Assessing the SAM threat

Introduction

SAMs are the new boogeyman of the USAF, one which they are also using in their political games. They want the F-35 because, they say, legacy aircraft are “unsurvivable”. They want to retire the A-10 and leave ground troops without any support because, they say, it is unsurvivable. But how much truth there is in their assertions?

Historical overview

During the Vietnam war, SAMs saw extensive usage. They were used primarly to defend key targets but were also deployed in the field; many were also mobile (though level of mobility they had does not even begin to compare with modern SAMs, thanks to excessive times necessary to either deploy or pack up).

Next table adresses heavy radar-guided SAMs performance during the Vietnam war.

Year SAMs launched US aircraft lost Pk
1965 194 11 5,67%
1966 1966 31 1,58%
1967 3202 96 3,00%
1968 322 3 0,93%
1972 4244 49 1,15%

As it can be seen, kill probability has danced up and down, but always stayed below 6%. Total gives 190 aircraft lost to 9.928 SAM launches, or Pk of 1,9% (or 1/4 of what radar-guided AAMs achieved). Many SAMs were crewed by Russian crews.

SAMs did have major indirect impact. Since USAF predominantly used thin-skinned “multirole” aircraft for air superiority as well as ground attack (including SEAD/DEAD), this meant that aircraft were exceedingly vulnerable to AAA during low altitude attacks on SAMs. NVA used SAMs as baits, drawing US aircraft into overlapping AAA fire – and since most of AAA used was optically-aimed, there was no warning until they opened fire. In the first DEAD mission of the war, 6 aircraft were lost out of 50 present – all of them to AAA, and all of them thin-skinned, sluggish F-105s. SAMs were also effective at their primary mission – shooting down (useless) strategic bombers. B-52s flew 724 sorties in the North Vietnam, losing 15 aircraft – a loss rate of 2,1%, just at or slightly above the limit for sustainable operations (for comparision, B-17s had a loss rate of 6% during 1943). To achieve this, over 2000 SA-2s were fired – a probability of kill of 0,75%. Still, the B-52 attrition rate was still ten times higher than the overall attrition rate in the Vietnam war, which was 0,35% in the 1966 and 0,15% in the 1968. By the end of the war, North Vietnam has mostly run out of the SAM stocks.

North Vietnamese also used some 100 MHz (VHF band) radars, which could not be attacked by anti-radiation missiles. They were not used for SAM guidance, however.

During the 1973 Yom Kippur war, Israel lost between 98 and 280 aircraft. An IAF officer (Cohen) admitted 15 losses in air-to-air combat, though figure might be as high as 21 (Dupuy). Zaloga in “Soviet Air Defence Missiles” p.240 quotes ‘Israeli sources’ as stating that Sa-7 caused 2 losses, 4 possible losses, 28 hits which did not result in losses. Since 5.000 SA-7 missiles were launched, this equals a Pk of 0,04-0,12%. Main dangers were SA-6 and ZSU-23.

There were several factors playing into SAMs success. Israelis were surprised and had to go after priority targets – attacking ground troops – with no time left to organize SAM supression. SAMs were fired in large salvos – often of 20 or more missiles. Obvious answer to SAM threat is to go below SAMs envelope, and that is what Israelis did. However, since they had no proper CAS aircraft, they had to use fast, thin-skinned fighter jets for ground attack, which made them vulnerable to AAA. Israelis also had no previous experience in dealing with SAMs, and had in fact ignored the problem alltogether. SA-6 was effective in particular – shooting down 36 aircraft on a first day – because of three factors. Israeli electronic countermeasures were designed to counter SA-2 and SA-3, and were useless against the SA-6. As a result, ALR-36 RWR used by Israeli Air Force was unable to pick up any radar emissions from the SA-6. Israeli aircraft also had no missile approach warners, which meant that pilots had to pick up SAMs visually. This, however, was hard to do – main Israeli aircraft were F-4 Phantom and A-4 Skyhawk, both aircraft with very bad cockpit visibility and low to moderate cruise speeds (510 kts / Mach 0,87 and 420 kts / Mach 0,62, respectively). After RWRs were modified to detect the SA-6 launches, losses dropped sharply since evasive maneuvers were typically effective against it, despite aircrafts’ less-than-ideal maneuvering performance (F-4 had a very high wing loading while A-4 had low thrust-to-weight ratio). Even then, majority of Israeli A-4 fleet had no RWR at all, and vast majority of all aircraft used had no chaff or jammers. Flares were not used at all. In the end, SA-6 achieved a Pk of 1-2%, and 30-40% of total Israeli losses happened during the first three days of the war.

Egyptians and Syrians lost 500 aircraft of initial 900, with over 2/3 of losses being in air-to-air combat.

