IMD-8

Pressure measurement principle inside the IMD-8 sensor

The IMD-8 operates by converting mechanical deformation of an elastic sensing element into a change in inductive parameters. Pressure enters the transmitter through the fitting and acts on the internal diaphragm or pressure-sensitive element. This movement changes the position of the magnetic armature inside the electromagnetic system. As the air gap changes, the inductance of the working coils also changes. The connected cockpit indicator reads this change through the aircraft electrical circuit and moves the pointer according to the measured pressure. This is why the transmitter must be checked together with the indicator, wiring and power supply.

IMD-8 use in oil, fuel and air systems

The IMD-8 can be installed in several aircraft system areas. In engine oil systems, it is used to monitor oil pressure supplied to engine lubrication and cooling circuits. In gearbox oil systems, it may be used for pressure indication in the main gearbox lubrication circuit. In fuel systems, the transmitter can monitor pressure in low-pressure lines, for example after boost pumps and before the high-pressure fuel equipment, depending on the installation. It may also be used in air and neutral gas circuits where pressure indication within the same measuring range is required.

Helicopter installations using the IMD-8 transmitter

The IMD-8 is used on aircraft and helicopters with compatible pressure indication systems, including Mi-26 and Mi-171E applications. It may also be found in systems of Mi-8 and Mi-24 type helicopters, depending on the installed equipment and documentation. Typical installation areas include the engine compartment, engine accessory area, gearbox housing, oil manifolds, pressure pipelines and compartments containing hydraulic, fuel or air system equipment. The exact installation point depends on the aircraft type, engine model, system diagram and measuring task.

Connected indicators and electrical circuits around IMD-8

The IMD-8 works with compatible aircraft indicators from the “I” series and with multi-pointer indicators of the UI1, UI2 and UI3 families. The transmitter is included in an electrical measuring circuit with the remote indicator. It uses aircraft AC power, so it should not be treated as a passive mechanical sender. A wrong indication can come from the transmitter, the cockpit indicator, the bridge circuit, an open wire, poor connector contact, incorrect power supply or mismatch between transmitter range and indicator scale. During troubleshooting, the complete measuring chain should be checked.

Identification and replacement of IMD-8

Before ordering or replacing IMD-8, the designation on the transmitter should be compared with the aircraft parts catalog, wiring diagram and system documentation. The measured medium, pressure range, installation point, connector type and compatible cockpit indicator should be confirmed. The IMD-8S version may have similar measuring characteristics, but replacement should still be verified by documentation. In some applications, ID-8 may be considered a close analog, but interchangeability must not be assumed by designation alone. The installation geometry, electrical parameters and approved aircraft documentation remain the final reference.