着氷防止システム (IPS: Ice Protection System)

What Is an Ice Protection System?

The Ice Protection System (IPS) encompasses all systems designed to prevent ice from forming on critical aircraft surfaces (anti-icing) or to remove ice after it has accumulated (de-icing). Ice accretion on lifting surfaces, engine inlets, and sensing probes poses severe safety risks by altering aerodynamic characteristics, blocking airflow, and degrading instrument accuracy.

How It Works

Thermal anti-icing — the most common method on transport aircraft — uses heat to prevent ice formation. Bleed-air systems route hot bleed air (typically 200–250 °C / 392–482 °F) from the pneumatic system through piccolo tubes embedded in wing leading edge slats and engine nacelle lips. This continuous heating maintains surface temperatures above 0 °C (32 °F) even in icing conditions.

Electric resistance heating is used for pitot probes, static ports, angle-of-attack vanes, and windshields — where bleed air routing is impractical. The Boeing 787 extends electric heating to wing leading edge surfaces as part of its no-bleed architecture, using approximately 100 kW per wing in maximum icing conditions, drawing from its large 1 MVA electrical generation capacity.

Pneumatic de-icing boots — inflatable rubber surfaces along leading edges — are employed primarily on turboprops and regional aircraft. Boots inflate cyclically (every 60–120 seconds) using pneumatic system pressure to crack and shed accumulated ice. They are not used on swept-wing jets due to ice bridging risk at lower accumulation levels.

The Environmental Control System provides windshield heat as a secondary function, maintaining cockpit visibility in precipitation and icing conditions. Engine inlet cowl anti-icing activates automatically or via crew selection when icing conditions are detected by ice detectors or when outside air temperature and visible moisture conditions meet EASA/FAA icing certification criteria.

Key Components

• Wing Anti-Ice (WAI) Valves: Bleed air shutoff valves controlling flow to leading edge slat piccolo tubes.
• Engine Anti-Ice (EAI) Valves: Control bleed air to engine nacelle lips; typically auto-activated by engine control computers.
• Ice Detectors: Vibrating rod or ultrasonic sensors detecting ice accretion rates; signal crew and auto-activate systems.
• Pitot Heaters: Electrical elements maintaining pitot tube temperatures above 50 °C (122 °F) continuously in flight.
• Windshield Heat Panels: Conductive oxide coatings on cockpit windows providing uniform resistive heating.

Aircraft Examples

• Boeing 737 NG: Bleed-air wing anti-ice on leading edge slats only; tail surfaces not anti-iced (design limit speed constraints in icing).
• Airbus A320: Three-zone wing anti-ice using bleed air; automatic activation when ice detected below 10 °C (50 °F) with visible moisture.
• Boeing 787-9: Fully electric wing anti-ice system; 200 kW total capacity eliminating bleed air dependency.
• ATR 72: Pneumatic de-icing boots on wing and tail leading edges; certified for flight in known icing (FIKI).