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These are used to sense if a device has moved or has reached its limit of travel, e.g. flap drive or undercarriage mechanisms the internal schematic and electrical contacts of a typical microswitch product.


The contacts are open and close with a very small movement of the plunger. The distance traveled by the armature between make/break is measured in thousandths of an inch, hence the name ‘micro ’ . A snap-action is achieved with a contact mechanism that has a pre-tensioned spring.


Micro-switches are attached to the structure and the wiring is connected into a control circuit. An example

of micro-switch application is to sense when the aircraft is on the ground; this is achieved by mounting a

micro-switch on the oleo leg.


When the aircraft is on the ground, the oleo leg compresses and the switch is operated. Micro-switches are used to sense the mechanical displacement of a variety of devices, including:

control surfaces


pressure capsules

bi-metallic temperature sensors

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