EP-309T

EP-309T magnetic amplifier in aircraft air conditioning systems

EP-309T is an aircraft electronic unit used as a magnetic amplifier and temperature regulator in onboard air conditioning systems. The unit is used on military and civil aircraft, including Mi-8 / Mi-17 family helicopters, Mi-24 helicopters and Il-76 aircraft modifications. EP-309T operates as part of automatic temperature control circuits and helps maintain the required air temperature in crew cabins, passenger or troop compartments and air distribution ducts, depending on the aircraft system configuration.

Temperature regulation function of EP-309T

The EP-309T unit receives signals from the temperature setting and sensing circuit and converts these signals into control outputs for the air conditioning system actuators. In typical installations, it works together with temperature setters such as RR-25 and air temperature receivers such as P-77. The unit compares the selected temperature with the actual air temperature and sends control commands to reversible electric motors that adjust air mixing flaps. This allows the system to regulate the supply of hot and cold air and maintain the required temperature automatically.

EP-309T in Mi-8 / Mi-17 and Mi-24 helicopters

EP-309T is used as part of aircraft technical equipment on helicopters of the Mi family. It may be installed on Mi-8 / Mi-17 helicopters and Mi-24 helicopters, including different modifications. In helicopter applications, the unit is associated with cabin air conditioning and temperature control functions. Since the exact installation may differ by helicopter model, modification and equipment standard, applicability should be confirmed through the aircraft equipment list, wiring documentation and air conditioning system documentation before supply or replacement.

EP-309T application on Il-76 aircraft

EP-309T is also used on Il-76 aircraft, including Il-76MD and Il-76TD modifications. On the Il-76, the unit operates in the aircraft air conditioning system as part of the RTA-32-9T automatic temperature regulator. The system uses signals from the P-77 air temperature receiver and controls actuator-driven flaps, including 5419T-type flap mechanisms, to regulate hot air supply from the engines into the air conditioning system ducts. In this configuration, several regulator sets may be installed onboard depending on the aircraft documentation.

Operating principle of EP-309T

EP-309T series 2 is described as a static two-channel magnetic amplifier operating in a relay-type follow-up control mode. The two channels are used for opposite actuator commands, typically opening and closing the hot air flap. The input signal is formed by a bridge measuring circuit that compares the temperature setter and temperature sensor resistance values. The output signal controls reversible aircraft electric motors used in air flap actuators. This operating principle allows the air conditioning system to react automatically to temperature deviation.

Identification and ordering of EP-309T

The unit may be referenced as EP-309T, EP-309T series 2, ЭП-309Т or ЭП-309Т серия 2. Before ordering, it is important to confirm the aircraft type, exact system installation, required series, condition, documentation requirements and whether the unit is needed for Mi-8 / Mi-17, Mi-24 or Il-76 air conditioning system maintenance. For replacement, the unit should be checked against the aircraft technical documentation, regulator set composition, wiring diagram and applicable test procedures.

Product Type: Aircraft magnetic amplifier / temperature regulator unit
Designation: EP-309T
Alternative Designations: EP-309T series 2, ЭП-309Т, ЭП-309Т серия 2
Function: Temperature regulation and actuator control in aircraft air conditioning systems
Purpose: Maintaining required air temperature in cabin and compartment air conditioning circuits
Application / Where Used: Aircraft air conditioning systems
Associated Systems: Aircraft environmental control system / air conditioning system
Associated Regulator: RTA-32-9T automatic temperature regulator, where applicable
Compatible Aircraft / Equipment: Mi-8 / Mi-17, Mi-24, Il-76, Il-76MD, Il-76TD according to aircraft documentation
Associated Units: RR-25 temperature setter, P-77 air temperature receiver, 5419T flap actuator mechanism, depending on system configuration
Operating Principle: Static two-channel magnetic amplifier in relay-type follow-up mode
Number of Channels: 2 independent channels
Channel Function: One channel for hot air flap opening, one channel for hot air flap closing
Input Signal: From bridge measuring circuit between temperature setter and temperature sensor / receiver
Output Signal: Switched current for control of reversible aircraft electric motors
Output Current: Up to 2 A
AC Power Supply: 115 V, 400 Hz
DC Power Supply: 27 V DC, permissible range 24–29.4 V
Construction: Protected aircraft block design in metal shielded housing
Connection Type: Standard aircraft plug connector
Approximate Weight: About 1.2–1.5 kg
Operating Temperature Range: −60 °C to +60 °C
Operating Altitude: Up to 25,000 m
Installation Area: Aircraft air conditioning / environmental control equipment area according to aircraft documentation
Condition: As applicable
Technical Documentation: Manufacturer passport, aircraft technical documentation, wiring documentation and test records upon request

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