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Protecting the sky trains: how do you protect large transport aircraft? Adapt EW systems designed for other aircraft types. (Expeditionary Forces).

Six US Army AH-64 Apache helicopters fly in formation towards an airfield on the fringe of a combat zone. Yet their engines are turned off, and their self-protection systems are useless. How is this possible, you ask? Simple. The helicopters are inside a US Air Force (USAF) C-5 Galaxy transport aircraft, one of the largest aircraft ever built.

Not just the Air Force but the entire US military relies on the heavy-lift capabilities of the USAFs transport fleet, as the example above demonstrates. Without the USAF's fleet of C-5 Galaxy, C-17 Globemaster, C-130 Hercules, and C-141 Starlifter aircraft (though the C-141 is being retired beginning this summer) -- as well as Air Force Speacial Operations Command (AFSOC) MC-130 Combat Talons -- the US military machine would not have the global reach it requires to get critical personnel and supplies into theaters worldwide. One would think, then, that protecting these valuable transport assets would be high on the Pentagon's list of priorities, but only recently have upgrades to the self-protection systems employed by USAF and AFSOC transports gotten underway -- using systems originally designed for other platforms, such as fighter aircraft and helicopters.

Self-Protection on the Line

One example of this migration of self-protection systems to transport aircraft is the towed decoy. Last year AFSOC began looking at equipping its MC1-130 Combat Talon aircraft, as well as its AC-l30 gunships, with a towed decoy (see "AFSOC Selecting Towed Decoy," JED, December 2002, p. 38). Proposals included the BAE Systems (Nashua, NH) AN/ALE-55 fiber-optic towed decoy, which was orginially developed under the US Navy's Integrated Defensive Electronic Countermeasures (IDECM) program for the F/A-18, and a new fiber-optic variant of the Raytheon (Goleta, CA) AN/ALE-50, earlier versions of which have been flown for some time now with USAF F-16 fighters and B-1B bombers. Flight tests of two candidate systems were conducted between May and November of 2002. AFSOC, however, put an interesting twist on its requirements: the ability to retract and redeploy the decoy. Industry sources told JED that AFSOC wanted to be able to perform 20 retractions of the decoy before requiring maintenance -- a new challenge for cont ractors over other towed-decoy programs, which did not call for such a capability, as retracting and redeploying the decoy causes additional stress on the decoy's towline.

Earlier this year, AFSOC chose its winner: a modified AN/ALE-55 that BAE Systems has dubbed the Fast Deploy and Retract (FDAR). Per AFSOC requirements, the decoy will be mounted in the pod used to carry the Northrop Grumman (Rolling Meadows, IL) AN/ALO-131 radio-frequency (RF) lamming pod (which is sometimes fitted to C-130s). The pod will be gutted of its -131 electronics in order to house the new decoy system, which is slated for redesignation. (For now, BAE Systems is calling it the Special Operations Forces Towed Decoy, SOFTD, system.) It will, however, not receive the "ALE" designation given to other decoys. Instead, the decoy will be given an "ALO" designation, as it ends up being more of an offboard transmitter, rather than an expendable decoy. "It's actually a smart piece of metal flying behind the aircraft," said John Steckel, BAE Systems' business-development manager for RF-countermeasures (RFCM) programs.

Modifying the AN/ALE-55 for the flight regime of the C-130 presented some unique challenges. "One of the things that makes the C-130, and especially the Special Ops C-130, unique is not so much its slow-flight capability, but the real big thing is controlling the amount of droop in the decoy," said Mike Williams, BAE Systems' director of RFCM programs. "You've got an aircraft that's going to, by its mission, fly very, very low, so you want to have a decoy that you can trim behind the aircraft and minimize droop so you don't knock it off in the trees, or on telephone wires or electrical lines, or those kinds of things."

Of course, this isn't the only difference that had to be taken into account when modifying a decoy that was originally designed for use with fighter aircraft. Fighters don't generally circle their targets, whereas transports, especially AFSOC transports, often do. Circling in an aircraft as large as a C-130 creates a lot of turbulence to begin with, but there are also the four-engine aircraft's propellers to take into account. The "prop wash," when added to the turbulence created by such a large plane circling, combines to create a very challenging environment in which to stabilize the flight of a decoy.

