BA-137 Series 3

Function of BA-137 Series 3 in the anti-icing system

The main function of BA-137 Series 3 is to control elements of the aircraft anti-icing system based on signals from icing detectors. When icing is detected, the block processes the incoming signal and issues commands to the corresponding cockpit warning indication and detector heating circuit. This allows the crew to receive an immediate warning about icing in the engine inlet area and helps maintain detector operation by clearing ice from the sensing element. The unit works as a relay / logic block within the complete anti-icing control circuit.

Operation with DO-206 and SPD-45-3 devices

BA-137 Series 3 is described in connection with DO-206 Series 2 icing detectors and SPD-45-3 differential pressure signalizers. In the supplied context, when ice blocks the openings of the DO-206 detector, a contact closes and the signal is sent to terminal No. 1 of the BA-137 block. The unit then energizes the heating element of the DO-206 detector and turns on the cockpit “Icing” / “Inlet Guide Vane Icing” warning indication. After the detector is cleared and the contact opens, the block switches off the circuits after a timed delay.

Timed delay logic of BA-137 Series 3

A characteristic function of BA-137 Series 3 is delayed switch-off after icing signal removal. According to the source context, after ice is removed from the detector sensing area and the detector contact opens, the BA-137 block does not immediately switch off the heater and warning indication. Instead, it keeps the circuit active for a fixed delay of approximately five seconds. This logic helps ensure that remaining ice fragments are cleared from the detector before the anti-icing signal and heater command are removed.

Installation and system integration on Il-76

In the supplied context, BA-137 Series 3 is installed in the technical compartment / radio equipment compartment of the Il-76 fuselage, on equipment racks together with other electrical and thermal control units. It works with engine icing detectors, detector heater circuits, cockpit warning lamps, anti-icing control panels and, depending on system configuration, flight data recording circuits. The number of blocks installed on board may correspond to the number of monitored engine channels. Exact location and quantity must be verified by aircraft documentation.

Identification and ordering of BA-137 Series 3

Before ordering BA-137 Series 3, the buyer should confirm the aircraft type, anti-icing system configuration, associated detector type, required series and documentation set. It is also important to clarify whether the request concerns BA-137 Series 3 specifically, BA-137-2S or another BA-137 modification. The unit may be required for Il-76 anti-icing system maintenance, replacement of a defective automation block, repair stock or restoration of aircraft electrical equipment. Passport, label data, series, storage condition and test records should be checked before shipment.