SS-78

Chip detection function of the SS-78 sensor

SS-78 is an aircraft chip detector used for monitoring ferromagnetic wear particles in oil systems of aviation engines and gearboxes. The unit is installed in circulating lubrication systems where metal particles may appear as a result of abnormal wear of gears, bearings, shafts or other friction-loaded parts. Its purpose is not to measure oil pressure or temperature, but to detect the presence of steel or cast-iron particles in the oil flow and trigger a cockpit warning. On helicopter powerplant installations, this indication helps the crew and maintenance personnel identify a possible internal defect before the damage develops further.

Magnetic operating principle inside SS-78

The SS-78 works on a magnetic contact principle. A permanent magnet inside the detector attracts ferromagnetic particles carried by the oil flow. When enough metallic particles collect on the sensing end, they can form a conductive bridge between insulated contacts. This closes the electrical circuit and sends a warning signal to the cockpit indication system. In practical terms, the detector acts as a simple but important condition-monitoring element. Its response depends on the presence of magnetic wear particles, so non-ferromagnetic contamination, dirt or oil sludge does not produce the same signal as steel particles from wearing mechanical components.

SS-78 installation in helicopter oil systems

The SS-78 is used in aircraft engine and gearbox oil systems, including installations on Mi-8 / Mi-17 family helicopters and related configurations. In engine applications, it can be installed in the oil scavenge line, where oil returning from the engine carries wear particles from internal friction pairs. One typical installation area is the line before the oil enters the air-oil radiator. This position allows the detector to monitor contamination before the oil is cooled and returned to the system. Depending on the aircraft and engine configuration, the detector may be associated with left-engine or right-engine warning circuits.

Warning output from the SS-78 chip detector

When the SS-78 contacts close through a bridge of ferromagnetic particles, the aircraft warning circuit activates the relevant cockpit signal. On helicopter installations, this may correspond to a “CHIPS” warning for the left or right engine, depending on the connected circuit. The detector itself does not analyze the quantity or origin of the particles. It only completes the signal circuit when magnetic material accumulates at the sensing element. After such an indication, maintenance personnel normally inspect the detector, clean the sensing end, identify the collected material and assess the condition of the related engine or gearbox system.

Construction features of the SS-78 unit

The SS-78 is generally built as a plug-type detector with a non-magnetic body, permanent magnet, insulated contacts and a connection point for the aircraft wiring. Many installations use a design with an integrated valve, allowing the detector element to be removed for inspection without draining oil from the complete system. This is useful during scheduled maintenance and troubleshooting, because the detector can be checked, cleaned and reinstalled with limited disturbance to the oil circuit. Depending on the installation, the retaining arrangement may use a threaded or bayonet-type locking design.

Identification and service use of SS-78

The SS-78 may also be referenced by drawing or catalog number 0780679740. Before ordering or replacing the detector, the marking, installation type, connection design and aircraft documentation should be checked. The same designation may appear in different catalog contexts, so the target engine, gearbox or oil system should be specified. During maintenance, the detector is normally inspected and cleaned from sludge or collected particles according to the aircraft maintenance schedule. If metallic particles are found repeatedly, the issue should not be treated as a sensor problem only; the related engine or gearbox requires further inspection.

Product Type: Aircraft chip detector / metal particle warning sensor
Designation: SS-78
Alternative Designations: 0780679740, СС-78
Function: Detection of ferromagnetic particles in aircraft oil systems and activation of cockpit warning signal
Application / Where Used: Aviation engine and gearbox oil systems
System / Installation Area: Oil scavenge line, circulating lubrication system, engine or gearbox oil circuit
Compatible Aircraft / Equipment: Mi-8, Mi-17, Mi-24 helicopters and related configurations, depending on aircraft documentation
Compatible Engines / Units: TV3-117 engine installations and gearbox oil systems, depending on configuration
Controlled Medium: Lubricating oil
Detected Particles: Ferromagnetic particles, including steel and cast-iron wear material
Operating Principle: Magnetic attraction of particles and electrical contact closure through collected metal chips
Nominal Bore: DN 20 mm
Nominal Medium Pressure: 0.63 MPa / 6.4 kgf/cm²
Output Signal: Electrical circuit closure for cockpit warning lamp / annunciator
Electrical Supply: Aircraft DC or AC power circuit, depending on installation wiring
Construction: Plug-type detector with magnet, insulated contacts and non-magnetic housing
Design Feature: Integrated valve for removal without complete oil drain, depending on installation version
Locking / Mounting Type: Threaded or bayonet-type locking arrangement, depending on configuration
Installation Point: Oil line or equipment housing according to aircraft and engine documentation
Technical Documentation: Aircraft maintenance manual, engine documentation, wiring diagram, parts catalog, manufacturer technical documentation

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