Učno okolje EMS · Pregled · 13 · §13.6 · English version

§13.6 Practical case: from RWR warning to countermeasure

Začetek

Ta razdelek je na voljo samo v angleščini.

A fictitious, simplified scenario that brings together the material of Izvajanje zaporedja požarnega nadzora z uporabo EMS, Smernice za izstrelke, Elektronski protiukrepi and this chapter. For each step, read what the crew hears and sees, work out yourself what it means and what you would do, and then open the analysis.

The situation

A transport aircraft flies into contested territory by daylight at low level (± 300 ft) on a resupply flight to a forward airstrip. On board: an RWR, a MAWS with UV sensors and a dispenser with chaff and flares. No jammer of its own, no escort. The briefing reported a mobile medium-range air defence system (fire control radar in the C/X band, semi-active radar-guided missile) somewhere north of the route, and MANPADS around the airstrip. All values are indicative.

Step 1 — a search radar. Twenty minutes before landing an "S" appears on the outer ring, bearing 330°. The RWR reports a low PRF and about ten seconds between illuminations. Now and then a short tick sounds in the headset.

Analysis and decision

A low PRF and a fixed period of about ten seconds fit an early warning or search radar (Značilnosti radarja zgodnjega opozarjanja): it rotates and sees the aircraft briefly on every revolution. This is not yet fire control; the aircraft is at most a plot on a screen. But the fire control sequence (Zaporedje požarnega nadzora) has started: whoever is seen can be handed on.

Decision: no countermeasures yet, but reconsider route and altitude. Flying lower and keeping terrain between radar and aircraft (radar horizon and terrain masking, Radarsko obzorje and Zamaskiranje terena) shortens the time the radar sees the aircraft. The crew reports the threat and arms the dispenser.

Step 2 — a second radar. Five minutes later a second symbol appears, "11", the system from the briefing, on the middle ring, bearing 010°. The illumination comes more often and more directed; the tone now sounds several times a second.

Analysis and decision

The RWR recognises the fire control radar of the system from the briefing, in acquisition mode (Pridobivanje in sledenje ciljev): the radar is trying to capture the aircraft. That this symbol sits at 010° and the search radar at 330° fits a system with dispersed components, but also two different sites. The RWR cannot tell the difference. Note: the symbol sits closer to the centre because it is more dangerous, not necessarily because it is closer (Sprejemnik radarskega opozorila (RWR)).

Decision: every second in view of the radar now counts. A change of course that puts the aircraft behind a ridge breaks the acquisition before there is a track. Chaff makes little sense yet: without a track there is nothing to decoy away from.

Step 3 — lock. The change of course only half works; the terrain here is flat. The "11" symbol jumps to the inner ring, gets a diamond around it and the tone becomes continuous. Shortly afterwards the RWR reports a CW signal from the same direction.

Analysis and decision

Continuous illumination at high PRF means track or lock: the radar has a fire control solution (Pridobivanje in sledenje ciljev). The CW signal says the most. With a semi-active radar-guided missile, the radar illuminates the target for the missile's seeker (Polaktiven radarski signal). CW illumination after a lock therefore means: a missile is probably on its way. The MAWS may not see it, because the motor of a missile at longer range may already have burnt out.

Decision: everything at once. A hard break across the threat direction brings the closing speed relative to the radar to almost zero. A Doppler radar then finds it hard to tell the aircraft from the ground clutter and the chaff cloud, which is being dispensed in salvoes right now (Izzivi glede Chaffa). Goal: break the track before the missile arrives. Without a jammer this is the only layer the aircraft has.

Step 4 — the threat the RWR cannot hear. The RWR goes quiet: the "11" symbol drops back to the middle ring and disappears. Two minutes later, on approach to the airstrip at 200 ft, the MAWS goes off: launch, left rear. There is no RWR symbol at all in that direction.

Analysis and decision

The track has been broken, by the manoeuvre and the chaff, or because the radar lost the aircraft behind the terrain. The new threat is of a different kind. A MANPADS with a passive infrared seeker (Pasivno vodenje) emits nothing, so the RWR cannot hear it; only the MAWS sees the motor plume (Sistem opozarjanja pred izstrelki). There are a few seconds.

Decision: the MAWS automatically starts the flare programme towards the threat (Značilnosti). The pilot turns the hot exhaust away from the missile, so that the flares come between missile and engines, and reduces power where possible (Taktika proti IR). A platform with DIRCM (Usmerjeni infrardeči sveti) would now capture and jam the seeker.

Step 5 — after landing. The aircraft lands undamaged. What happens now to what the RWR and the MAWS recorded?

Analysis and decision

After the flight the recordings go to the analysts, with three questions. Was the identification right: was "11" really the system from the briefing, or another radar with similar parameters? Where were the emitters? A series of bearings during the flight gives an estimated position by cross-bearing (Direction finding and location). And did the radar behave as the library expects? Deviations go back to the library via ELINT (Identification: the library, and where it comes from). That way the next crew flies better protected than this one.

The lesson

The RWR let the crew read along with the opponent's fire control sequence: search, acquire, track, guide. Each step called for a different answer, from route and altitude to manoeuvre and expendables. The most dangerous moment came from a weapon the RWR could not hear. That is why RWR and MAWS never stand alone, and why the debrief matters as much as the flight.