Magnetic Chip Detectors

The third component we will be discussing under AircraftLubrication systems is the Magnetic Chip Detector (MCD’s). As the name implies, it is a detector, which functions on the principal of magnetism.

Main function of the magnetic chip detector is to provide condition monitoring of the engine and its lubrication system components. To give an early warning of bearing failure, magnetic chip detectors are fitted in the system. 

They are normally of the bayonet type fitting with auto sealing adaptors thus,  can be removed, inspected and replaced very quickly, with no oil spillage. They are often found  in gearboxes and in the scavenge pump return lines where the metal debris are often found.

See below for details of a lubrication pump MCD.


 
 

In earlier versions of engines, the detection is done visually by removing and inspecting the chip detector at periodic intervals. However, On modern engines this is done electronically. If there are metallic debris that comes into contact, it completes an electrical pathway and provides a cockpit indications. Magnetic Chip Detectors (MCD’s) alerts / indication to the flight deck informs the pilot of contamination that requiring attention. 

Often the low resistance across the MCD, can be caused by small carbon deposits or tiny metallic deposits that are insignificant as far as engine wear is concerned. In such cases, there may be a ‘fuzz burner’ fitted that will pass an sufficient electrical charge through the MCD and clear off the fine debris and leave only major particles. If the warning light still remains ‘ON’ then the pilot knows that the debris is of a more serious nature.
 

Below illustration shows the location of MCDs in a Lubrication Pump scavange lines.