How does the Missile lock-on alarm in an aircraft work?

Question

How does the aircraft know whern its being locked on. (Please give answer for both Heat-seeking and radar missiles)

Answer 1

heat seeking missiles - none they are passive so the only way to recognize their launch is surveillance for a sudden source of heat - the rocket engine

radar - the radar waves are detected, verified, and the targeting device is recognized due to the specific wavelength, impulse characteristics etc. The mode of the radar is solved, whether surveillance mode or targeting mode and then appropriate warning is given to the crew.

imagine the RWR warning as if you were sneaking somewhere, and suddenly happen to be illuminated by a searchlight. - you know that you are illuminated - probably detected. once the searchlight moves away, you can proceed. if it stays at you or other beams, like laser pointers are pointing at you , you are in a serious trouble, being located, locked and targeted, knowing that it is time for employing countermeasures.

the detection of the IR missiles is baypsed by their flaw - they are usually augmented by a radar at the TELAR that is used for night time/ adverse weather targeting and range assesment. -typically SA 13 Gopher which in fact is radar equipped tracked vehicle carrying Russian version of stinger MANPADS. Thus detecting of the radar waves typical for the SA 13 system equals possibility of IR missile interception.

same goes with the airborne IR missiles - their carriers - planes- are using radar to improve the kill probability by assessing optimal azimuth of target interception.

Please notte that the RWR are useful for warning against radar augmented AAA that is artilerry! such as ZSU-23-4 Shilka, which incorporates range finder and targeting radar, while it is dedicated short range battlefiled AD system. -once again, here you only detect the targeting /=precise/ mode that warns you that the system is ABOUT to fire at you. the physical moment when it opens fire is only detectable visually by seeing the bursts...

Answer 2

For radar guided missiles... You can detect the energy sent toward you, both the direction and signal strength. Based on previous analysis of that radar's capabilities, as well as timing of subsequent pulse's timing, you can determine the radar's range. When the radar's locked on, it shifts to higher frequency (sends out more pulses per second) to provide better resolution to the missile. This is readily detectable by the receiver as well, and triggers the "lock-on" alarm. This is true both for beam-rider missiles (like Sparrow) as well as autonomous self-guiding missiles (like AMRAAM).

Generically speaking, the "receiver" that detects all this is called the RWR, or "radar warning receiver". It has antennas all over the aircraft in order to give you 360 coverage, and existing database of enemy radars will give classification types, such as airborne vs. ground, wave vs. pulse, vs. doppler, and so on.

Heat-seeking lock-on alarm currently does not really exist for combat aircrafts (i.e. there are no unclassified systems that are thoroughly documented).  Theoretically, one could build a system by having IR sensors all over the aircraft body, to look for a specific 'pulse' of IR energy that shows a missile's rocket motor is launched. However, IR resolution is quite poor, and even today's technology with advanced signal processing can go only so far. Missiles can use cryogenically cooled detector as they have "limited life", but aircraft detectors can't use cryogenics as they need much longer operating life. It also needs to ignore its own IR signature, and avoid flares and sun and other sources... all of them adds to a nightmare to compute in realtime.

I'm not saying that it doesn't exist. I'm just saying that if one exists, it'd be a secret.

Answer 3

Both air/air and surface/air systems work in basically the same way.  Their radars search, acquire/track, and launch.  Don't want to get into radar design, but these different modes operate on different frequencies (sometimes different radars).  Receiver(s) in the target aircraft detect, classify and display the information for the crew.  The library of the processors will enable the system to determine what the signal is, and its relative threat.  

A threat system in lock-on/launch is more serious than one in search mode.

Depending on the sophistication of the electronic counter measures, jammers could automatically start disrupting the radar energy from the threat.  They can also start automatically dispensing chaff-which is anodized aluminum pieces cut to 1/2 the wavelength of common threat radars.  These show up as a huge return, masking the aircraft.

Finally, one starts a visual scan to pick up the launch signature.  A combination of all three measures is used to defeat a missile (air/air or SAM)

IR missiles CAN be detected during launch, but the circuitry to both find the distinct IR flare of the missile, AND ignore other IR energy is complex.  It's close, but not quite as mature a technology as for radar.  (Laser countermeasures are not unlike IR in this regard.)

If one detects an IR launch one dispenses flares, which burn at a higher intensity than engine exhaust.  There's also other type decoys available.  Since it's had pick out which missile is which, typically one drops both flares and chaff simultaneously.

Answer 4

There is an antenna on the aircraft that is tuned to the same frequencies the radar guided missile emits for tracking.  It then activates a threat alarm or light in the cockpit.

Heat seeking missiles are passive; they only receive infrared waves from the aircraft, they don't emit waves; so there is no warning for them.  Fortunately, they are mostly short range missiles so they are easily seen if the pilot is looking at them.

Answer 5

Think of a RWR as a very sophisticated radar detector like people use in their cars.  It is just tuned to pick up different radar bands, pulse patterns and such that identifies tracking and targeting radar as opposed to police bands.  Simple RWR systems merely give a signal strength and direction.  More sophisticated systems can identify the weapon system associated with that radar, and what mode the radar is operating.

While detecting if a IR missile has locked on may not be possible, since it is a passive system, there are missile launch indicators that can identify the rocket motor signature and tell if a missile is heading toward the aircraft---radar guided or IR.

An example of this system is the AAR-47

http://www.fas.org/man/dod-101/sys/ac/eq...

Answer 6

Jim is the only one that seems to know what he is talking about. IR missiles are detectable.