ICE PROTECTION Incomplete
ICE PROTECTION GENERAL The Ice and Rain Protection Systems allow the aircraft to operate in icing conditions or heavy rain. Aircraft Ice Protection is provided by heating in critical areas using either: Hot Air from the Pneumatic System o o o Wing Leading Edges Stabilizer Leading Edges Engine Air Inlets Electrical power o o o o Windshields Probe Heat Pitot Tubes Pitot Static Tube AOA Sensors TAT Probes Static Ports ADC Pressurization Service Nipples Lavatory Water Drain Potable Water Rain removal from the Windshields is provided by two fully independent Wiper Systems. LEADING EDGE THERMAL ANTI ICE SYSTEM Ice protection for the wing and horizontal stabilizer leading edges and the engine air inlet lips is ensured by heating these surfaces. Hot air supplied by the Pneumatic System is ducted through perforated tubes, called Piccolo tubes. Each Piccolo tube is routed along the surface, so that hot air jets flowing through the perforations heat the surface. Dedicated slots are provided for exhausting the hot air after the surface has been heated. Each subsystem has a pressure regulating/shutoff valve (PRSOV) type of Anti-icing valve. An airflow restrictor limits the airflow rate supplied by the Pneumatic System. The systems are regulated for proper pressure and airflow rate. Differential pressure switches and low pressure switches monitor for leakage and low pressures. Each Wing's Anti Ice System is supplied by its respective side of the Pneumatic System. The Stabilizer Anti Ice System is supplied by the LEFT side of the Pneumatic System. The APU cannot provide sufficient hot air for Pneumatic Anti Ice functions. ENGINE ANTI ICE SYSTEM Engine Anti Ice is provided by heating the Engine Air Inlet Lip. This Bleed Air comes directly from the compressor upstream of the High Stage Valve and is independent of the aircraft Pneumatic System. There is NO temperature control as there is sufficient air flow around the Inlet Lip to prevent any overheating. There is no limitation for using the EAI System when the aircraft is on the ground. ICE DETECTION SYSTEM Ice accumulation can be seen by the pilots on the Windshield corners and Wiper arm. At night use the Inspection Lights to illuminate the Wing Leading Edges. The Ice Detection System is primarily a fully automated system. When in icing conditions it activates the required Hot Air Protection Systems and configures the Integrated Pneumatic Bleed System. It also signals the Stall Protection System (SPS) to reduce the AOA Set Trigger Values. The Ice Detectors 1 and 2 are installed on the airplane's Left and Right Nose section. They are shaped to quickly detect ice formation. The Ice Detectors will detect ice before the pilot can see ice form anywhere. 0.5 mm of ice accumulation will trigger the system. The Detector is a nickel alloy tube mounted on a strut, with one inch exposed to the air stream. It vibrates ultrasonically. As the Ice Detector enters an ice condition the vibration frequency of the Probe decreases. The Ice Detector unit is heated periodically to remove the ice that caused the automatic response. When the Probe's natural frequency is restored the heating is stopped and it is ready to detect for ice again. Once de-iced the Ice Detector is cooled enough in a few seconds to begin detecting for ice once again. Within ice conditions the Ice signal remains active for 60 seconds. The Ice Detectors remain active in all flight phases. The Ice Detector TEST Switch checks the system by simulating an ICE CONDITION signal. EICAS will display a Caution Message if the Anti Ice is ON when outside icing conditions. ICE DETECTION OVERRIDE KNOB The system logic corresponding with knob selection is as follows: ENG ENGINE WING and STAB ON ON when ICE CONDITION AUTO ENGINE WING and STAB ON when ICE CONDITION ON when ICE CONDITION ALL ENGINE WING and STAB ON ON NOTE: WING and STAB inhibited on ground < 25 kts. The Wing and Horizontal Stabilizer Subsystems are INHIBITED