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Anti-icing Systems Print E-mail
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Written by Sabc   
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Engine Anti-Ice
Pitot Anti-Ice
Windshield Anti-Ice and Anti-Fog
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anti-ice_imageClimbing into high altitudes will cause the surrounding air temperature to decrease drastically, regardless of the general climate or weather conditions. At low temperatures moisture condensation takes the form of ice buildup on places of the airframe where it can cause several problems for operating the aircraft.

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To prevent this situation the F-15E is equipped with a couple of anti-icing systems. These systems generally consist of two sections: one sensor section (which senses if an icing condition occurs) and one anti-ice section (which actually takes measures to stop the icing condition). These anti-icing systems, though common in their working principles, are discussed separately below.

Engine Anti-Ice

The engines themselves are operating at extremely high temperatures, hence icing condition can occur only in the air inlet ducts. For this purpose there is an ice detector located on the inner side of the left engine air inlet duct. This probe (which looks much like as a pitot tube) senses ice buildup and turns on the INLET ICE caution. This caution remains turned on as long as ice buildup is sensed, regardless of the aircrew took measures against it or not (with other words: it cannot be turned off once acknowledged). In this sense the ice buildup sensor and the actual anti-icing systems work functionally independently from each other.

Engine anti-icing is done by an anti-ice airflow, whic is directed to the engine nose cone and the stationary inlet guide vanes. Besides this the inlet pressure probe is heated electrically. Note that the DEEC (Digital Electronic Engine Control) automatically shuts down the anti-icing system if the altitude is above 30,000 feet or the engine inlet temperature is above 15 °C (60 °F).

The operation of the engine anti-icing system is controlled by a switch, located on the front cockpit ECS panel (see illustration below).

anti-ice_engine_switch

It is a three position switch. It turns the engine anti-icing system on and off in its 'ON' and 'OFF' positions, respectively. Once placed in 'TEST' position it checks detector operation and turns on the INLET ICE caution.

Pitot Anti-Ice

The pitot tubes can be heated to prevent them from freezing at higher altitudes. They can be covered when on the ground, the cover protecting them from physical harm. Note, that the covers are made of heat resistant material, which can withstand the heat generated by the pitot tube heaters in case heating is accidentally turned on while the covers are still on.

The switch for the pitot tube heating is located on the environment control systems ( ECS) panel at the forward end of the pilot's right console (see illustration below).

anti-ice_pitot_switch

When engaged, the switch sends an electric current to a heating coil in the root of the pitot probe assembly. The pitot tube's metal body conducts the heat to the entire surface and makes it impossible for ice to accumulate.

Windshield Anti-Ice and Anti-Fog

Fog formed on the inner surface of the windshield is removed by blowing with air. Windshield anti-fog air is supplied when cockpit air conditioning is operating. The anti-fog air temperature is regulated by the pilot using the anti-fog switch.

Ice formed on the outer surface of the windshield is removed also by blowing it with hot air. For this purpose there are exterior air nozzles in front of the cockpit. These nozzles blow hot air coming from the primary heat exchanger to the windshield. Since this is a high pressure, hot air, using the windshield anti-ice system under non-icing conditions may result in windshield damage. If windshield anti-ice air temperature is excessive, then a WINDSHIELD HOT caution comes on.

Both the windshield anti-fog system and the windshield ati-ice system can be operated by their respective switches on the ECS panel in the right side of the front cockpit (see illustration below).

anti-ice_windshield_switch

The windshield anti-fog switch is electrically held either in the 'HOT' or 'COLD' position, but reverts to 'NORMAL' if electrical power is lost from any reason. At 'NORMAL' position, anti-fog air is supplied at normal temperature. At 'HOT' position, anti-fog air is supplied at a hotter than normal temperature. At 'COLD' position, anti-fog air temperature is regulated by the cockpit temperature controls and can be varied from colder than normal to hotter than normal.

The windshield anti-ice switch simply turns on or off the windshield anti-ice system. Note, that although th WINDSHIELD HOT caution is available for the aircrew, this reflects anti-ice air temperature only and does not detect the actual temperature of the windshield and may not warn of impending windshield damage.

Sources

  • F-15E Flight Manual TO 1F-15E-1 (courtesy of eFlightManuals.com)

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Last Updated on Monday, 18 October 2010
 


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