How does a fighter plane know it’s been locked on by an enemy fighter?

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How does a fighter plane know it’s been locked on by an enemy fighter?

In: Technology

Military craft have a device called a radar warning receiver. It has antennae that look for RF energy, and if it detects a pattern of a known hostile radar system or missile, it alerts the pilot and engages countermeasures if applicable.

In order to home in on something, you have to know where it is, and one way to know where things are is to use *radar* — that is, send out a beam of radio waves that bounces off of objects and comes back to the transmitter, painting a picture of what’s around it. A radar system that’s looking for targets has to scan the entire sky, so the number of times the radar track hits a target aircraft in a minute is relatively low.

When a radar system sees something it wants, it turns on a different radar that scans much more quickly to provide more accurate tracking data to the missile. Aircraft have cameras that see the radio waves being scanned across them; if they’re being painted very rapidly, that probably means a radar-tracking missile has acquired them.

There are other types of missile guidance that are harder to detect; heat-seeking missiles, for example, can’t be detected before launch, but can be tracked and evaded afterward, as it closes with the target.

Radar beams out a radio signal and listens for its return from objects to be tracked. A radar in search mode will be scanning back and forth across the entire sky at a relatively low frequency.

When that radar locks on to an aircraft it will start rapidly scanning just that area where the aircraft is, greatly increasing the frequency of the signal. That lets the aircraft which can also detect the scanning know there is increased interest.