A fictitious, simplified scenario that brings together the material of Executing the fire control sequence using the EMS, Missile Guidance, Electronic Counter Measures 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.
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 (Characteristics of the Early Warning (EW) radar): 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 (The fire control sequence) 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, Radar horizon and Terrain masking) 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 (Target acquisition and tracking): 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 (Radar Warning Receiver (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 (Target acquisition and tracking). The CW signal says the most. With a semi-active radar-guided missile, the radar illuminates the target for the missile's seeker (Semi-Active Radar Homing). 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 (Challenges for chaff). 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 (Passive homing) emits nothing, so the RWR cannot hear it; only the MAWS sees the motor plume (Missile Approach Warning System). There are a few seconds.
Decision: the MAWS automatically starts the flare programme towards the threat (Characteristics). The pilot turns the hot exhaust away from the missile, so that the flares come between missile and engines, and reduces power where possible (Counter-IR tactics). A platform with DIRCM (Directional Infrared countermeasures) 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 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.