Defense Advanced Radar-Equipped F-15Cs Develop Cruise Missile Defenses Aviation Week & Space Technology 10/04/2004, page 49
David A. Fulghum Elmendorf AFB, Alaska
F-15Cs with advanced radars develop cruise missile defenses, new long-range tactics
Future Radar
F-15C fighter pilots of the 12th and 19th squadrons here are flying the radar of the future. It uses sensor technology that is to be operational on the F/A-22 Raptor, F/A-18E/F Super Hornet, F-35 Joint Strike Fighter and upgraded F-15E Strike Eagle.
The radar's performance numbers are classified, but the new Raytheon APG-63(V)2 radars, the first that are operational with active electronically scanned arrays (AESA), can see a small cruise missile or an airframe with stealth shaping at around 50 mi., the distance at which the standard F-15C radar would see a manned-fighter target. The sub-scale, cruise missile-like targets that pilots practice against are 12-14 ft. long while an Su-27 is about 72 ft. long and a MiG-29, 57 ft.
Another way to make the comparison, says a long-time Pentagon radar specialist, is: What older radar detect at 50 naut. mi. (its functional combat range) the X-band AESA radar can locate at 100 naut. mi.
But detection range and resolution are not the only two advantages. Also near the top of the list is the V2's ability to track more targets simultaneously. That's important because cruise missiles are typically launched in salvoes.
"Chances are, with a V1 [the standard F-15 radar] you are going to be targeting one or maybe two cruise missiles," says Maj. Mike Benham, the 3rd Wing's chief of advanced programs. "With a V2 you can track multiple targets at the same time and guide multiple Amraams [Advanced medium-range air-to-air missiles] into the targets with greater accuracy."
SINCE THE RADARS were delivered in 2000, these two squadrons, both belonging to the 3rd Wing, have been defining new battle tactics and broadening the numbers and types of targets pilots can meet in combat with confidence. That's part of the reason senior Defense Dept. officials and analysts were startled when it became known that six of the wing's F-15s had been beaten in simulated air-to-air combat in India early this year. Only much later did the Air Force acknowledge that those F-15Cs did not carry the AESA radar. Missile ranges were limited to 20 mi. and fought at odds of 3 to 1.
Each squadron of 18 F-15Cs has half its aircraft equipped with V2 radar, which uses an aperture made up of hundreds of first-generation "brick"-shaped transmitter/receivers about the size of a small candy bar. The next-generation T/R modules are already less than 1 in. square. Greatly reduced energy losses result from putting the transmitter within fractions of an inch of the radiators and low-noise amplifiers, say radar specialists. A total of 3,600 transmitting and receiving elements, grouped into a square in staggered rows, make up its antenna. The combination of an agile-beam AESA and rapid-beam steering enables the radar to simultaneously track many targets and guide missiles to intercept them.
A few Alaskan F-15C pilots, educated in the magic of first-generation AESA radar, have developed the concept of operations and tactics for cruise missile defense.Credit: BRIAN R.
WOLFF/BRWOLFF@IIPINET.COM
The radar allows the fighters to find small or stealthy cruise missiles at ranges great enough to intercept and destroy them before they can be seen. But even larger AESA arrays, like those planned for the E-10A multisensor command-and-control (MC2A) aircraft, would push the small-target detection capability out to about 200 mi. It could then tell AESA-equipped fighters carrying AIM-120C-6 air-to-air missiles (specialized for small, relatively slow, cruise missile-size targets) where to look for targets. Previously, only very low-frequency radars could detect a stealth design, but they lacked the precision to steer a missile to it. The X-band AESA radars are designed to do both. The system also sends target location updates to the missile during flight, which increases kill probability.
The major tactical impact of the V2 AESA radar comes from its "multitarget track capability and the ability to guide multiple [AIM-120] Amraams against different targets even when they are widely spaced," says Benham. "Initially, when the V2 hit the street, all it could do was cruise missile defense. It didn't have the combat ID capability [and] a lot of the traditional counter-air capabilities. But software updates have now given it all the capability of the V1 and some extra. And it's more powerful so it has greater detection range."
THE NEW AESA antenna also offers a reduced radar cross section for the F-15C making it harder for a foe to detect.
"With a mechanically scanned antenna, the minute you lock on to somebody, you're pointing that plate at them, and that's a huge radar reflector. If they hadn't seen you before, they would see you then. The AESA antenna plate is mounted at an angle [pointing several degrees toward the ground], similar to the F/A-22, so you have much less RF reflection."
Despite its significant advantages, the V2 uses older technologies that will be replaced in the follow-on V3 radar now in development.
