Aircraft De-Icing Systems

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Questions and Answers

What is the primary purpose of an overheat control unit in conjunction with an 'override' thermistor and flame-stat?

Ice protection of engine intakes

Final overheat protection system (correct)

Automatic control and normal operation

Anti-icing and de-icing of wing and tail leading edges

Where is the entry point for the heated air in the thermal anti-icing system?

At the root of the aerofoil

At the tip of the aerofoil

At the stagnation point of the leading edge (correct)

At the trailing edge of the aerofoil

How does the system work in principle?

By maintaining the temperature of the skin above that at which ice occurs (correct)

By decreasing the temperature of the engine intakes

By increasing the temperature of the engine intakes

By reducing the temperature of the skin below that at which ice occurs

What is the purpose of the corrugations in the thermal anti-icing system?

To allow hot air to flow back chord-wise to the main aerofoil section Signup and view all the answers

What is the difference between anti-icing and de-icing systems?

Anti-icing systems use a continuous supply of heated air, while de-icing systems use a cyclic supply Signup and view all the answers

What is the purpose of wing and fuselage cross over ducts in the hot air bleed system?

To ensure a supply to all surfaces in the event of an engine shut down in flight Signup and view all the answers

What is the purpose of the hot air bleed system?

To prevent the shedding of ice accretions into the engine intakes Signup and view all the answers

What is the source of hot gas in an EXHAUST GAS HEATING SYSTEM?

All of the above Signup and view all the answers

At what temperature do the anti-icing shut off valves on each engine open to supply air to the leading edge ducting?

200ºC Signup and view all the answers

What is the purpose of the electrically actuated flaps in the EXHAUST GAS HEATING SYSTEM?

To partially divert exhaust gases to flow between the tubes of the heat exchanger Signup and view all the answers

What happens when the temperature sensor fails to control the temperature of the leading edge?

The overhead sensor controls the temperature by regulation of the hot air valve Signup and view all the answers

What is the purpose of the temperature sensors in the leading edge?

To monitor the temperature rise and control the cold air valve Signup and view all the answers

What is the purpose of the interlock between the gas flap actuator and the hot air valve actuator?

To ensure the hot air valve is fully open before the gas flap opens Signup and view all the answers

What happens if the gas flap fails in the open position?

The hot air valve closes and the spill valve opens to direct the hot air overboard Signup and view all the answers

What is the advantage of grading the distribution of air along the wing leading edges on aircraft with engines mounted on the rear fuselage?

To prevent the shedding of ice accretions into the engine intakes Signup and view all the answers

What type of temperature control is provided in the EXHAUST GAS HEATING SYSTEM?

Automatic temperature control with a standby 'manual' facility Signup and view all the answers

Study Notes

Thermal De-icing/Anti-icing Systems

Thermal de-icing/anti-icing systems in aerofoils use heated air ducted span-wise along the inside of the leading edge to prevent ice formation.
The heated air enters the leading edge at the stagnation point, where maximum temperature is required, and flows back chord-wise through corrugations to exhaust points.

Exhaust Gas Heating System

Ambient air is drawn into an intake on the engine nacelle and passes through a heat exchanger, where it is heated by diverted exhaust gases from the jet pipe.
The heated air is then ducted to the leading edges, passing through an electrically operated hot air valve.
The system has an emergency manual override facility to prevent overheating of the heat exchanger in case of failure.

Temperature Control

Temperature control is automatic, with a standby manual facility.
A control unit, with normal control and overheat thermistors, provides automatic control and overheat protection.
An overheat control unit, with an override thermistor and flame-stat, provides a final overheat protection system.

Hot Air Bleed System

In this system, air is bled from a late stage of the gas turbine engine compressor and distributed to aerofoil leading edges.
The system can be used for anti-icing or de-icing purposes on wing and tail leading edges, and for ice protection of engine intakes.
The system maintains the skin temperature above that at which ice occurs or raises the skin temperature to melt the ice after it has formed.

System Operation

Anti-icing shut-off valves open to supply air to the leading edge ducting at temperatures of about 200ºC.
Wing and fuselage cross-over ducts ensure a supply to all surfaces in the event of an engine shut down in flight.
Temperature sensors monitor the temperature rise and control the skin temperature by regulating the hot air valve and cold air valve.

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Description

Learn about thermal de-icing and anti-icing systems in aerofoils, including exhaust gas heating systems used to prevent ice formation in aircraft.