de-icing boots work by:
Inflating to crack accumulated ice offHeating continuouslySpraying fluid4. Pitot and static probes are protected by:
Electrical heatingBleed airPneumatic boots5. De-icing boots are cycled (ice allowed to build) to avoid:
Ice bridging over the inflated bootOverheatingFuel loss6. Rain is removed from the windshield by:
Wipers, repellent and hydrophobic coatingsBleed air onlyThe fuel system7. Windshields are also:
Electrically heated for anti-ice/demistCooled by bleed airLeft unprotected8. An ice-detection system:
Warns the crew or auto-activates protectionSets the thrustMeasures fuel