6S2.553.002 series 1

6S2.553.002 compensation sensor in AP-34B control loops

The 6S2.553.002 Series 1 is an aircraft compensation sensor used in automatic flight control systems of Mi-8 and Mi-17 family helicopters. In AP-34B autopilot installations, the sensor works inside the control loop and provides an electrical signal related to the angular position of its lever. This signal is used by downstream autopilot electronics for feedback and stabilization tasks. The sensor is not a cockpit control unit and is not adjusted by the pilot during normal operation. It is a technical component inside the automatic control chain.

Position feedback from the 6S2.553.002 sensor

The main job of the 6S2.553.002 is to convert lever position into electrical output values. As the sensor arm moves relative to the stator, the voltage between specific terminals changes according to the angular position. This gives the autopilot equipment a usable feedback signal. In a helicopter control system, feedback is essential: without it, the system cannot correctly compare commanded movement with actual mechanical position. The compensation sensor therefore helps the autopilot work more smoothly and prevents uncontrolled or poorly damped corrective action.

6S2.553.002 in the AP-34B autopilot assembly

The 6S2.553.002 Series 1 is used as part of the AP-34B automatic flight control equipment installed on Mi-8T, Mi-8MT, Mi-17, Mi-171, Mi-172 and related variants. It interfaces with control amplifiers, signal distributors and other units that process autopilot commands. In the complete AP-34B system, the compensation sensor supports stability of the control loop by feeding position-related information back into the electronics. Because the autopilot set includes multiple units, replacement should be made by exact designation, series and documentation reference.

Electrical output of the 6S2.553.002 sensor

The sensor operates from the aircraft AC power supply and produces output voltages across defined terminal pairs. The values depend on the angular position of the lever. Positive rotation is referenced as clockwise rotation, which is important during bench checks and installation verification. If the sensor is connected incorrectly, has excessive mechanical play, or produces an output outside the allowed range, the autopilot channel may behave incorrectly. For this reason, the unit is usually checked not only visually, but also by measuring output voltages at the specified lever positions.

Installation and inspection of 6S2.553.002

The 6S2.553.002 is mounted as part of the autopilot unit assembly. Its mechanical position, lever movement and electrical connections must remain stable, because small errors in feedback components can affect the behavior of the whole automatic control channel. During inspection, attention is normally given to the housing, lever movement, mounting points, connector condition, wiring, signs of corrosion, mechanical damage and previous repair. A sensor may look serviceable from the outside but still be unsuitable if its output values do not match the required angular positions.

Identification and alternate designations of 6S2.553.002

In parts lists and maintenance documents, the sensor may appear with different writing styles: 6S2.553.002, 6C2.553.002, 6С2553002, 6S2-553-002 or 6S2 553 002. These variations normally refer to the same compensation sensor type, but the exact series must still be confirmed. For procurement, the safest identification method is to compare the marking on the unit with the manufacturer passport and AP-34B documentation. The item should also be checked for condition, storage history and availability of quality documents before shipment.

Supply and documentation for 6S2.553.002 Series 1

The 6S2.553.002 Series 1 belongs to certified aviation technical equipment. It may be supplied as new, from storage, repaired or inspected equipment depending on availability. Since it works inside a flight-control system, documentation is especially important. Manufacturer passport, acceptance records, precious-metals table, serviceability confirmation and compatibility with the required AP-34B configuration should be checked before installation. If the sensor is ordered separately, the request should clearly state that the requirement is for the compensation sensor KD, not for the complete autopilot set.

Product Type: Compensation sensor / KD
Designation: 6S2.553.002 Series 1
Alternative Designations: 6C2.553.002; 6С2553002; 6S2-553-002; 6S2 553 002
Function: Generation of positional electrical output for automatic flight control systems
Application / Where Used: Automatic flight control systems and AP-34B autopilot assemblies
System / Installation Area: AP-34B automatic flight control system; autopilot unit assembly
Compatible Aircraft / Equipment: Mi-8, Mi-8T, Mi-8MT, Mi-17, Mi-171, Mi-172 and related variants depending on AP-34B installation
System Role: Positional feedback for control-loop stability, actuator response and automatic control accuracy
Interfaces With: Control amplifiers, signal distributors and downstream autopilot electronics
Power Supply: 36 ±2 V AC, 400 Hz
Angular Reference: Positive rotation = clockwise
Output Voltage Between Pins 4–5: +30° → 38 +4 / −8 V; 0° → 33 +4 / −8 V; −30° → 33 +4 / −8 V
Output Voltage Between Pins 4–6: +30° → 38 +4 / −8 V; 0° → 33 +4 / −8 V; −30° → 33 +4 / −8 V
Output Voltage Between Pins 5–6: +30° → 66 +7 / −16 V; 0° → 55 +7 / −16 V; −30° → 46 +7 / −16 V
Mounting: Installed as part of the autopilot unit assembly
Weight: Not more than 0.7 kg
Precious Metals Content: Gold and silver according to manufacturer passport table
Condition: As applicable
Technical Documentation: Manufacturer passport available

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