Stealth also applies to fighters, so in 1991 the USAF launched the programme for an ATF (advanced tactical fighter). Prototype contracts were awarded to Lockheed Martin for the YF-22 and to Northrop Grumman for the YF-23. Two examples of each were ordered, one to be powered by the Pratt & Whitney YF119 and the other by the General Electric YF120. Though the YF-23 was judged stealthier, and the YF120 the more powerful engine, the winner was the YF-22 powered by the Pratt & Whitney engine. Among many other challenging requirements was the ability to supercruise, to sustain supersonic speed with the two engines in dry (non-afterburning) thrust. Cutting a huge story short, while the engine was refined into the F119-PW-100, with rectangular vectoring nozzles, the aircraft was almost completely redesigned into the F-22A Raptor. The enormous wing (840 square feet is roughly the same as five Bf 109s!) has sharp taper but no sweepback. As far apart as possible, the twin vertical tails are canted outward and are fixed, incorporating powered rudders in the traditional way. In contrast, the tailplanes are fully powered and incorporate some sweepback. Overall the shape is very like that of the Russians of the previous generation, but an innovation is to preserve stealth by carrying missiles in three internal bays, a big one underneath between the engine air ducts and a shallow bay on each side outboard of the duct. When stealth does not matter, two pylons can be attached under each wing, each rated at 5,000 lb, principally for air-to-ground stores. The planned initial buy of 648 F-22As had by 2003 been reduced to 339, with the prospect that it might be increased again by funding for a Naval variant and for an enlarged attack version. Price of the latest batch in production in 2003 was US$3,920 million for thirteen aircraft.

Such aircraft are too costly for all but a handful of nations, but in the late 1980s several US teams began studying smaller and more affordable aircraft, which included jet-lift Stovl (short-take-off, vertical landing) versions to replace the AV-8B (Harrier). After the merger of several studies the result in 1995 was the JSF (joint strike fighter). Following competitive tests of very different prototypes made by Lockheed Martin and Boeing, the former was chosen in October 2001 to develop three versions of JSF with the designation F-35. These are the F-35A, a conventional long-runway aircraft for the USAF; the F-35B, a jet-lift Stovl aircraft for the Marine Corps, RAF and Royal Navy; and the F-35C, a big-wing carrier-based version for the USN. The original partners require 3,002, and it is expected that this number will be doubled by other customers, which are expected eventually to include about half the world’s air forces.

There is always unlimited scope for new possibilities and new problems in ECM. For example, several SAMs are guided not by pulsed radar but by CW (continuous-wave) illuminating sets. So are several AAMs, such as Sparrow. Not until the CW-guided lethality of the Soviet ‘SA-6 Straight Flush’ SAM radar became apparent in the Middle East war in October 1973 did the United States suddenly wake up to the fact it had no ECM capability except against pulsed radars. Today even quite small tactical aircraft are being outfitted with complex passive warning receivers, active jammers, IR deceivers, and RF deception jammers which send back hostile radar signals with steadily increasing delay on each pulse to make the enemy think the aircraft is further away and moving faster than is actually the case.

Some modern fighter radars no longer have parabolic or Cassegrain dish reflectors, but flat ‘planar arrays’. These make better use of available space, have a lower moment of inertia and, for a given gimbal geometry and radome size, have about ten to twelve per cent bigger aperture (ie, the scanner can be larger). They should not be confused with phased-array radars, which are exceedingly complex though they also have flat faces. Unlike the phased array, the planar aerial is still scanned mechanically.

We have come a long way in fighter radars in thirty years. The number of electronic components per cubic foot in AI.IV was about 198. In SCR-720 it was about 600, and in AI.IX it reached 3,300. In the Hughes E-1 and Westinghouse APQ-35 the figure rose to over 60,000. In the MG-10 it went to 330,000, and in MA-1 it almost reached a million. The AWG-9 of the F-14 hit 3 million, and the APQ-63 of the F-15 reached 7 million. Today’s radars, such as the Westinghouse chosen for the F-16, invariably use LSI (large-scale integration) and advanced constructional forms in which the circuit forms the structure and also serves as a cooling duct, and 20 million components per cubic foot is now a good figure. This is the main factor underlying the sheer cleverness of today’s radars. Earlier sets had ‘blind velocities’ like radial spokes along which targets could not be seen. They were unable to see moving targets against clutter; or, having got MTI (moving-target indication), they were unable to see hostile aircraft against any background of fast vehicle traffic on the ground. STAE (second-time-around echoes) and MTAE (multiple-time-around echoes) kept on appearing at two, three or more times the true range, causing more clutter. Even rain clutter was often a severe problem. But with 20 million components per cubic foot, today’s night-fighter pilot can see a picture on which positively nothing appears except the precise items he needs.

To every radar there is appropriate ECM. To every ECM – if we can quickly find out all about it – there is the appropriate ECCM. It is the situation of weapon and counter-weapon that has characterized the history of warfare, and which re-emphasizes its ultimate futility. I like the story about the Luftwaffe night-fighter pilot who in 1944 was posted from the Soviet Union to Germany to help shoot down the lavishly equipped RAF heavy bombers. He found it a marvellous change from the Eastern Front. ‘The task there’, he said, ‘was terribly difficult. The Russians were so backward they had no radar.’


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.