Wild Weasels

What is needed today is a means to create the electronic analogue of the night-time operations that made the manned bomber such an effective weapon system right up to the end of 1940. In the longer term, this objective may be achieved by stealth technology, ie, by designing an aircraft that is almost invisible to radar and other electronic sensors.

In the short term, the penetration-aid aspect of electronic warfare is being carried out in three principal ways: by adding equipment to the attacking aircraft, by support from dedicated jamming aircraft that carry much more powerful and comprehensive equipment, and by the use of Wild Weasel escort aircraft (and at shorter ranges, harassment drones) which can detect and destroy ground radars and missile or AAA batteries.

How It Began

Electronic warfare (EW) began seriously in 1940 with Britain’s jamming (code-named “Headache”) of the German radio beam system (X-Geraet) used to guide night-bombers to their targets. Three years later it was Germany that was under attack, with British bombers using a device called “Airborne Cigar”, or ABC, to jam the GCI radio frequencies of the defending fighters.

Then, on the night of 24-25 July 1943, “Window” was employed for the first time, bundles of aluminium strips being dropped from the attacking bombers and from decoy aircraft to produce spurious radar responses. This was the first of a four-night offensive against Hamburg in which the RAF flew 2,630 sorties with the loss of only 87 bombers, an attrition rate of 3. 3 per cent.

To put this loss rate into perspective, Bomber Command appears to have had a target attrition rate of around 3 per cent, in order to give aircrews something approaching a 50-50 chance of surviving a 30-mission tour. Due to an immense air defence effort by Germany, the monthly loss rate kept creeping up to around 10 per cent, at which stage new equipment or tactics had to be introduced, if only for the sake of morale. “Window” was one classic example of such new equipment on the British side; for the USAAF making daylight attacks with B-17s, the best analogy may be the introduction of the P-51 long-range escort fighter late in 1943, which immediately brought the monthly attrition figures down from 9. 1 to 3. 5 per cent. For the Luftwaffe, the switch to night raids was made in late 1940, when daylight bomber attrition averaged 8. 6 per cent.

Since attrition rates are the core of the defence penetration problem, it might be added that for fighter-type aircraft, flying a much higher sortie rate than the heavy bombers, loss rate criteria in anything but the shortest conflict are presumably much lower than the limits suggested above. Looking for guidance from historical records, the overall fighter loss rates in the Battle of Britain were 2.6 per cent for the Messerschmitt Bf 109, 3.3 per cent for the Bf 110, 4.4 per cent for the Spitfire, and 5.7 per cent for the Hurricane. Anything over 3.0 per cent was regarded as a very high loss rate, although this figure was exceeded by a factor of 10 for Germany’s piston-engined fighters in the last eight months of the war! However, in planning for any future war, it may be reasonable to aim to keep the attrition of fighter-type aircraft below 1 per cent and to do something drastic if loss rates exceed 3 per cent.

For at least 20 years after the end of World War II Western air forces lived in a fool’s paradise over the penetration problem, since none of the small wars involved aircraft attacking in the face of really advanced defences. The Korean War (1950-53) involved little EW, aside from manually-operated jamming of flak radars, and the early days of the Vietnam War (1964-75) were mainly concerned with counter-insurgency operations in the south.

Vietnam

The first indication of the new reality came in July 1965 when SA-2 Guideline missiles were used by North Vietnam against US aircraft. Isolated air strikes north of the DMZ had occurred ever since the attack by Communist gunboats in the Gulf of Tonkin in August 1964, but a sustained bombing campaign against the North (code-named “Rolling Thunder”) had been launched by President Johnson only in February 1965. By the end of the year the F-100F (“Wild Weasel 1”) had begun attacking the SA-2 sites. The activities of the Wild Weasels were largely credited with halving the loss rate over the North from 0. 32 per cent (ie, 3. 2 losses per thousand sorties) in 1965 to 0.16 per cent in 1967.