Israelis learned from the experience. Nine years later, during the first Lebanon war, they destroyed every single Syrian SAM battery deployed in Lebanon, without losing a single aircraft.

In 1981, Israeli F-16s destroyed Iraqi Osirak nuclear plant, 12 miles southeast of Baghdad. They flew at altitude of less than 300 ft, and no aircraft were damaged.

In the 1982 Falklands war, British SAMs had relatively high Ph of 6,4-13% (15-21 hits for 165-235 launches), with the most widely used SAM – Blowpipe – achieving 1-2 hits in 95 launches (1,1-2,1%). However, they were being used against aircraft that were at the end of their operational range (thus leaving little fuel to maneuver), typically had no RWR or MAWS, had bad out-of-cockpit visibility thanks to the poor design and salt that would accumulate on the canopy during low-level flight, and during the ingress were loaded with bombs and forced to fly predictable attack profiles. Out of all aircraft downed, only 2-4 had RWRs. None had chaff or flares, except few that had chaff crudely improvised at the end of the war. Even so, SAMs were ineffective against low-altitude targets, which led to the British hastily mounting as many light AAA emplacements as they could. On British side, of 10 Harrier losses 1 was to a SAM and two collided; rest were to AAA, as Harrier was very vulnerable (no armor, no redundant systems, single, very complex engine) and during attack missions often operated at the end of its range, making it unable to maneuver (same situation as with Argentine aircraft).

In 1986, US mounted a 55-aircraft raid of Lybia; one F-111 was shot down. In October 1989 a lone Syrian MiG-23 successfully evaded interception by flying at low altitude and landed at an Israeli airfield.

In the 1991 Gulf War, stealth F-117s were touted for their ability to attack Baghdad on the first night, without losses, thus destroying SAMs and allowing non-stealth aircraft to enter. This impression is wrong on all levels. Network nodes and other major hubs were attacked before the first aircraft appeared over Baghdad – destruction was done not by stealth aircraft but by attack helicopters, special forces teams and cyberwar attacks. On the first night 167 “Wild Weasel” and other EW and SEAD aircraft engaged the SAMs, in the same high-threat areas F-117s operated in; this compares to 15 F-117 sorties in first two nights. Out of 15 SAM batteries attacked by the F-117s, 13 continued to operate. They did not “knock the door down” either; two F-16s were shot down by SAMs on day 3. While the F-117s were compared favorably with A-10s in light of latter’s losses, this is also based on a PR spin: F-117s operated only at night, which is a much safer combat environment. Two A-10 squadrons that operated only at night flew as many sorties, and in as dangerous (or more so) environment, as the F-117s did; yet they suffered no losses either, despite the A-10 having a huge RCS for an aircraft of its size (but average visual signature and small IR signature).

In the 1999 Kosovo war NATO managed to destroy only 3 out of 80 missile batteries despite firing 743 HARMs, as missile batteries were camouflaged and highly mobile. On the other hand, while SAMs have proven themselves very survivable, they were very ineffective as well – only 3 kills have been achieved in 845 launches, a Pk of 0,36%, or 1/5th of what radar-guided SAMs achieved in the Vietnam war (this would also imply that radar-guided AAMs will have become less, not more, effective against properly flown and equipped fighters, compared to their Vietnam war performance). Two of these three kills were F-117s – “stealthy” light bombers with crappy maneuverability and situational awareness (bad out-of-cockpit visibility, no MAWS. Interestingly, untested performance of radar stealth was bureocracy’s excuse for omitting MAWS on the F-117, just as the then-untested performance of radar-guided BVRAAMs was bureocracy’s excuse for omitting gun on the F-4 before the Vietnam war. Apparently, bureocracy inhibits one’s ability to learn.). F-117s were detected by VHF radar, which then cued IR SAMs in their direction.

Combining data for the Gulf and Kosovo wars, A-10 suffered a total of 4 losses in 12.400 sorties while the F-117s suffered 2 losses in 2.600 sorties. As it can be seen, A-10s loss rate of 0,032% is only 42% of the F-117s loss rate of 0,077%. In other words, A-10 was 2,4 times as survivable as the F-117 was. Further, both F-117 losses were to radar-guided SAMs while all A-10 losses were to far more dangerous man-portable IR SAMs (unlike the A-10, F-117 never dared fly within MANPADS range). One F-117 loss was a shootdown and another was a mission kill; out of the A-10s losses, 3 were shootdowns and one was a mission kill. Overall, shootdown rate is 0,038% for the F-117 and 0,024% for the A-10. By this measure, A-10 is still 1,58 times as survivable as the F-117.

