BU-32

BU-32 control unit in SPUU movable stops system

The BU-32 is an aircraft electronic control unit used in SPUU-type movable control stops systems. It is part of the automatic control equipment that limits movement in the control system according to flight conditions. The unit is not a mechanical stop by itself. It receives electrical signals, processes them, and sends commands to the actuator mechanism that changes the position of the movable stop. In helicopter documentation, BU-32 is normally listed together with pressure and temperature sensing elements, feedback circuits, and the actuator used in the SPUU system.

Signal processing and automatic limitation through BU-32

During operation, the unit works with signals related to outside air pressure and temperature. These inputs are used to form the command for the movable stop actuator. The purpose is to limit the travel of the relevant control channel when operating conditions require it. In practice, the crew does not manually adjust the stop during each change of altitude or temperature. The BU-32 handles this part automatically through the SPUU system. If the system response is incorrect, the cause may be in the control unit, sensors, wiring, feedback element, or actuator.

SPUU system work around the BU-32 control unit

In the SPUU installation, BU-32 works with the pressure sensor, temperature sensor, feedback sensor, actuator mechanism, relays, cockpit switch, and test connector if these are included in the aircraft configuration. The system compares the measured conditions with the required travel limitation and moves the stop through the actuator. Because several components are involved, troubleshooting should not start and end with the control unit alone. Wiring condition, sensor signals, actuator travel, and feedback response all matter during maintenance.

Aircraft application of control unit BU-32

The BU-32 is used in movable control stops systems installed on helicopters and aircraft where automatic limitation of control travel is required. Public technical references most often mention it in relation to the SPUU-52 system used on Mi-series helicopters, including Mi-171E equipment lists. Exact application depends on the aircraft type, SPUU version, and modification standard. Some systems may use BU-32 variants such as BU-32-1, BU-32-2, or BU-32-3, with different settings. The installed marking should therefore be checked before supply.

Identification and ordering checks for BU-32

Before ordering, the marking on the installed unit should be compared with the aircraft parts catalog, SPUU system documentation, or passport. A general request for “BU-32” may not be enough if the aircraft uses a specific variant or setting. It is better to provide the unit designation, aircraft type, SPUU version, and a photo of the data plate if available. The product is also known under alternative designation БУ-32.

Product Type: Aircraft electronic control unit
Function: Processing of pressure and temperature signals and control of movable stops
Application / Where Used: SPUU movable control stops systems
System / Installation Area: Automatic control and regulation circuits
Compatible Aircraft / Equipment: SPUU-type movable control stops systems
Operating Voltage (AC): 36 V, 400 Hz
Operating Voltage (DC): 27 ± 2.7 V
Current Consumption (AC): Not more than 0.3 A
Current Consumption (DC, Continuous): Not more than 0.5 A
Current Consumption (DC, Short-Term): Not more than 2.5 A
Transmission Ratio by Temperature: 1.05 ± 0.32 % of actuator travel per °C
Transmission Ratio by Pressure: 0.39 ± 0.12 % of actuator travel per mm Hg
Weight: Not more than 1.3 kg
Technical Documentation: Passport BU-32

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