But there's another aspect to designing a decoy for a large transport. As Williams explained, "Here's an airplane where the whole back end opens up, and when it opens up, stuff falls or lumps out of it, so the last thing you want to do is have to cut your decoy every time you drop something, because dropping is your mission."

Thus, AFSOC required the aforementioned ability to deploy, retract, and redeploy the decoy, a requirement BAE Systems met with its FDAR concept. The FDAR concept, though, also brings another valuable capability: if one decoy is taken out by enemy fire, another can be deployed -- hopefully, before the enemy gets off another shot. And although AFSOC only required the ability to perform 20 such retractions, BAE Systems demonstrated up to 27 during flight tests held last year without any degradation of fiber-optic continuity (i.e., damage to the towline). This has the additional bonus of cutting life-cycle costs as well; instead of replacing the decoy after every sortie, only the towline will need to be replaced -- a much cheaper alternative to replacing the decoy itself.

Direct and to the Point

While RF decoys provide protection against radar-guided threats, infrared-guided missiles, especially those fired from man-portable air-defense systems (MANPADS), are seen as an ever increasing threat to military aircraft in general and to transports in particular, as they generally operate at lower altitudes and at slower speeds, making them easier targets. To address this threat, the USAF and AFSOC are installing new infrared countermeasures (IRCM) systems on their transport aircraft.

Here, AFSOC has taken the lead. In mid-2002, AFSOC ordered the Northrop Grumman (Rolling Meadows, IL) Directed Infrared Countermeasures System (DIRCM), originally designed for helicopters like the UH-60 Blackhawk, for all 59 of its C-130s (see "DIRCM for Special Ops C-130s," JED, July 2002, p. 27). First up to receive the new system will be the MC-130E/H Combat Talon aircraft, to be followed later by the command's other C-130 variants -- the AC-130H/U Spectre, the EC- 130E Commando Solo, and the MC-130P Combat Shadow. Currently, the Combat Talon is the only one of the C- 130 variants that has been granted a production release for the DIRCM system, but the others are already being tested for the system. The Combat Thlon aircraft, though, will not have to wait very long to receive their DIRCM systems. According to Jack Pledger, Northrop Grumman's director of EO/JR marketing and business development, the company produced the systems in advance and built up its inventory in anticipation of a production release fo r the command's C-130s.

The DIRCM system to be installed on the Combat Talons generates a large amount of lamming energy to defeat incoming missiles. As such, the system possesses two large transmitters, one fitted on each side of the aircraft, each with two lamps to generate the necessary IR energy. But the DIRCM system is not solely a countermeasures system; it also includes its own ultraviolet missile warner: the AN/AAR-54, which Pledger claimed is the only missile warner with the requisite threat-declaration range and angle-of-arrival accuracy for a DIRCM system.

Not long after the AFSOC decision, the USAF Air Mobility Command jumped on the directed-IRCM bandwagon, awarding Northrop Grumman a $23.3-million contract for the provision of its Large Aircraft Infrared Countermeasures (LAIRCM) system (see "LAIRCM for USAF Transports," JED, October 2002, p. 34). The LAIRCM system, however, represents a technological step beyond the system ordered by AFSOC in that it employs a laser jammer, as opposed to the lamp-based DIRCM system (though AFSOC has expressed interest in the possibility of upgrading to the laser version down the road).

At first, AMC will acquire four low-rate, initial-production (LRIP) LAIRCM systems for C-17 transports, but the contract contains options for a total of 20 systems -- 12 for C- 17s and eight for C-130s. This plan was accelerated earlier this year (see "USAF Wants LAIRCM Stat!" JED, February 2003, p. 20). As a result of a Combat Mission Need Statement issued by AMC, the Northrop Grumman received a $7.2-million contract to design, develop, test, and deliver a single-transmitter configuration of its LAIRCM system for up to 12 C-17s "as rapidly as possible." Normally, the C17 would be fitted with three LAIRCM lamming transmitters, but by scaling the system back to only one, the USAF will had LAIRCM systems onboard the aircraft by May of this year and was set to begin flight testing.