"It requires a tremendous amount of cooling and electricity, so we've had to modify the jets significantly [for] the radar," Benham says. "It requires tremendous cooling and electricity, so [consequently] we've had to modify the jets significantly. [The radar] is also extremely heavy. We had to add 600 lb. of lead ballast to the tail of the airplane to keep the nose from being too heavy. The jet is 1,000 lb. heavier than the standard F-15."
WHILE THERE IS NO major impact on range and fuel consumption, there is a minor penalty in slower maneuvering during air-to-air engagements. However, compensation is being provided with the introduction of the AIM-9X short-range (around 12-16-mi.) missile and the helmet-mounted cuing system.
The V2 AESA array has chalked up an impressive 714 hr. mean time between failures, according to a senior Boeing technician who overseas the radar maintenance. He says the most onerous part of the maintenance job involves moving valves and lines on the environmental control system to allow Air Force technicians access to other areas of the aircraft to perform maintenance.
By comparison, the Raytheon APG-63(V)3 in development now will be the same weight as the V1 mechanically scanned radar, will not require tail ballast and will work better with the existing electrical system. Moreover, the V3 will reduce manpower and equipment requirements to improve the squadron's mobility. A total of 12 Raytheon and Boeing employees maintain the 18 radars, says Tim Flohrschutz, Boeing's logistics support contractor for the V2 radar. The civilian support staff debriefs every mission with the pilots and deploys and goes to war with the squadrons.
Instead of the V2's T/R "brick" modules, the V3 uses the same "tile" modules as those in the APG-79 designed for the Navy's F/A-18E/F Super Hornets. The reduced width, depth and weight of the next-generation tiles take 240 lb. out of the array, Flohrschutz says. "The V3 will also include better self-diagnostics for better supportability."
But even with its older technology, pilots here say they would like to have V2 radars on all their aircraft. In fact, the radar is so effective it has created other concerns.
"THE BIG LIMITATION now is whether we can run the intercept geometry to target all those groups [of cruise missiles] and whether we have enough missiles," Benham says. "Because you see so much, it lets you manage the battlefield much better. You're not worried about missing anyone."
However, it means the F-15Cs will go through their weapons load quickly.
"I would love to figure out a way to put more missiles on the jet," he says. "The F-15 has two weapons stations out toward the wingtips that don't get used. I'd like to find a way to put a couple of Amraam's out there or move the AIM-9s there and put Amraams on the current AIM-9X stations."
Another drawback of fighter radar is its limited field of view. While the V2's view is greater than the standard F-15 radar, it is still not all-aspect. Pilots say they would like a digital radar-warning receiver like the ALR-69A(V) to fill in those uncovered areas.
"It has the disadvantage of being a passive system," Benham says. "If the bad guys don't have their radars on, they probably can't shoot you, but you're not going to find them either [except with the radar]."
Nonetheless, the squadrons' pilots believe their tactics offer little opportunity to be surprised from behind.
"The AESA is a forward hemisphere system," Benham says. "The assumption is that things behind us are friendly. We go forward and sanitize the airspace with our radars. We know no bad guys are there unless they make a wide end-around and then [AWACS] surveillance will pick them up. We might do a defense in-depth where we send a two-ship behind [to trail the main force], but typically we want everyone up front because you've got more radars looking. A target may pop up in front of you, but not behind."
Usually the squadron pairs one aircraft carrying an AESA radar with another that does not. For the most part, the AESA radar, with its ability to pick targets out of clutter, is assigned to look low, while the other scans the higher altitudes.
"With V2, once you've sanitized that low area and figured out who's down there, I can roll it up into the high [area of responsibility] and sanitize it," Benham says. "Even then, the radar will continue to send beams to the low AOR to [monitor] weapons quality tracks. If you have a four-ship [formation], flight leads will have V2s, and the wingmen, V1s. Now you have one V2 looking high all the time and one V2 looking low."
THE 3RD WING'S F-15S also carry a communications device, the fighter data link (FDL), which amplifies the radars' impact. "The biggest thing with V2 is it tracks everything, and when combined with everyone else's data through the FDL, situational awareness is huge," says Maj. Mark Snowden, 3rd Wing's chief weapons officer. "Typically, we will designate one [target] in every group we see beyond shoot range as a weapons-quality track [and broadcast it] to wingmen or anyone else on Link 16 so they can see a 3D picture of what's happening.
"If there are six adversary groups and two aren't being shot, with V2 you can broadcast [location] and shoot them later or hand them off if there are more than you have missiles for," he says.
"The power to Destroy the planet, is insignifigant to the power of the Air Force----Mudd Vader
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