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Let's imagine a swarm of fighter jets intercepting another swarm. Both groups are moving head-on towards each other. Once they get in range, they will probably lock on and fire missiles.

Do fighter jets have radar that will show and warn of a missile coming head on? Or do they only scan their tails?

I'm interested in when, if ever, such capability was implemented. To me it seems like the 50's and 60's and maybe even the 70's, they would only worry about scanning their tails. It would also be good to document this for both NATO and Warsaw Pact jets.

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Radar Warning Receiver systems (RWRs) used by military aircraft are omnidirectional. However, they do not warn of incoming missiles (unless that missile is at least semi-actively radar-guided, like an AMRAAM). What they warn of are various patterns of radar activity, including a radar lock (which is a constant, high-intensity scanning of the aircraft's position, more than just a "blip" as the antenna passes by on a wide-angle scan pattern).

If another aircraft has a radar lock on you, you should be expecting an incoming missile of some kind. However, IR missiles (AIM-9 Sidewinder, AA-11 Archer, MICA IR, ASRAAM) do not emit any EMR that indicates they're incoming; they use a passive FLIR sensor to identify and track the heat source they were told to kill (they don't even require a radar lock; the seeker can be cued to a pilot's helmet, or it can be "uncaged" and will lock on to the most significant heat source in front of it). Passive radar-guided missiles like the old AIM-7 Sparrow also do not emit their own radar; they track the radar returns from the firing aircraft. Only semi-active and active radar-homing missiles emit their own radar noise that can be used by the RWR to know one is on the way. A few older passive missile systems used radio control to guide the missile to the target, and RWRs can also detect these "sideband" radio signals as a clue a missile has been launched.

More modern Missile Approach Warning Systems (MAWS) have additional features that can help detect and track incoming missiles of multiple types. The biggest clue of a missile launch is a new heat signature, especially in the direction of an incoming radar lock; a suite of IR sensors can be used by MAWS to put 2 and 2 together and warn you of the missile launch.

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    $\begingroup$ Can you tell me if RWRs, as you defined them, have been common to NATO and WP fighter jets ever since WWII? Also, can an IR missile be fired head-on? I figured they need to chase the heat exhaust (tail) of a jet. $\endgroup$ – DrZ214 Aug 7 '15 at 19:02
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    $\begingroup$ The first U.S. aircraft to be equipped with RWRs were Vietnam-era fighters as a countermeasure against Soviet-built NVA SA-2 sites. The first ones in theater were F-100F Super Sabres as a trial for a new "Wild Weasel" strategy, whose success led to follow-up Wild Weasel variants of the F-105 and F-4. B-52s got a similar system around the same time. RWRs were incorporated defensively into other Phantom and Thud variants by the end of the war, and became standard issue on the F-5 and all subsequent aircraft. $\endgroup$ – KeithS Aug 7 '15 at 19:42
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    $\begingroup$ @DrZ214 While the engines obviously give off the hottest heat signature, the rest of the airplane is warm relative to the cool air around it and head on IR missile shots are a possibility. $\endgroup$ – Rhino Driver Aug 8 '15 at 18:10
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    $\begingroup$ @DrZ214 - Rhino Driver is correct about IR missiles. The technology is called "all-aspect lock-on" and it became available to U.S. pilots as of the "L" variant of the AIM-9 Sidewinder beginning around 1977. Practically all IR missiles now in active service are all-aspect. $\endgroup$ – KeithS Aug 10 '15 at 23:12
  • $\begingroup$ @RhinoDriver Thanks for the radar info. I opened a related question about the IR stuff: aviation.stackexchange.com/questions/18775/… $\endgroup$ – DrZ214 Aug 11 '15 at 1:05

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