But AMC has even more ambitious goals than simply equipping these 20 airplanes with the LAIRCM system. Pledger told]ED that AMC has a requirement to outfit one "small-scale contingency fleet" of 79 transports in the 2006 timeframe and is looking to extend this form of protection to cover its entire fleet as funding becomes available.

Tale of the Comet

The DIRCM and LAIRCM systems, of course, provide reactive self-protection -- i.e., they are cued when they detect a threat. But what about employing preemptive countermeasures? For decades now, flares have been the norm for preemptive countermeasures. Who by now hasn't seen a photograph of a large transport launching a slew of flares in the hopes of countering the lR threat before it's launched? But flares have their inherent drawbacks. First, chucking a flare is like tossing a match: it bums out in seconds. Secondly, there are the obvious environmental and safety concerns of tossing combustibles out of an airplane.

Enter the Comet, designed initially for the A-b ground-attack plane. To the idea of a simple heat source to decoy IR-guided missiles, the Raytheon (Goleta, CA) Comet system adds multi-spectral heat sources, dynamic trajectory (kinematic adaption), area burning (non-spot source), and two-color heat sources using pyrophoric materials. Also, since it's designed for pre-emptive use, the Comet enhances the capability for deploying decoys before a specific weapon is located inbound for the intercept, thus eliminating reaction time from the equation that determines whether the aircraft is shot down or not, and Raytheon bills the Comet as a countermeasures system that doesn't require missile warning.

Indeed, though testing of the Comet was originally intended to demonstrate self-protection for the A-10, Raytheon spokesman Ron Colman said that "the C- 130 was added as kind of an afterthought." Flight tests of the system last year on both aircraft used a system that had been customized for the A-b, but further testing, begun on May 5 and still underway at press time at the Yuma Proving Ground in Arizona, is seeing a system flown on the C-130 that has been modified for use on the larger and slower aircraft. These tests, according to Dennis Lewis, Raytheon's Comet program manager, aim to demonstrate "pre-emptive effectiveness against MANPADS primarily and some other surface-to-air IR threats," especially at low altitudes, the flight regime in which Lewis said the USAF has always been the most interested.

Assuming all goes well with the latest series of flight tests at the Yuma Proving Ground, Lewis said that he expects the Air Force to make a production decision on the Comet for the A-10 first and the C-130 shortly afterward. The Comet, then, could soon begin replacing the traditional flare-based countermeasures on the service's C-130s, as well as perhaps AFSOC C-130s, as the Command had been kept in the loop regarding development of the system for the Hercules.

RELATED ARTICLE: Current USAF Transport Self-Protection

Upgrades to the EW capabilities of USAF transport aircraft are in the works, but here's what the big boys currently rely on for self-protection.

C-5 Galaxy

Missile Warner: BAE Systems AN/AAR-47

Chaff/Flare Dispenser: BAE Systems AN/ALE-47

C-17 Globemaster

Missile Warner: BAE Systems AN/AAR-47

Chaff/Flare Dispenser: BAE Systems AN/ALE-47

C-130 Hercules

Missile Warner: BAE Systems AN/AAR-47

Radar-Warning Receiver: Raytheon AN/ALR-69

Chaff/Flare Dispenser: BAE Systems AN/ALE-47

C-141 Starlifter

Radar-Warning Receiver: Raytheon AN/ALR-69

Chaff/Flare Dispenser: BAE Systems AN/ALE-47

Special Operations MC-130 Combat Talon I/II

Missile Warner: Cincinnati Electronics AN/AAR-44

Radar-Warning Receiver: Raytheon AN/ALR-69

Electronic-Support Measures: EDO AN/APR-46A

Radar Jammer: ITT AN/ALQ-172
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Title Annotation:electronic warfare
Comment:Protecting the sky trains: how do you protect large transport aircraft?
Author:Rivers, Brendan P.
Publication:Journal of Electronic Defense
Geographic Code:1USA
Date:Jun 1, 2003
Words:2083
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