Vietnam also spawned a series of quick fixes to assist in penetrating North Vietnam defences, including radar warning receivers (RWR), jamming pods, cluster bomb units (CBU) for flak suppression, and various chaff (the new word for “Window”) provisions, including pods and stowage inside airbrake apertures. The principal aircraft used by the USAF in the early strikes against the North we. s the Republic F-105, which began operations in March 1965. In the following year, after some use of the single-seat F-105D, the two-seat F-105F took over from the F-100F in the Wild Weasel role, while the Douglas EB-66 was employed for stand-off jamming. The F-105F had the advantages of longer range and higher speed, relative to the F-100F, and it augmented the basic anti-radar armament of 2. 75-inch (70 mm) rockets and 20 mm cannon with the Shrike radar-homing missile, which considerably reduced the time for which the missile radars could safely be operated.

The original concept of the Fan Song radar for the SA-2 was that it would track the target long enough to predict a lead angle for the missile, then continue to track both the target and weapon throughout the missile flight, generating guidance signals that are transmitted by UHF datalink. The threat of the Shrike missile on the Wild Weasel reduced the safe tracking time, initially forcing the SAM operators to fire directly at the target (rather than using lead angle information), and ultimately to fire in a purely ballistic mode using optical tracking. Both measures (and particularly the latter) produced a significant degradation of lethality.

Operation of the SAM system was then changed so that the target was initially tracked by separate radars (Spoon Rest long-range surveillance radar and Side Net height finder radar), and Fan Song was used only for a very brief time at launch and as a terminal homing aid. This move was countered late in 1966 by fitting an ECM pod to the ground attack aircraft. This proved extremely effective in jamming enemy radars, denying range, height and bearing information, and achieving a major reduction in losses from both SAM and radar-predicted flak. Returning to the Wild Weasel side of the story, in 1968 the Standard ARM (anti-radiation missile) entered service, but at that stage, radar operating techniques had reduced opportunities for its use.

It is instructive to review the various phases that USAF attack techniques had passed through between 1965 and 1972 when Linebacker I was mounted against the North. Initially, all intrusions were made “on the deck”, where they encountered considerable fire from light automatic weapons (AW) and anti-aircraft artillery (AAA), but were safe from the SA-2. It may be noted that in the view of many European experts, the fundamental mistake of the Americans was to ingress at 500-1,000 ft, rather than 100-200 ft. Whether or not this criticism is valid, the USAF then switched their attacks to 4,500-6,000 ft, where they were above AW (which topped out at 4,000 ft) and could be protected against the SA-2 by Wild Weasel aircraft. When the effectiveness of the latter was reduced by special SAM operating techniques, the USAF put ECM pods on the attack aircraft and pulled up to around 15,000 ft, where they were above the reach of anything but SAMs and the heaviest AAA, and the radars for both of these could be jammed. This higher altitude gave the aircraft more range, made it easier to find the target, and produced better bombing accuracies through the use of long-dive attacks. The main threat then became the MiG fighter.

For Linebacker I the USAF developed a highly complex attacking force, in which the supporting aircraft sometimes numbered five times the strike aircraft! A typical strike force would consist of 32 F-4s with laser-guided bombs (LGBs) and conventional bombs. Supporting the entire operation from outside the target area would be an RC-121 Constellation for radar cover and to act as an airborne command post, an EB-66 for standoff jamming, KC-135 tankers, and a rescue force of CH-53 “Jolly Green Giants” with A-7Ds for fire support. Ahead of the strike force flew a Wild Weasel flight, clearing the way for four or eight A-7 or F-4 “chaff bombers”, which had an F-4 escort flight trailing behind on either flank in addition to a MIGCAP flight. Leading the main force came four more Wild Weasels and a hunter-killer team of two F-105s and two F-4s for SAM/AAA suppression, supported by one or two flights of four F-4s for close escort against MiGs. Finally, the strike force itself arrived, with two flights of four F-4s in the MIGCAP role. Following this armada came one or two RF-4Cs to record target damage.

Yom Kippur

The tremendous advances in defence penetration made by the American services in the attacks on North Vietnam were, however, only a prelude to the problem that the Israelis faced in the war of October 1973. In the first few days of that war the Israeli Air Force suffered very high losses in ground attack sorties: because Arab defences had virtually the latest Soviet equipment; because the Israelis were obliged to go for quick results, and because they tried to use American tactics without the benefit of US technology.