on the ground below 25 knots to prevent overheating and structural damage. At American Eagle, when planning an icing takeoff, the Override Knob is selected to ENG so as to establish an ANT I ICE ON N1 target for the FADECs to achieve. An N1 change that may or may not occur somewhere in the takeoff roll above 25 knots (due to icing conditions detection) is not desirable. To prevent a loss of thrust from the Engines on Takeoff, when the Anti Ice Systems are active, the FADEC incorporates and automatic Ice Compensation Logic. This is selected on by the MFD Takeoff Page's REF A-ICE: ON option. In-flight the FADEC re-establishes idle thrust to satisfy Anti-Ice System needs. This logic is inhibited when the Landing Gear is DOWN to improve Rate of Descent and Glideslope compliance. The Bleed Air Thermal Anti Icing Systems may be individually deactivated by buttons on the Overhead Panel. WINDSHIELD HEATING SYSTEM The Windshields are electrically heated for Anti Icing protection and Anti Fogging prevention. A conductive film imbedded within its inner layer acting as an electrical resistor. Left and Right Windshields are individually controlled. There are separate power sources for each Heating Element and each Control Circuit. Each Heating Element has a dedicated Temperature Controller that receives a signal from the associated Temperature Sensors. The control range is: 40°C to 45°C (104 - 113°F). When the Upper Temperature Limit is reached the power supply is interrupted. When the Lower Temperature Limit is reached the power supply is restored. Each Windshield has 3 Temperature Sensors. One is used for Temperature Control, One is used for Overheat Protection (>55 degrees C) One is used as a Maintenance backup in case of failure in the others. SENSOR HEATING SYSTEM: All the Sensors and electrically heated and controlled by 3 overhead panel buttons. The aircraft provides automatic Sensor Heating for: Pitot Static Tubes, Pressurization System & ADS Static Ports, TAT Sensors 1 (2), and AOA Vanes 1 (2). In the Automatic Mode the System operates according to 3 Logic sets: These are heated whenever one Engine is operating with N2 > 56.4%: o Pitot 1 and 2, o Pitot/Static 3, o AOA 1 and 2, o ADS Ports 1, 2 ,3, and 4, and o Pressure Static Ports 1 and 2. These are heated in any and all flight conditions, o Pitot/Static 3, o Pressurization System Static Port 2 These are heated provided either Engine 1 or 2 Anti Icing Subsystems are functioning or the aircraft is in-flight: o TAT 1 o TAT 2. Sensor Heat deactivation is accomplished either when the above conditions are NOT met or when the associated Control Button is manually released. LAVATORY WATER DRAIN AND NIPPLE HEATING SYSTEM This system prevents lavatory water from freezing and clogging under all ground and flight conditions. The aircraft provides automatic DC BUS 1 powered heating for the Lavatory Waste Water Drain, and Potable Water Service Nipples [Overflow and Fill Nipple ICE COND-A/I INOP: Any Bleed Air Thermal Anti Ice Subsystem NOT functioning properly in icing conditions. NO ICE-A/ICE ON Any Anti-Icing Valve OPEN, and: In-flight, and NOT in icing conditions. A/ICE SWITCH OFF Any Bleed Air Thermal Anti Ice Button is turned OFF. E1 (2) A/ICE FAIL OR WG1 (2) A/ICE FAIL OR STAB A/ICE FAIL Low Pressure condition Valve failure Any Switch failure Overpressure condition Any System activation device failure WG A/ICE ASYMMETRY Asymmetrical degradation of the Wing Anti Ice System W/S 1 (2) HEAT FAIL Associated Windshield Heating System failure, < 38°C Associated Windshield Overheat condition, > 55°C. PITOT 1 (2), (3) INOP Associated Sensor Heating is inoperative. AOA1 (2) HEAT INOP Associated Sensor Heating inoperative. TAT 1 (2) HEAT INOP Associated Sensor Heating inoperative. ICE DETECTORS FAIL Both Ice Detectors have FAILED. ICE DET 1 (2) FAIL Respective Ice Detector has FAILED. ICE CONDITION Aircraft is flying in ice conditions.
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