SAM tactical limitations

One limitation is a radar horizon. Since surface of the Earth is curved, aircraft beyond some distance will be hidden by the planet itself. If we take aircraft altitude to be 10 meters, 93KK Osa with 4,2 meter mast will detect it at distance of 21 kilometer, Buk with 21 meter mast will detect it at distance of 32 kilometers and S-400 with 40 meter mast will detect it at 40 kilometers. If aircraft is at altitude of 30 meters, then Osa will detect it at distance of 31 kilometer, Buk will detect it at distance of 41 kilometer and S-400 will detect it at distance of 49 kilometers. Nominal missile ranges are and up to 15 kilometers for Osa, up to 50 kilometers for Buk and up to 400 kilometers for S-400, meaning that neither Buk or S-400 will make use of their longest-ranged missiles.

Another issue are terrain obstacles. Radio waves are disrupted or stopped by solid objects, which means that radars are typically positioned at high vantage points, making them easier to find. This also means that aircraft can use terrain to hide from detection even at relatively short ranges. While this leaves it in danger of MANPADS and optically-aimed AAA, it is a viable tactic for heavily armored CAS aircraft. Not so for thin-skinned fast jets and “attack” helicopters – former take damage too easily, while latter can pull no more than 3 g and cannot be anywhere as protected – in terms of armor, system redundancy or countermeasures – as CAS aircraft can. CAS aircraft such as the A-10 are actually ideal for SAM supression due to their resillience to AAA and long loiter time

Even when aircraft is detected, there is an issue of range. A premier Russian SAM S-400 has an engagement range from 3 to 200 kilometers against an aerodynamic target. With air-to-air missiles, effective range is cut to 1/4 if target is attacked from the rear, to 1/2 if target is maneuvering, and every 100 knots of speed advantage cut effective range by 5-25%. Thus (and this is optimistic in this case due to target aircraft having few thousand meters of altitude advantage over SAMs), an S-300 will have an effective range of against a Mach 0,9 (516 kts at 40k ft) Rafale of 128 km if Rafale does not turn away, and 20 km if it does. S-400 will have an effective range of 255 km if Rafale does not turn away and 38 km if it does. If Rafale speeds up to Mach 1,4 (802 kts at 40k ft), then S-400 will have an effective range against a retreating Rafale of only 33 km. This will allow a pair of Rafales to easily play “peek-a-boo” with S-400, with one Rafale acting as a bait and providing targeting info to another Rafale.

Alternatively, Rafales can simply go in, fire ARMs once SAMs lit up, and leave. Issue is that a radar-guided SAM battery will have to give away its position to launch a missile. This means that aircraft attacked can lob an anti-radiation missile before having to begin evasive maneuvers, since SAMs cannot launch as soon as radar is turned on – targeting process will take at least several seconds.

(This tactic is viable for any aircraft, though as it can be seen, good endurance, low-altitude flight characteristics and supercruise are major advantages if present; only fighter aircraft that combine all three are Rafale and upcoming Gripen NG).

In effect, a “circle of death” so engrained in a public psyche when discussing SAM’s is a myth. However, it is used to promote expensive and typically unnecessary systems, such as stealth aircraft, drones and UCAVs.

Mobile radars are not invulnerable either. Most mobile radars can only scan when deployed (static), and need several minutes to either deploy or pack up. While it is technically possible to design a radar that can scan “on the move”, vibrations and unsteady platform will cause problems. This means that, once they give up their position, they are just as vulnerable as any other SAM.

IR MANPADS are a greater threat: since they do not reveal themselves with active emissions, have excellent maneuverability and IR seeker, and being used to typically attack low-altitude aircraft, they leave little time for reaction – this results in a very high (for a SAM) probability of hit. Optically-aimed AAA have the same advantages.

Conclusion

Primary element in surviving a SAM threat is situational awareness. Most aircraft that have been shot down by SAMs have been unaware; if pilots attempted to evade SAMs they were typically successful, especially if SAMs in question were radar-guided. Since most modern fighter aircraft are equipped with missile approach warners – many of them of IR or UV variety – SAM success rate can be expected to be far less than it was in any war previous to Gulf War I.

Most important impact that radar SAMs have is the effort required (or believed to be required) to defeat them. Most sorties flown by USAF in recent wars were of SEAD/DEAD nature. Threat from SAMs and MANPADS is used by USAF as an excuse to get rid of the supremely useful A-10 close air support aircraft, and to justify development of “stealth” aircraft and UCAVs. In retrospect, it is clear that actual threat from radar-guided missiles does not justify either measure.

Further, high mobility of modern SAMs combined with development of counter-stealth VHF radars means that high flying aircraft may not be effective in attacking them (except maybe for a few supercruisers, and even then, F-22 at Mach 1,72 and 36.000 ft – the only altitude where it can reach such speed without afterburner – needs 5,6 minutes to cover 100 kilometers.) This again returns us to the SEAD A-10.

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