Whereas the missiles encountered in Vietnam had been the SA-2 Guideline and SA-3 Goa, both relatively static systems relying on command guidance, in 1973 the Israelis encountered the SA-6 Gainful, a fully mobile system using tracked vehicles and with semi-active terminal homing. In addition, at lower levels, their aircraft received intense fire from the radar-directed ZSU-23-4 (self-propelled quadruple 23 mm flak) and the man-portable SA-7 Grail. The SA-7 has only a lightweight warhead and was rarely lethal, but it was used in large numbers and removed many Israeli aircraft from operations for the duration of the 18-day war. 25-30 years of operations is expected. Other EW equipment includes the self-protection subsystem, composed of an ALQ- 137(V)4 jammer and ALE-28 countermeasures dispenser set, and a terminal threat warning subsystem (TTWS} composed of an IR receiver set and an ALR-62(V)4 countermeasures receiver set.

The EF-111A has an empty weight of 25,000 kg and a maximum gross of 40,300 kg. It is powered by two Pratt & Whitney TF30-P-3 turbofans with an after-burning thrust of 8,391 kg each. It is supersonic at sea level, and can reach Mach 2.0 at altitude. With 14,700 kg of internal fuel, it has an endurance of over four hours without refuelling in the standoff jamming role.

Turning finally to the USAF’s Wild Weasel aircraft, the principal types used to date have been the F-100F, the f-1050 (the only single-seater to be operated in this role), the F-105F and -105G, the EF-4C, and (most recently) the F-4G. The F-4G is a converted F-4E, with ECM antennas in a fin-tip fairing and in a fairing under the nose, replacing the M61 Vulcan gun. A total of 52 additional antennas are carried (rather less than the 55 extras on the F-105). Other modifications include various cockpit changes associated with the EW equipment, an ALQ-119 jamming pod in the forward port Sparrow groove for self-protection against ground threats, and an F-15 combat tank of 2,270 litres capacity, which is stressed for 5g, rather than the 3g of the F-4 ferry tank. Chaff “scabs” are fitted to the rear of the inboard pylons, which can also carry AIM-9 Sidewinders laterally in conjunction with certain ordnance loads.

Targets are located and identified by means of the APR-38 radar homing and warning system. From the computed position of the threat radar (shown head-up in the front cockpit as a red symbol), a blind attack with ballistic weapons such as the Rockeye CSU can be made simply by turning the aircraft to place the ground track symbol over the indicated target position and pressing the release button. The computer will then release the selected weapon c;1t the correct time however the pilot manoeuvres the aircraft in the vertical plane. The principal guided weapons available are the radar-homing AGM-45 Shrike, AGM-78 Standard and AGM-88 HARM (High-speed Anti-Radiation Missile), and the TV-guided AGM-65 Maverick, which (like the LG) can provide accurate strikes regardless of whether the radar is in operation. A total of 116 F-4Es are scheduled for conversion to F-4G standard, the first aircraft having been delivered in April 1978.

The F-4G is a convenient short-term solution to the USAF problem of finding a modern Wild Weasel since the supply of F-15s and F-16s is providing a surplus of F-4Es. However, the F-4 is a relatively expensive aircraft to operate, and the F-4G has the further disadvantage of lacking a gun, which is useful both for self-defence and for strafing soft radar targets.

General Dynamics has suggested that the two-seat F-16B or -160 would form a suitable basis for a new Wild Weasel aircraft, especially for America’s allies that have purchased the F-16 for fighter or strike duties. Such an aircraft· would be considerably less costly than the F-4G to operate, would retain the M61 cannon, and would provide much longer range or endurance.

Even with its existing avionics, the F-16 could use its RWR to cue defence suppression weapons. With the full APR-38 system of the F-4G, the Wild Weasel F-16 would use antennas fitted on the present wingtip missile stations and additional antennas in the nose to provide complete 360-degree cover, Further improvements on APR-38 would extend the threat frequency coverage, and give wide-band signal processing and reduced mean-time-to-intercept.

To summarise, the task of penetrating modern defensive systems is an extremely difficult one, in which electronic warfare plays a very important role. Although little hard information is available on the subject, many air forces are now fitting their attack aircraft with jamming pods and chaff, and are probably equipping somewhat older aircraft to provide standoff jamming. The USAF has pioneered the development of dedicated jamming aircraft that can accompany a supersonic strike force, although the Soviet Air Forces may not be far behind in this field. Despite the very high expense involved, penetration aids in general and the Wild Weasel aircraft, in particular, are features of the electronic battlefield that smaller air forces will ignore at their peril.