Radar Liquid Cooling Systems

  • Purpose: Remove heat from the Radar Transmitter and maintain temperature within operating limits. 

Radar Liquid Cooling System Components

  • Liquid to Air Heat Exchanger

    • Extracts heat from liquid coolant

    • A Temperature Control Valve controls coolant flow through the Liquid to Air Heat Exchanger to maintain a minimum coolant temperature level. 

  • Centrifugal Pump Unit: A self-priming, submerged, centrifugal pump with a cylindrical two-section reservoir that circulates liquid coolant through the system. 

  • Ram Air Scoop/Actuator 

    • The Ram Air Scoop is a mechanical mechanism that extends out of the left Leading Edge Extension (LEX) and provides cooling air to the Liquid to Air Heat Exchanger. 

    • The actuator is driven by an electric motor and opens and closes the Ram Air Scoop. 

    • The actuator closes with weight on wheels or with an input from the Air Data Computer when ram air is hot. 

    • The Ground Cooling Fan is electrically driven. It supplies a flow of ambient air for heat transfer from the Liquid to Air Heat Exchanger during ground operations. 

  • Fluid Pressur Filter

    • Filters coolant before it passes through the Radar Transmitter. 

    • When the replaceable filter element is contaminated, differential pressure will extend an indicator. 

    • Indicator provides visual indication of filter contamination (red showing). 

  • Low Pressure Sensor

    • Located in the coolant line, provides a ground to the Maintenance Status Display and Recording system (MSDRS). 

    • Loss of preset pressure will cause loss of ground and cause Weapon System Fail (WPN SYS FAIL) Code display. 

  • High Temperature Warning Sensor 

    • Located in coolant line, provides a ground to MSDRS. 

    • Temperature above preset limits will cause loss of ground and cause WPN SYS FAIL Code display. 

  • Liquid Coolant Temperature Sensor 

    • The temperature sensor is located in the coolant line. It provides temperature readings to the ACS Temp/Flow Controller. 

    • ACS Temp/Flow Controller can modulate RLCS Airflow Valve when Environmental Control System (ECS) cooling is used. 

  • Airflow Valve 

    • Pneumatically modulated to limit, as necessary, conditioned air to the Liquid to Air Heat Exchanger. 

    • ACS Temp/Flow Controller supplies electrical power to the Airflow Valve torque motor, which opens or closes pneumatic pressure to the Airflow Valve. 

  • Servicing Panel 

    • Located in the left forward fuselage 

    • Provides indication of fluid quantity 

    • Has two switches that test the operation of: 

      • RLCS Pump Unit

      • RLCS Ram Air Scoop Actuator/Ground Cooling Fan

Radar Liquid Cooling System Operation

  1. The Radar Liquid Cooling System circulates liquid coolant to remove heat from the Radar Transmitter. Coolant heated by the Radar Transmitter is circulated through a closed loop system by the Centrifugal Pump Unit to a heat exchanger, which ejects heat to the cooling air. 

  2. One of three sources of air is induced across the Liquid to Air Heat Exchanger to provide coolant temperature control. 

    1. Ram air – During normal in-flight operation, ram air is induced across the Liquid to Air Heat Exchanger through the Ram Air Scoop. 

    2. Conditioned air from the Air-conditioning System – During normal in-flight operation 

      • At high ram air temperature conditions, the Ram Air Scoop is closed by a signal from the Air Data Computer and conditioned air from the Air Cycle Air-conditioning System is delivered to the Liquid to Air Heat Exchanger. 

      • Cooling airflow and temperature control is modulated by the Temperature Control Valve and the Airflow Valve in response to signals from the Radar Liquid Cooling Temperature Sensor and the ACS Temperature/Flow Controller. 

    3. Ground cooling air/ground operation with aircraft weight on wheels – With the Ram Air Scoop and Airflow Valve closed, the Ground Cooling Fan in the left LEX supplies cooling air to the Liquid to Air Heat Exchanger